Planet Earth Spring 2010

www.planetearth.nerc.ac.uk

Spring 2010

Gardening for greenhouse gases

Finding Solomon’s gold? • Watching water dry • Volcanic secrets in the ice • A mighty wind

Contents

Planet Earth

FEATURES

18

10 Finding Solomon’s gold?

How hot springs can help find gold deposits even in

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heavy forest.

12 Watching water dry New insights into evaporation.

14 Survival of the fattest Unravelling the mysteries of marine algae and their viruses.

16 Groundwater – returning to the sources Old studies could save lives in Africa.

18 Corals in a changing world Going back to basics to understand how corals grow.

20 COVER STORY Gardening for greenhouse gases How will moorland plants respond to climate change?

22 A mighty wind Greenland’s weather and global ocean circulation.

28 30

24 Volcanic secrets in the ice Tiny ash particles tell of long-ago eruptions.

K. Telnes/www.seawater.no

26 Finding the wisdom in teeth Isotopes and the science of archaeology.

28 High and dry in the Andes Looking into Peru’s past to shed light on its future.

30 Getting to the bottom of biodiversity How is marine life distributed around the seabed?’

Editor:

32 Measuring the changing environment from space New satellite instruments help us understand the Earth.

Design and production:

NERC scientists: we want to hear from you Planet Earth is always looking for interesting NERC-funded science for articles and news stories. If you want to see your research in the magazine, contact the editor to discuss. Please don’t send in unsolicited articles as we can’t promise to publish them. We look forward to hearing from you.

Front cover:

Sue Ward taking CO2 samples using a portable Infra Red Gas Analyser at Moor House National Nature Reserve, see p.20. Richard Bardgett

Tom Marshall, 01793 442593, thrs@nerc.ac.uk

Science writers:

Tamera Jones, 01793 411561, tane@nerc.ac.uk Sara Coelho, 01793 411604, sarelh@nerc.ac.uk Candy Sorrell, cmso@nerc.ac.uk

Print: Broglia Press is registered to ISO 14001 for

environmental management systems. Printed using chemical-free plate technology and 100 per cent vegetableoil-based inks on Revive Pure Offset, a recycled grade containing 100 per cent post consumer waste and is totally chlorine free (TCF).

ISSN: 1479-2605 Planet Earth is the quarterly magazine of the Natural Environment Research Council. It aims to interest a broad readership in the work of NERC. It describes new research programmes, work in progress and completed projects funded by NERC or carried out by NERC staff. Some of this work may not yet have been peer-reviewed. The views expressed in the articles are those of the authors and not necessarily those of NERC unless explicitly stated. Let us know what you think about Planet Earth. Contact the editor for details.

BEYOND CLIMATE CHANGE

Alan Thorpe Chief Executive, NERC

Beyond climate change C limate science is at the centre of very public controversy at the moment, arising from the theft of emails from the Climatic Research Unit (CRU) at the University of East Anglia (UEA) and errors or misinterpretations in the Intergovernmental Panel on Climate Change Working Group 2 report.

The email issues, including the availability of datasets and the accusations of deceit and bias, are the subject of two separate independent inquiries. It would not be appropriate for me to comment in any detail on these issues until these inquiries are completed. But as a meteorologist myself, I can reiterate that there is a large body of evidence showing that the main cause of global warming over the last 50 years, and more, is human emissions of greenhouse gases into the atmosphere.

But while the climate change debate is played out in the media and through the inquiries, we should not forget that environmental science is about much more than climate change.

The current controversy should not distract us from the fact that there

are many other environmental issues that society and environmental scientists urgently need to address.

The Haitian earthquake and many other examples of natural hazards leading to human disasters show how vulnerable people are to the environment.

Even if the planet was not undergoing long-term changes, research about risks like storms, volcanoes, earthquakes, tsunamis and landslides would still be vital to society at large.

But we know that there are longer-term changes happening in the natural environment, many of them caused by human activities. Climate change is one of a sizeable array of environmental, and increasingly economic and social, issues that humanity has to face up to in the 21st century. Irrespective of their climate impact, dwindling stocks of fossil fuels challenge science to come up with alternative and renewable energy supplies.

The environment provides us with a very wide range of so-called ‘ecosystem services’, and these vital services depend on biodiversity. But we need

research to pin down the link between biodiversity and how these ecosystems function. The fact that biodiversity is falling worldwide shows how important this research now is.

It is, of course, fiendishly difficult to develop an understanding of how the physical, chemical and biological environment of planet Earth works. This requires top-quality science that crosses the boundaries between disciplines to unravel the forces and feedbacks that operate to connect the different parts of the Earth system – sea, air, ice and land.

UK environmental science, much of it funded by NERC, is tackling this very broad range of environmental issues. In many fields our science leads the world.

At this point in Earth’s history, the case for environmental research is overwhelming. But as scientists we cannot be complacent about this.

We must continue to articulate the case for investing in research, and accept that openness and transparency throughout the science process are essential if we are to keep the public’s trust.

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News Mongoose teamwork hides darker side Mark MacEwen/OSF

BANDED mongoose society looks harmonious and cooperative, but research over a decade and a half shows this is just a thin veneer hiding fierce competition.

Mongoose groups have an unusual social structure that is helping scientists understand why some animals are willing to make sacrifices to help others, and what the limits are to this kind of cooperation.

The findings are emerging from a long-term study monitoring ten mongoose packs living in Uganda.

The research inspired BBC documentary Banded Brothers: The Mongoose Mob. Unusually, mongoose mothers synchronise their childbearing. In meerkats and many other social animals, only one female at a time gets to breed, and those further down the pecking order have to content themselves with looking after the breeding female’s young.

But among banded mongooses,

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several females breed at the same time, and they give birth on the same day. This helps protect their pups. If young mongooses are born too early, higher-status females are likely to kill them in an effort to increase the chances their own young will survive. Once these high-ranking females have young of their own they won’t kill pups – female mongooses don’t seem to be

Mongoose groups have an unusual social structure. able to tell one pup from another, and so they don’t risk killing their own offspring.

But there are also costs to giving birth too late: if pups are born later than their peers, there’s a good chance they’ll lose out to older pups in the competition for food and adult attention. The result

is a remarkable degree of birth synchrony, whereby up to ten females all give birth at the same time.

By dosing female mongooses with contraceptives to limit the number of births, the researchers have learned that the optimum number of females that can give birth at the same time is around three. A mongoose born with no peers of the same age has almost no chance of living to adulthood.

‘The adults just don’t seem to take things seriously if there aren’t enough pups,’ says Dr Michael Cant of the University of Exeter, who initiated the project in 1995.

‘They don’t spend much time looking after them, or feeding them, and they sometimes fail to leave babysitters behind to protect them when the group goes off to find food.’ But if there are too many pups, there is not enough food to go round and several will starve.

Because it lets more pups avoid death by infanticide, synchronised childbirth improves low-ranking females’ chances of breeding successfully. But it is also likely to push the number of pups in the group well over the optimum total, so it harms the group as a whole. If the food supply runs out, middleaged females are driven out in often-violent ejections.

So while synchronised birth looks on the surface like a cooperative way to let more individual mongooses bear children, it seems to have evolved in response to routine infanticide and is effectively a way for young females to seize advantage at the expense of their more senior rivals.

‘Birth synchronisation seems to be a cooperative behaviour, but as you look deeper you see lots of conflict beneath the surface,’ says Cant. ‘Mongoose society is balanced on the edge between cooperation and conflict.’

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News Sea squirts spotted in Scotland THE sea squirt isn’t just ugly – it’s also an invasive species that poses a serious threat to UK marine life. Now the critter has been found in Scotland.

Carpet sea squirts (Didemnum vexillum) come from Japan, but they have travelled the globe causing havoc in ports and marinas. The brownish, tube-shaped animals live in colonies and spread fast once established on the seabed.

As a colony grows, it smothers local marine life and becomes a serious threat to biodiversity.

Colonies are also a problem for port authorities and fish farms, as they are ‘especially good at growing over underwater structures such as boat hulls and pontoons’, says Dr David Donnan, Policy and Advice Manager at Scottish Natural Heritage.

‘We have been on the lookout for this species in Scotland as it was found in Holyhead Harbour in North Wales in 2008 and more recently in the south of England,’ he says. ‘This recent finding in Largs Yacht Haven is the first sighting in Scotland.’

The sponge-like leathery creatures were spotted during a routine survey by Christine Beveridge, a support scientist at the Scottish Association for Marine Science. ‘This is one of our target species, so when I spotted a mussel on a pontoon, covered with a fawn-coloured growth, I immediately suspected the invasive sea squirt,’ she says, adding that the animals may have arrived on the hulls of boats. Readers can find out more and report any sightings at https://secure.fera. defra.gov.uk/nonnativespecies.

Reefs grow in spurts

CORAL reefs do not grow continuously and some reefs off Australia are dead relics from past periods of growth. But this is not necessarily a sign of ecological catastrophe – when the opportunities arise, reefs know how to make the most out of it and can grow very quickly.

Reef growth depends on several environmental factors, but two are especially important – sunlight and space to expand. This means that reefs can grow extensively in clear, mud-free water where sunlight penetrates deep. In the long term, rising sea levels also come in handy as they provide vertical space for reefs to grow into.

‘Our recent studies demonstrate that whole suites of reefs on the innermost parts of the Great Barrier Reef grew very rapidly between about 8000 and 5000 years ago, but not much since,’ says Professor Chris Perry, a specialist in tropical coastal geosciences

at the Manchester Metropolitan University.

Perry analysed two reef areas off Queensland to see how reef growth has changed there over time.

With Dr Scott Smithers, from the Australian James Cook University, he extracted cores from them to analyse mud content, carbonate sediments and coral species.

‘We found two distinct areas of coral-reef development within this area,’ says Perry. Radiocarbon dating shows that the reefs grew at very different times, one between about 6500 and 4500 years ago, and one much more recently, in the last 1500 years or so.

‘Both, however, have grown rapidly to sea level and have reached the end of their natural life under present sea-level conditions,’ he adds. The reefs cannot continue to grow up because the sea level is stable, and further seawards growth is limited by muddy water conditions around the island that

restrict sunlight penetration.

Some of these reefs look alive and are covered by a thin layer of coral. But scratch the surface and you find an old, relict reef.

The findings, published in Geology, show that these reefs grew only at certain depths. But when the time comes, ‘these reefs can grow very quickly – they appear to be very good at making the most out of their opportunities,’ Perry says.

Although the studied coral reefs are dead, if the conditions change they may be able to return to growth. And this might happen sooner rather than later with the sea-level rises predicted for the next few decades.

In practice rising sea levels could give corals new space to grow, but Perry says global warming and climate change may also bring other less beneficial effects, such as coral bleaching and ocean acidification.

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News How the butterfly got its spots THE SAME small portion of DNA, dubbed a ‘hotspot of evolution’, defines the wing spots of two different species of butterfly that have evolved to copy each other’s wing pattern. This means evolution may be concentrated in small regions of the genome, while the rest does not change very much.

Heliconius butterflies have striking wing patterns, often with yellow and red spots and bands to warn predators they are toxic.

Some species are remarkably similar because it pays to mimic patterns and bank on each other’s toxic reputation with birds.

‘When two species are very similar they reinforce the warning signal and gain an added protection against predation,’ explains Dr Chris Jiggins, leader of the Butterfly Genetics Group at the University of Cambridge.

Heliconius melpomene, known as the postman butterfly, and Heliconius erato are a good example; they are only distantly

related but their wing markings are almost identical.

Scientists knew about the practical benefits of copying warning signals, but not how it happens. The same wing pattern evolved separately in separate species, but is it controlled by the same genes? Or are different genes doing the same thing? To find out, the researchers isolated the genes that control wing-pattern variation in the butterflies.

Their results, published in PLoS Genetics, suggest a small number of genes control major changes.

‘It seems that evolution might be concentrated in small hotspot regions of the genome, while the rest does not change very much,’ says Jiggins.

‘This tells us something about the limitations on evolution, and how predictable it is,’ he says. ‘Our results imply that despite the many thousands of genes in the genome there are only one or two that are useful for changing this colour pattern.’

Ocean acidification accelerates CARBON dioxide released from fossil fuels and dissolved in the ocean is making seawater more acidic and causing trouble for marine life. Now a new model suggests that seawater is acidifying at a rate that exceeds anything seen on Earth in 65 million years.

The change may be too fast for marine animals to adapt.

Scientists from the University of Bristol developed a model to compare current predictions of ocean acidification with what happened during a greenhouse gas event 55 million years ago, called the Palaeocene-Eocene thermal maximum. Their research

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appears in Nature Geoscience.

During this event, which saw a 5-6°C increase in surface water temperature, the oceans acidified and dissolved large quantities of carbonate rocks. All this happened over thousands of years – very sudden from a geological viewpoint.

The tiny animals and plants that make up the plankton at the surface of the sea did not suffer much during the event, perhaps because they moved to cooler waters or had time to adapt to changing conditions.

Even so, the Palaeocene-Eocene acidification was severe enough to kill off many benthic foraminifers, tiny organisms that live at the

bottom of the sea protected by calcium carbonate shells.

This mass extinction has been linked to the high levels of carbon dioxide dissolved in seawater making it difficult for foraminifers to build their shells.

Nowadays, ocean chemistry may be changing even faster.

‘What we found was a geologically unprecedented rate of acidification,’ says co-author Dr Andy Ridgwell. The change seen today is taking place over hundreds of years, and this could be too much for marine life to handle.

‘Given that we had an extinction in the past, it’s quite possible that this will happen again in the future,’ Ridgwell explains.

Benthic foraminifers might not attract as much sympathy as giant pandas, but their demise ‘has implications for the cycling of nutrients and it’s a good indication of the extent to which we’re affecting the oceans,’ he adds, suggesting that even ocean organisms may struggle this time.

Scientists have an idea of the consequences of ocean acidification on marine animals such as foraminifers or corals thanks mainly to experiments. But how will animals adapt to changing conditions? ‘Experiments don’t tell what will happen over 100 years’, says Ridgwell. ‘And we can’t wait 100 years.’

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News Springing forward – changing seasons threaten wildlife

BRITISH springs and summers are starting sooner, a new study shows. Winter now ends 11 days earlier on average than in the mid-1970s.

The research is the first systematic attempt to survey longterm trends in phenology – the science of seasonal timing – in ecosystems spanning freshwater and marine environments as well as dry land.

It examines more than 25,000 such trends between 1976 and 2005, covering 726 species ranging from plankton to plants and from insects to mammals.

More than 80 per cent of these trends show seasonal changes happening earlier. On average, events like the start of animals’ breeding seasons are starting 11 days earlier than in 1976, and the trend seems to be accelerating. This is probably a response to climate change.

‘This is the first time that data

have been analysed with enough consistency to allow a meaningful comparison of patterns of changing seasonal timing in the UK among such a diverse range of plants and animals,’ says Dr Stephen Thackeray of the Centre for Ecology & Hydrology (CEH), one of the project’s leaders.

Changes have been fastest for species near the bottom of food chains, such as plants and herbivorous animals. Plants saw the fastest changes on average, while predators have experienced slower changes in the timing of the important events in their life cycles.

Reproduction is often timed to happen when there’s plenty of food around, to ensure young animals don’t starve in their vulnerable first few weeks. At present we don’t know how well the animals further up the food chain will adapt to the changing schedules of the organisms below them.

If they don’t respond quickly, they will find it harder to raise their young, as their breeding seasons become increasingly mismatched with the periods when their food supply is at its most abundant – often, these are the breeding seasons of their prey.

‘The recorded changes need urgent investigation, particularly for species with high economic or conservation importance,’ adds Professor Sarah Wanless of CEH, the report’s other lead author.

Scientists have broadly agreed that seasons are moving forward across much of the northern hemisphere, but this research, published in Global Change Biology, is the first detailed investigation of how this is affecting different species. Its authors argue that its findings may be applicable throughout midlatitude regions, and may even be relevant worldwide.

In brief Cutting fishing can help reefs bounce back Protecting coral reefs from fishing could help them recover from damage more quickly than previously thought possible. Reefs are some of the planet’s richest habitats, but they are threatened by climate change, ocean acidification and destructive fishing methods. Because corals grow slowly, scientists have feared reefs are doomed.

But researchers compared reefs in marine reserves with similar habitats elsewhere, and found that in the reserves, where fishing isn’t allowed, coral cover area increased much more quickly than in unprotected areas, perhaps because grazing fish protected the corals from competition from plants.

Scientists probe Southern Ocean black smokers for first time Scientists on the British research ship RRS James Cook have explored deep-sea volcanic vents in the Southern Ocean for the first time with a remotely operated vehicle.

The team have been working a mile and a half deep on the ocean floor to understand the extreme environment around the vents. They found complex ecosystems and are now studying the animals they recovered, which ultimately depend not on sunlight but on energy in the chemicals vented from the Earth’s interior.

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News Dinosaur colours revealed Chuang Zhao and Lida Xing,/Institute of Vertebrate Paleontology and Paleoanthropology, Beijing

WHAT colour were dinosaurs?

We’ve never known, so artists have been free to use whatever outrageous colours they fancied.

But no longer – scientists have found the first evidence of colour in fossil feathers.

A British-Chinese team found that the dinosaur Sinosauropteryx had a feathered tail striped with ginger and white rings, and that Confuciusornis, an early bird, had

patches of reddish, black and white feathers.

For Professor Mike Benton, a palaeontologist at the University of Bristol, the discovery opens up an exciting new field of research.

‘We can now go back and look for evidence of colour in other fossils.

This will bring new insights on the behaviour of dinosaurs and on the evolution of feathers and birds,’ he says.

Feathers’ colour comes mainly from a protein called melanin. It is probably not preserved in the fossil record, but the tiny organelles that encase it, called melanosomes, can survive for millions of years, long after the protein is gone.

Modern bird feathers have two kinds of melanosomes: sausageshaped structures which give a black colour, and spherical casings that provide reddish-brown tones.

‘If no melanosomes, or other colouring agents, are present, then the feather is white,’ says Benton.

The team looked for melanosomes in fossils of dinosaurs and early birds collected from north-east China. The 125-million-year-old remains were so well preserved that they could recognise the different types of melanosomes in their feathers.

The feathers along Sinosauropteryx’s tail have rings with spherical melanosomes alternating with bands with no visible casings. This suggests that the tail was striped ginger and white. Some hues remain elusive, though. Bright yellow, blue or green shades come from other proteins. These are not contained in casings, so they are less likely to be preserved in fossils.

Published in Nature, the findings aren’t just a relief for dinosaur artists interested in accuracy. The feathers along Sinosauropteryx’s tail are closer to whisker-like filaments than modern feathers with a central quill and barbs. Some researchers concluded they weren’t feathers at all, just skin tissue.

‘The discovery of melanosomes embedded within the Sinosauropteryx filaments is the definite proof that they are indeed feather precursors,’ says Benton. ‘This is a very important conclusion to our understanding of the evolution of feathers and birds.’

Scientists have debated the function of feathers and filaments in dinosaurs. Since they did not have wings, the feathers weren’t there to help them fly. Some have suggested they evolved as insulation to keep the animal warm.

But the feathers in the Sinosauropteryx fossils cover only part of the body, as a crest, along the midline of the back, ‘so they would have had only a limited function in thermoregulation,’ says Benton. He suggests feathers were originally for display, but were later adapted to insulation and flight.

First visitors to the Galápagos were European THE first visitors to the Galápagos Islands were 16thcentury European explorers, not pre-Columbian voyagers as was previously suggested.

The findings, published in Vegetation History and Archaeobotany, come from the radiocarbon dating of charcoal remains found close to pottery shards in old coastal campsites.

The pottery remains were identified as of South American origin by Thor Heyerdahl, the Norwegian archaeologist who rafted across the Pacific from

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South America to Polynesia in the Kon-Tiki expedition during the 1950s. Heyerdahl suggested the Galápagos were colonised

by South Americans before their official discovery in 1535.

But later research cast doubt on this conclusion. ‘The pot shards were mixed with later European remains,’ explains Dr Cynthia Froyd, a palaeoecologist working at the University of Oxford.

So the pottery was probably brought from the South American mainland by European seafarers.

One way to solve the

conundrum is to discover when these historic campsites were occupied. Froyd and colleagues radiocarbon dated nine charcoal samples found near the pottery.

They found that all were burned between 1575 and 1825. ‘These campsites are too young for the pottery shards to be interpreted as evidence of pre-Columbian visitors,’ says Froyd.

The findings add to other clues provided by the archaeological evidence. Drs Atholl Anderson and Simon Haberle, archaeologists from the Australian National

University and co-authors of the recent study, analysed coastal campsite locations in detail and concluded that there is no evidence humans were in the Galpágos before the Europeans’ arrival.

So it seems that Europeans were indeed the first people to set foot on the remote Galápagos, about 1000km west of South America. These first visitors were mainly buccaneers, whalers and traders who set up camp near the few freshwater springs available.

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News Stunning photos reveal rich Antarctic marine life CLOSE-UP photographs of bizarre marine animals in one of the fastest-warming seas on Earth show the area is home to a huge diversity of life.

The creatures include ice fish, octopus, sea pigs, giant sea spiders, rare rays and basket stars.

An international team of scientists collected the creatures in West Antarctica while on an expedition to study the diversity of life in the continent’s shelf seas.

Expedition leader Dr David Barnes from the British Antarctic Survey reported the team’s findings from Antarctica.

Comparing the area to coral reefs, Barnes says, ‘Few people realise just how rich in biodiversity the Southern Ocean is – a single trawl can reveal as fascinating an array of weird and wonderful creatures as would be seen on a coral reef.’

One of the expedition’s aims is to figure out how some of these marine animals will respond to environmental change.

‘These animals are potentially very good indicators of environmental change. Some live in the shallows, which are changing fast, while others live in deeper water which will warm much less quickly,’ says Barnes. ▶ Sea pig (sea cucumber or holothuroid). This was one of the most common animals.

▶ Amphipod (sand-hopper). Gigantism (due to high oxygen levels in polar waters) was first demonstrated in amphipods. This important group often fills the ecological niche of animals like crabs, which are almost unknown in Antarctica.

▶ Scale worm, Laetmoice sp. Polychaete worms like this are often the most abundant large organisms on the continental shelf around the region.

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News Taking a tern round the globe

Carsten Egevang/ARC-PIC.COM

ARCTIC terns make the longest migration of any animal on the planet, scientists can confirm.

They fly up to 80,000 kilometres every year while migrating from the Arctic to the Antarctic and back again.

As Arctic terns can live for 30 years, this is like making three trips to the moon and back over their lives.

Scientists have long suspected that Arctic terns top the list of long-distance migratory birds, but previous estimates suggested they averaged about 40,000 kilometres every year. Now, technology has doubled this distance.

‘This is a mind-boggling achievement for a bird that weighs just over 100 grams,’ says the lead author of the research, Dr Carsten Egevang from the Greenland Institute of Natural Resources.

Egevang and colleagues from the British Antarctic Survey, Greenland, Denmark, the US and Iceland describe in Proceedings of

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the National Academy of Sciences how they tracked the birds using tiny instruments called geolocators.

They attached them to 50 Arctic terns’ leg rings towards the end of the breeding season on Greenland in July 2007. Another 20 instruments were attached to birds breeding on Iceland in June 2007.

The geolocators weigh just 1.4 grams and, including attachments, make up around 1.9 per cent of an adult’s body weight. They record light intensity; when this data is fed into a computer program, scientists can calculate when and where the birds travelled.

The following year the team managed to retrieve ten of the logging devices from the Greenland birds and one logger from the Iceland colony.

As well as confirming their wintering grounds in Antarctica, the researchers discovered that after leaving Greenland and Iceland in August, the terns

stop over in the North Atlantic for around a month en route to Antarctica.

‘This part of the Atlantic is a region of high marine productivity so it’s clear they’re using the area to refuel before crossing less productive parts of the Atlantic Ocean,’ explains Dr Richard Phillips of the British Antarctic Survey, co-author of the paper.

While birds from the same colony followed either the African or South American coastlines, all of the birds followed the same route home. This means that birds from different breeding colonies mix when they’re in the Antarctic.

‘It looks like these incredible birds are exploiting the prevailing global wind systems in the Atlantic, which go clockwise in the north and counter-clockwise in the south, making their trip north that much easier. Interestingly this is the same strategy used by Manx and Cory’s shearwaters,’ says Phillips.

Call for new members of the NERC Science and Innovation Strategy Board NERC is calling for nominations to its key advisory board, the Science and Innovation Strategy Board (SISB), to commence 1 September 2010 for a threeyear period.

Applications with the following backgrounds would be particularly welcome: relevant business, public and voluntary sectors, climate modelling, ecology, geomorphology and marine science. NERC recognises that women, disabled people and those from ethnic minorities are currently underrepresented on SISB, and we are especially keen to receive applications from these areas of our community.

SISB is the key source of advice to NERC Council on science and innovationrelated issues. Members are appointed to SISB as individuals, rather than as representatives of a particular organisation, and NERC aims to see that SISB membership is balanced across science areas wherever possible.

Deadline Monday 24 May 2010.

Interviews London on 7 and 8 July 2010.

Further information Sinéad Darker sirk@nerc.ac.uk 01793 411621 www.nerc.ac.uk/about/ work/boards/science/ nominationandselection.asp

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News Isotopes –

Earth’s atmosphere may weapons of mink destruction have come from meteorites

John McAvoy

This means that ‘if trapping can be focused on coastal areas, then inland areas on larger islands do not become an increasingly difficult logistical challenge requiring more and more traps and man hours to cover,’ says Bodey.

American mink are not native to the Hebrides and became a problem after animals that escaped or were released from fur farms adapted well to the islands and quickly multiplied.

‘The Hebrides are a very important breeding area for many sea and shorebird species, with internationally important numbers of several species,’ says Bodey.

‘The breeding birds are under threat now because mink eat eggs, nestlings and adults if they get the chance,’ he adds. ‘They have been implicated in the extirpation of many small seabird colonies on the west coast of Scotland.’

Eradicating mink is hard because they are spread over a wide area and can easily swim to new islands. But the main difficulty is trapping the last few individuals – without this, the population will gradually recover.

‘Isotopes allow us to identify the types of places in which most mink are feeding and thus target the trapping campaign more efficiently,’ says Bodey. He says these techniques aren’t just relevant to mink, and could help control many other invasive species.

come from 600 to 700 metres down and have been trapped for several million years.

These gases are 99.9 per cent CO2; the rest contains traces of noble gases like helium, neon or krypton. Noble gases are chemically inert, so scientists can use them to understand what happened inside the Earth millions of years ago.

The researchers found that the chemical fingerprint of krypton showed more of the heavy isotopes (different types of atoms of the same chemical element) krypton-86 and krypton-84 than the light isotope of krypton-82.

This ratio is essentially the same as scientists find in gascontaining meteorites.

‘We thought that mantle gases would come from the Sun, but we found that the noble gases in the mantle are like the gases you’d find in meteorites,’ says Holland.

‘This was a big surprise. It’s difficult to make models of the Earth’s atmosphere without a solar composition. Gas has to come out of the Earth when volcanoes erupt. But our results suggest the atmosphere couldn’t have come from the inside of the Earth. So it must have come from outside, from meteorites,’ adds Holland.

▶ The findings mean textbook images of ancient Earth with huge volcanoes spewing gas may have to be redrawn.

Mark Garlick/Science Photo Library

THE BATTLE to remove the American mink from the Hebrides is almost won. Now scientists have analysed the invasive creature’s whiskers to find out where the last feral populations are lurking, and where the last push for eradication should be focused.

The team collected whiskers from American mink (Neovison vison) killed during the eradication programme and analysed the ratios of carbon and nitrogen isotopes.

Isotopes are different forms of the same chemical element, and the proportion between light and heavy isotopes is a ‘chemical fingerprint that can tell us about what animals have been eating and where they have been feeding,’ explains Dr Thomas Bodey from the Queen’s University Belfast.

‘This is because the ratios of heavy to light isotopes vary according to a range of biological and physicochemical processes,’ he adds. Whiskers collected from mink feeding inland have a higher proportion of the lighter carbon-12 isotope than those from animals living near the coast on seafood.

The research, published in the Journal of Applied Ecology, shows that as the cull proceeded, inland mink moved towards the vacated territories on the coast. Mink are semi-aquatic mammals, and in the Hebrides they prefer coastal habitats with access to plentiful seafood.

THE GASES that formed the Earth’s atmosphere may have come from outer space and not from gases spewed from ancient volcanoes, according to a report published in Science.

Scientists have long thought that the gases in our atmosphere came from the mantle inside the Earth and were released when huge volcanoes erupted.

The theory is that our solar system formed when a huge cloud of dust and gas collapsed under its own weight. The Sun was the first to form and then the planets followed. So it makes sense that gases inside the Earth must be similar to gases in the Sun. ‘But no-one has proved this and we haven’t had the technology to test this out until now,’ says Dr Greg Holland from the University of Manchester, lead author of the report.

An alternative possibility is that our atmospheric gases may have come from comets, meteorites and other dust from outer space. A team of scientists led by Professor Chris Ballentine from the University of Manchester collected ancient gases from a commercial carbon dioxide (CO2) mine in the Bravo Dome gas field in New Mexico in the United States. The gases

Planet Earth Spring 2010

9

Finding Solomon’s gold?

Finding gold deposits isn´t easy in heavily forested tropical regions.

Dan Smith, Gawen Jenkin and Jon Naden describe how precipitates from hot springs could lead us to a gold mine beneath.

▶ Solomon Islands geologist Gilly Albert prepares water sampling equipment. The stream in view is fed by hot springs, and measures 45°C here, 2km away from the springs. The channel is lined and surrounded with sinter and travertine (here coated in bright green algae).

10 Planet Earth Spring 2010

I

n 1567, the Spanish explorer Álvaro de Mendaña discovered an island chain in the South Pacific. Finding traces of gold in the streams that washed from the highlands, he believed he had stumbled on a nation of unimaginable wealth. He decided to christen the archipelago the Solomon Islands, after the biblical king and his fabled wealth.

But despite early indications, the generations following Mendaña have found little gold in the Solomons. Despite small discoveries, the gold has remained largely elusive – perhaps because deposits are difficult to find in the heavily forested islands. But the rewards for finding gold can be enormous – a single deposit can be worth billions of pounds.

Our team, including researchers from the University of Leicester and the British Geological Survey (BGS), didn’t set out to find gold though. We were looking for something far more common – seawater.

Savo volcano is young, having last erupted in the mid-nineteenth century. Only the upper third of the volcanic cone is above sea level, forming Savo Island. Numerous hot springs and steam vents around the island discharge boiling water and superheated steam – in some places only a few metres above sea level. We were investigating these springs, to see whether they contained seawater. We knew this played an important role in the formation of the Emperor gold deposit in nearby Fiji – could Savo be a modern, active example of a seawater-volcanic system?

The answer was a resounding ‘no’. Much like the fabled wealth of Solomon, seawater can’t be found in Savo’s springs. Using a variety of tracers for seawater (including stable isotopes of oxygen, hydrogen and sulphur, strontium isotopes, and fluid salinity), it became clear it hadn’t made its way into the hot springs.

Instead, we found the springs were dominated by rainwater and volcanic gases, and contained

FINDING SOLOMON’S GOLD?

▼ Dan Smith sampling fluids from boiling springs and steam vents on Savo.

elements leached out of the volcanic rocks.

Another surprise was that Savo’s springs are slightly alkaline – very unusual for water containing acidic volcanic gases. Around them, precipitates of sinter (silica from cooling waters) and travertine (calcium carbonate) occur, often interlayered or even intimately mixed.

This is unusual in itself – the two precipitate types are traditionally considered to form from different fluids – sinter from high temperature, deeply sourced waters, and travertine from shallow, cooler waters produced from rainwater and volcanic CO2. These mixed precipitates suggest the cool carbonate waters mix with and dilute high-temperature fluid released from magma at depth; the fluids became alkaline by reacting with the surrounding volcanic rocks.

Gold in those hills And then we found some gold! Chemical analysis of the hot spring precipitates showed gold present at concentrations of a few parts per billion. This is a tiny amount, but significant given that the precipitates formed from dilute water. Along with the gold were elevated levels of tellurium, an element that is strongly associated with volcanic-hosted gold deposits.

It is one of the rarest elements at the Earth’s surface. Fewer than five parts per billion are typically present in most rocks, but the hot spring precipitates at Savo contain up to 100 times more. Rare samples of material erupted from deeper parts of Savo contain up to one part per million (ppm) gold, as well as high tellurium, and can be chemically related to the springs at the surface. If there is enough of it, rock with 1ppm gold can be economically mined, so our results hint that Savo could form a gold deposit.

The chemistry of the hot spring precipitates is a key find. The presence of the tellurium and trace gold is a good indicator of the overall

nature of the system – a mixture of rainwater and high temperature fluids from magma at depth. Such precipitates may help us locate similar systems elsewhere, including those with commercially viable gold. Given that the precipitates form by the simple process of hotter waters mixing with cooler rain-derived groundwater, the chances of finding them elsewhere are good.

This type of hot spring precipitate may help mineral exploration geologists in the South Pacific find potential gold deposits. These form at the top of the system, so erosion is not necessary to expose them – a critical factor given that volcanic systems in this part of the world are too young to have been eroded much yet. The precipitates are found lining stream channels, and are not usually hidden by vegetation. Rock exposure is limited by dense jungle and rainforest across much of the Solomon Islands, making a geologist’s job that much more difficult. Being able to identify a potential gold-hosting volcanic system based on a set of well-exposed rocks is extremely useful.

In terms of social relevance, finding and using mineral resources is important for the economic development of the Solomon Islands and many other developing nations. The Gold Ridge Mine, on Guadalcanal in the central Solomons, generated an estimated 30 per cent

◀ Steam billows from vents and boiling springs at one of the major thermal areas on Savo.

of the country’s GDP in 1998−2000. Discovery of even a modest-sized deposit such as Gold Ridge can mean a massive injection of wealth into the economy.

It seems that King Solomon’s riches will remain hidden for a little while longer, but the islands that bear his name are providing insight into how gold deposits form in the South Pacific, and how systems hosting gold are expressed at the surface. Our study at Savo has identified unusual hot spring precipitates which provide chemical evidence of the system beneath, and may be useful as tracers for similar activity elsewhere. It is perhaps fitting, given the ancient king’s story, that we find wisdom before the wealth.

MORE INFORMATION Dr Dan Smith recently completed a NERC CASE PhD on the Savo volcano in the Solomon Islands with BGS and is now working in its Carbon Capture and Storage team. Email: dani1@bgs.ac.uk.

Dr Gawen Jenkin is Senior Lecturer in Applied Geology at the University of Leicester.

Dr Jon Naden is an economic geologist at the BGS and works in the Minerals for Development team.

Special thanks to Adrian Boyce (SUERC), Thomas Toba (Solomon Islands Geology Division) and the Society of Economic Geologists.

FURTHER READING Smith DJ, Jenkin GRT, Naden J, Petterson MG, Boyce AJ & Toba T (2009). Sinter and travertine deposits from volcanic hot springs and their potential in exploration. Applied Earth Science (Trans. Inst.

Min. Metall. B ), 118, 36-37.

Planet Earth Spring 2010

11

Watching water dry New satellite data and sophisticated computer models are transforming our understanding of the water cycle. Eleanor Blyth explains how insights into evaporation could improve our ability to predict the climate of the future.

S

ometimes environmental science involves things that are so everyday and normal that you can forget how important they are. For example, the way a puddle dries out might seem rather boring at first sight, like watching paint dry.

But, if you consider all the areas over the world that are wet at any one time, you might believe me when I say that the way water evaporates from a damp surface has a huge effect on the climate and weather.

The problem is that it’s very hard to estimate how much water is evaporating in remote parts of the world. Most of our efforts to quantify evaporation, whether by measuring it directly, diagnosing it indirectly from things we can measure from space, or modelling it, fail to capture the process completely.

Evaporation from wet surfaces is an important part of the overall amount of evaporation from the surface of the land worldwide, and is particularly important in the tropical rainforests of South America and Africa. Other processes that contribute to the land’s total evaporation are soils drying out and water loss through the leaves of plants.

Across the world, the fraction of rain that evaporates back into the atmosphere varies from around 15 to 85 per cent. This variation, combined with the changing amount of heat coming from the oceans, is the driving force behind much of the world’s weather. As well as being important for the climate, it also defines how much water is left over in rivers and

12 Planet Earth Spring 2010

groundwater stores – and this is the water that people rely on to live.

To predict how the climate and the distribution of water will change in the future, we need to build computer models of evaporation and to test these models against observations. But until now, the only observations we have had were detailed data from a handful of places around the world. That was until researchers started to use information from satellites to estimate evaporation.

A group of us at the Centre for Ecology & Hydrology (CEH) in Wallingford have spent the last 20 years working with detailed data on evaporation at specific sites and have developed

on Global Land-surface Evaporation and Climate in July 2009 at Wallingford.

The symposium brought together experts in modelling, researchers working on measuring evaporation in situ and the scientists who specialise in estimating it from satellite measurements. After several presentations from these experts and plenty of discussion, it became clear that new data and new ideas are beginning to come together to solve this problem.

At the meeting we decided that the combined estimates of evaporation using the satellite data would provide a very useful benchmark dataset for the models. If we combine the satellite products with data from on-site measurements and models we will begin to have a fuller idea of the global water cycle, including all-important but hard-tomonitor areas like the tropics.

With this new information we are going to see a step change in the performance of the world’s climateprediction models. models of how the process works. We decided it was time to bring together the scientists from around the world who are developing these new methods of measuring evaporation with satellites, to see what they had all come up with.

So we held a two-day International Symposium

Evaporation on film

But what will we do with the data? It goes back 30 years, and the main way we’ll be using it is to check whether we are modelling evaporation around the whole planet correctly. We can combine this data with other information we have on vegetation growth patterns around the world, as well as our datasets on river flows and atmospheric carbon dioxide concentrations.

With this combination we will be able to

WATCHING WATER DRY

Upperhall Ltd/Robert Harding Travel/Photolibrary.com

understand how the land works at the global scale: where and why plants thrive or die, whether they are stunted through lack of nutrients or water. In areas like Africa, where there is very little infrastructure to support a dense network of in situ measuring devices to gather data, and where the vegetation is very responsive to the availability of water, this satellite data will give us new information about how ecosystems function. I think with this new information we are going to see a step change in the performance of the world’s climateprediction models.

While organising the meeting, we

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realised that it might be a little bit special. It might be the first of its kind, and we might want to refer back to ideas that were formed during the meeting. So, as an experiment, we decided to explore a new way of communicating its results: to capture the workshop on film.

As the day arrived I was severely regretting agreeing to this film; it added to the stress of organising the meeting. I even had a dream the night before about people tripping up over cables and having cameras crawling all over the meeting room, completely

◀ The water cycle.

disturbing the meeting’s intellectual ambience and confidentiality. However, as the camera crew predicted, after about an hour, the scientists all forgot about the cameras and happily fell back into their comfort zone of discussing the physics of evaporation. I think the only person who tripped over the camera wires was a member of the camera crew.

One of the benefits of having a film made and distributed was that many senior scientists could give personal opinions of the state of the science and comment on the meeting. This type of wisdom and expertise can often be lost unless you manage to go to the meeting.

The film lets us share such an overview across the whole scientific community. We have yet to see whether this technology will help us communicate and build international communities without the need to travel around the world to meet up – but at least we can say we tried.

The film is available for viewing at www. eu-watch.org (see Events and Project Events).

Watching it, you get a taste of the excitement of the world’s leading hydrological scientists that such a new perspective of the science is emerging, and that it may help take the field to a new level of understanding. It feels far from everyday!

MORE INFORMATION Dr Eleanor Blyth is a land surface modeller at the Centre for Ecology & Hydrology in Wallingford.

Email: emb@ceh.ac.uk.

rest ry

Planet Earth Spring 2010

13

Survival of the fattest There are 1031 viruses in our oceans. Placed end to end, they’d stretch for 200 million light years (about 60 galaxies away) and would have a combined mass equivalent to around a million blue whales. Yet we know surprisingly little about what they do. Mike Allen and Willie Wilson describe their work on one fascinating family, the coccolithoviruses.

14 Planet Earth Spring 2010

Steve Gschmeissner/Science Photo Library

â–ś This small algal organism (coccolithophore) is surrounded by a skeleton (coccosphere) of calcium carbonate plates (coccoliths).

SURVIVAL OF THE FATTEST

V

iruses are like lubricants in the Earth system’s engine room, and their role in transforming planktonic cells into dissolved material means they are crucial to global biogeochemical cycling – the pathways that all elements and molecules move along in an ongoing cycle, passing through both living things and inorganic processes.

Coccolithophores are some of the most abundant and widespread organisms in the oceans. These photosynthetic microscopic algae form the base of the oceans’ food chain and play a major role in the global carbon cycle, drawing down vast volumes of carbon dioxide from the atmosphere.

They use this carbon to build hard chalklike shells of calcium carbonate. Emiliania huxleyi is the most numerous coccolithophore in our oceans, and satellite observations often show massive blooms that grow rapidly before abruptly disappearing. Until recently, the mechanisms of Emiliania huxleyi bloom disintegration were poorly understood, but most scientists now accept that viruses play an important part in these sudden crashes.

Analysis of these viruses’ genetic make-up revealed large double-stranded DNA viruses with genomes of approximately 410,000 base pairs. These viruses belong to the newly-created genus Coccolithovirus. When researchers sequenced the genes of the type species, EhV-86, they discovered a circular genome with 407,339 base pairs, making it the largest algal virus ever sequenced.

This giant of the viral world revealed a truly mysterious genome, full of genes of unknown function. Yet the few genes whose function we did know were baffling. Along with the usual suspects, the genes that code for common proteins and enzymes, was a pathway that codes for the production of sphingolipids.

Sphingolipids are an important class of lipid, a type of fatty acid. We know they are used for cellular signalling and recognition. Yet the viral pathway’s origin was a mystery until very recently. Newly-available data from a project aiming to sequence the genome of Emiliania huxleyi showed that the mysterious metabolic pathway came from closer to home than we ever imagined.

It turns out the virus has stolen a nearcomplete pathway for the production of sphingolipids from its host. It’s long been known that viruses can pick up the odd gene or two from their hosts, but this is the first known case of one helping itself to genes controlling the production of multiple enzymes from a metabolic pathway.

This isn’t the first time the giant

coccolithovirus’s quirky nature has attracted attention. Its complex interaction with the coccolithophores has revealed new insights on the constant and ongoing arms race between hosts and their viruses.

Red queens and Cheshire cats The Red Queen’s race in Lewis Carroll’s Alice’s Adventures in Wonderland is a common metaphor for the evolutionary arms race: ‘It takes all the running you can do to stay in the same place.’ In an interesting take on the Red Queen hypothesis, this novel system has spawned what has been dubbed the ‘Cheshire Cat’ escape strategy, after the disappearing antics of another famous character in the same book.

Emiliania huxleyi seems to use an intriguing strategy to avoid viral infection – it switches to an entirely different state in its life cycle so that an attacking virus can’t get a foothold. By completely changing its physical appearance it makes itself impenetrable to infection. The algae’s later phase is calcified, or covered in chalky armour plates, and is susceptible to infection, but its earlier non-calcified stage is unrecognisable to the coccolithovirus, so it resists infection.

long as possible. Sphingolipids are known to be important in a wide variety of cellular processes.

It’s not implausible that the hijacked pathway may even be linked to the victim’s ‘Cheshire Cat’ escape strategy, and that it may stop it switching to the earlier, infection-resistant phase in its life cycle.

Another of our theories is that sphingolipids are used to form ‘lipid rafts’ to help the virus escape from the algal cells. Or the sphingolipids may even help disrupt programmed cell death by manipulating signalling pathways. Programmed cell death (PCD) is the process by which cells ‘commit suicide’ in a controlled and orderly manner. If infected cells can kill themselves, they can limit the spread of the virus. We know that sphingolipids play a role in PCD, so the hijacked virally-encoded sphingolipid pathway could help prevent the pathway from activating and so let the virus keep spreading.

Whatever the reason it was originally acquired, the virally-encoded sphingolipid pathway is probably crucial to a successful infection, since the virus throws a lot of resources at keeping it turned on and active. We call it ‘survival of the fattest’ between the host and the virus – the winner is decided by who can manipulate sphingolipid production more effectively.

The coccolithophorecoccolithovirus system is truly remarkable. The more we discover, the more we realise how little we know about it. But crucially, we are generating ideas and concepts that are being applied to totally unrelated systems. The theories we’re proposing have attracted interest from a whole new field of evolutionary researchers.

Last year marked the 150th anniversary of the publication of Darwin’s seminal work On the Origin of Species, from which the phrase ‘the survival of the fittest’ was born. Research into this novel marine host-virus system is providing crucial insights into many of Darwin’s evolutionary theories. It’s a shame that Darwin isn’t around to see this research; one can only imagine what he would make of this amazing virus system (whose host takes part of its name from his most ardent supporter, TH Huxley) where the survival of the fittest could depend on the survival of the fattest.

It turns out the virus has stolen the entire pathway for the production of sphingolipids from its host.

It turns out that the host doesn’t have things all its own way, though. Indeed, the virus seems to have other tricks up its sleeve. In what could be the ultimate insult, it looks like the virus may actually use the host’s own sphingolipid pathway against it.

Our research has shown that during a natural algal bloom, the expression of Emiliania huxleyi’s normal sphingolipid pathway is almost totally replaced by the virally-encoded pathway.

When the virus infects a coccolithophore, it quickly turns on this sphingolipid pathway and expresses it to a level two orders of magnitude greater than the normal Emiliania huxleyi pathway.

Unfortunately, we still have only limited information on this virus-host system, so we can only speculate on why the virus produces sphingolipids. There are a few clues – for example, we know that the virus disrupts cell signalling and keeps the infected host healthy as

MORE INFORMATION Dr Mike Allen is a molecular biologist and virologist at Plymouth Marine Laboratory.

Dr Willie Wilson is a viral ecologist at Bigelow Laboratory for Ocean Sciences.

Email: mija@pml.ac.uk or wwilson@bigelow.org

Planet Earth Spring 2010

15

Many people in Africa depend on groundwater, but exploiting it effectively depends on accurate information about where to find it – and this information is expensive to obtain. Yet in many cases, researchers did the work years ago – it's just a matter of tracking down their results. Jude Cobbing and Jeff Davies describe a new initiative to make data from old studies more accessible – and in doing so, improve scientific cooperation and the availability of water in Africa.

Groundwater -

returning to the sources

W

hat do a faded report on borehole drilling in Nyasaland written in 1952, an unpublished 1973 study of groundwater levels in northern Zambia and the field notes of a British geologist seconded to the Botswana Geological Survey in the 1980s have in common? They’re all part of a sizeable archive of so-called ‘grey data’ on African groundwater held by the British Geological Survey (BGS).

Groundwater – the huge resource of underground water that keeps springs flowing and wells and boreholes working – is the main source of water for most Africans. Indeed, it is vital worldwide – for instance, groundwater makes up about a third of public water supplies

16 Planet Earth Spring 2010

in England and Wales.

Understanding where to find it, and how to manage it, is the role of specialists called hydrogeologists. The trouble with groundwater is that you usually can’t see it, and so hydrogeologists rely on records of water-level measurements and other data. The properties of the aquifer rocks that the groundwater flows through are also important.

It is usually time-consuming and expensive to carry out hydrogeological studies, especially in remote areas where we know little about groundwater. Boreholes must be drilled and tested, water levels measured and samples sent off to laboratories for analysis. To repeat such work because the results of the original surveys

are inaccessible, unknown or simply lost is very expensive – and in the context of providing water supplies in Africa, a huge waste of very scarce resources.

Hydrogeologists have always known the value of unpublished reports, databases and notes on African groundwater, plus specialist material published in small quantities but now long out of print and hard to find. The secondment of British staff to former colonial geological surveys, and more recently close cooperation between British scientists and African state organisations, resulted in a large and valuable archive of grey data held in the UK. When British scientists finished their tours of duty in Africa, they would naturally take

GROUNDWATER – RETURNING TO THE SOURCES

home copies of reports produced and databases assembled during their stay abroad. Mostly these were fragile paper copies, since much of the work was done before computers and digital archives were common.

With the urgent need for better water supplies and sanitation in Africa, and interest in historical ‘baseline’ conditions for water resources to help us better understand the effects of changing weather and land use, grey data on groundwater has never been so important. Added to that, the capacity and resources of the public sector in some African countries have declined over the last two decades or so, leading to the loss of many important grey reports.

In some cases the material in the BGS archives in the UK may now be the only accessible copies remaining. Even where it is theoretically possible to access grey data on African groundwater, it is still very difficult to know what was done and what is available – it can be a nightmare trying to unravel half-forgotten endeavours in remote parts of the continent, and what reports and other documents they led to. There is no single catalogue of African groundwater grey data, and many crucial details now exist only in the heads of the scientists who originally did the work.

Using the grey matter The BGS estimates its archives contain many thousands of grey items on African groundwater, ranging from paper reports and hand-drawn maps to graphs and charts of water levels. Of course, some of this material is confidential, and some of it is subject to copyright or other restrictions.

However, a substantial proportion of the archive was always intended for wider distribution and was originally produced with no strings attached. In mid-2009 the BGS, in collaboration with South Africa’s Water Research Commission (WRC), obtained EU funding to carry out an 18-month project entitled ‘Groundwater Knowledge Sharing and Cooperation in the Southern African Development Community (SADC)’, known as the Grey Data Project.

The Grey Data Project will catalogue and describe at least 2000 important grey items on groundwater in the southern African region held at BGS, in the process compiling a digital ‘metadatabase’ or catalogue describing what has been produced over the years. The project will also digitise at least 500 of these items and make them available, together with the metadatabase, via a web portal to interested

▶ Jeff Davies collecting a sample from a drilling rig in Botswana in the 1970s.

It can be a nightmare trying to unravel half-forgotten endeavours in remote parts of the continent. researchers, service providers and policy-makers.

The project is already yielding practical benefits. Martin Holland, a South African student at the University of Pretoria, is working on a PhD which will unravel some of the reasons for varying yields of water from boreholes in different parts of the granitic ‘basement’ rocks that underly more recent geological formations in southern Africa.

Distinct periods of stability over millions of years have established discrete ‘weathering surfaces’ on the ancient African basement rocks, of different ages and altitudes.

Research has shown that these weathering surfaces affect how these rocks hold groundwater, and therefore have implications for important qualities of boreholes in different places, such as how much water they yield and how they might respond to changes in climate.

Using grey data from BGS and other projects – hard to obtain until recently – Martin is piecing together the evidence linking weathering and borehole characteristics.

This promises to make groundwater development in African basement rocks more predictable, letting us plan better. Millions of people in Africa depend on groundwater from basement rock aquifers, so that even small steps in our understanding of this resource can have disproportionately large benefits. Martin is planning to publish a joint paper with his BGS counterparts on the work in 2010.

Crucially, the project is led by a BGS scientist with a lot of experience in Africa and wide knowledge of potential grey-data material

– you need grey hair to make sense of grey data archives! Having worked in more than 30 African countries in his career so far, Jeff Davies took part in many of the projects which produced the grey data in the first place.

Mention northern Botswana to Jeff, or eastern Tanzania, and he can reel off a list of obscure projects and documents produced on the groundwater of the region – some of them little-known even in the countries themselves. Project partner the Water Research Commission, on the other hand, knows about information requirements and current research projects in southern Africa, and has secured the support of the SADC groundwater office.

Together, the BGS and the WRC are supporting the restoration of groundwater information and institutional memory across the region, with the aim of making it cheaper and easier to manage groundwater.

In the meantime, the BGS team are rolling up their sleeves and blowing the dust off the old material on African groundwater, which fewer and fewer people in the UK today really know their way around. The team aims to involve other European geological surveys in a later phase of the project, and in doing so to strengthen scientific links and encourage collaboration.

MORE INFORMATION Jude Cobbing is a hydrogeologist at Water Geosciences Consulting and a former BGS employee.

Jeff Davies is a hydrogeologist at BGS. Email: jude@watergc.co.za or jdav@bgs.ac.uk

Planet Earth Spring 2010

17

Corals in a changing world Coral reefs are among the world’s richest ecosystems, but environmental change is fast putting them at risk. Scientists are revisiting fundamental questions in coral research to understand how corals will fare in the future. David Suggett and colleagues explain.

Alex Mustard

P

roductive and diverse coral reef ecosystems exist because of coral growth. To grow optimally, corals need specific conditions of light intensity, temperature and pH. But these conditions appear to be changing faster than ever, as tropical waters are subjected to both global climate change and local problems like pollution and sedimentation. How such altered environments will affect reefs is still largely unknown, but certainly any change to the rate and extent of coral growth will be vital in determining reefs’ future form and function.

We can already see the effects of rapid environmental change on how fast corals grow.

For example, slower growth rates of Porites, a key reef-building coral, have been recorded within the Great Barrier Reef over the last two decades, alongside accelerated increases of seawater temperature. However, it is unlikely that temperature alone is fully responsible.

Warmer waters are ultimately driven by more CO2 in the atmosphere; this CO2 also dissolves into seawater to lower pH, making it more acidic – a process known as Ocean Acidification (OA).

Several experimental studies now show that OA not only slows corals’ growth, but may also make them more vulnerable to temporary stresses that can cause coral bleaching – this is when corals turn pale and ultimately die.

Physiological resistance to transient stresses, such as unusually warm or cool waters, requires

18 Planet Earth Spring 2010

corals to use energy that they would otherwise be able to invest in growth. The findings to date are alarming but highlight a key issue: we need to consider the combined effects of multiple climate change variables to predict future coral growth accurately. Curiously, many studies have focused on temperature and OA, but little attention has yet been paid to the key limiting resource for coral growth in every reef – light.

Too much of a good thing?

The availability of light is the main regulator of coral growth, and is also predicted to change in future environments, along with temperature and CO2, and hence acidity.

The tiny animals that build coral reefs are dependent on a symbiotic relationship with algae, called zooxanthellae. These algae live within the coral animals’ surface tissue; the carbon they fix by photosynthesis is used to ‘feed’ the coral. Up to a point, more light means more photosynthesis, to the benefit of the coral.

But too much light eventually makes the zooxanthellae – and in turn the corals – more susceptible to the stresses that lead to coral bleaching. Photosynthesis increases the rate at which corals can ‘calcify’, or lay down their calcium carbonate skeletons. But unfortunately, calcification also becomes compromised as seawater becomes more acidic – hence the lower growth rates seen under OA.

So the ultimate effect of climate change on the form and function of tropical reefs depends on the combined changes of light, temperature and OA, as well as on how specific corals and zooxanthellae respond to these changes. This is where we come in.

Since 2004, several NERC-funded research projects within the University of Essex’s photosynthesis laboratory have focused on the responses of marine organisms, in particular a globally abundant phytoplankton species, Emiliania huxleyi, to OA. Unfortunately, mimicking the effects of OA in the laboratory is not as easy as simply tweaking water’s pH by adding acid or alkaline substances. Adding biology to the picture further complicates the inorganic carbon chemistry that determines the pH of seawater. Organisms change the pH of their surroundings through photosynthesis and/or respiration, and by producing calcium carbonate (chalk) skeletons or shells.

This meant that from the outset of our OA projects, we needed to develop and optimise experimental ‘microcosm’ systems to provide full control over the continually changing chemistry. In developing this technology, we produced the crucial tool needed to examine the complex interactive effects of light, temperature and pH on coral growth. This is the subject of a new NERC-funded project within Essex’s Coral Reef Research Unit (CRRU): ‘A community metabolism approach to examine the environmental regulation of coral growth’.

CORALS IN A CHANGING WORLD

We can already see the effects of rapid environmental change on how fast corals grow.

How do corals grow?

This new project has reignited a key question.

Just how – and how fast – do corals really grow?

This may seem like an obvious question, yet it still remains unanswered. Surprisingly few publications report coral-growth rates. Such a lack of core information highlights a central problem: how does a coral grow and how is growth best measured?

The growth form, or ‘architecture’, of a coral colony is highly variable. Environmental conditions such as exposure to currents and light levels can play major roles in sculpting a coral colony, but the extent to which environments regulate architecture varies within and between species. The complexity and variability of coral architecture makes assessing colony growth – defined as the change in a reef’s size per unit of time – extremely difficult.

No single measure can be truly reflective of growth. So to find out how changing climates will influence colony growth, we need to learn

▶ Measuring corals.

how to assess coral growth accurately, as well as to identify the factors that control it.

This has led to another new NERC-funded project, the Coral Aquarist Research Network (CARN), also run within Essex’s CRRU. To assess what drives growth requires the capacity to carefully control (and manipulate) the environment for as many species as possible; the resources for this are far outside the scope of most research facilities.

But they are readily available in the industrial sector, specifically from coral growers and national and public aquaria, which for many years have independently been establishing the best way to grow coral species. CARN was launched to provide a forum through which UK coral researchers and academics could exchange information with the nation’s aquarist and coral husbandry industry. It is primarily focused on how to benefit industry by exchanging detailed knowledge of coral growth, mortality and fecundity.

Initiating these two new NERC-funded projects alongside existing research within the CRRU has encouraged further investment by the University of Essex, which has funded a new coral-growth aquarium facility.

This facility has been designed in close collaboration with the coral husbandry industry and will provide a resource for researchers to continue the UK’s momentum in coral science, which until now has largely been based on studies in the field. Such investment is certainly a sign of the times. Our environment is changing quickly, and so are the priorities for the research community. We are revisiting perhaps the central issue in coral research, so as to shed new light on how corals grow, both now and in the future.

MORE INFORMATION Dr David Suggett, Dr David Smith and Dr Tracy Lawson are members of the Coral Reef Research Unit within the Department of Biological Sciences, University of Essex. Email: dsuggett@essex.ac.uk FURTHER READING CARN is the main information gateway (and will ultimately act as the central data repository) for all aquarists, including scientists, industry and the general public interested in the Coral Aquarists Research Network. www.carnuk.org.

Riebesell U, Fabry VJ, Gattuso JP. Guide to Best Practices in Ocean Acidification (www.epoca-project. eu/index.php/Home/Guide-to-OA-Research). This document is a reference to provide guidance for research in the rapidly growing field of OA.

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Britain’s moorlands store carbon in vast quantities, but it may not stay put as the climate changes and people put the land to new uses. Sue Ward explains how researchers are setting up experimental plots to find out how different kinds of plants determine the fate of peatland carbon.

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eneath the heather-clad British moorlands lie valuable stores of carbon, built up in layers of peat over thousands of years. These carbon stores are at risk, both from changes in climate and from changes in vegetation caused by land management practices such as grazing, burning and drainage. This could lead to the release of carbon in the form of gases like carbon dioxide and methane, and into water as dissolved organic carbon.

We want to know more about how shifts in the make-up of plant communities, which occur as a result of land-use change, affect our peatlands’ ability to continue to store, or ‘sequester’, carbon. We also want to know how climate changes, such as warming, interact

with peatland vegetation to influence carbon loss. To do this, we have set up a new plant manipulation and warming experiment high in the North Pennines of England funded by a NERC grant. Our experimental site is in the Moor House National Nature Reserve, one of four NERC Carbon Catchments run by the Centre for Ecology & Hydrology (CEH), where long-term measurements are used to produce annual carbon budgets. The area is also a flagship site for the UK Environmental Change Network.

Setting up a field experiment in one of the most exposed places in England wasn’t without its trials and tribulations. We set off one sunny spring morning in April 2008, armed with tape measures and boardwalks, only to be greeted

Gardening for greenhouse gases

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Richard Bardgett

Setting up a field experiment in one of the most exposed places in England wasn’t without its trials and tribulations.

GARDENING FOR GREENHOUSE GASES

Sue Ward

by an unexpected late season snowstorm!

Undaunted, our small army of volunteers (fortified by hot tea and cakes) marched up the hill with 150 boardwalks to lay the foundations of our new experiment. We returned several more times in spring – fortunately in more clement weather conditions – to ‘garden’ the experimental plots.

In UK peatlands, plants belong to one of three main ‘functional groups’: dwarf shrubs such as the heather Calluna vulgaris, grasses and sedges such as cotton grass Eriophorum vaginatum, and mosses like Sphagnum and Hypnum. In our experiment we selectively removed plants by hand, to create all possible combinations of these three groups.

How is this relevant to carbon cycling? We know that the rate at which peatlands sequester carbon depends on the balance between inputs from plant productivity – plants taking in carbon as they grow – and outputs from decomposition, respiration and other physical losses, which release carbon back into the atmosphere. We also know that each of the three peatland plant functional groups has a different set of characteristics, or ‘traits’, such as nutrient content, growth rate and tissue lifespan, which affect how much atmospheric carbon a plant can absorb by photosynthesis.

These plant traits also govern how much carbon dioxide is lost through respiration and decomposition, by affecting the amount of nutrients below ground where the soil decomposers live. Finally, plant traits affect their ability to recover after disturbances like fire and overgrazing, with fast-growing, nutrient-rich grasses generally winning at the expense of slower-growing shrubs and mosses.

Our new gardened plots mean we can now test which of the three plant functional groups, or which combination of them, is best for peatland carbon sequestration.

We also want to know how climate change will affect our moorland plant groups. To answer this question, the final part of our highaltitude gardening exercise was to build ‘minigreenhouse’ warming chambers over half of the plots. These open-topped chambers are designed to increase temperatures by 1-2°C, mimicking the predicted effects of global warming. This experimental approach lets us test the impact of vegetation change and climate using a real ecosystem as our laboratory.

After many days of carrying, constructing and gardening, our site is finally ready. We have installed temperature, water-table and gasmonitoring equipment and now visit the site each month to measure a range of key carboncycling processes. We’re measuring greenhouse

▲ The plant manipulation and warming experiment at Moor House National Nature Reserve, showing the passive warming chambers designed to increase temperatures by 1-2°C to mimic global warming.

gases like carbon dioxide, methane and nitrous oxide. We also measure concentrations of dissolved organic carbon in water, soil nutrients, the composition of the soil’s microbial community and how fast litter decomposes.

Our results so far show that a warming climate does speed up peatland carbon cycling, and that the three plant groups do behave very differently. For instance, the lowest uptake and release of all greenhouse gases is by the slow-growing, water-retaining mosses. Woody, slow-growing heather absorbs the greatest net amount of carbon dioxide. Nutrient-rich cotton grasses are also good for increasing the overall intake of carbon dioxide, but their presence can also increase release of methane – a greenhouse gas that can cause more warming than carbon dioxide.

Work on this experiment on plant diversity and climate builds on our past research into the effects of land use on peatland carbon cycling. We did this work at a unique 50-yearold burning and grazing site, also at Moor House National Nature Reserve. Vegetation in areas regularly burned to manage moors for grouse had less heather, less mosses and more cotton grass than the unburned areas, but there was little difference in soil chemistry or the decomposer organisms that lived in the soil.

When we compared carbon dioxide fluxes, we found that burned areas were a bigger sink for atmospheric carbon dioxide. We also saw similar, but smaller, effects in grazed areas – long-term grazing meant these peatlands took up more carbon. We concluded that it was the differences in the plant community’s composition that was responsible for making

burned areas absorb more carbon dioxide. But in this study we couldn’t completely discount the idea that this was the direct effect of the burning or grazing, rather than of the changes in plant life they caused, hence the need for our new plant-manipulation experiment.

This research gives us the opportunity to study the effects of peatland plant functional groups on carbon cycling, and how plant change interacts with climate. We still have a great deal to learn about moorland carbon cycling in a changing world, especially about the feedbacks between plant and soil processes that control greenhouse gas emissions. Our research continues to look into this fascinating subject, and we hope that in future we can help landowners maintain their peatlands for future carbon storage by managing the plants growing on them. So, if you are ever in the North Pennines and come across a set of greenhouses, or a group of scientists armed with gardening equipment, you’ll know what we are up to.

MORE INFORMATION Dr Sue Ward works as a Post-doctoral Research Associate in the Soil and Ecosystems Ecology Group at Lancaster University headed by Prof. Richard Bardgett, and at CEH Lancaster with Dr Nick Ostle and colleagues. Email: s.e.ward@lancaster.ac.uk FURTHER READING Ward et al. (2007), Ecosystems 10, 1069-1083 (work on burning and grazing) Ward et al. (2009) Functional Ecology 23 (2), 454-462 Environmental Change Network www.ecn.ac.uk NERC carbon catchments www.ceh.ac.uk/sci_programmes/CarbonExchangeat theCatchmentScale.htm

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A mighty wind The effects of Greenland’s extraordinary weather patterns are felt worldwide – they influence the movement of water all around the globe. To find out more, intrepid scientists have to brave some of the harshest conditions imaginable. Ben Harden describes his recent trip to Arctic waters.

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this is covered by the largest ice sheet in the Northern Hemisphere, containing enough ice to raise global sea levels by over seven metres were it to melt. Greenland’s size and freezing temperatures cause many strong wind phenomena around the island.

Much as a boat’s hull travelling through the sea pushes water to the side and produces a turbulent wake, Greenland deflects and distorts the air flowing towards it. The situation on Greenland is a little more complicated though. The air that travels over and around the island rarely comes from one direction. Swirling weather systems constantly arrive from the south and west, pushing and pulling air on and off the continent from all directions.

This leads to a variety of strong coastal winds: winds that whip around the southern tip of Greenland; winds that cool down and flow down the steep coastline; winds that stir up new weather systems; winds that are forced along the coast because they can’t climb Greenland’s mountains. Many of these winds can reach 60 miles per hour at the surface, and they lead to incredibly stormy seas.

Arctic winds, global ocean circulation OK, so this is an interesting set of wind conditions. But why is it important to study them? Well, apart from the need for accurate predictions of dangerous conditions at sea, there is mounting evidence that winds produced around Greenland could be affecting the wider climate system.

To put it briefly, they can make surface waters sink. To see why this is important, let’s look at how water moves around the Atlantic.

Dan Torres

outh of Greenland are the stormiest seas in the world, and that’s where I found myself aboard a research vessel in October 2008. I was there to measure the strong winds along the coast using radiosondes – weather balloons equipped with instruments to measure wind speed, pressure, temperature and humidity and relay that information back to us as they rise into the atmosphere.

This was no mean feat – with wind speeds in excess of 50 miles per hour, hanging on to a metre-wide helium balloon while creeping out on to the deck of a ship being tossed on waves the height of a four-storey building was both frightening and exhilarating.

Along with coordinating the launch between two people, it also proved extremely difficult.

Timing was everything – would the balloon be consumed by the sea? Crash back into the boat? Have its instruments doused in water and destroyed? Would I be able to hold in the umpteenth bout of seasickness? All of the above occurred at one time or another, but perseverance resulted in many successful launches and some unique data.

This was very exciting – although these winds have been measured once before by aircraft (see Planet Earth Summer 2007, pp. 22-23), this was the first time that we were in a position to find out how they develop as a storm passed us by.

Measurements of the winds near Greenland are very rare due to the severe conditions and the usual coating of sea ice.

Greenland is massive. More than two kilometres up, the Greenland plateau is as high as much of the Alps and covers an area the size of Western Europe. Over 80 per cent of

Warm surface water from the Caribbean flows northward to Western Europe in the Gulf Stream. With no exit to the north, these waters have to sink somewhere in the subpolar North Atlantic before returning south at depth.

Oceanographers have been debating where in the North Atlantic these sinking regions are for going on 100 years.

In fact, even now, there are only a few generally agreed-upon locations where sinking is believed to take place. These are the Nordic Seas (between Greenland and Norway) and the Labrador Sea (between Greenland and Canada).

Here, surface waters are held in one place.

A MIGHTY WIND

Thomas Spengler

Hanging on to a metre-wide helium balloon while creeping out on to the deck of a ship being tossed on waves the height of a four-storey building was both frightening and exhilarating.

Subjected to cold winds blowing for a long time over a wide area, the water loses a lot of heat and as a result becomes denser, eventually making it sink. The need for cold winds is why sinking mainly happens in subpolar regions.

But how could the winds off Greenland cause sinking? Yes, they are cold. But they’re neither consistent nor spread over a large area. Amazingly, one wind type – the tip jet – can. Tip jets are strong eastward winds that accelerate around the southern tip of Greenland, like a wake from a boat, and out into the Irminger Sea, a small stretch of water between Greenland and Iceland.

They last for a day or two, with only a handful occurring each month. They are very cold and follow a curved path as they pass Greenland. This pushes surface water to one side, exposing slightly deeper water.

Surface water is very stratified – it forms a distinct layer, within which its density increases very quickly with depth. This means it takes a large amount of cooling before it sinks. In contrast, slightly deeper waters in the region are much less stratified and hence easier to sink when exposed to the freezing winds.

The amazing revelation is that these small, sharp winds are affecting the huge, slow process

of waters moving around the world’s oceans.

It’s like keeping a bicycle wheel spinning by applying small pushes with your hand. The pushes are small and sharp but keep the wheel continuing on its slow rotations.

This begs the question: if the tip jet can do this to the ocean, what effects do all the other wind phenomena around Greenland have? The task ahead now is to look closely at the other types of winds around Greenland and, as with the tip jet, start to ask questions. How strong are they? How often do they occur? How much heat do they remove from the ocean? How much of a push do they impart? The answers should yield some exciting revelations about how small but intense wind storms can affect the slow progress of water around the planet.

MORE INFORMATION Ben Harden is a NERC-funded PhD student in the School of Environmental Sciences at the University of East Anglia. His research is part of the NERCfunded Greenland Flow Distortion Experiment on which a special issue of The Quarterly Journal of The Royal Meteorological Society was published recently.

Email: b.harden@uea.ac.uk

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Volcanic secrets in the ice â—€ A section of ice core brought to the surface in the drill trench.

How is a sprinkling of ash connected to the climate of the last warm interglacial period? Siwan Davies and Peter Abbott explain how microscopic particles buried deep in the Greenland ice can date climatic events and reveal a hidden history of volcanic eruptions.

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ce cores drilled from the polar ice sheets represent a rare and valuable window on the past. The ice, together with air bubbles locked within it, provides a detailed record of how the climate has changed. This is particularly important in light of concerns about future climate. Also trapped within the ice are tiny ash particles from volcanic eruptions. These provide a unique chronicle of volcanic events, which can help to pinpoint when the climate changed in the past. A new NERC-funded project involving scientists from Swansea University, the University of St Andrews and Aberystwyth University aims to look for these volcanic traces in a new, deep ice core from Greenland.

In June 2009, Siwan Davies joined 30 other scientists in a remote corner of the Northwest Greenland ice sheet to take part in a new deep drilling project entitled NEEM (North

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Greenland EEMian ice drilling). Led by the University of Copenhagen, this large-scale international collaboration aims to drill a 2.5km-long ice core and retrieve, for the first time, a complete record of the last warm period (or interglacial) from the northern Arctic.

Known as the Eemian, this period occurred about 130,000 years ago, in between two cold glacial periods.

Thought to have been a few degrees warmer than the present, the Eemian’s climate is considered to be the nearest comparison to the warmer world we expect as a result of climate change. Up until now, efforts to recover ice from this warm episode by drilling in Greenland have been hampered by melting at the base of the ice sheet or distortions caused by ice flowing over time. The new NEEM drill site has been chosen as the best place to recover

an entire record of the Eemian period. Our work focuses on the record of volcanic events contained within the ice.

The ashes of ancient eruptions Ash blasted into the atmosphere during a volcanic eruption is often dispersed over a wide area within a few days or weeks. If the ash falls on the surface of an ice sheet, it can be buried by snowfall. Beautifully preserved, centimetrethick ash layers have long attracted the attention of ice-core scientists working in Antarctica and Greenland. But eruptions can also be recorded by a small scattering of microscopic ash particles that do not form a layer visible to the naked eye. Many of these volcanic eruptions have gone unnoticed in previous studies of ice cores.

In our pursuit of these microscopic particles,

VOLCANIC SECRETS IN THE ICE

we have so far identified several previously unknown volcanic eruptions from Iceland and Jan Mayen Island in two ice cores drilled further south, near the summit of the Greenland ice sheet, in ice that accumulated between 25,000 and 100,000 years ago. Very few records of volcanic eruptions from before 10,000 years ago are preserved on land, so these discoveries add considerably to our knowledge

ice core as a ‘master record’ to reconstruct the volcanic eruptions of the warm Eemian period as well as the cold episodes before and after.

With Dr Bill Austin at the University of St Andrews, we are also searching for traces of eruptions preserved in marine sediments from the North Atlantic and comparing these to what we learn from the ice cores.

Ice cores provide one of the most detailed pictures of the climate of the past. ▶ An ice core being recovered from the drill.

NEEM ice core drilling project, www.neem.ku.dk

of the region’s volcanic history much further back in time. We have now turned our attention to the challenges of the last warm period and the new NEEM ice core.

Although ice cores provide one of the most detailed pictures of the climate of the past, comparing and correlating them with other environmental records is notoriously difficult. The Eemian episode was too long ago for radiocarbon dating, and other dating techniques are plagued by difficulties, with error estimates often too large to allow a meaningful comparison to records from lakes and the deep sea. We need to overcome these difficulties before we can answer key questions.

When did the Eemian episode begin and end in Greenland? Did these major climatic changes occur at the same time in different areas? Can we build up a more accurate picture of climatic and environmental changes in the North Atlantic region during a period when the climate fluctuated between glacial conditions and temperatures warmer than the present day?

Our project, SMART (Synchronising Marine And ice-core Records using Tephrochronology), uses volcanic ash to tackle these questions. Over the next three years we will use the NEEM

Core questions So what is our progress so far? After a recordbreaking ice-coring season at NEEM in 2009, the drilling has reached a depth of 1800m, where the ice formed around 38,000 years ago. We expect Eemian ice will be retrieved during the fast-approaching 2010 season. In the last field season we established and tested a new way of sampling the ice directly at the drill site. Working round the clock, ultraclean meltwater samples are collected using a dedicated set-up that continuously melts the ice on a hotplate to create a stream of water for chemical analysis. Some of this water is retained to hunt for volcanic particles. These samples are then prepared on glass slides, before each sample is meticulously scanned using a highmagnification microscope. Some samples are analysed in Greenland, but most are shipped back to the much warmer laboratory in Swansea.

Once we identify volcanic layers, a critical stage of the work involves geochemical analysis of individual particles to assign a unique ‘fingerprint’ to each layer and determine its volcanic origin. At the NERC Tephrochronology Analytical Unit at the University of Edinburgh, we will measure

concentrations of ten chemical elements abundant in volcanic material. The electron microprobe at this facility determines the concentration of each element by bombarding particles with electrons and measuring the X-rays they produce.

With Dr Nick Pearce at Aberystwyth University we are also using an innovative technique that measures elements present in extremely low concentrations in even the tiniest grains of volcanic material. A highenergy laser removes material from volcanic particles, and trace element concentrations in the vapour that is produced are measured using a mass spectrometer, providing data for around 30 additional elements. This extra information gives us a more comprehensive chemical signature for each layer, letting us better characterise it and match it with volcanic deposits in other climate records.

If we can match the geochemical fingerprints of particles from both ice and sediment cores, we can assume they were laid down at the same time. These can be used to synchronise the climate records in North Atlantic marine sediments and Greenland ice cores, without worrying about the uncertainties associated with different dating methods and timescales.

Our work will also contribute to detailed reconstructions of wind directions and changes in atmospheric circulation in ancient climates.

It will also provide long-term datasets of the frequency and magnitude of past volcanic eruptions, which helps scientists assess hazards from present-day volcanoes.

So what next? The first crew are due to fly into NEEM in early May to set up camp ready for the influx of drillers, scientists, plumbers, carpenters, cooks and doctors. Peter Abbott will be in their midst, helping the chemistry team with their work as well as stockpiling the priceless meltwater samples that will allow the painstaking search for the volcanic secrets hidden in the ice.

MORE INFORMATION Dr Siwan Davies is Senior Lecturer in Geography at the School of the Environment and Society, Swansea University. She is also principal investigator of the SMART project. Email: siwan.davies@swansea.ac.uk Dr Peter Abbott has recently completed his PhD research at Swansea University and is now a Post-doctoral Research Assistant at the School of Geography and Geosciences at the University of St Andrews working directly on the SMART project.

Email: peter.abbott@st-andrews.ac.uk NEEM project www.neem.nbi.ku.dk

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Scientific techniques are transforming the study of the past, and the analysis of isotopes is shedding new light on the origins of archaeological finds and human migration in prehistoric Britain.

What are isotopes, and how do they help us understand longvanished cultures? Sara Coelho explains.

Finding the wisdom in teeth I ndiana Jones might be the world’s most famous archaeologist, but finding the secrets of the past rarely involves hunting treasure in glamorous locations. Archaeology is more about understanding how and where ancient people lived, and how they related to their environment. To do that, archaeologists study artefacts, burial sites and other remains of ancient cultures. But some questions are difficult to answer with traditional techniques, and the field is drawing more and more on scientific methods.

One of the tricky problems is pinpointing the origin of archaeological artefacts like glass, clothing or weapons, because you can’t tell where objects are from just by looking at them.

Roman coins, for example, were minted across the Empire and a denarius found in Britain could easily have been issued far away. But knowing where things are from is essential to understand ancient trading routes and networks.

The same is true of people. The discovery of the so-called Boscombe Bowmen near an airfield in Wiltshire raised more questions than answers. ‘The site’s features were very unusual for Bronze Age Britain,’ says Dr Jane Evans, science-based archaeology theme leader at the NERC Isotope Geosciences Laboratory (NIGL) in Keyworth, Nottingham. It was a mass grave with seven bodies buried with plaited cord beaker pots, bone toggles and the flint arrowheads that inspired archaeologists to call the adults the Boscombe Bowmen.

Dave Norcott, Wessex Archaeology

◀ The grave of the bowmen during excavation. Unlike most contemporary graves in southern England, this one contained the remains of seven individuals: three adult males, a teenage male and three children.

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Where were these people from? Were they born in Wiltshire or in Eastern Europe like the Amesbury Archer found nearby buried in a similar way?

‘It’s very hard to find a definite answer about provenance from grave features,’ says Evans.

Burial rites depend on cultural traditions that may change throughout life; migrants can adopt local customs and locals can be influenced by foreign partners, neighbours or their own experiences abroad. But there’s something else in ancient graves that may record the origin of their occupants – teeth.

‘Teeth grow during early life and as they do, they take up oxygen, strontium and other elements from food and drinking water,’ Evans explains.

A matter of neutrons Not all atoms of the same chemical element are equal and the different types are called isotopes.

‘The number of protons in the nucleus is equal in all isotopes – that is why they remain the same element – but the number of neutrons changes,’ explains Professor Randy Parrish, head of NIGL. ‘Take oxygen, for example,’ says Parrish.

‘99.8 per cent of oxygen atoms on Earth are oxygen-16, with eight neutrons but about two atoms in 1000 are the heavier oxygen-18, which has two extra neutrons.’

Isotopes are a goldmine of information for archaeologists, who started to tap into this resource in the 1990s. Since then, ‘the whole field has mushroomed,’ says Evans, who started in the British Geological Survey as a geochemist and has since specialised in isotope science.

‘Isotopes are a huge plus for archaeology because you can look at origin from what you are, not from burial rite.’

FINDING THE WISDOM IN TEETH

Jane Brayne 2004

So were the Boscombe Bowmen among the builders of Stonehenge?

Stable vs radioactive isotopes Oxygen and nitrogen isotopes are stable and keep the same number of neutrons. But isotopes of radioactive elements like uranium or thorium have too many neutrons to be stable, and tend to shed the extra load over time. In doing so, they transform into other elements in a process called radioactive decay. As time goes by, the initial amount of radioactive isotopes decreases as they decay into stable ‘daughter’ isotopes.

The proportion between radioactive and daughter isotopes can be used to keep track of time. carbon-14, for example, decays into nitrogen relatively fast and is used to date recent organic materials such as wood or bones. To do this, scientists measure how much carbon-14 remains in a sample.

They know the speed at which it decays, so they can estimate how long ago the plant or animal

that provided the material died.

Radioactive uranium isotopes, on the other hand, have long and complicated decay sequences and lose about 30 neutrons before turning into lead atoms after many millions of years. The decay series of uranium isotopes is well known and is used to calculate the age of very old rocks. This process has shown that some crystals of the mineral zircon, which is naturally rich in uranium isotopes, and its daughters are more than four billion years old.

Isotopes provide a wealth of information but to reveal their secrets ‘you need very accurate equipment and qualified personnel’, says Parrish. Just five or six extra strontium-87 isotopes for every 1000 strontium-86 can make all the difference for archaeological problems like the Boscombe Bowmen.

Evans collected two teeth from each of the three Boscombe Bowmen and analysed their strontium content at NIGL. ‘The isotope ratio of the teeth is derived from the isotope composition of their diet, which is determined by the properties of the soil and underlying rocks,’ she says.

The mix of heavy strontium-87 and light strontium-86 isotopes depends on how old rocks are: older rocks are richer in the heavier isotope than younger ones. So by comparing the strontium isotopes in someone’s teeth with a map showing where different isotope proportions are found, researchers can work out where they grew up.

Isotopes cannot be used to pinpoint precise locations, ‘but they’re very useful to exclude places,’ says Evans. For example, if someone’s teeth have a very low strontium isotope ratio, this person couldn’t have grown up in an area with very old rocks.

‘The analysis provided the best evidence for childhood migration yet seen,’ Evans says. In all three cases there was a significant drop in the strontium ratio, between the second and third molar tooth. This means that the men left their homeland when they were between 9 and 13 years old, before they developed their third molars.

‘We don’t know if they travelled together, but the findings suggest a cultural pattern where people spent their childhood somewhere and then moved elsewhere in their early adolescence,’ Evans explains.

But where did the bowmen come from? ‘They were obviously not from Wiltshire,’ she says.

Wales is the nearest possible area, which means that they travelled at least 150 to 200km during childhood. This is a tantalising possibility since the Preseli Hills, where Stonehenge’s famous bluestones come from, fall within the range of possible birthplaces for the men.

Isotopes can be applied to a variety of finds, not just human remains. Evans’ group at NIGL has used isotopes to look at everything from the migration routes of British cattle during the Bronze Age to prehistoric pottery from the Shetlands and Viking fishing weights. ‘It’s also possible to use lead isotopes to find out where Roman coins were minted,’ she adds.

So were the Boscombe Bowmen among the builders of Stonehenge? We may never know for sure, but without isotope analysis we wouldn’t even be aware of the possibility.

MORE INFORMATION NERC Isotope Geosciences Laboratory www.bgs.ac.uk/nigl

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▼ Retreat of the Qoyllur Riti glacier near Cuzco, between 1930 (inset) and 2009.

Paolo Greer/Martin Chambi

High and dry in the Andes Climate change is threatening water supplies in the highlands of Peru. But research into how indigenous cultures coped with limited water supplies in the past could suggest ways forward. Mick Frogley and colleagues explain how.

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gainst the background of global warming, the ready availability of fresh water is coming under increasing strain in many parts of the world. Peru is particularly vulnerable – between 60 and 70 per cent of the 28 millionstrong population lives in a narrow strip of desert that runs along the Pacific coast. The communities here – including the capital Lima, home to more than nine million people – rely heavily on melt-water from the Andean glaciers to feed major rivers and lakes for drinking, agriculture, industry and health purposes.

But these glaciers are now disappearing at an alarming rate. A recent report by the Intergovernmental Panel on Climate Change (IPCC) suggests that over the past 35 years,

the area covered by major Andean glaciers in Peru has fallen by around 22 per cent, with smaller glaciers experiencing reductions closer to 80 per cent. This has led to a significant decrease in the availability of fresh water both in the coastal zone and further inland – many rural highland areas also rely on glacially-fed rivers. Water supplies are expected to continue declining markedly over the next 20 years.

While this situation has serious political, social and economic implications for Peru, it is by no means a new phenomenon.

Getting the most out of water For centuries the forerunners of modern Peruvians realised that efficient management of water resources was the key to their survival and, ultimately, their success. We know from archaeological studies that the people of the Nazca culture, for example – creators of the famous Nazca lines – were able to occupy and exploit part of the southern coastal strip by building innovative covered aqueducts and underground water storage chambers.

In the highlands, problems of seasonal water availability were compounded by also having to cope with large temperature ranges and steep terrain. Here, in the first millennium AD, the Tiwanaku people built networks of raised fields

HIGH AND DRY IN THE ANDES

Sedimentary secrets To try to answer these questions, we decided to concentrate initially on the last 1200 years or so of the lake sediment record, as this was the period when human activity on the landscape was most widespread. In piecing together the evidence, we again used pollen to show which plants were growing in the catchment, either naturally, or as arable crops. Charcoal particles indicated how often fires were being used to clear the landscape, and tiny mite fossils associated with livestock dung gave us a good idea about domestic animals being pastured around the lake.

ECOAN

to make the most of seasonal rainfall, whilst the Huari built extensive canal systems to irrigate their terraced slopes. Successful water management strategies have been employed in this region in the past, so can we learn any lessons about how to cope with water stress both now and in the future?

Our research has focused on understanding changes in climate and water availability in the Peruvian highlands, using evidence preserved in lake mud over the last few thousand years.

We have to use indirect ‘proxy’ evidence like this because the Pre-Colombian cultures in the Andes never developed any form of writing, so history was only passed down orally. This has made it difficult for modern-day scientists to understand all the factors that allowed numerous Andean societies to develop, flourish and then disappear – often very rapidly.

Lakes often respond to climatic changes in predictable ways and maintain a record of these changes in their sediments. One lake that has behaved just like this is Marcacocha, located about 3350m above sea level in the Patacancha Valley, itself a tributary to the Sacred Valley of the Incas. A small lake has existed here for almost 4000 years, fed by the melt-waters from glaciers higher up the valley. In 1993, an 8m-long core was obtained from the centre of the lake site (which finally silted up after a drought in the early 1800s). This sequence has turned out to be a treasure-trove of information, having captured a continuous record of how the catchment has changed through time.

For example, variations in pollen from sedge vegetation, which normally colonises the marshy edge of the basin, have shown us how the lake has experienced seriously low water levels throughout its history, roughly every 500 years. This suggested the region went through sustained periods of aridity at these times – but were they warm or cold, and could people still live and farm in the valley under these conditions?

The sediments themselves also gave us clues about past conditions. The team at the NERC Isotope Geosciences Laboratory in Keyworth analysed the chemistry of the organic material in the lake muds to help us understand not only how the vegetation had changed through time – backing up and refining our pollen evidence – but also how the basin’s soils had changed under different climatic conditions.

When we compared our data with the rich archaeological story from the area, we saw some interesting parallels. The Huari culture were successful predecessors to the Inca, dominant in the region from around AD 600 until their sudden demise around AD 1000. During their final century, the region experienced a sustained drought. Human activity around the catchment seems to have ground to a halt – there is very little evidence for any agriculture, burning of vegetation or the presence of livestock like llamas and alpacas. This suggests that these prolonged conditions were not only dry, but also too cold to successfully exploit these higher-altitude areas – perhaps contributing towards the fall of the Huari.

A similar dry period occurred some centuries later, but this time it was accompanied by warmer temperatures. This coincided with the rise of the Inca, who famously went on to establish the largest and most successful native empire in the Americas, stretching at its height from what is today southern Ecuador to central Chile and supporting a population in excess of eight million.

The Inca and the drought The evidence from the Marcacocha sediments shows that human activity around the basin

actually increased throughout this period.

To us this suggests that, despite conditions of increasing water stress, temperatures were warm enough to let the Inca move up the valleys and apply their irrigation and landscaping technologies to exploit these higher altitudes. The pollen data from Marcacocha, supported independently by documents written immediately after the Spanish arrived, also suggests that the Inca cleverly employed agroforestry techniques to stabilise newlyterraced slopes and to increase soil fertility.

This ability to adapt means that the Inca were able to expand their population and develop food surpluses even when faced with difficult environmental conditions. It also let them maintain a standing army, which they employed ruthlessly to subjugate neighbouring cultures.

Were the Inca just in the right place at the right time? Perhaps. But there are also important lessons that can be learned for today.

Although water stress is again a critical issue across Peru, many of the highland areas are currently lying derelict, with ancient terraces and irrigation systems left abandoned and decaying. Since the Spanish conquest, the slopes have been stripped of native trees, and today the trend is to plant faster-growing but incredibly thirsty exotic species like eucalyptus.

This is increasing pressure on already limited water resources and causing conflict in many Peruvian regions, both in the highlands and in the much more densely populated coastal strip.

Replacing imported trees with hardy native species and repairing terraces and irrigation channels could help ease these problems.

As the glaciers continue to retreat and water stresses increase, Peruvians need to look to the past to see how their ancestors coped under changing environmental conditions. Native agroforestry and the restoration of formerly productive highland areas may help create a sustainable future.

MORE INFORMATION Dr Mick Frogley specialises in investigating changing Quaternary palaeoenvironments, Department of Geography, University of Sussex.

Email: m.r.frogley@sussex.ac.uk Dr Alex Chepstow-Lusty is a palaeoecologist at the Institut Français d’Etudes Andines (IFEA), Lima, Peru. Email: alexchepstow@gmail.com Professor Melanie Leng is an isotope geochemist at the NERC Isotope Geosciences Laboratory, Keyworth. Email: mjl@bgs.ac.uk FURTHER READING Chepstow-Lusty, AC, Frogley, MR, Bauer, BS, Leng, MJ, Boessenkool, KP, Carcaillet, C, Ali, AA & Gioda, A (2009). Putting the rise of the Inca Empire within a climatic and land management context. Climate of the Past 5, 375-388. www.clim-past.net/5/375/2009/cp-5-375-2009.html

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Getting to the bottom of biodiversity The new technique of macroecology lets ecologists take isolated samples of plant and animal life and piece the results together to understand how species are spread across a wide area.

Tom Webb explains how marine science is helping in the search for a general theory of biodiversity.

â–ś The catworm, Nephtys hombergii.

Hans Hillewaert/www.eol.org

â–ś The sea potato, Echinocardium cordatum.

K. Telnes/www.seawater.no

NOAA Library Collection

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GETTING TO THE BOTTOM OF BIODIVERSITY

T

he chilly waters of the North Sea don’t feature on many eco-tourists’ lists of must-see marine biodiversity hotspots. Yet despite the oil rigs, the fishing and the ferries, the surprisingly diverse animal communities of this humdrum sea are revealing important new facts about how life on Earth is distributed. By linking the natural history of individual species to patterns in diversity across the entire sea, we are also beginning to understand how future impacts such as climate change may alter biodiversity across large areas.

In a study funded by NERC’s Strategic Oceans Funding Initiative, we looked at the North Sea benthos – those animals living on or in the seabed – and showed that we can predict the distribution of species based on their biological characteristics. In particular, traits such as body size seem to determine the spatial patterns of the whole North Sea benthic community. But these effects are subtle: big species are not necessarily more widely distributed than small species; rather, they are more evenly distributed within their ranges.

On the other hand, small species, and species which can’t move long distances, appear to have very clustered distributions.

This is important because human activities in the North Sea affect some species more than others. Commercial fishing, in particular trawling, has a disproportionate effect on large species, even those not deliberately targeted by fishermen. If those large species are lost from the system, this has implications for the structure of the whole community. It does suggest, though, that we can monitor an activity’s effects on the system by looking for changes in the relative degree of clustering of species. This may be useful because it is easier and faster to assess the numbers of species in samples than it is to obtain detailed knowledge of their biology.

Size matters In fact, as part of the same project we’re finding out just how difficult it is to get information on the biological characteristics of most marine animals. For many species, there is simply no documented knowledge of their ecology and behaviour – things like what they eat, how many offspring they produce, or how long they live. Typically we have this data for fewer than a quarter of species. If this is true for the North Sea, our ignorance surely plumbs even greater depths in less well-studied and less accessible regions, including much of the developing world and the vast abyssal plains of the deep sea.

A lack of available information may explain the fact that our study did not identify other facets of animal biology as important drivers of species distribution. For instance, most bottom-dwelling species are relatively sedentary as adults, and so their best chance of moving large distances comes when they reproduce.

Broadly speaking, species fall into two camps: those which launch their larvae into the plankton where they drift around for days or even weeks before settling back to the seafloor as adults; and those which keep their offspring close to them. We expected that the choice of larval developmental strategy would have a big effect on adult distributions, with species with a planktonic phase spread more widely. Although we did observe a trend in this direction, it was not statistically significant – but this may be because we had data on developmental mode for only 124 of 575 species.

Body size is the trait that bucks this trend for lacking data – it is far easier to measure an organism than to find out anything about its lifestyle, and we can usually find basic estimates of size for around two thirds of the species in our samples. Studying body size in combination with information on the distribution and abundance of species thus promises more insights in future.

Such insights are possible due to a ‘macroecological’ approach – a relatively new technique well suited to address the difference in scales between ecological samples and the big environmental questions that we face. Most field ecologists work at small spatial scales, typically identifying and counting organisms in a series of small samples – the classic ecologist’s quadrat usually measures between 10cm and 1m on each side.

The equivalent sample for marine benthic systems is the grab sample, where sediment from a small area (most often 0.1m2) of the seabed is extracted, brought up to the surface and then sieved to reveal the species living in it. Macroecology lets us combine many such samples – in this case, taken from more than 230 locations throughout the North Sea – so that ecologists can address far bigger questions, such as how species are moving in response to climate change.

Biodiversity on land and sea Our study is unusual because most of our knowledge of biodiversity comes from ecosystems on land. Macroecology, in particular, has developed largely through the study of a few well-known groups like birds and butterflies. But any study of birds is only focused on a small component of diversity. In

taxonomic terms, all birds belong to a single group called a class; the next level up in the taxonomy, the phylum, groups birds with all other vertebrates.

Other animal phyla include molluscs, arthropods and annelid worms. So although birders might get excited by small differences between bird species, all birds are more similar to each other than any worm is to any mollusc, and it’s only by studying more diverse systems that we can start to understand how major differences in biology affect patterns in geographical distribution.

This is where the advantages of working in marine systems become most apparent.

For example, a single 0.1m2 sample of North Sea sediment may contain up to 90 species, and these species are very diverse – there are many worms, but also molluscs, starfish and crustaceans. In the dataset we used, single samples contained representatives of as many as seven different phyla. Studying systems with such taxonomic diversity means that in the same set of samples, there is tremendous variety in biological characteristics too.

There are other good reasons to study marine systems. Over 90 per cent of the socalled ‘habitable volume’ of Earth – regions suitable for life – is marine. Life originated in the sea, and the diversity found in the North Sea is not a fluke of sampling: around two-thirds of animal phyla are found only in the oceans. But the seas are increasingly threatened by many human activities.

As well as climate change, which is not only warming the oceans but also making them more acidic, marine fish make up an important part of the diet of a large proportion of the world’s people, and the seabed is an important source of natural resources including oil and gas.

Any general theory of biodiversity therefore has to encompass the marine environment. 1.2 billion people live near the coast and this total is expected to continue increasing rapidly. If this happens, then understanding how marine species are distributed may be crucial to our future well-being.

MORE INFORMATION Dr Tom Webb is a Royal Society Research Fellow and marine ecologist at the University of Sheffield.

Email: t.j.webb@sheffield.ac.uk A full report of this work, carried out in collaboration with Dr Elizabeth Tyler in Sheffield and Dr Paul Somerfield at Plymouth Marine Laboratory, is published as an Open Access paper in Marine Ecology Progress Series 396: 293-306. www.int-res.com/abstracts/meps/v396/p293-306/

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Measuring the changing environment from space The technology to monitor the Earth from space is growing ever more sophisticated, letting scientists do research that would once have been impossible.

Mick Johnson describes the latest developments.

S

ince the beginning of the space race, we have been sending instruments into space to help improve our understanding of the planet. Over the last 20 years, observing the Earth from space has become increasingly sophisticated, but also increasingly necessary to monitor the impact people are having on the global environment.

The Earth system is in a dynamic balance.

The sun supplies huge amounts of energy to the oceans and atmosphere. The Earth absorbs some of this energy, but also reflects and radiates energy into space. The recent UN Copenhagen climate conference highlighted the ways in which man’s industrial and other activities are shifting this balance, by changing the composition of the atmosphere through emissions of carbon dioxide and other greenhouse gases.

Observations from space provide global and consistent measurements of the Earth at daily intervals or better – measurements which are not available by any other means. We use a sophisticated array of instruments, operating at all wavelengths of the electromagnetic spectrum that can penetrate the atmosphere, including

32 Planet Earth Spring 2010

visible light, and ultraviolet, infrared and microwave radiation.

These instruments can work passively, by detecting reflected sunlight and radiated energy using imagers and spectrometers, or they can use an artificial source mounted on the satellite, such as a radar or lidar, to illuminate an area of interest and detect the radiation that is reflected back.

At the Centre for Earth Observation Instrumentation (CEOI), we are developing new instruments and technologies using the combined expertise of universities and industry. The technologies build on existing UK strengths in space instrumentation – see the examples below. British groups have significant experience of building advanced systems, with world-class instruments already flying on major ESA and NASA satellites.

Spectrometers for monitoring air quality A CEOI team at the University of Leicester, in cooperation with Surrey Satellite Technology Ltd (SSTL) of Guildford, is developing a prototype instrument called CompAQS which

monitors air quality. It is a novel compact spectrometer – an instrument which measures the properties of light by splitting it into its different wavelengths. This one operates in the visible part of the spectrum, analysing the sunlight reflected and scattered back into space.

Each gas absorbs light at characteristic wavelengths, letting scientists calculate their concentration in the air. The challenge for the design team is to make the spectrometer as small and light as possible without compromising its performance, since a larger instrument requires a larger spacecraft, leading to a costlier launch and mission.

Using lidars in space A laser flying on a satellite together with a sensitive detector pointing in the same direction provides a system collectively known as a lidar.

This works a bit like a radar, except it uses laser light rather than radio waves to sense information about far-off objects.

Applications include determining the height of a forest canopy – the tree-top height – by

MEASURING THE CHANGING ENVIRONMENT FROM SPACE

Building the next generation of instruments ‘In early 2008 the optical designer for this project, Dan Lobb of SSTL produced a fantastic design, which could move the field of atmospheric remote sensing forwards significantly. It fell to my colleague Christopher Whyte and me to build a prototype and demonstrate its potential.

Finding suppliers for the beautifully shaped mirrors, lenses and gratings was a huge challenge. It is these components that make this design so elegant and effective, but it was only after carrying out global searches and fact-finding missions that we found one or two potential suppliers of some of the most intricate parts. The compact nature of the instrument is a fantastic attribute for space missions, but it also causes really difficult practical problems when you’re trying to fit components into a small volume.

However, the trials of construction were worth the reward.

The finished spectrometer provided its first atmospheric measurements in late 2008 and is now incorporated into a highly novel system of air quality and emission monitoring instruments, CityScan. This uses a number of CompAQS-like units mounted on tall buildings or towers around the periphery of an urban area and sophisticated data analysis to build a 3D picture of the distribution of pollution. We also have plans to see it on a satellite where the true capabilities of all those beautiful bits of glass can be appreciated.’

Dr Roland Leigh CompAQS project manager at the University of Leicester

measuring how long it takes the laser light to be reflected back to the receiver; measurement of the speed of the wind using the signal reflected from airborne particles, by detecting the Doppler shift – similar to the way the pitch of an ambulance’s siren seems to change as it drives past – or monitoring atmospheric composition by measuring how it absorbs the laser light.

But there are significant problems in putting these ideas into action, both because of the spacecraft’s speed relative to the Earth’s surface – typically 7km a second – and because of the laser power needed to ensure enough of the light is reflected back to the spacecraft. The resulting system is very complex, and the first few minutes of a satellite’s journey into space provide a hard test of the mechanical design of a delicate instrument: there are no second chances.

This means instruments must be designed to be robust enough to survive the very severe acoustic noise, mechanical vibrations and shock associated with being launched on a rocket.

CEOI has funded projects to look at how to

build these instruments so they can survive the launch and achieve their objectives.

GNSS Reflectometry Engineers and scientists at Surrey Satellites are developing a new method of Earth observation, making use of the signals which are continuously broadcast by the constellations of navigation satellites such as the US GPS system and in the future the European Galileo system. Whilst some of the signal these satellites broadcast is picked up by sat-nav receivers on Earth, much of it is reflected back into space from the Earth’s surface.

By using dedicated, sensitive receivers mounted on another satellite, we can investigate the reflecting surface – be it land, ocean or ice – and the atmosphere above it. Because there are so many navigation satellites in operation – each constellation has about 30 – very frequent measurements are possible, providing wide coverage of the Earth’s surface.

The future The UK currently funds much of its Earth observation through the European Space

Agency (ESA), with UK industry and academia competing with others in Europe to supply the instruments.

The work being carried out at CEOI will give UK teams a significant technological advantage in these competitions and help retain the UK’s capabilities in space technology. But as well as technology we need the next generation of instrument designers. Therefore the CEOI supports NERC PhD studentships and runs training workshops.

There is a new space race under way to build the Earth observation satellites and provide the data we need to understand our changing environment. This is a vital component of the global monitoring systems required to understand the causes and consequences of climate change, and the Centre for Earth Observation Instrumentation is determined to play its part.

MORE INFORMATION Mick Johnson is Director of the Centre for Earth Observation Instrumentation. www.ceoi.ac.uk Email: mick.johnson@astrium.eads.net.

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