5 minute read
PROTECTING LORD HOW ISLAND
Protecting Lord Howe Island
Professor Brett Summerell, Chief Scientist and Director Science, Education and Conservation, returns to Lord Howe Island and summits Mount Gower to survey for Phytophthora, a root pathogen that has impacted the precious natural ecosystem there.
A year ago I embarked on a field trip to Lord Howe Island to work on the potential impact of Phytophthora root rot pathogens on the vegetation of the island. At that time we were aware of an infestation at a farm on the outskirts of the settlement area in some fruit trees and our task then was to determine how far the pathogen had spread and whether it had impacted the extremely precious natural ecosystem there.
The vegetation of Lord Howe is, as you might expect, incredibly unique. Of the approximately 241 native
plant species found on the Island, 47 per cent are endemic and found nowhere else on the planet. Some of the plants on the island are iconic, from the kentia palms Howea fosteriana and Howea belmoreana, that many of you might grow in your garden or patio, and seem ubiquitous across the lower parts. Other icons include the large Hedyscepe canterburyana and small mountain palms Lepidorrhachis mooreana that are found at the tops of the two mountains, and the giant banyan fig Ficus macrophylla f. columnaris and the mountain rose Metrosideras nervulosa
“Phytophthora is a group of plant pathogenic fungal-like organisms that mainly cause root disease –they are microscopic and are easily spread by humans as soil adhering to boots and tyres and in water moving through the landscape.“ - BRETT SUMMERELL
These plants support a unique fauna, again mostly endemic to the island. Anything that is likely to negatively impact their survival or continued existence is of major concern. Fortunately following the eradication of rats on the island more than two years ago, the level of seed and subsequent seedling production has increased hugely and there is a lot more natural regeneration of different plant species.
The topography of the island creates numerous ecological communities, from coastal beach and shore communities, mid-altitude forest communities and at the very top of Mount Gower and Mount Lidgbird mist forest communities that are often shrouded in cloud. Most of these communities form the Permanent Park Preserve on the Island that is afforded the highest conservation status and forms the basis of Lord Howe Island’s World Heritage listing.
Combatting Phytophthora’s silent spread
Phytophthora is a group of plant pathogenic fungallike organisms that mainly cause root disease – they are microscopic and are easily spread by humans as soil adhering to boots and tyres and in water moving through the landscape.
While some species appear to be native to Australia the most problematic are exotic pathogens that have been introduced and have had, in some cases, devastating effects on our native plants, causing some species to become threatened and endangered. It is one of the concerns, for example, for the continued existence of the Wollemi pine at the location where the pine naturally grows.
Since that first trip we have been back twice to collect further soil samples from the more remote parts of the Island, as well as the more populated areas of the settlement, and to better map the extent of infestation by this very difficult-to-control plant pathogen.
The data now indicates that the pathogen is more widely spread and is associated with signs of dieback at a number of locations. This has resulted in a ramping up of hygiene strategies, increased foot bath stations and some engineering activities to reduce the potential for the pathogen to be spread.
Summiting Mount Gower for samples
The highlight on this latest trip in mid-September was finally being able to get to the top of Mount Gower and to sample across the full extent of the walking track and across the summit. This was an amazing, but challenging walk that involved ascending the full 875 metres of Mount Gower often at very dizzying heights, and taking samples of soil from locations where either plants were showing signs of dieback, where touring parties have rest stops or at drainage points where the pathogen might be expected to accumulate and be easier to detect.
Hiking the Mount Gower track is only permitted in guided touring groups because of the potential risks and the need to protect the sensitive environment. As a consequence it is relatively easy to communicate the problems associated with Phytophthora to the operators running the tours – and anxious to protect the environment – and ensure that everyone follows the hygiene protocols.
Future work will focus on completing as full as possible a survey of the presence of Phytophthora, and, funding permitted, to start to determine the actual susceptibility of the endemic plant species to Phytophthora.
Our PlantClinic team is currently developing a rapid batch testing device and procedure that will allow us to test multiple plants at the same time. This will reduce the cost of the testing and to ensure that any plants being brought onto the island, such as fruit trees and landscape plants in the settlement, are free of the pathogen.
It is highly likely that the pathogen is here to stay on the island. The future will involve managing it and the impact it causes by preventing the introduction of new species and strains of Phytophthora, particularly into the Permanent Park Preserve areas or further along the walking tracks.
It will also be critical to start a program of ex situ conservation of the endemic species and ensuring that there are genetically representative collections of these species in seed banks, cryopreservation and in our botanic gardens. It will be extremely important to have these back-up populations stored away to prevent these plant species from heading towards extinction.
