ORFORD NESS AND ITS REMARKABLE INVERTEBRATE FAUNA STUART WARRINGTON
Introduction
Orford Ness is a large and highly significant site for its wildlife and geomorphology. The major feature is the 16 km long shingle spit with a cuspate foreland, jutting into the North Sea. The dynamic processes of shingle erosion and deposition can clearly be seen, and the speed of change can be dramatic (Packham et al. 2001). A specialised and rare vegetated shingle habitat has developed at Orford Ness, with vegetation along the top of shallow ridges where finer sediments hold a little more moisture and organic matter. The ridges nearest the sea have extensive patches of beautiful and scarce Sea Pea Lathyrus japonicus. The older ridges have numerous lichen species amongst the vascular plants. The vegetated shingle habitats are fragile and have been lost where the shingle was disturbed by vehicle movements or trampling (Warrington et al. 2013).
Orford Ness also supports an interesting and rare habitat where there is a natural transition from the shingle into a sheltered saltmarsh, which is present all along the eastern edge of Stony Ditch, a tidal creek that runs through the site. Elsewhere the saltmarsh succession is truncated by river wall embankments.
On the Alde-Ore river side of the Ness are a series of grazing marshes within the clay river walls. These are not classic freshwater marshes as the only freshwater input is from rainfall and seawater seepage frequently occurs, thus the clay soil has a strong saline content and the ditches and pools vary from almost fresh after heavy rain to hyper-saline after dry, hot weather. Within these marshes, there are also two patches of reed-swamp.
The numerous saline and brackish lagoons and pools across Orford Ness, which total over 40 ha, are also of great nature conservation significance, as they support a range of unusual flora and fauna. There are also many, varied ‘brownfield’ habitats on the Ness where human activity has left roads, buildings and other structures, on the shingle and marsh areas, which have been colonised by nature. An overview of the layout of Orford Ness and a summary of the habitats are illustrated in Figure 1 (overleaf).
Thus, Orford Ness hosts several unusual and rare habitats and, not surprisingly, it has every UK and European nature conservation designation (Warrington et al. 2013). The majority, but not all, of the site is owned and managed by the National Trust.
This article is a review of the terrestrial and aquatic invertebrate fauna currently known at Orford Ness (including lagoon and saltmarsh species but excluding the fully marine species). It investigates the characteristics of this fauna, the habitats and highlights some of the rare and special species.
Invertebrate Recording
Orford Ness missed out on the Victorian surge in interest in studying and recording natural history, probably due to its remoteness and then the War Office acquired the site and closed it to the public. Fewer than 3% of the 13800 invertebrate records collated for the site are dated prior to the National Trust purchasing most of the site from the Government in 1993. Most of these records come from surveys of the
Figure 1. An oblique schematic view of Orford Ness from the south-west showing the layout and the broad habitats.
coastal lagoons in the north of the site by R. N. Bamber, R. S. K. Barnes, M. Drake and M. Sheader (Bamber 1999).
The moths are the best investigated taxon group, although there is nothing pre1989. Keith Zealand and Ken Saul visited from Norfolk to provide some initial data in the mid-1990s. However, since 2000, the NT is indebted to the extensive work of Jim Askins, Mike Marsh, Dave Crawshaw, Andrew Capell and frequent visits by the Suffolk Moth Group, especially Neil Sherman, Jeff Higgott, Tony Pritchard and Matthew Deans. A mercury vapour light trap is regularly run by the Office Block on Airfield Marsh and currently 67% of all of the collated invertebrate records are moths.
Coleoptera (beetles) are pretty well worked, with 1440 records, mostly by S. Warrington and commissioned surveys by Mark Telfer and Paul Lee (mainly pitfall trapping in the shingle habitats), plus some occasional visits by Nigel Cuming, David Nash, Tony Allen and J. A. McGill.
Diptera (true flies) are a highly diverse Order, but most require a high level of expertise to identify and many have a short flight season so that many sampling trips are needed to sample the fauna. With few visits by Dipterists there are only 440 records although thanks to J. A. McGill, Ivan Perry and Peter Vincent, several species that are nationally or locally rare have been found. There are about 800 records, collectively, of the Hemiptera, Orthoptera, Odonata, Hymenoptera, butterflies and other insect orders.
Of the other invertebrate groups, the spiders (Araneae) are the best worked thanks to visits in 1994 and 1997 by the British Arachnological Society and Paul Lee’s pitfall surveys in 2002 and 2009. With occasional other observations, the spiders total 805 records. Paul Lee’s surveys also made the main contribution to the records of Crustacea (especially Isopods), Millipedes and Centipedes. Surveys by Toby Abrehart have greatly increased the knowledge of the site’s Mollusc fauna, alongside the lagoon surveys by Telfer (2013) and Bamber (1999).
Records for Orford Ness are sent to Suffolk County Recorders and/or to the Suffolk Biodiversity Information Service.
Invertebrate Species Richness and Rarity
The invertebrate fauna totals 1651 species (Table 1). This is a good, but not especially high, number and it amounts to about 40% of the total species recorded at Orford Ness. The flora, birds and lichens are also notably diverse groups at Orford.
This 40% is low compared to inland National Trust sites in East Anglia (all with a good amount of species recording), for example, invertebrates make up 57% of the species at Hatfield Forest (Essex), 68% at Wimpole (Cambs), 69% at Ickworth Park (Suffolk) and a remarkable 77% at Wicken Fen (Cambs) (Warrington, from NT Recorder6 database).
Taxon
Insects
No. of Species No. of Records Notes
Moths 671 9385
Coleoptera 341 1440 Beetles
Diptera 206 440 True flies
Hemiptera 71 250 True bugs, froghoppers
Hymenoptera, Aculeata 41 110 Bees, wasps, ants
Hymenoptera, Others 11 25 Sawflies, parasitic wasps
Butterflies 24 240
Odonata 18 145 Dragonflies, damselflies
Orthoptera 9 35 Grasshoppers, bush-crickets
Insects, Others 5 20 Earwig, mayfly, Springtail, Other Invertebrates
Arachnida, Araneae 154 805 Spiders
Arachnida, Others 11 25 Mites, pseudoscorpions, harvestmen
Crustaceans 41 335 Isopods, amphipods
Molluscs 36 315 Snails, slugs
Centipedes, Millipedes 12 35
Total 1651 14055
Table 1. The Species Richness and Records of Invertebrates at Orford Ness. (terrestrial, aquatic, saltmarsh and lagoon species)
The high diversity of the moths reflects both the diligent, regular survey work of the recorders and the varied habitats and plant species across the site, plus the likelihood of dispersing and migrant moths being picked up on the Ness.
The analysis of the invertebrates is based on the species richness and the local or national status (rarity) and the Pantheon online tool which has been used to investigate the habitat associations and assemblages of the fauna (Webb et al. 2018). The analysis includes all of the species of the groups in Table 1, except the microcrustaceans, some Hymenoptera (parasitic wasps, sawflies), mites and springtail.
With regard to feeding guilds (Table 2), the importance of plants is clear with the majority of larvae being herbivores (consuming leaves, stems, roots, flowers) and the use of flowers by adults. These numbers clearly reflect the diversity of plant species across Orford Ness. The low numbers associated with decaying biological material (saprophagous) is unusual for invertebrate faunas and is related to the low cover of woody plants and low amounts of soil organic matter on this site, especially compared to woodlands and fens. There was information for the majority (78% adults, 85% larvae) but not all species.
Predator 422 (32%)
(33%)
Herbivore 137 (11%) 830 (59%)
Nectivore
(53%)
(4%)
(1%)
(2%)
Table 2. Feeding Guilds of the Invertebrates Species (number, %) for which there is information in Pantheon
The broad biotype and habitat associations of the invertebrates shows the importance and extent of the open habitats, including bare ground, at Orford Ness, with 48% of the species (Table 3). The coastal, wetland and tree-associated habitats are each about 17% of the species. The SQI (species quality index) is a value based on the rarity of species, with common and widespread species scoring 100, and species with a more restricted distribution, such as nationally scarce and rare scoring higher. The SQI thus gives an indication of the proportion of common to rare species present in a habitat.
Open habitats, especially grasslands of various sward heights, are clearly important for many species, and although most of these are common, there are also some rare species. The crumbling concrete roads produce some small areas of calcareous soil and flora, and here 25 insect species have been found that have moderate to high association with calcareous grassland. Places with dumped shingle within the marshes have developed acid grassland and gorse scrub, with a very different fauna. The abundance of the open habitat species is also a key aspect for the ecology and food webs of the site, and clouds of insects can emerge into the air as you walk through the grasslands.
At first, the high number (184) of arboreal species might seem at odds with the habitats present, but almost all of these are mobile and common species such as many moths and Hemiptera, which is reflected in the SQI of 114, the lowest of any of the habitats. The low number of species associated with decaying wood, a huge resource in woodlands, but only a minor component at Orford Ness, reflects the lack of woody habitats, although some of these are associated with very dry timbers of fallen buildings and beach driftwood. Of the coastal habitats, saltmarsh is the most biodiverse and this seems to reflect the extent of this habitat and its quality (note the SQI of 320), especially the superb saltmarsh succession present alongside Stony Ditch, as already mentioned. The brackish and saline habitats have lower species richness, but these can be harsh environments, with a specialised and uncommon fauna (higher SQIs), especially where the salinity can change significantly within them, as occurs at Orford Ness. The highest SQI of 453 is for sandy beach and there is a small amount of this habitat, almost undisturbed, on the estuary side of Orford Ness and amongst the shingle.
Table 3. Broad biotype and habitat associations of the invertebrate species (for 1436 species for which information is in Pantheon)
The wetland communities are rich with both common and scarce species. Many of the peat and marshland species have been found in the two reedbed areas which have abundant Phragmites australis and have developed deep decaying litter zones, plus a few wet scrub areas. An interesting feature are a few pools in the main area of shingle which have the least brackish aquatic habitat and this is where most of the freshwater species were found.
Rarities and Specialities
The assessment of national threat, rarity or scarcity of the species in various invertebrate groups is at different stages of understanding and publication. Using the best available information, from Pantheon and Status Reviews (e.g., Telfer 2016), it is possible to collate the number of nationally rare, scarce and red-listed species.
For the invertebrate fauna of Orford Ness in Table 1, there are 245 species with a status of red-list, nationally rare, or nationally scarce, which is 14.8% of the fauna. This is a notably high percentage, especially when compared to other National Trust sites of known importance and diversity for invertebrates, such as Wimpole with 6.4%, Hatfield Forest with 6.9% and Wicken Fen with 7.2% (Warrington, pers. comm.).
The beetle fauna is especially interesting. There are 89 species of ground beetles (Carabidae), the most species-rich beetle family, in contrast to the sites above where the rove beetles (Staphylinidae), weevils (Curculionidae) and leaf beetles (Chrysomelidae) are the most diverse families. With 4 Nationally Rare (NR) and 21 Nationally Scarce (NS) species (Telfer, 2016), 28% of the ground beetles are rare/ scarce. Orford Ness is the most northern extant site in GB for Amara strenua and Bembidion nigropiceum (both NR and Near Threatened) which are associated with shingle and shingle/mud areas. Ophonus parallelus (NR and Vulnerable) has only been found once in a bare, open area, in contrast, Anisodactylus poeciloides (NS) was discovered in pitfall traps in Airfield Marsh in 2004 and further surveys revealed that this uncommon species was widespread on the ditch and lagoon margins with minimal vegetation. Several other NS ground beetle species have been found on the mud or under debris on lagoon edges, such as Bembidion ephippium, B. fumigatum, B. normannum, Pogonus littoralis and Tachys scutellaris.
Airfield Marsh lagoon drawdown
The water beetles also have a high 28% NR/NS of the 58 species recorded (families Dytiscidae, Hydrophilidae, Hydraenidae, Gyrinidae, Haliplidae and Noteridae). The diving beetle Agabus conspersus (NS) thrives, with thousands in the brackish ditches and lagoons across the marshes, along with Hygrotus parallelogrammus, Enochrus halophilus, E. bicolor (all NS) and the Vulnerable, NR Berosus fulvus, at its most northern GB site (Warrington 2012). The interesting pools in the main mass of shingle seem to be the least brackish water and here was discovered the Vulnerable, NR diving beetle Graphoderus cinereus, new to Suffolk in 2012, and a larva of the redlisted great silver water beetle Hydrophilus piceus, adults of which also turn up occasionally in the moth trap (Warrington 2013).
Other notable beetles include a tiny rove beetle Brundinia kraneana found on lagoon margins by Mark Telfer in 2012, which after research was discovered to be new to Britain and occurs at Orford Ness and only two other GB sites (Telfer et al 2021). Three uncommon species of ant-like beetles (Anthicidae) occur, Cyclodinus constrictus (NS) and C. salinus (NR) around lagoons, and the Vulnerable Anthicus angustatus (NR) was found under tidal debris by David Nash. The Vulnerable leaf beetle Longitarsus absynthii (NR) is recorded on the Sea Wormwood Seriphidium maritimum, which has a strong population at Orford Ness due to the quality of the upper saltmarsh habitats (Hubble 2014). The large expanses of shingle may seem to be devoid of life, but here wind-dried carcasses of animals (rabbit, hare, fish) provide
the habitat for the very rare and Vulnerable Dermestes undulatus (a hide beetle). The dry, open shingle also provides habitat for several scarce spider species, including Drassyllus lutetianus (NS), Haplodrassus minor (NS), Phaeocedus braccatus (NR), Pseudeuophrys obsoleta (NS), Calositticus inexpectus (NS), Zelotes subterraneus (NS), Zelotes petrensis (NR), Trichoncus affinis (NR) and Gnaphosa lugubris (NR, Vulnerable), the last a species with its only East Anglian population in the shingle at Orford Ness.
The spider community at Orford is important, with 20% of species Nationally Rare or Scarce. There are also uncommon spiders that utilise the saltmarsh and strandline habitats, notably Argenna patula (NS), Enoplognatha mordax (NS), Arctosa fulvolineata (NR), and most significantly the Endangered Praestigia duffeyi, for which there are 4 Orford Ness records, the most recent being 1 male and 1 female grubbed from a small shingle ridge in saltmarsh in 2009.
In addition to beetles, several other rare species are associated with the lagoons, such as the Lagoon Sand Shrimp Gammarus insensibilis, the snail Hydrobia acuta subsp. neglecta and the Starlet Sea-Anemone Nematostella vectensis. Nematosella is a priority species for conservation and its presence helps to identify and protect sites with high quality lagoons, however, recent DNA-based research has suggested it might be non-native and originates in north-east coasts of America (Barfield 2016). Three NS shore bugs are associated with the drawdown zone habitats of the shallow
lagoons, Salda littoralis, Saldula opacula and S. pilosella. Uncommon Diptera species have also been netted around lagoons (all NS); Thinophilus ruficornis, Coenosia karli and the Long-horned Cleg Haematopota grandis. Sweep-netting in the marshes by Ivan Perry discovered two Diptera species new to Suffolk, Xanthocanace ranula (Canacidae) and Townsendiellomyia nidicola (Tachinidae).
The scarce, conservation priority species Narrow-mouthed Whorl Snail Vertigo angustior was only discovered at Orford Ness in 2008, yet further surveys by Toby Abrehart showed it to be to be widespread and abundant, especially in King’s Marsh. It often occurs in grassy habitats near the river walls, which are also favoured by the Grey Bush-cricket Platycleis albopunctata (NS) which is close to its northern GB limit at Orford Ness. Many spider species are also found in the grassy swards, such as the wasp spider Argiope bruennichi.
The Hymenoptera community looks interesting and would repay further visits as some rare coastal bees have been noted, such as Hylaeus annularis, Lasioglossum sexnotatum and Colletes halophilus, and several sightings of the priority Brownbanded Carder Bumblebee Bombus humilis. The scarce ant Ponera testacea was found on the vegetated shingle habitat.
The moth community, as already mentioned, is highly diverse, although many species probably do not breed on the site. The Ground Lackey Malacosomacastrensis is a notable resident, its larvae living in groups under webs on the sheltered saltmarshes and are able to survive twice-daily inundation by sea water.
Examples of other NS moths associated with saltmarsh habitats are Sea-purslane Case -bearer Coleophora salinella (NS), Glasswort Case-bearer C. salicorniae, Sea-blite
Groundling Scrobipalpa suaedella, Sea-aster Groundling S. salicorniae, Buck's-horn
Groundling S. samadensis, Saltmarsh Grass-veneer Pediasia aridella and Maritime Bell
Eucosma lacteana.
Scarce species associated with the vegetated shingle include Silver-edged Knothorn Pima boisduvaliella (NS) which is widespread at Orford Ness, its larvae can feed on Sea Pea. Also widespread is Coast Groundling Caryocolum vicinella (NS), its larvae feed on the abundant Sea Campion Silene uniflora. Pygmy Footman Eilema pygmaeola (NR) has been occasionally recorded, its larvae may feed on the shingle lichens and there is one record of the very scarce Starry Pearl Cynaeda dentalis, its larvae feed on Viper's Bugloss Echium vulgare on the coast. Thrift Neb Aristotelia brizella (NS) utilises the abundant Thrift Ameria maritima along the shingle-saltmarsh boundary and in the same zone using Sea Wormwood is Star-wort Cucullia asteris (NS).
Scarce moths associated with the coastal marshes and wetlands include the Near Threatened Dotted Footman Pelosia muscerda (NR), Saltern Dwarf Elachista scirpi (NS) (larvae on Sea Club-rush Bolboschoenus maritimus) and Flame Wainscot Senta flammea (NS).
Although none of the dragonfly, damselfly and butterfly species recorded are scarce, they can occur in high numbers especially Blue-tailed damselfly Ischnura elegans, Small Heath Coenonympha pamphilus and Meadow Brown Maniola jurtina.
Discussion
From the collated species records, almost all from the last 25 years, there is no doubt that Orford Ness is of very great importance for invertebrate conservation. The fauna is quite remarkable and heavily weighted with rarities, especially those associated with the unusual habitats of vegetated shingle, full range of saltmarshes and saline/ brackish lagoons and pools. There can be very few places in Britain where 15% of the invertebrate species (and higher % for some taxon groups) have national rarity or scarcity status.
There are certainly more species to discover, especially if invertebrate experts visit the site at different times of the year, use different sampling techniques, sample the full range of habitats and broaden the taxon coverage. However, there are challenges, as it is a difficult site to access, there are few tracks or paths and it can be hazardous (weather exposure, military debris, wetlands). In addition, there are some habitats, such as the vegetated shingle and the small saline pools, where disturbance needs to be kept to a minimum.
Orford Ness is a hugely important site for nature conservation, for its geomorphology, habitats and plants, birdlife, and its invertebrates (Warrington et al. 2013). Yet, outside of Suffolk, it is relatively unknown. It is also a dynamic site that will continue to change in the future due to the drivers of climate change, floods and droughts, sea level rise and human activities. Its wildlife, including the invertebrate communities, will change too, however, it is certain that many uncommon and special species will continue to find their niche on Orford Ness.
Acknowledgements
The National Trust is deeply grateful to all of the people who have contributed to the knowledge of the fauna and flora of this remarkable site. Access to the site remains controlled due to its sensitivity and hazards. If you wish to visit to record on the site, please contact the NT for permission and to understand the necessary access restrictions. Email orfordness@nationaltrust.org.uk or write to the NT, Quay Street, Orford, Suffolk, IP12 2NU.
References
Bamber, R. N. (1999). Survey of selected saline lagoons, Suffolk Coast, September 1998. English Nature Research Report 300.
Barfield, P. D. (2016). The UK non-native species Nematostella vectensis (starlet sea anemone). Bulletin of the Porcupine Marine Natural History Society 5: 33–37.
Hubble, D. S. (2014). A review of the status of the beetles of Great Britain: The leaf beetles and their allies. Natural England Commissioned Report NECR161.
Packham, J. R., Randall, R. E., Barnes, R. S. K. & Neal, A. (2001). Ecology and Geomorphology of Coastal Shingle. Westbury Academic.
Telfer, M.G. (2013) Invertebrate survey of lagoons at Orford Ness 2012. Report to the National Trust.
Telfer, M. G. (2016). A review of the beetles of Great Britain: Ground Beetles (Carabidae). Natural England Commissioned Report NECR189.
Telfer, M. G., Booth, R. G. & Vorst, O. (2021). Brundinia kraneana (Scheerpeltz, 1931) (Staphylinidae) new to Britain and The Netherlands. The Coleopterist 30: 1–7.
Warrington, S. (2012). Berosus fulvus (Kuwert) (Hydrophilidae) at Orford Ness NNR, Suffolk (VC 25). The Coleopterist 20: 124–125.
Warrington, S. (2013). Graphoderus cinereus new to Suffolk and the Dragonfly pool on Orford Ness NNR, England. Latissimus 33: 8–9.
Warrington, S., Lohoar, G. & Mason, D. (2013). Orford Ness, a place of conflict and conservation. British Wildlife 25: 30–39.
Webb, J., Heaver, D., Lott, D., Dean, H. J., van Breda, J., Curson, J., Harvey, M. C., Gurney, M., Roy, D. B., van Breda, A., Drake, M., Alexander, K. N. A., Foster G. N. (2018). Pantheon. (database version 3.7.6) https://pantheon.brc.ac.uk/ (site accessed 1 Feb 2023).
Stuart Warrington
National Trust Nature Conservation Advisor 2003–2019 Stuart.warrington7@gmail.com
8 Redwoods
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