Important Stonewort Areas
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Important Stonewort Areas An assessment of the best areas for stoneworts in the United Kingdom (summary) IMPORTANT STONEWORT AREAS Report written by Nick Stewart This project was commissioned as part Edited by Gail Vines of Plantlife International’s species recovery programme Back from the Brink, This report is a summarised version of with generous financial support from Important Stonewort Areas of the United English Nature. Kingdom (see back cover for details). Report citation: Stewart, N.F. (2004). Acknowledgements: There have been Important Stonewort Areas. An assessment a large number of contributors to this of the best areas for stoneworts in the report, in the form of site and survey United Kingdom (summary). Plantlife information, provision of specimens for International, Salisbury, UK. determination, assistance in field surveys and loan of herbarium specimens. In Plantlife International is a charity particular, we would like to thank Jenny dedicated exclusively to conserving all forms of plant life in their natural Bryant, Ruth Davis, Lynne Farrell, Alan habitats, in the UK, Europe and across Hale, Jane Harris, Richard Lansdown, the world. We act directly to stop Tim Pankhurst, Chris Preston, Stephen common wild plants becoming rare in Ward Penny Williams and Andy Byfield, the wild, to rescue wild plants on the Nicola Hutchinson and Amanda Miller of brink of extinction and to protect sites the Back from the Brink team at Plantlife of exceptional botanical importance. International. The charity carries out practical In addition, this report draws together conservation work, influences relevant and makes use of data collected through policy and legislation, involves its regional stonewort surveys, funded by members in many aspects of its work, the Countryside Council for Wales, and collaborates widely to promote the Anglian Water Services Ltd, English cause of wild plant conservation. Nature, Scottish Natural Heritage and Plantlife International – The Wild Plant Thames Region Environment Agency. Conservation Charity Their support is gratefully acknowledged. 14 Rollestone Street, Salisbury, Wiltshire, SP1 1DX, UK Tel: +44 (0)1722 342730 Fax: +44 (0)1722 329035 e-mail: [email protected] website: www.plantlife.org.uk Front cover: Uath Lochan is one of 44 key nationally or internationally important ISAs in Scotland, notable for one of the few UK populations of least stonewort Nitella confervacea 2 IMPORTANT STONEWORT AREAS BOB GIBBONS/NATURAL IMAGE The extensive network of ditches on the Somerset Levels support the largest UK populations of great tassel stonewort. Summary Contents Summary 3 Where are the best places in the UK for stoneworts? This report provides the Why stoneworts? 4 answer. It offers a comprehensive list of important sites for these fascinating Ideal homes for stoneworts 6 algae, and prioritises those most in need of in-situ conservation action. How sites were chosen 8 By collating records from a wide group of organisations and individuals over many years, we have collated an inventory of 118 Important Stonewort Areas (ISA), of Overview: results, protection both national and European importance, as a prelude to targeted conservation and threats 10 effort. Key stonewort sites have been identified and assessed on the presence of Map and list of sites 12 threatened or rare species; of overall species richness; and/or of excellent examples of habitats of particular importance to stonewort conservation. This Next steps 14 knowledge will be fed into existing conservation programmes as well as the References 15 project to identify and protect a network of the best sites for plant conservation throughout Europe - the Important Plant Areas (IPA). 3 IMPORTANT STONEWORT AREAS Why stoneworts? Stoneworts are a unique group of with flowering aquatic plants, so a great Box 1: Revised threat status of UK complex algae that typically grow in fresh deal is now known about their red list stoneworts or brackish water that is clear and distribution and ecology. Stoneworts are (Stewart – in preparation; and can be unpolluted. Thirty species are found in the amongst the first plants to arrive in a seen on http://www.jncc.gov.uk/species/ United Kingdom. They take their name new pond or ditch, where there is plenty plants/threatened/charo.htm) from their encrusted appearance, as most of bare substrate for them to attach stoneworts build an external skeleton of their rootlike rhizoids. They are often Britain calcium carbonate instead of using pioneers on the open beds of newly Baltic stonewort Chara baltica VU cellulose for structural support as seen in cleaned or created water bodies, often Bearded stonewort Chara canescens EN the flowering plants. Evolutionists suspect quickly forming dense underwater ‘meadows’. As long as nutrient levels Bird's nest stonewort Tolypella nidifica EN these remarkable plants may have played a part in the evolution of the earliest land remain low, they can persist quite well, Convergent stonewort Chara connivens EN plants (Graham, 1993). If another group but in more nutrient-rich sites they are Dwarf stonewort Nitella tenuissima EN of algae - the seaweeds - are the botanical often swamped by the vigorous growth Foxtail stonewort Lamprothamnium papulosum nt masters of the sea, sometimes reaching of flowering plants. In these Great tassel stonewort Tolypella prolifera EN hundreds of metres in length, stoneworts circumstances, they can survive only if Intermediate stonewort Chara intermedia EN are the principal algae of freshwater. the habitat is kept open by some sort of Least stonewort Nitella confervacea nt disturbance – for example, by dredging, At first glance, stoneworts don't look Many-branched stonewort Nitella hyalina EX livestock poaching, or even wave like algae at all. In fact, they look rather turbulence near a lake edge. These Mossy stonewort Chara muscosa DD like vascular plants with what appear to exacting requirements restrict them to Rugged stonewort Chara rudis nt be roots, stems and whorls of slender certain habitats such as coastal lagoons, Slender stonewort Nitella gracilis VU leaves. This appearance led, for a time, to ditches, seasonal pools or meres, marl Slimy-fruited stonewort Nitella capillaris EX their mistaken classification, with the lakes and calcareous fen pools. Luckily, Starry stonewort Nitellopsis obtusa VU horsetails Equisetum, even though they their durable spores, which can remain Strawberry stonewort Chara fragifera VU grow completely under water. Only an dormant yet viable for decades, allow Tassel stonewort Tolypella intricata EN anatomical examination reveals their true them to persist through periods when affinities: these are algae with enormous conditions are unsuitable. cells, up to 20 centimetres long, the Nationally Scarce species without largest known to science. Most stoneworts are unable to tolerate an IUCN designation significant levels of phosphates and Clustered stonewort Tolypella glomerata Over the years, pond-dipping botanists nitrates from nutrient pollution and, as a Hedgehog stonewort Chara aculeolata have often scooped up stoneworts along result, they are exceptional indicators of Lesser bearded stonewort Chara curta Pointed stonewort Nitella mucronata Smooth stonewort Nitella flexilis SUE SCOTT Northern Ireland Least stonewort Nitella confervacea nt Pointed stonewort Nitella mucronata EN IUCN threat statuses, according to IUCN (2001): EX – Extinct; EN – Endangered; VU – Vulnerable; DD – Data Deficient; nt – Near Threatened Under suitable conditions stoneworts can form dense underwater meadows, such as Chara hispida shown here. 4 IMPORTANT STONEWORT AREAS BOB GIBBONS/NATURAL IMAGE Formerly the single richest aquatic system in Britain for macrophytes, the Basingstoke Canal has suffered the effects of excess boating, heavy stocking of fish and shading by overhanging trees. water quality. This pollution is Conservation priority detrimental to stoneworts primarily In recent years, stoneworts have because it encourages competitors, undergone a catastrophic decline that particularly epiphytic algae, which coat has resulted from both the nutrient the surface of the stonewort plants, or enrichment, eutrophication, of water makes the water too turbid for sunlight bodies, and from the loss of traditional to penetrate. Epiphytic algae inhibit management practices that kept fenland nutrient exchange: stoneworts have no ditches and small ponds and the like vascular system and largely rely on open rather than overgrown. movement of ions through their cell Over 10 years ago, the status of the 30 walls. At the same time, stoneworts UK species of stonewort was recorded in themselves help to promote clear water. the Red Data Books of Britain and Ireland: They capture nutrients and help to clarify Stoneworts (Stewart & Church 1992). This the water by stabilising sediments, and was the first Red Data book in the UK for perhaps even by production of inhibitory any group of non-vascular plants. Today, chemicals. 17 species in Britain are deemed Stoneworts are well worth conserving in nationally rare or extinct, together with a their own right, and their sensitivity to further two species in Northern Ireland pollutants makes them the ‘canaries’ of (see Box 1) that remain relatively the freshwater world. As clean water widespread in Britain, using the 2001 bodies become contaminated with IUCN threat category criteria (IUCN sewage, farming effluent and agricultural 2001). Accordingly, stoneworts are among run-off, stoneworts are often the first the