Coastal soft cliff invertebrates are reliant upon dynamic coastal processes

Abstract

Coastal soft cliffs in the UK support rich assemblages of invertebrates including species restricted to soft cliffs Howe (Br Wildl 4: 323–331, 2003). Recent analyses have identified a total of 29 species confined to coastal soft cliffs, with a further 78 species having a high degree of dependence (Howe et al. Br Wildl 19: 172–181, 2008). A handful of species once more widespread in the UK, both on the coast and inland, such as the Large Mason Bee Osmia xanthomelana and the Long-horned Bee Eucera longicornis, are now found only or mostly at soft cliff localities. Key habitats include bare sand or glacial till, extensive swards of leguminuous and ruderal plants and hydrological features including seepages, pools and reedbeds. Unhindered dynamic processes such as erosion and cliff failure and unimpeded drainage are critical to soft cliffs retaining their invertebrate interest. By far the richest sites for soft cliff invertebrates are on the Dorset and the Isle of Wight coasts, but other important localities include south Devon, the Llŷn coast in Gwynedd, north Norfolk, Yorkshire and the south Gower coast. The most obvious threats to soft cliff invertebrates are cliff-protection and stabilization schemes and drainage. However, agricultural improvement of cliff-top hinterlands at many sites restricts nesting and foraging activities to the immediate cliff slopes, and acts to fragment and isolate sections of soft cliff. More sympathetic management of these areas is needed to reconnect sites and their associated invertebrate populations, to reduce a dependence upon the cliff slope and to increase the availability of suitable nesting and foraging habitats.