Geology and Habitats

Geologically, the Common is part of the Bagshot Sands, with overlaying alluvial soils and gravel. Most of the water drains into the River Bourne and there are many wet areas and ponds.

The Common has a rich mosaic of heathland habitats, ranging from open heath and acidic grassland to bog, heathland pools, secondary woodland and scrub. It supports a variety of characteristic heathland plants and animals, including several which are local or rare. English Nature has commended Horsell Common for its outstanding wildlife value. Large areas of the Common have been designated as Sites of Special Scientific Interest (SSSI). The open heathland areas form part of the Thames Basin Heaths Special protection Area, under the terms of the European Birds Directive. The Common is of European importance for supporting breeding populations of three species: nightjar, woodlark and Dartford warbler.In dry parts of the site, ling and bell heather are dominant, often mixed with dry acidic grassland. Other plants found here include dwarf gorse, dodder (a parasite of ling), and common cudweed, which is rapidly decreasing in south-east England.In wet hollows and in extensive areas around the Danewell Gutter, a mosaic of boggy grassland and wet heath occurs, dominated by cross-leaved heath, purple moor-grass, heath rush and bog moss. Plants growing amongst these include white beak-sedge, bog asphodel and round leaved sundew. Horsell Common is probably one of the richest areas in Surrey for bees, wasps and ants, with 180 species having been recorded, including 15 species of spider-hunting wasps. Many solitary bees and wasps nest in exposed sand occurring alongside paths and on the faces of the sand pit. Other locally-distributed insects found within the site included the silver studded blue butterfly and a rare stilt-legged fly.

Many birds characteristic of heathland breed within the Common including nightjar, stonechat, Dartford warbler and grasshopper warbler.