1. In 1986 work began which led to the foundation of Pond Conservation, the UK NGO which promotes the conservation of ponds and other freshwater habitats. In 1989 the organization initiated the UK National Pond Survey (NPS) to provide baseline data on the biota and physico-chemical characteristics of ponds. 2. Survey data have been used to demonstrate the importance of small water bodies for freshwater plants and animals, to establish techniques for assessing the ecological status of ponds and to provide the basis for a new national pond monitoring network in the UK. 3. Comparisons with extensive river and lake datasets show that, at a UK level, ponds support slightly more macro invertebrate species than rivers, and more uncommon species. They support similar numbers of wetland plants to lakes. Farmland ponds generally have lower site diversity than rivers;, however, in terms of regional diversity they make a greater contribution than other aquatic habitats. 4. Although ponds are an important biodiversity resource, studies have shown that ponds outside nature reserves Lire significantly degraded: thus ponds in the lowlands supported only half the number of wetland plant species that would be expected in minimally impaired ponds. 5. The environmental factors most highly correlated with species number and rarity in minimally impaired ponds were area, isolation, PH (and the related chemical measures alkalinity, calcium, conductivity) and abundance of vegetation. 6. Studies of degraded ponds showed strong negative relationships between potentially damaging environmental factors (e.g. intensive land use, nutrient levels) and species richness and rarity. 7. Although considerable progress has been made in characterizing the plant and invertebrate assemblages of ponds, comparatively little is known about the way ponds function or how they are affected by management. Given the importance of ponds in maintaining aquatic biodiversity at the landscape scale, further research is needed on ponds in the catchment context. Copyright (c) 2005 John Wiley & Sons, Ltd.
