Ponds are high profile freshwater habitats of interest to the general public and scientific community. Some ponds can be extremely ancient and may have occupied prominent positions in the landscape or life of a community. Ponds support a substantial proportion of the native British freshwater flora and fauna. It is estimated that 400 species of aquatic higher plants can be found in and around ponds and 50% of the aquatic invertebrate species are likely to be found in ponds (Drake, 1995). Some of these species are considered nationally rare. For example, Drake (1995) states that approximately 150 of the 280 wetland invertebrates listed in the Red Data Books (Shirt, 1987;Bratton, 1991) occur in ponds.
Ultimately ponds are transient habitats as their basins accumulate sediment and diminish in extent as a result of vegetation succession. In addition, activities such as land drainage, land-fill and water pollution can have detrimental effects on the natural ecology of ponds. Therefore the maintenance of the biodiversity supported by ponds is dependent on the protection of existing ponds and the creation of new pond habitat. A recent survey illustrated the size of the resource with an estimate that in 1990 there were just over 300 000 standing waters in Britain, with 90% smaller than 0.2 ha and considered `ponds' (Barr et al., 1990). However, the rate of pond loss in the previous six years was in the range 4% to 9%. A smaller re-survey in 1993 suggested that new ponds created for farming and wildlife reasons were beginning to offset earlier losses and highlighted the contribution that conservation projects can make towards the protection of this aquatic habitat.
As statutory public bodies with a responsibility for the promotion of nature conservation, the Countryside Council for Wales (CCW) and the Environment Agency play an important role in pondrelated issues. Advice on pond creation and management is one of the most frequent information requests received by CCW staff from the public and other organizations active in conservation. Ponds have been created on some nature reserves owned or managed by the CCW with the intention of adding to the biodiversity of a site. Individual ponds and groups of ponds have been designated as aquatic Sites of Special Scientific Interest (SSSIs), and have also been recognized as important components of several large mixedhabitat SSSIs. Pond creation is a component of the Tir Cymen farmland stewardship scheme (CCW, 1992) managed by the CCW.