Thornhill, I,. Ledger, M., Batty, L. Urban ponds and small lakes: A challenge and opportunity for maintaining aquatic biodiversitiy in urban landscapes. The International Association for Ecology (INTECOL) Congress, ExCel London, UK, August 2013
Rural ponds have been shown to contribute significantly to regional biodiversity. However, their biodiversity in urban areas has been largely overlooked. Urban ponds face a number of stressors due to the process of urbanisation including habitat loss and contaminated surface run-off from impermeable surfaces. This talk presents the main findings of a geographical information system (GIS) survey of the historical Birmingham, UK, pond-landscape and a field study of 30 ponds distributed across the conurbation. We investigated the conservation value of urban ponds and the local (water quality, physical habitat) and spatial (land-use, connectivity) factors that influence community composition.
Since ca1904, >80% of ponds in Birmingham have been lost due to land-use intensification, resulting in an increasingly diffuse pond network with lower spatial resilience. In addition, the majority of ponds were highly eutrophic. Despite this, a total of 193 macroinvertebrate taxa from 14 orders were found across the 30 ponds with a median species richness of 32, which compares favourably to other studies. Ponds that were macrophyte-rich and well connected supported macroinvertebrate assemblages of high conservation value.
Statistically, local physical variables such as shading and macrophyte complexity explained more variation, both in water quality and macroinvertebrate community composition than regional factors such as the degree of urbanisation (impermeable surface within 100m) and connectivity (within 1000m).
The results indicate that many urban ponds are threatened habitats that require active management to protect and restore water quality, biodiversity and ecosystem functioning. However, urban ponds may present a more tractable management option for freshwater conservation in urban areas owing to their discrete boundaries and relatively small catchments when compared to lotic systems.