The macroinvertebrate biodiversity and conservation value of garden and field ponds along a rural-urban gradient

The biodiversity and conservation value of semi-natural and field ponds in rural locations are widely acknowledged to be high compared to other freshwater habitats. However, the wider value of urban ponds, and especially garden ponds, has been largely neglected in comparison. This study examines the biodiversity and conservation value of aquatic macroinvertebrates in ponds along an urban-rural continuum over three seasons. Macroinvertebrate faunal richness and diversity of garden ponds (in both urban and sub-urban locations) was markedly lower than that associated with field ponds. The fauna recorded in garden ponds were largely a subset of the taxa recorded in the wider landscape. A total of 146 taxa were recorded from the 26 ponds examined (135 taxa from field ponds and 44 taxa from garden ponds); although only 10 taxa were unique to garden ponds. Garden ponds were frequently managed (macrophytes removed or sediment dredged) and contained artificial fountains or flowing water features which allowed a number of flowing water (lotic) taxa to colonise and persist. Despite the relatively limited faunal diversity and reduced conservation value of garden ponds they have the potential to serve as refugia for some taxa, especially Odonata with highly mobile adults. At the landscape scale, garden ponds provide a diverse and abundant range of freshwater habitats that could play an important role in conserving urban-macroinvertebrate biodiversity. However, for this to be achieved there is a need to provide guidance to home-owners on how this potentially valuable resource can help support freshwater biodiversity.