Stormwater ponds can contain comparable biodiversity to unmanaged wetlands in urban areas
Urban freshwaters provide a range of ecosystem services, including stormwater management, water treatment, biodiversity, and aesthetics. Management of freshwaters should aim to maximise as many of these services as possible, but managers are often focused on individual services. To test for the biodiversity value of stormwater management ponds (SMPs) in Ottawa, Canada, 20 SMPs were surveyed for macroinvertebrates using standardised sampling techniques. These were compared against 10 wetlands that were not managed for stormwater control (a combination of ornamental lakes, natural lakes, and nature reserves) in and around the same urban area (a total of 30 ponds). Natural wetlands and SMPs were very different in their water chemistry, which was correlated with the proportion of urban land use within 1 km of the site, with higher conductivity in SMPs with increasing urban land cover (P = 0.046). Despite this, natural wetlands and the richest SMPs contained similar levels of biodiversity and similar macroinvertebrate community structure. This study highlights that stormwater management can occur alongside biodiversity enhancement in urban areas, but correlations between urban land use, water chemistry, and the structure of biological communities suggests that run-off from urban areas is likely a major factor in structuring biological communities in built-up regions.