Urban Waterways Can Be Wildlife Rich Too
Despite the frequent public preconception that urban waterways such as canals and ditches are polluted eyesores, devoid of almost all wildlife, recent research has shown that they can have more macroinvertebrate diversity than similar water systems in rural areas. They can also provide habitat for several endangered species.
Urban habitats may provide an important refuge for biodiversity in the face of climate change and increasing fragmentation. However, to date there has been little data provided to assess the conservation value of urban areas, and very few studies focusing on urban water systems.
A new Dutch study compared the biodiversity value of urban waterways in two towns in the Netherlands with natural and manmade drainage systems in rural areas, such as small streams and rivulets. Macroinvertebrate species, including snails, mites, flies and exotic crustaceans, were studied.
Urban waterways with low levels of nutrients (particularly nitrogen and phosphorous), were found to have the highest diversity of macroinvertebrates, and the highest number of endangered species. Waters with high levels of nutrients and poorly developed vegetation meanwhile had low macroinvertebrate diversity. The number of exotic crustaceans was high in nutrient-rich waters, probably because they are better able to cope with harsher conditions, such as low oxygen levels, than native species.
The researchers concluded that the key factors for macroinvertebrate biodiversity in urban water systems are levels of nitrates, sediment composition, transparency and submerged vegetation.
For further information, please see: Vermonden, K., Leuven, R.S.E.W., van der Velde, G. et al. (2009). Urban drainage systems: An undervalued habitat for aquatic macroinvertebrates. Biological Conservation. 142: 1105-1115.
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