Ecosystem function in urban rivers: what effect does restoration have?

Over the last 20 years there has been an increasing focus on the restoration of urban rivers to improve river environments and provide aesthetic and recreational value. Given the large number of stressors affecting urban rivers, however, it is unclear whether restoration at the reach scale leads to improvements in river ecology. In order to evaluate the impact of urban river restoration this poster presents the results of new research on ecosystem function in London rivers. Rates of leaf litter decomposition were assessed at 10 pairs of restored-unrestored sites on tributaries of the Thames as an integrative way of evaluating ecosystem function. Despite large differences in decomposition between sites on different rivers, little difference was found within restored-unrestored pairs of sites. This suggests that water quality, rather than reach-scale habitat availability, is the dominant constraint on ecosystem function in urban rivers. Assessing ecosystem function rather than simple habitat availability provides a more robust measure to assess the status of river ecosystems. If restoration is to achieve its goal of improving river ecology then reach-scale habitat improvement must go hand-in-hand with programmes to address stressors such as sewer misconnections and stormwater run-off.