9. Understanding and Managing Climate Change Effects on River Ecosystems
- Philip J. Boon3 and
- Paul J. Raven4
Published Online: 17 FEB 2012
Copyright © 2012 John Wiley & Sons, Ltd
River Conservation and Management
How to Cite
Ormerod, S. J. and Durance, I. (2012) Understanding and Managing Climate Change Effects on River Ecosystems, in River Conservation and Management (eds P. J. Boon and P. J. Raven), John Wiley & Sons, Ltd, Chichester, UK. doi: 10.1002/9781119961819.ch9
Scottish Natural Heritage, Edinburgh, UK
Environment Agency, Bristol, UK
- Published Online: 17 FEB 2012
- Published Print: 23 MAR 2012
Print ISBN: 9780470682081
Online ISBN: 9781119961819
- river temperatures;
- environmental stress;
- ecosystem function;
- adaptive management;
The realization that rivers are highly sensitive to climate change has been among the defining issues of the last 20 years in river conservation. This chapter outlines some of the empirical evidence for effects, but also draws attention to considerable knowledge gaps that limit the ability to implement adequate management responses with confidence.
Extensive data from Europe, North America, Asia and Australia show that some rivers have warmed over the last 20-30 years or more by 0.1-1.0 °C per decade. This is consistent with increasing ambient air temperature. While increased insolation is the most likely cause of summer warming, long-term heat budgets are required to assess whether altered heat transfer, advection from warmer groundwaters or reduced heat loss from rivers might have contributed to winter warming.
Long-term changes in river discharge are more difficult to identify because inter-annual variations can exceed 350% in temperate regions. There are some suggestions of increasing seasonality locally as well as large-scale changes in continental runoff, but the relative effect of anthropogenic contributions is not yet clear.
Despite considerable difficulties in interpretation, ecological changes consistent with either warming or varying discharge have been identified in Europe, North America and Australia. They include alterations in species abundance and community composition, the occurrence of rare or endemic species, trait structure, body size and emergent properties such as food webs. Effects appear to be complex, involving multiple phenomena, and they are highly dependent on local context, varying for example between alpine, temperate and desert locations. There is a dearth of evidence of climate change effects on groups other than fish or invertebrates.
Beyond its ecological significance, climate change engenders threats to the conservation of important species or habitats; for example, it is likely to affect river restoration and management and therefore progress towards management targets for ‘good ecological status’. It could confound the bioassessment of river water quality unless correctly diagnosed and will also affect critical ecosystem goods and services for which rivers are crucial.
We suggest that there are large knowledge gaps about climate change effects on rivers with respect to: (i) the exact ecological mechanisms involved; (ii) interactions with other stressors such as pollution, land-use change and abstraction; and iii) the effectiveness of different management options. The last of these is particularly acute and threatens to undermine support for actions that, if implemented, could have wider conservation benefits beyond climate change adaptation.