Glaciers, climate warming and stream ecology

Posted on June 26, 2010


Recent reviews of the impacts of glacial change on stream hydrology and ecology note that glaciers have shown a consistent retreat over the last 20-30 years, and that continued climate warming over the next century is likely to lead to significant changes to glacier-fed streams.  In response to warming trends, streamflows are predicted to rise initially, but then fall to a lower level due to glacier retreat and a reduction in the area available for snowmelt.  Recent modelling for the BridgeRivercatchment in British Columbiapredicts a long-term decline in glacier area and summer streamflows of around 30%.  Other work suggests that a 10% loss in glacier cover would increase stream temperatures by 1.2 – 1.6% in summer.   This is likely to be ecologically significant since, for example, a warming of 2oC in water temperature is sufficient to produce a shift in the dominant species of trout by affecting the balance of competition.  Increased temperatures will encourage higher levels of biological production and species diversity, but lower flows will slow the movement of nutrients downstream, reduce the availability of side channel habitats, and favour organisms with less streamlined and flattened body shapes.  As glaciers retreat they initially deliver more sediment to streams, which can alter channel morphology and water quality.   However, in the longer term, sediment transport is more likely to decline as glacial erosion and runoff decrease.  Non-environmental impacts will also be felt, including a reduced capacity for hydropower generation as a result of lower streamflows.

References:

Moore, R.D., Fleming, S.W., Menounos,B., Wheate, R., Fountain, A., Stahl, K., Holm, K. & Jakob, M.  2009.  Glacier change in western North America: influences on hydrology, geomorphic hazards and water quality.  Hydrological Processes  23, 42–61. 

Milner,A.M., Brown, L.E. & Hannah, D.M.  2009.  Hydroecological response of river systems to shrinking glaciers.   Hydrological Processes. 23, 62–77.

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