Countering warming by streamside planting

Posted on December 15, 2011

Global biodiversity hotspots support unusually high numbers of species but are threatened by climate change and habitat loss.  Southwestern Australiawas one of the first biodiversity hotspots to undergo significant climate change, in the form of increased temperatures and reduced rainfall over the last century, and as a result is attracting interest as a potential climatic bellwether area.  Temperatures in southwestern Australiaare predicted to rise by 2oC by 2050.  However, many freshwater species in the region are cool water forms with an upper temperature tolerance of about 21oC, and this temperature is already often exceeded in cleared catchments.  The good news is that field measurements and modelling suggest that rises in stream temperatures can be controlled by planting bankside vegetation to boost shade.  It seems that 50-70% shade is required to keep temperatures below the critical 21oC level.  In general, a 10% increase in shade gives a 1oC decrease in temperature, a rule of thumb that should apply to other global biodiversity hotspots.  Priority should be given to the revegetation of east-west running streams, with the northern banks being targeted in the southern hemisphere.

Reference:  Davies, P.M.  2010.  Climate change implications for river restoration in global biodiversity hotspots.  Restoration Ecology 18 (3), 261–268.