With rising temperatures there’s growing concern for some of our freshwater fish. Many UK fish have quite tight temperature ranges that they survive in and if the water gets too warm then it can change their behaviour and fertility. For important species such as trout and wild salmon the river water needs to stay below 20C. The problem is as the climate warms up so to does the streams and rivers. The problem is particularly of concern for the smaller streams and rivers which respond to air temperature changes much more than the deeper and larger rivers.
The solution to keeping the temperatures of rivers down could be as simple as planting woodlands along the river course. Research as just shown how tree cover over lowland streams can keep water temperatures 5C lower than streams running through treeless environments. That 5C can make the difference between the water temperature being habitable for fish or being too warm for their survival.
While it looks like the ideal solution to a problems – it’s green and sustainable – there are things that need to be considered. We need to remember that trees are not the favorite habitat of all creatures. A lot of wetland habitat require open countryside. Trees also can bring their own problems. A nutrient poor stream has it’s own rich diversity of life. Plant trees alongside it and leaves fall in the stream and decompose changing the nutrient make up of the stream which will impact on the stream ecology and local species. Sites chosen for this type of management will have to be chosen carefully, but this method does offer a real opportunity to mitigate freshwater habitats against climate change and increasing temperatures.
As Ms Broadmeadow – from Forest Research of the Forestry Commission - said, “Although more work is needed to refine its findings. However, this study will provide some reassurance that there are relatively simple, natural and sustainable measures that can be taken to protect fish populations and the biodiversity of our cold-water stream habitats from rising temperatures.”
photo credit : Margaret Anne Clarke
