The Engineer

River habitats threatened

News

According to research by the UK Environment Agency, fish, invertebrates and other water species will be the first to feel the devastating effects of climate change as river temperatures rise, and more frequent flooding and drought change traditional river habitats.

Fish such as Atlantic salmon and trout, which need cold water to thrive, may struggle to survive. As river temperatures have risen, there is evidence that they are already declining in the warmer estuaries and rivers in the south of England. Invertebrates, which form an integral part of the aquatic food chain, are also under threat, with numbers falling by around 20 per cent for every one degree rise in temperature in sensitive upland streams.

While some native plants and animals decline with increasing temperatures, foreign species could spread rapidly, killing off native species and habitats, and even causing flooding. African Clawed Toads, which carry a fungus lethal to other amphibians and eat the fry of our native fish, already have small colonies in England and Wales. If temperatures continue to rise as predicted, this species could breed and spread easily throughout the UK.

The Environment Agency further claims that fast-growing plants such as South American water primrose could take over Britain’s waterways helped by warmer temperatures, impeding water flow and increasing flooding. Without the colder temperatures that keep them in check, some alien fish species could become pests, crowding out other fish popular with anglers and even destroying habitat.

Climate change is also causing sea levels to rise, destroying areas of salt marshes and mudflats that migrating birds such as redshank, plovers and wildfowl have used for centuries as a winter refuge.

Lord Chris Smith, chairman at the Environment Agency, said: ‘What we see in our rivers, gardens, seas and skies here in the UK is already changing and delays in reducing harmful greenhouse gas emissions will lead to more severe impacts.’

Prof Steve Ormerod of Cardiff University School of Biosciences said: ‘Rivers and streams, particularly in the cooler uplands of Britain, are extremely sensitive to climate change because rising temperatures and altered rainfall affect them directly.

‘Our own studies in Welsh streams show that temperatures have risen by almost two degrees over the last 25 years and these changes appear to have affected river insects, whose numbers have fallen by around 20 per cent for every one degree rise. Knock-on effects are inevitable for the fish, birds and bats that use river insects as food.’