Tiny, trickling streams, meandering rivers, gushing waterfalls and vast estuaries represent just some of the diversity of our natural watercourses. With such a variety of flow patterns, channels and meanders, coupled with a whole range of different bank habitats, rivers and streams provide shelter and feeding opportunities for a wide range of plants and animals.
Riffles and pools support aquatic species, while exposed sediments, like shingle beds, are important for invertebrates, notably ground beetles, spiders and craneflies. Wild flowers bloom in profusion along the banksides and are used by small mammals, butterflies and damselflies for shelter and basking.
Rivers and streams also provide wildlife with ‘corridors’ which they can use to move between fragmented habitats.
Where are they found?
Rivers and streams are found throughout the UK, although few have not been modified or affected by human intervention. Notable rivers in England and Wales include the Thames, Severn, Trent, Wye and Exe; while Scotland holds two thirds of all Britain’s river systems.
Why are they important?
Both the form and the wildlife of rivers and streams are affected by where they are in the country, their underlying geology and their water quality. In upland areas, running waters are typically steep, with a bed of rock and cobbles; their flow rates vary with heavy rain and snowmelt. These nutrient-poor rivers support sparse vegetation such as mosses and liverworts. Insects found here include stoneflies, mayflies and caddisflies, which are hunted by salmon and brown trout, and birds like dippers.
In contrast, lowland areas tend to have nutrient-rich watercourses, with beds of sand and shingle and a wide range of higher plants and coarse fish such as chub, dace and roach. These more stable habitats harbour rich and varied aquatic life including the rare lamprey, white-clawed crayfish and depressed river mussel.
Downstream, nutrient levels increase and rivers become more sluggish; in turn, diversity increases with aquatic plants like water-crowfoot and alternate water-milfoil providing cover for fish, and the early adult stages of damselflies and dragonflies. Seasonally wet meadows along the banks of these rivers provide vital habitat for breeding waders like lapwing and curlew, as well as a profusion of wildflowers such as ragged-Robin and cuckooflower.
Obviously our waterways support many species of fish including brown trout, eel, stickleback, pike, grayling, roach, perch and salmon. In turn, these rich supplies attract otters and other predators such as herons.
As well as providing places for wildlife, rivers and streams provide key services for people such as water supplies, recreational areas and flood defence. In fact, their provision of goods has enabled us to thrive – everything from agricultural and navigation, to defence, art and spirituality have relied on, and still rely on, our watercourses.
Are they threatened?
There are few rivers in the UK that we haven’t had an impact upon. Canalisation and tree removal has led to bank erosion, pollution has caused the devastation of species, dam and reservoir construction has changed water flows and the introduction of invasive plants and animals has had terrible effects. Added to this, our floodplains – natural places where rivers can deluge their loads after heavy rains – are threatened by development.
How are The Wildlife Trusts helping?
We have started to recognise that healthy rivers are important, not just for wildlife, but also to help prevent flooding. River and floodplain restoration projects carried out by local Wildlife Trusts are aiding these vital habitats by reinstating natural river courses and flow rates, improving bankside vegetation, providing homes for rare species like water voles and re-wetting floodplains.