A major scheme has begun on Exmoor to clear harmful invasive species from the National Park's waterways.
Non-native plants like Japanese Knotweed, Himalayan Balsam and Skunk Cabbage are being removed, along with American crayfish which have been damaging riverbanks on the moor.
The River Barle flows through a Site of Special Scientific Interest and is an important habitat for kingfishers, dippers and other wildlife.
But American Signal crayfish, a species not native to this part of the world, has been eating the eggs of salmon and trout, and burrowing into the riverbanks.
This means the sides of the river become eroded, the silt slows the general flow of the river and affects the whole dynamics of the system.
They're also responsible for a 75% decline in our native White-Clawed crayfish.
On this stretch of the river near Withypool, teams of volunteers have spent the past four years setting traps so that dominant males can be caught and sterilised to control breeding.
The project to clear invasive non-native plants and animals on Exmoor is now being radically scaled up with a £185,000 grant.
More volunteers will be recruited as the scheme expands and new techniques will be tried out such as electrocuting the roots of invasive weeds.