Beavers could be the answer to reducing flooding in British towns, an extensive five-year trial has found.
The presence of the aquatic mammals, which have been living on the River Otter in south Devon, were found to have also benefited wildlife like fish, water voles, amphibians and birds.
Researchers found they provided more benefits to people and the landscape, including in the flood-prone community of East Budleigh, than the costs they caused.
The way the beavers ‘engineer’ the landscape creates wetland, water channels and marshy grassland, which provide homes for a wide range of wildlife including threatened water voles and wading birds, found the study.
The findings are the culmination of a five-year study of the first licensed release of beavers into the wild in England since they were hunted to extinction more than 400 years ago.
Beavers constructed six dams upstream of East Budleigh, which have measurably and significantly reduced peak flood flows through the community, the report said.
Evidence from another trial in north Devon, where beavers in an enclosure have built 13 dams and ponds, shows they also play a role in filtering soil, manure, slurry and fertilisers from farmland.
Despite concerns that beaver dams might affect fish populations, the opposite was discovered – there were 37 per cent more fish in pools created by damming the streams than in comparable stretches of the river with no dams.
The mammals have caused some localised problems for several landowners, but these could be addressed successfully with ‘active management’, said scientists overseen by Professor Richard Brazier from the University of Exeter.
Beavers flooded land at five sites, including a field with an organic potato crop, while there were also incidents of the animals eating maize and windfall apples and trees in riverside orchards.
But researchers said the majority of issues can be addressed by moves such as installing the beaver deceivers, which allow water to flow through a dam without the animals detecting and plugging the leak, or removing dams.
Beavers had been living wild on the Devon river for up to a decade when the trial began in 2015, but faced being re-homed in captivity after evidence emerged that they were successfully breeding.
Government agency Natural England approved a Devon Wildlife Trust proposal of a monitoring trial allowing the two beaver families to remain on the water.
There are now at least eight pairs of beavers, occupying the main River Otter and the connected Tale, as well as some smaller tributaries.
The species has been given protected status in Scotland, where it returned through an official trial and illegal releases or escapes, while England also has a number of fenced enclosures with beavers in to manage the landscape.
Devon Wildlife Trust’s Mark Elliott, who leads the River Otter Beaver Trial, said: ‘I think we’ve all been surprised by these amazing animals’ ability to thrive, once again, in our wetland ecosystems.
‘It also shows their unrivalled capacity to breathe new life into our rivers and wetlands, very few of which are in good health.’
He said beavers played a crucial role in the benefits society could get from healthy, naturally-functioning rivers and streams.
