After years of uncertainty, England's first wild breeding population of beavers for 400 years will now become permanent residents of the River Otter.

The decision announced today by Defra is a landmark one, as it signals the first legally sanctioned reintroduction of an extinct native mammal to England. It means that the beaver population, which lives on the River Otter and is estimated to consist of up to 15 family groups, now has a secure future.

The announcement comes after the successful completion earlier this year of a five-year trial overseeing the animals and their impacts led by the charity Devon Wildlife Trust.

In February the project published a 'Science and Evidence Report' overseen by independent researchers from the University of Exeter. This concluded that the beavers' presence had brought benefits to people and wildlife living along East Devon's River Otter.

Key findings in the report highlighted how:

-Other wildlife – especially fish, insects, birds and endangered mammals such as water voles - had greatly benefitted from the beavers' presence because of the ways in which beavers enhance wetland habitats.

-The beavers' dam building activities had also helped reduce the risk of flooding to some flood-threatened human settlements.

-The positive role that beavers could have in improving water-quality, with their dams acting as filters which trap soil and other pollutants from surrounding farmland.

-The report highlighted some localised problems for a small number of landowners where beavers were present, but that these had been successfully managed with support and intervention from Devon Wildlife Trust.

Peter Burgess, Director of Conservation at Devon Wildlife Trust, said: "This is the most ground-breaking government decision for England's wildlife for a generation. Beavers are nature's engineers and have the unrivalled ability to breathe new life into our rivers and wetlands. Their benefits will be felt throughout our countryside, by wildlife and people.

"At Devon Wildlife Trust we've worked hard with our partners and local communities along the River Otter over the past five years to see what impact beavers have had. In that time their population has grown steadily so that they have successfully colonised nearly all of the river's catchment. As their numbers have grown so has local people's awareness and appreciation of them. We're delighted that these beavers have now been given leave to stay permanently."

Beavers were driven to extinction in the UK more than four centuries ago as they were hunted for their meat, fur and castoreum – a highly prized secretion used in medicine and perfumes.

In 2013, a family of the semi-aquatic rodents – which can grow to more than 20kg and live on an exclusively vegetarian diet (they do not eat fish) – were found to be living on the River Otter in East Devon. The population's origins are still unclear and at first they were threatened with removal by officials.

In 2014, with local community support, Devon Wildlife Trust and a partnership including the University of Exeter, Clinton Devon Estates and the Derek Gow Consultancy, successfully secured a license from government which would allow the beavers to stay and be studied over a five-year period.

This license established the River Otter Beaver Trial which ran until August 2020. Today's decision that the beavers can remain permanently in their Devon home is based on evidence submitted by the Trial.

Devon Wildlife Trust's Mark Elliott has led the charity's beaver work since its beginnings in 2010. He said: "Our rivers and wetlands really need beavers, and this is brilliant news. Those of us involved with the Trial have seen just how critical beavers are for restoring more naturally functioning rivers, which will be so important during the ecological and climate emergency that we now face.

"Naturally functioning rivers support healthy fish populations and also protect us from the extremes of weather that can bring so much misery to communities that live in floodplains, and to those suffering from acute water shortages in summer.

"Whilst this announcement by Defra is very welcome, it's now vital that decisions are made on the national status of beavers that allows them to be reintroduced into other river systems in England.

"There also needs to be funding to support landowners who wish to allow beavers to restore wetlands on their land, and to assist landowners who do not wish beavers to affect their farming practices. This is vital if we are to see beavers welcomed back into the English landscape after such a long absence."

Professor Richard Brazier led the University of Exeter research team which has studied the impacts of the Devon beavers. Prof Brazier said: "I welcome today's announcement that safeguards the future of the River Otter beavers. The outcomes of our 5 year study demonstrate the wide range of positive benefits that beavers can bring.

"These include flood attenuation, water quality improvement, carbon storage, greater biodiversity and socio-economic benefits to local businesses through wildlife tourism. We show that any conflicts can be managed swiftly and efficiently and also that the benefits of beavers far outweigh any costs associated with their management.

"Finally, our research illustrates that the overwhelming majority of society would like to see this native species return to our waterways. It is therefore encouraging to see government support for reintroduction of this iconic species, in line with the ambitions of their 25 Year Environment Plan."

Dr Sam Bridgewater, Head of Wildlife Conservation at Clinton Devon Estates, said: "Clinton Devon Estates has been proud to have played a key role in the delivery of the River Otter Beaver Trial (ROBT). Through our involvement with the Trial we have seen at first hand the benefits beavers can bring to society.

"We have also seen the conflicts that can arise and believe that there is a need to manage this species going forward. The ROBT partnership has recommended an approach to management to help avoid the negative impacts of these creatures whilst allowing benefits to be maximised. Alongside all members of the ROBT we are calling for the government to support this.

"The strategy includes ensuring that landowners are supported financially to make more space for water, so that land-based businesses can co-exist alongside beavers and their wetlands."

Craig Bennett, Chief Executive of The Wildlife Trusts said: "This is fantastic news and a great testament to all the hard work of Devon Wildlife Trust and their partners. It's not enough to talk about conserving wildlife anymore – instead, we need to reverse these declines and put nature into recovery, and help create robust, flourishing, fully functioning ecosystems at landscape scale once again. Beavers will play an important role in this.

"Now we need to see the Government produce a national beaver strategy which will provide a roadmap for their future across the rest of the country."