Bringing Eurasian Beavers to an estate in Essex has delivered improvements in biodiversity while helping prevent flooding in a nearby village.

The positive consequences of reintroducing a species that became extinct in Britain in the late 18th century were described by Sarah Brockless, ecologist at the Spains Hall Estate, when she gave the Gerald Salisbury Memorial Lecture in Welwyn Civic Centre on Wednesday 28 February.

Photo: Eurasian Beaver at Spains Hall Estate © Russell Savory

Spains Hall itself is now home of celebrity chef Jamie Oliver, but the surrounding estate of 830 hectares is still owned by the Ruggles-Brice family who have lived there since the 1760s. The decision to release two adult beavers into an extensive 4.45 hectare enclosure in May 2019 was taken to diversify woodland and the surrounding farmland, while tackling flooding affecting the ‘picture-book’ village of Finchingfield.

Breeding success means that up to 14 Beavers (the world’s second-largest rodent) now occupy an enclosure whose dams have transformed a former plantation into a wildlife-rich mosaic of ponds, pools, ditches and sunken woodland. They have also slowed a stream flowing towards the village and spread water onto surrounding land.

Photo: Beaver enclosure at Spains Farm Estate viewed from the air © Dave Gasca

Remarkably, the beaver dams hold back an estimated 55 mega-litres of water. Combined with man-made ‘leaky dams’ on another tributary of the River Blackwater they have prevented further flooding in Finchingfield since their introduction.

The dams simultaneously halt the progress of sediment containing fertiliser – with a result that vegetation in the enclosure has become noticeably lush. The ground flora has diversified, while the number of water invertebrates, fish and frogs has increased dramatically. 

Photo: Beaver-created habitat at Spains Hall Estate © Sarah Brockless

Kingfishers have returned to nest and the change is benefitting Marsh Tits, Chiffchaffs and Willow Warblers among other bird species. An impressive list of bat species has been detected, while Oxlips, scarce moths and resident Dormice have also benefitted.

Sarah said: “I think it’s a great demonstration of what you can do if you just put a few simple things together.”

Success has led to the creation since 2022 of two further beaver enclosures on former farmland on the floodplain.

However, Sarah emphasised that reintroducing beavers would not be suitable as a measure to increase biodiversity everywhere. Their dams would be poorly suited to valleys with steep sides and could impact adversely on migratory fish populations. They also have the potential to inflict damage on water-supply infrastructure if allowed to spread freely in urban areas.

Nevertheless, ‘wild’ populations already exist due to illegal releases. Sarah’s prediction was that after 200 years of evolving without beavers in Britain, humans may soon require education on how to live with them.

The Gerald Salisbury Memorial Lecture, attended by almost 70 people, was jointly organised by the HNHS and Welwyn Natural History Society.