Ecotalk, which manages a 250-acre rewilding project in the wood, released the beavers with the help of charity Green Britain Foundation (GBF).
Conservation officer and beaver lead for the GBF, Grace Garland, described beavers as a “keystone species” that had a “disproportionate” environmental impact compared with others.
She said: “When they back up the water, that’s creating breeding grounds for fish behind the dams…[and] taking out the trees is allowing more flora and fauna to come up for nesting birds.”
The beavers have the ability to restore wetlands, reduce flood risk, improve water quality and boost biodiversity.
With water levels rising since their introduction, Garland said the semiaquatic mammals had made an “incredible” difference in a short space of time.