A flagship rewilding project in West Sussex has recorded a staggering 916% increase in breeding bird numbers since 2007, with new ecological surveys revealing an unprecedented explosion of wildlife at Knepp estate. The 20-year review shows species richness has more than doubled, while butterflies, dragonflies and damselflies have soared to record levels at the estate.
The southern part of the estate saw breeding bird populations surge from just 55 individuals of 22 species in 2007 to 559 individuals of 51 species in 2025. Around 27 species of conservation concern now breed at Knepp, including 12 red-listed birds facing severe population declines across Britain.
Nightingales have become a remarkable success story. The estate now hosts 62 singing males, up from just nine in 1999 before rewilding began. Knepp now accounts for around 1% of the entire UK nightingale population. Turtle doves, another critically threatened species, increased from two singing males in 2008 to 22 in 2024, though numbers dropped to 14 in 2025.
Other species showed explosive growth. Common whitethroats increased by 2,200% between 2007 and 2025, while lesser whitethroats rose 1,000% and chiffchaffs 1,150%. Even wrens, a typically common bird, saw numbers jump 500%.
Insects flourish across estate
Butterfly species in the middle and northern parts of the estate increased 107%, with surveys recording 283 purple emperor butterflies in a single day in 2025. Dragonflies and damselflies showed an 871% increase between 2005 and 2025, with species diversity up 53%. Red-eyed damselflies alone surged 2,000% over five years.
Ecologist Fleur Dobner said the transformation was dramatic. "We've gone from a very open monoculture landscape to a real mosaic of parkland, scrubland, billowing hedgerows, open glades, rides and grassland. It's a positive trajectory and it's increasing still, year-on-year, we're getting higher and higher numbers of what we're recording," she said. The "biodiversity uplift is huge," Dobner added.
How rewilding transformed the land
The project began in 2000 when owners Isabella Tree and Charlie Burrell halted conventional farming. They introduced large grazing animals including longhorn cattle, red and fallow deer, Exmoor ponies and pigs to restore natural processes. The animals create diverse habitats through their grazing and foraging patterns. The estate has also restored the river and introduced beavers to create wetlands, while reintroducing white storks.
Tree said they had "absolutely no idea" what would happen when they started. "We were a depleted, polluted farmland, so any uplift in nature was going to be positive. Of course, in a rewilding project you don't have goals, don't have targets and so we weren't striving for anything in particular, we were literally sitting back and seeing what would happen," she explained.
The insect abundance proved "absolutely key, because that's what counts in the food chain," Tree said. She told the Press Association that "every single day is astonishing" at Knepp, citing a recent sighting of a white-tailed eagle being mobbed by red kites and white storks over the beaver wetland.
Tree said the results challenge assumptions about what nature reserves can achieve. "We're actually showing that nature reserves can be much more ambitious for the carrying capacity of the land, which is exciting," she said.
The project is reversing the "shifting baseline" phenomenon, where gradual environmental decline becomes accepted as normal, with birders now "blown away" by the numbers and insect experts discovering rare species not seen in West Sussex for 50 years.
Note: This article was created with Artificial Intelligence (AI).
