Ancient woodland campaigners fear a drive to build more houses could put some of England's oldest habitats under increasing pressure, despite government protections designed to prevent their loss.
The protected areas can only be built on or near in "wholly exceptional circumstances", according to planning policy.
But the Labour government's pledge to build 1.5 million new homes by the end of 2029 and the recent creation of the "grey belt" - areas of poorer quality open spaces that can be built on - are leaving ancient woodlands at threat, campaigners say.
A spokesman for the Ministry of Housing, Communities and Local Government said ancient woodlands continued to benefit from "very clear and strong protections".
But the BBC has found dozens of individual sites which feature planned developments immediately next to the woods.
Among them are approved plans for 450 homes within yards of Hook Wood in Gillingham, Kent, which residents fear will have a devastating impact on local wildlife.
"We are already seeing cases where the existing protections are struggling," said Ancient Woodland UK chairwoman Lucy Graebe-Watson.
"We have seen a rise in concerns and alerts from local groups since recent planning reforms."
An ancient woodland is classed as existing continuously since at least the year 1600. The sites, described as "irreplaceable by Graebe-Watson, are considered some of the UK's richest habitats for wildlife.
The National Planning Policy Framework (NPPF), external guidelines for local councils deciding planning applications in England say woods can be built on in "wholly exceptional circumstances", such as major infrastructure projects like HS2.
But Graebe-Watson said the grey belt policy made it more likely areas directly next to ancient woodland - previously protected under green belt laws - could be developed.
In the East Midlands, the growing demand for housing is raising concerns about development proposals on land bordering Chaddesden Wood Nature Reserve in Derby.
Helen Cherry, who has lived nearby for 40 years, is among more than 1,500 people objecting to plans for about 150 houses there.
"The wood is at least 400 years old, with mature hazel and oak trees," said the former cafe owner, who regularly walks her dog there.
She said building to the edge of the ancient woodland would leave the site "closed on all sides", making a "mockery" of the nature reserve and undermining its protected status.
"Many a day I've been brought to tears, stopped and looked across the field where the buildings may occur and you can see right out across to the Derbyshire Dales," she added.
"It's absolutely beautiful. If houses went ahead, the view would be completely obliterated - it would be very sad."
Derby City Council refused the plans in 2025, but surveyors were seen at the site over the summer. People living near the site said they feared developers JGP Properties Limited would come back with amended proposals.
JGP Properties told the Local Democracy Reporting Service its assessments demonstrated "no loss or deterioration of the ancient woodland and veteran trees".
The Royal Society for the Protection of Birds said protections for irreplaceable habitats had improved under the recent changes to the NPPF.
However, Carl Bunnage, head of nature policy for the charity, said they remained inadequate.
He argued allowing development in "wholly exceptional circumstances" represented a loophole for developers, especially in areas with a shortage of houses.
He said planning reforms were in favour of development, with housing and economic growth policies often carrying greater weight than nature conservation.
"If we can give the strongest protections to built heritage features such as historic buildings, then why shouldn't we also be giving the strongest protections to those habitats?" Bunnage said.
In South Yorkshire, concerns are being raised over the impact of a 130-home development on land surrounding Gelster Wood.
It has sparked a campaign in the village of Rossington, near Doncaster, with residents worried the proposal could permanently alter a centuries-old landscape.
More than 2,000 people have backed efforts to challenge the plans.
A spokesman for the government's housing department said national planning rules "explicitly" stated developments that would cause the loss or deterioration of ancient woodland should be refused.
He added there were "very limited exceptions" to the policy, limited to some nationally significant infrastructure projects. He added in those cases compensation measures would be required.
The department said a revised NPPF published in August contained clearer policies for assessing development proposals affecting irreplaceable habitats.
