Thousands of hectares of tree-covered heaths, which could be sold by the government, should be restored for wildlife, say conservationists.
Part of the public forest estate is to be sold to commercial timber companies, raising concerns for 30,000 hectares of woodland planted on heaths.
The government is consulting on plans to offload up to 100% of England's 258,000-hectare public forest estate
The RSPB says England has lost five-sixths of the heathland it had in 1800.
And is also says only 0.2% of the country's land is covered in heaths, which support wildlife that ranges from nightjars and Dartford warblers to tiger beetles, sand lizards and rare butterflies.
Mark Avery, RSPB conservation director, said: "Whoever owns our forests, it is vital that areas of lowland heathland which are planted with conifers are restored to benefit species like sand lizards, Dartford warblers, nightjars and natterjack toads."
The public forest estate is currently managed by the Forestry Commission.
A spokesman for the Department for Environment, Food and Rural Affairs said: "We will set out our ambitions for landscape-scale habitat restoration in the forthcoming Natural Environment White Paper and the new England Biodiversity Strategy and following the consultation on the public forest estate."