Concerns have been raised over the fate of threatened wildlife such as red squirrels and nightjars in woods which could be sold to private companies under Government plans.
The Wildlife Trusts say that woodlands classed as "commercial" forest in proposals to offload the country's public forest estate to business, charities and communities, do still support rare wildlife which could be put at risk.
The plans put out to consultation last month divide the Forestry Commission's 258,000 hectare public forest estate into large and small commercial forest, which could be sold on a leasehold basis to timber companies, mixed-use woods and "heritage" woodland.
But Kent Wildlife Trust has raised concerns about forests classed as small commercial forests which are home to rare species ranging from nightjars and firecrests, to Heath Fritillary and Duke of Burgundy butterflies.
And Northumberland Wildlife Trust has labelled the proposals to sell Kielder Forest, which has been categorised as a large commercial forest, as "misguided", warning that breaking the forest up among a series of private owners could risk England's greatest stronghold for red squirrels.
Northumberland Wildlife Trust's chief executive, Mike Pratt, acknowledged the habitat was sub-optimal for red squirrels, but said it supported about 70% of the English population because grey squirrels, which elsewhere compete with reds and spread disease to them, fail to thrive among the conifers.
It is also home to birds such as goshawks and crossbills, while another Forestry Commission forest in Northumberland, Kidland, has one of England's rarest animals - the pine marten.
Mr Pratt said he was concerned about the "over-simplicity of trying to categorise forestry into commercial and non-commercial and the assumption that purely commercial crops don't have wildlife value - they do".
At the moment, the timber operations pay for conservation measures within the multi-use forest, he said, a benefit which would be lost if the commercial plantations were sold.
And fragmentation of the woods, which are currently well managed for conservation by the Forestry Commission, among different owners would make it harder for the forest to be managed successfully as a whole for conservation.
"It would mean a patchwork quality in terms of the impact on wildlife, in some places it might be good, but some may be a lot worse," Mr Pratt warned.
He said promises to include wildlife measures in the terms of the leases under which the commercial sites would be sold would ensure a bare minimum in protection, but would not guarantee the conservation management which the Commission currently delivers in the forest.
Kent Wildlife Trust's head of conservation and policy Richard Moyse agreed, warning that for wildlife to be protected, the leaseholds would have to set out a detailed management plan for the site, and private owners may not earn enough from timber operations to undertake conservation measures.
He said that in a number of the county's woods, the Forestry Commission was taking targeted conservation action, particularly for butterflies.
"If there is no driver for whoever owns the woods in the future to continue that, then the future is very bleak," he said.
Kent Wildlife Trust is concerned about one multi-purpose site, Bedgebury Forest, which under Forestry Commission management has plans that aim to restore ancient woodland and heathland, and five small commercial woodlands.
They include Lyminge Forest which is a breeding site for firecrests and two of the largest populations of lady orchids, Denge/Eggringe Wood which contains Kent's only population of threatened Duke of Burgundy butterflies, and King's Wood which is home to nightjars.Reuse content