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 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 is 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, he said.