The destruction of ancient woodland is non-negotiable, Mr Paterson

The Environment Secretary's proposals for 'biodiversity offsets' raise serious issues

The Environment Secretary Owen Paterson has put forward proposals for "biodiversity offsets". This is a policy that will require developers to compensate for damage caused to wildlife habitats in one place by creating or restoring new ones somewhere else.

In an interview with The Times Mr Paterson suggested that ancient woodlands could be destroyed to make way for housing, so long as developers planted 100 new trees for each one felled. At first glance that seems a persuasive ratio but, on closer inspection, the proposal raises serious issues.

For a start, many of the little fragments of habitat that remain in the UK are, by definition, irreplaceable – ancient woodlands, for example. New plantings will not restore what has been lost, at least not for centuries. Others in this "no go" category, I'd say, include raised bogs, limestone pavements, certain kinds of heathland, ancient fen and old chalk grasslands.

While many remaining examples of notable habitats are protected in theory, development pressures are huge and mounting. The Woodland Trust is campaigning to protect the 33 ancient woodlands that would be affected by the HS2 rail project alone. The Wildlife Trusts are attempting to protect habitats from developments such as the proposed M4 extension across the Gwent levels, while the RSPB is embroiled in campaigns to conserve wildlife areas from housing development in Kent.This is why offsetting is such a hot topic, and why it is so vital to get it right. So what should Owen Paterson do?

It is important to place offsetting in its correct context. It requires a clear statement to the effect that rare, protected and other officially designated habitats should be sacrosanct. No development should be permitted in these last remnants of our native nature. In places with regional or local wildlife value, developers should be required to show that they have exhausted all other options before making an application.

If the case is made that development in lower-value green space is the only solution, then a nature enhancement and mitigation plan for the development site would be set out. At this point an offset that is subject to regulatory oversight should be compulsorily required, explicitly designed to achieve a "net conservation gain" and determined in consultation with conservation groups. Developers would pay for it.

Our Government's obsession with growth at any cost cannot be permitted to destroy nature's final surviving crown jewels. Ministers are working in Brussels to weaken EU conservation laws; at home, they have slashed the budgets of official conservation bodies and are now looking for ways to smooth the path for development, even in special areas.

Offsetting can be a way of channelling resources for conservation, but only if it is done right. We have not yet reached that point.

Tony Juniper's most recent book is 'What has Nature Ever Done for Us?'