Leading article: Our planet must discover a new way forward

Today sees some rare good news for the environment. The state of Para, in northern Brazil, will announce a plan to protect 16.4 million hectares of rainforest. This will outlaw any human activity not connected to conservation or research in the last great tract of untouched forest in Brazil.

We must be realistic about the prospects of success. The Brazilian government has made ambitious promises of protection for the rainforest in the past, but deforestation continues apace. During President Lula's first term of office, the removal of forest cover reached its highest level in history. A fifth of the Amazon has now been cleared. At this rate the Amazon rainforest will disappear entirely by the end of this century.

But the Para plan opens the prospect of a new way forward. While it creates a vast area solely for conservation, it also designates a number of zones for sustainable development for the benefit of local communities. Here, any logging or clearing will have to be offset by the panting of new trees. The plan thus acknowledges that Brazilians have a right to utilise their land's natural resources, but demands that it is done on a sustainable basis.

Part of the problem with President Lula's approach to protecting the rainforest over recent years has been that loggers have often simply flouted the law, by travelling deep into the interior to do their work. A local initiative should find it easier to crack down on illegal loggers. Para's initiative also suggests that a new breed of local governors, such as Para's Simao Jatene, are ready to take matters into their own hands. This reflects a welcome recognition that while deforestation may bring attractive economic returns for Brazil in the short term, it will ultimately prove a disaster.

But this initiative has implications that go far beyond Brazil. Sir Nicholas Stern's report on climate change argued that global forest conservation is as vital as cutting emissions in combating climate change. Rainforests are a vast carbon sink, extracting C02 from the atmosphere. If they are cleared, a vital stabilising agent is removed. And when trees are chopped down, a good deal of the carbon they have accumulated over the centuries is released. Deforestation thus has a doubly negative impact on the climate. Sir Nicholas strongly recommended that the international community work with nations such as Papua New Guinea and Costa Rica to promote sustainable forestry and prevent deforestation. But Brazil especially. The Amazon accounts for more than half the world's rainforest. Few countries can do more than Brazil to reduce the levels of carbon in our atmosphere. Para needs all the help it can get.

Yet the Stern report demands action from all of us. Sir Nicholas makes it clear that developed nations have a responsibility to "reduce consumer demand for heavily polluting goods and services". This has to mean dramatically higher tax rates on environmentally damaging modes of transport such as flying and driving. The Chancellor, Gordon Brown, must use his pre-Budget report this week to prove his green credentials.

He has a lot to prove. The Environmental Audit Committee warned over the weekend that, despite commissioning the Stern report, the Treasury has not been heeding recent warnings on climate change. Green taxes as a share of the national tax-take have fallen while Mr Brown has been at the Treasury. The fuel tax escalator was frozen in 2000. His rise in road tax rates for gas-guzzling vehicles in the last Budget was too small to have any real effect. The Chancellor has great power to change behaviour for the good of the planet. It is time he began to use it. From the Brazilian rainforest to the Treasury, business as usual is no longer an option.