Scientists from around the world have urged the Canadian government to take action to protect its northern landscapes. They claim that development is threatening one of the last great tracts of woods and wetlands on Earth.

In a 14 May letter delivered to Bob Mills, chair of the environment committee in Canada's House of Commons, 1,521 scientists from 51 countries asked the Canadian government to support the principles that were laid out in the 2003 Boreal Forest Conservation Framework.

That agreement between industry, indigenous people and conservation groups said that at least half of the 6 million square kilometres of boreal region should be off-limits to development, and the rest should be managed sustainably. The boreal region contains forest, wetland and other landscapes, and covers much of northern Canada.

Provincial governments are left free to support unlimited development.

The campaigners say that the region is crucial to ecosystems worldwide. It serves as a breeding ground for 3 billion migratory birds, and is an important source of fresh water and the largest terrestrial carbon sink on Earth. So far, it has sequestered more than 180 billion tonnes of carbon.

One of the letter's signatories is Ken Caldeira, a climate modeller at the Carnegie Institution based at Stanford, California, who last month published a study suggesting that the total destruction of Canada's boreal forests would actually ease global warming (see Nature, doi:10.1038/news070409-2; 2007). Some say that press coverage of the study raised public doubts about the need to conserve the boreal region. “It is certainly something we are struggling with,” says Jeff Wells, science adviser for the International Boreal Conservation campaign in Seattle, Washington.

Canadian prime minister Stephen Harper has said that he will designate almost 100,000 square kilometres of land in the Northwest Territories as protected, but those deals have yet to be finalized. That leaves provincial governments free to support unlimited development, says David Schindler, a boreal ecologist at the University of Alberta in Edmonton.