A UN plan to protect the world's tropical forests to fight climate change could threaten more animals and plants with extinction, according to scientists.
The UN scheme, to be discussed at climate talks in Copenhagen next month, could save some species, while inadvertently endangering many others, according to the team of international researchers.
Under the plan, called Redd, or reduced emissions from deforestation and degradation, poor countries will be paid to protect their trees to try to reduce carbon dioxide emissions.
Funded by a carbon market, it will let rich nations cut their emissions more cheaply.
In a paper published in Current Biology magazine, the scientists warned that the market may target forests that are cheap to protect and rich in carbon and neglect those that have less carbon but more endangered animals and plants.
"We are concerned that governments will focus on cutting deforestation in the most carbon-rich forests, only for clearance pressures to shift to other high biodiversity forests which are not given priority for protection," said the team's joint leader, Alan Grainger, of the University of Leeds.
Clearing forests for timber and farmland emits nearly a fifth of the greenhouse gases blamed for climate change, according to UN estimates. Deforestation has threatened species such as the mountain gorillas of Africa and the giant pandas of Asia.
The scientists, from Britain, the US, Germany, Switzerland and Singapore, said concentrations of carbon and biodiversity in tropical forests only partially overlap. They said up to 95 per cent of damage to Redd-protected forests could be displaced to nearby unprotected forests.
Their report cited the example of the Peruvian Amazon, where the creation of forest reserves contributed to a 300 to 470 per cent rise in damage to forests in adjacent areas.
State workers and public money may be switched to Redd forests, leaving unprotected areas at risk, the paper said.
The scientists also fear that Redd could, perversely, lead countries to delay forest protection measures that they might otherwise have taken anyway, as they await the new agreement and the rewards it might bring.
They urged countries meeting in Denmark to add rules on safeguarding biodiversity to the text of any deal and consider giving incentives to poor nations that address the issue.
"Despite the best of intentions, mistakes can easily happen because of poor design," Mr Grainger added. "A well-designed Redd can save many species."