A new atlas shows how conservation efforts can most efficiently make use of limited resources by laying out which forests store large amounts of carbon and are also home to a great diversity of animals and plants.

The UN Environment Programme, which released the maps at the ongoing UN climate summit in Poznan, Poland, believes they could guide investments in forest conservation.

"At a time of scarce financial resources and economic concerns, every dollar, euro or rupee needs to deliver double, even triple dividends," says Achim Steiner, executive director of UNEP. "By pinpointing where high densities of carbon overlap with high levels of biodiversity, the atlas spotlights where governments and investors can deal with two crises for the price of one."

Forests absorb carbon dioxide from the atmosphere and store it as plant material. But different forests contain varying amounts of carbon depending on a number of factors, including local climate and the species of trees involved.

Chopping down trees releases large amounts of CO2 back into the atmosphere when they decay or are burned.

Targeted conservation

So far, UN mechanisms for fighting climate change do not include forest preservation, so countries are not rewarded for the carbon they store in their forests.

But negotiators at Poznan will be fine-tuning a scheme that would reward "avoided deforestation" - another term for forest conservation - at the Poznan summit. The maps reveal that parts of the tropical Andes and Amazon region are high in carbon and biodiversity.

More detailed analysis is possible as well. For instance, the map of Papua New Guinea shows that the centre of the county, which is very biodiverse, also stores large amounts of carbon. At the moment, protected areas overlap with just one tenth of the high-carbon regions.