The report said better management of forests, more careful agricultural practices and the restoration of peatlands could soak up significant amounts of carbon dioxide, the most common of the gases blamed for global warming.
"We need to move toward a comprehensive policy framework for addressing ecosystems," said co-author Barney Dickson, releasing the report at the U.N. climate negotiations in Bonn, Germany. The event was Webcast worldwide.
Millions of dollars are being invested in research on capturing and burying carbon emissions from power stations, but investing in ecosystems could achieve cheaper results, the report said.
It also would have the added effects of preserving biodiversity, improving water supplies and boosting livelihoods.
Halving deforestation by mid-century and maintaining that lower rate for another 50 years would save the equivalent of five years of carbon emissions at the current level, said Dickson, the agency's head of climate change and biodiversity.
The loss of peatlands, mainly drained for palm oil and pulp wood plantations in Southeast Asia, contributes 8 percent of global carbon emissions. China could capture about 5 percent of its carbon emissions from burning fossil fuels by returning straw to croplands, it said.
Agriculture has the largest potential for storing carbon if farmers use better techniques, such as avoiding turning over the soil and using natural compost and manure rather than chemical fertilizers, it said.