Washington (dpa) - Earth lost 18 million hectares of tree cover in 2014, with the worst spots topped by the Mekong River Basin and West Africa, a report released on Wednesday showed.
The losses, equivalent to an area twice the size of Portugal, were the highest since 2001, the report said.
Global Forest Watch released the data that had been compiled by the University of Maryland, just outside Washington DC, and Google.
The data showed a surprising trend that much of the forest destruction happened outside the most notorious spots of rampant deforestation - Brazil and Indonesia.
Cambodia ranks at the top of the list of countries with the fastest acceleration of tree cover loss in 2014, followed by Sierra Leone, Madagascar, Uruguay, Paraguay, Liberia, Guinea, Guinea-Bissau, Vietnam and Malaysia, the report said.
"This analysis identifies a truly alarming surge in forest loss in previously overlooked hotspots," said Nigel Sizer, global director of the forests programme at the World Resources Institute.
He said forests are giving way for commodities such as rubber, beef, soy and palm oil.
He called for improved oversight of forests to prevent illegal clearing and greater demand for "sustainable commodity production".
Trees absorb carbon dioxide, and massive deforestation across the globe has contributed in no small measure to rising Earth temperature that is blamed on carbon emissions, experts say.
Reforestation has become a major push from the UN climate programme. A new round of commitments by developing countries was made in September 2014 at a climate summit at the UN in New York. The goal was to double the goal for restoring forests to 350 million hectares by 2030.
In December, climate negotiators are to meet in Paris to hammer out a post-2020 climate action plan.
Climate scientists agree that the Earth's temperature increase must be limited to 2°C over pre-industrial levels to avoid catastrophic weather patterns and rising sea levels that threaten large populations.
Between 1880 and 2012, average land and ocean surface temperatures have already risen about 0.85°C, the UN's Intergovernmental Panel on Climate Change says.