Tropical Forests Suffered Near-Record Tree Losses in 2017 In Brazil, forest fires set by farmers and ranchers to clear land for agriculture raged out of control last year, wiping out more than 3 million acres of trees as a severe drought gripped the region. Those losses undermined Brazil’s recent efforts to protect its rain forests. In Colombia, a landmark peace deal between the government and the country’s largest rebel group paved the way for a rush of mining, logging and farming that caused deforestation in the nation’s Amazon region to spike last year. And in the Caribbean, Hurricanes Irma and Maria flattened nearly one-third of the forests in Dominica and a wide swath of trees in Puerto Rico last summer. In all, the world’s tropical forests lost roughly 39 million acres of trees last year, an area roughly the size of Bangladesh, according to a report Wednesday by Global Forest Watch that used new satellite data from the University of Maryland. Global Forest Watch is part of the World Resources Institute, an environmental group. That made 2017 the second-worst year for tropical tree cover loss in the satellite record, just below the losses in 2016. The data provides only a partial picture of forest health around the world, since it does not capture trees that are growing back after storms, fires or logging. But separate studies have confirmed that tropical forests are shrinking overall, with losses outweighing the gains. Trees, particularly those in the lush tropics, pull carbon dioxide out of the air as they grow and lock that carbon in their wood and soil. When humans cut down or burn trees, the carbon gets released back into the atmosphere, warming the planet. By some estimates, deforestation accounts for more than 10 percent of humanity’s carbon dioxide emissions each year. But figuring out precisely where forests are vanishing has long been a challenge. For decades, the United Nations’ Food and Agriculture Organization has relied on ground-level assessments from individual countries to track deforestation. Yet not all tropical countries have adequate capacity to monitor their forests, and the measurements can be plagued by inconsistencies. In 2013, scientists at the University of Maryland unveiled a fresh approach. Using satellite data recently made free, they have been tracking changes in tree canopy area around the world. This method has its own limits: More work is still needed to distinguish between trees that are being intentionally harvested in plantations and those that are being newly cleared in older, natural forests. The latter is a much bigger concern for habitat loss and climate change. Concern in Colombia, Brazil and Congo From the satellite imagery, researchers noticed that Colombia lost 1 million acres of forest in 2017, a stunning 46 percent uptick from the previous year. Many of these losses took place in the Colombian Amazon, in areas that used to be strictly controlled by the Revolutionary Armed Forces of Colombia, or FARC, a guerrilla group that imposed tight controls on logging and land-clearing but disarmed last year amid a landmark peace accord. “As FARC has demobilized, large areas are opening up once again, and you’re seeing this rush of people grabbing land for different reasons, like planting cocoa or cattle ranching,” said Mikaela Weisse, a research analyst with Global Forest Watch. She added that the Colombian government recently announced new policies to work with indigenous communities to protect forests, but said it was too early to declare success. The satellite data also provided a clearer picture of Brazil’s vast Amazon rain forests, long vulnerable to widespread deforestation. Over the past decade, the Brazilian government has moved to reduce illegal logging, and Western agriculture companies like Cargill have pledged to farm more sustainably. But the Global Forest Watch analysis showed that Brazil lost a record amount of tree cover in 2016 and 2017, in part because of large fire outbreaks in the Amazon. These fires are typically started by farmers and ranchers to clear land, but a severe drought last year caused them to spread rapidly, particularly in the parched southeast. The satellites also picked up evidence of large-scale land-clearing that may be occurring in areas where enforcement is weak. “The big concern is that we’re starting to see a new normal, where fires, deforestation, drought and climate change are all interacting to make the Amazon more flammable,” Ms. Weisse said. Elsewhere in the world, the satellite data showed that the Democratic Republic of Congo last year saw more forest loss than any other country outside of Brazil — some 3.6 million acres, up 6 percent from the previous year — with small-scale logging, charcoal production and farming all likely playing key roles.