The orange flames that dot the Permian Basin have sparked criticism from investment bankers and shale pioneers who say the energy industry is wasting a valuable resource by burning off natural gas. Yet the flares are proving a bigger contributor to climate change if they are unlit. The Environmental Defense Fund surveyed more than 300 sites in the Permian and found that roughly 1 in 10 flares was unlit or malfunctioning. That means more gas is being released straight into the atmosphere, contributing a lot more to the basin’s methane emissions than previously thought.

The findings are part of EDF’s PermianMAP initiative, launched last year as a way to quantify the methane emissions from America’s biggest oil field, which until recently was considered a black box. The environmental group used satellite images to identify areas where flaring is prevalent, and then flew helicopters with infrared cameras to detect which sites — called flare stacks — were releasing methane. Two surveys have been conducted, one in February and another in late March, and EDF plans a third in the near future.

Flaring is meant to get rid of fuel that companies can’t or don’t put into pipelines by burning off methane, a greenhouse gas at least 30 times more potent than carbon dioxide at heating up the planet. The practice has skyrocketed in the last few years as output in the Permian, which stretches across West Texas and southeastern New Mexico, has surged.