Trees do wonders when it comes to cooling Earth. They suck planet-warming carbon dioxide from the atmosphere, locking it into their trunks, leaves, and roots to the tune of about 2.4 billion metric tons of carbon each year. But a new study has found, somewhat counterintuitively, that more trees might not always mean a cooler planet. In fact, researchers examining 260 years of changes in European forest management found that—despite a 10% increase in wooded land—the continent’s forests have actually caused a slight increase in regional temperatures since 1750.