Most of the world’s old-growth forests actively absorb more carbon dioxide than they release into the atmosphere, making them effective carbon sinks, according to a new study in the journal Nature. The new research, which relies on data from over 500 forests around the world, refutes the commonly held assertion that old-growth forests are merely carbon neutral, absorbing only as much carbon as they release. Instead, the study found, forests between 15 and 800 years old typically not only act as active carbon sinks, but collectively act as a storehouse for up to 1 billion metric tons of carbon dioxide — some 10 percent of the world’s total net CO2 uptake. “The absolute amount of carbon stored in these forests is significant,” said forest-science professor Beverly Law. And because they are active carbon absorbers as well as large carbon reservoirs, destroying them is doubly stupid climate-wise (and dumber still if you factor in their conservation value and unique ecology). “If you have an old forest on the ground, it’s probably better to leave it there than to cut it,” Law said.