Something Weird Is Happening to China’s 66-Billion-Tree ‘Great Green Wall’

China’s enormous environmental experiment has been watched for decades, but its latest development is not what researchers expected. A new study has uncovered a striking difference hidden inside the country’s expanding forests.

The finding sounds like an obvious victory at first. Look more closely, however, and the picture becomes far more complicated, raising questions about carbon, forest age and what happens when human-planted landscapes begin to mature.