Forests around the world are quietly transforming, and not for the better. A massive global analysis of more than 31,000 tree species reveals that forests are becoming more uniform, increasingly dominated by fast-growing “sprinter” trees, while slow-growing, long-lived species are disappearing. These slower species act as the backbone of forest ecosystems, storing carbon, stabilizing environments, and supporting rich webs of life—especially in tropical regions where biodiversity is highest. …The research also highlights the growing role of naturalized tree species, meaning trees that originated elsewhere but now grow wild in new regions. Nearly 41 percent of these species share traits like rapid growth and small leaves, which help them survive in disturbed environments. …The study shows that tropical and subtropical regions are likely to experience the most severe impacts from forest homogenization. …According to the researchers, human actions are the main force behind these changes in forest composition. …This makes protecting slow-growing tree species increasingly urgent.