As the forests grow they lock away more carbon, so human activities are directly changing the dynamics of the carbon cycle. The finding has implications for forest management as well as our understanding of the global carbon and nitrogen cycles. And the results show that mankind is ultimately controlling the carbon balance of temperate and boreal forests, either directly through forest management or indirectly through nitrogen deposition. Professor Peter Högberg, SLU, comments the article in the same issue of Nature., +46-18-67 25 55, +46-90-78 68 353