Species-rich subtropical forests can take up twice as much carbon as monocultures. This has been reported by an international research team in SCIENCE. The study was carried out as part of a unique field experiment with forests grown specifically for this purpose in China. Data from plots with a total of over 150,000 trees were analysed. The results speak in favour of using many different tree species during reforestation. Thus, both species conservation and climate protection can be promoted.