Nature Climate Change, Published online: 27 July 2026; doi:10.1038/s41558-026-02698-7The authors integrate tree species richness with satellite-derived photosynthesis proxies to show that richness correlates with greater current levels of photosynthesis and greater increases over time. Projected biodiversity loss by 2050 could lead to cumulative forest photosynthesis loss of 4.4–35.7 PgC.