The relative increase in GPP per unit of increased atmospheric CO2 declined from 1982 to 2015, indicating a weakening of any CO2 fertilisation effect . Increased growth from CO2 fertilisation has begun to shorten the lifespan of trees due to a trade-off between growth rate and longevity, based on analyses of tree rings of 110 species around the world . Furthermore, water availability controls the magnitude of NPP , including water from precipitation , soil moisture , groundwater storage  and atmospheric vapour . Drought stress reduced NPP across tropical forests from 2000 to 2015  and GPP in the tropics from 1982 to 2016 . Drought stress has also reduced GPP in some semiarid and arid lands . In addition, nitrogen and phosphorus constrain CO2 fertilisation , although phosphorus limitation of tropical tree growth is species-specific . NPP has decreased during some time periods and in some regions where drought stress has exerted a greater influence than increased atmospheric CO2 .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report