Drought-Induced Reduction in Global Terrestrial Net Primary Production from 2000 Through 2009

TLDR

Terrestrial net primary production (NPP) quantifies atmospheric carbon fixed by plants, and earlier studies noted an upward trend from 1982 to 1999 as climate constraints relaxed. From 2000 to 2009, global NPP fell by 0.55 Pg C, driven by large‑scale droughts that reduced regional NPP—especially in the Southern Hemisphere—thereby weakening the terrestrial carbon sink and heightening future competition between food demand and biofuel production.

Abstract

Terrestrial net primary production (NPP) quantifies the amount of atmospheric carbon fixed by plants and accumulated as biomass. Previous studies have shown that climate constraints were relaxing with increasing temperature and solar radiation, allowing an upward trend in NPP from 1982 through 1999. The past decade (2000 to 2009) has been the warmest since instrumental measurements began, which could imply continued increases in NPP; however, our estimates suggest a reduction in the global NPP of 0.55 petagrams of carbon. Large-scale droughts have reduced regional NPP, and a drying trend in the Southern Hemisphere has decreased NPP in that area, counteracting the increased NPP over the Northern Hemisphere. A continued decline in NPP would not only weaken the terrestrial carbon sink, but it would also intensify future competition between food demand and proposed biofuel production.