The dominant role of semi-arid ecosystems in the trend and variability of the land CO ₂ sink

TLDR

The terrestrial biosphere absorbs about a quarter of anthropogenic CO₂, but its uptake varies yearly, especially in semi‑arid regions where productivity is water‑limited and tied to precipitation, unlike wetter tropical areas. The study seeks to understand carbon uptake in these marginal semi‑arid ecosystems to improve predictions of global carbon cycle variability. The authors found that semi‑arid savannas and low‑latitude shrublands drive most of the variability in the land CO₂ sink. Published in Science, p.

Abstract

The difference is found at the margins The terrestrial biosphere absorbs about a quarter of all anthropogenic carbon dioxide emissions, but the amount that they take up varies from year to year. Why? Combining models and observations, Ahlström et al. found that marginal ecosystems—semiarid savannas and low-latitude shrublands—are responsible for most of the variability. Biological productivity in these semiarid regions is water-limited and strongly associated with variations in precipitation, unlike wetter tropical areas. Understanding carbon uptake by these marginal lands may help to improve predictions of variations in the global carbon cycle. Science , this issue p. 895