Grasslands, covering 40% of the Earth's vegetated surface, play a crucial role in the global carbon balance but are increasingly threatened by climate-driven water scarcity. A new study published in Science Advances finds, however, that a widespread wind speed decline—a phenomenon known as "terrestrial stilling"—is enhancing the ability of global grasslands to absorb more carbon while minimizing water loss. This shift offers a crucial buffer for these water-limited biomes under climate change.
The study was led by Profs. FU Congsheng and YANG Guishan from the Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, in collaboration with researchers from Sun Yat-sen University, France's Laboratory for Climate and Environmental Sciences, and the United States' Lawrence Berkeley National Laboratory and Oak Ridge National Laboratory.
The research team integrated observations from over 1,000 sites, climate reanalysis, satellite-derived products, and predictions from six Earth-system models. By coupling statistical analysis with wind-manipulation experiments, the researchers isolated the impact of wind speed on ecosystem water-use efficiency (WUE)—the ratio of carbon uptake to water loss—across global grasslands from 1983 to 2100.
The study reveals that a decline in wind speed increases long-term WUE across more than 80% of global grasslands. Under both historical warming conditions and future warming scenarios, wind speed emerges as the second most critical driver of this WUE increase, surpassed only by rising atmospheric carbon dioxide concentrations.
According to the study, slower winds reduce water loss from evaporation and enhance the retention of soil moisture, thereby stimulating leaves to remain open for more effective carbon dioxide capture. In this way, grasslands can maximize carbon gain while "spending" less water.
Notably, the study finds that the wind effect intensifies as soil moisture decreases, strengthening the resistance of global grasslands to frequent droughts caused by global warming.
These findings highlight wind speed as a key regulator of the Earth's carbon and water cycles. The study suggests that global grasslands have greater inherent resilience than previously assumed, giving policymakers a better scientific basis for conservation strategies to protect these vital ecosystems in a changing world.
