Warming diminishes the stability of primary productivity in global grass- and forb-dominated ecosystems

Global warming has induced increases in productivity in open, grass- and forb-dominated (OGFD) ecosystems. However, little attention has been given to the temporal stability of productivity responses to global warming. We show that the stability of productivity in OGFD ecosystems decreased significantly over the past 40 years. Using the satellite-derived normalized difference vegetation index (NDVI) data from the Global Inventory Modelling and Mapping Studies (GIMMS) group, we analyzed global patterns of the stability in productivity among OGFD ecosystems. We found that the global mean stability of NDVI-based productivity estimates significantly decreased from 1982 to 2015. Comparing different trends, we found that stability decreased by 36%, and increased by 27% of the total area of OGFD ecosystems. The stability of productivity in OGFD ecosystems decreased in the northern hemisphere, especially in the Mongolian plateau and Eurasian steppe. In contrast, stability increased significantly in the southern hemisphere. Increases in both mean annual temperature and annual temperature variability were correlated with decreases in the stability of productivity in the northern hemisphere. Although the productivity of OGFD ecosystems has generally increased with warming, the stability of production has decreased. OGFD ecosystems, particularly northern hemisphere systems with low baseline productivity may be vulnerable to the loss of grazing potential and grazing consistency in the warmer future. These observations highlight the need for adaptation strategies for animal husbandry to respond to variability in productivity and reduce the negative impact of climate change on grazed ecosystems.