Decadal trends in global grassland growth peaks and their drivers since the 1980s
Cuihai You, Shiping Chen, Zhiqin Tu, Chenyu Bian, Erqian Cui, Kun Huang, Fangxiu Wan, Jiaye Ping, Ning Wei, Jianyang Xia
Abstract
Grasslands, Earth’s most widespread terrestrial ecosystems, are vital for global carbon sequestration and food security. A key indicator of these functions is vegetation growth peak, reflecting maximum seasonal productivity. However, whether this growth peak consistently increases across global grasslands remains unknown. Here, using satellite-derived vegetation data from 1982 to 2021, we reveal a widespread increase in grassland growth peaks, with 71% (20/28) IPCC climate regions exhibiting significant trends. However, this trend reverses between 1998 and 2009 in 64% of regions, notably across the Tibetan Plateau and East Asia. The reversal is supported by a global gross primary productivity dataset generated via machine learning, trained on eddy covariance flux data. The interruption is primarily associated with a global-scale decadal drought. These findings demonstrate that persistent drought can disrupt the upward trajectory of grassland growth peaks, posing a spatially uneven but widespread threat to ecological functions of grasslands under climate change. Global vegetation growth peaks have been increasing over recent decades, but grasslands are highly sensitive to climate, and it is unclear whether this upward trend can be sustained. This study shows that over the past four decades, decadal droughts have temporarily disrupted this global increase in grassland peak productivity.