Evidence Is Growing That Alternative Stable States in Semiarid Grasslands Are the Exception, Not the Rule

Abstract

Woody shrubs have increased in abundance in arid and semiarid grasslands around the globe. This can have negative consequences for communities dependent on grasses for grazing and other ecosystem services. A study by Zheng et al. (2020, https://doi.org/10.1029/2019JG005439) shows that grasslands in Inner Mongolia, China, which have long been invaded by shrubs, may naturally return to a grass-dominated state when grazing is eliminated. This result emphasizes the primary importance of grazing in driving vegetation change in grasslands and argues against the existence of critical thresholds and alternative stable states in semiarid ecosystems.