Global ecosystem thresholds driven by aridity

Abstract

Aridity, increasing worldwide due to climate change, affects the structure and functioning of dryland ecosystems. Whether aridification leads to gradual (vs. abrupt) and systemic (vs. specific) ecosystem changes is largely unknown. We investigated how 20 structural and functional ecosystem attributes respond to aridity in global drylands. Aridification led to systemic and abrupt changes in multiple ecosystem attributes. These changes occurred sequentially in three phases characterized by abrupt decays in plant productivity, soil fertility and plant cover/richness at aridity values of 0.54, 0.7 and 0.8, respectively. Over 20% of the terrestrial surface will cross one/several of these thresholds by 2100, which calls for immediate actions to minimize the negative impacts of aridification on essential ecosystem services for the more than 2.5 billion people living in drylands.