Concerns on the Groundwater Earth System Boundary: Scientific Debate & Implications for Drylands

Groundwater is the largest accessible freshwater store on Earth and a lifeline for millions in tropical drylands. A proposal to define a global “groundwater Earth System Boundary” (ESB) aims to indicate when groundwater use risks planetary stability. But a recent exchange in Nature highlights important conceptual and practical questions about how such a boundary should be defined and used — questions that carry big implications for local water management, justice and policy.