Study Identifies 36% Rainfall-Origin Threshold for Farm Drought Risk

Overview

• Researchers from UC San Diego and Stanford used nearly two decades of satellite water‑isotope data and physical models to map where cropland rain originates.
• When roughly a third or more of rainfall comes from land‑sourced moisture, farms face markedly higher odds of soil‑moisture deficits and drought.
• The U.S. Midwest’s reliance on land‑recycled rain can trigger self‑reinforcing dry spells as parched soils reduce evaporation and future precipitation.
• Tropical East Africa risks weakening its own rainfall through cropland expansion and forest loss, threatening local food security unless ecosystems are conserved.
• The Nature Sustainability paper urges targeted adaptations such as irrigation, water storage, soil‑moisture management, and protection of upwind forests.