Amazon deforestation threatens South American farms and climate stability, new studies show

New research in Nature finds that deforestation lowers the warming threshold at which large parts of the Amazon could lose stability. Without deforestation, the critical warming threshold is about 3.7 to 4.0 degrees Celsius. With 22% to 28% deforestation and 1.5 to 1.9 degrees of warming, up to 77% of the forest could face a system-wide transition. The forest's moisture recycling is key: trees draw water from soil and release it, sustaining rainfall for farming, hydropower, and cities across South America. A separate PNAS study shows that Amazon deforestation reduces soybean yields in Brazil. Tree evaporation contributes about one-third of growing-season precipitation across soybean states. Recent deforestation cut seasonal rainfall by 6% to 30%, leading to cumulative production losses of roughly 700,000 metric tons. The 2023-2024 drought pushed radar-measured forest moisture to its lowest level since 1992, with less than half of affected areas projected to recover within seven years. El Nino conditions this year raise fire risk in already degraded areas. Fires set for pasture management or land clearing are more likely to escape during dry periods, damaging standing forest and reducing carbon storage. Protecting intact forests, restoring degraded areas, and reducing fire are increasingly important for climate resilience, biodiversity, and South America's food system.