Increasing dry-season vapor pressure deficit in the Amazon Basin: historical trends, future projections, and links to deforestation

Abstract

Vapor Pressure Deficit (VPD) strongly influences agricultural productivity, vegetation health, and ecosystem resilience in the Amazon Basin. Rising VPD intensifies plant water stress by increasing atmospheric evaporative demand, exacerbating drought-induced vegetation mortality. We analyze historical (1983–2016) and projected (∼2050) seasonal and extreme VPD trends across the Amazon. Using CMIP6 projections and CHIRTS observational data, we quantify future dry-season VPD shifts and changes in extreme VPD event frequency under moderate (SSP245) and high-emission (SSP585) scenarios. Historical analyses reveal increasing dry-season VPD, driven primarily by warming-induced rises in saturation vapor pressure (∼7% increase per °C, Clausius–Clapeyron) and declining actual vapor pressure associated with deforestation-reduced evapotranspiration. Quantitative attribution analyses further indicate that recent deforestation significantly amplifies local atmospheric drying, with VPD increases strongest near recently deforested regions. SSP585 projections indicate severe atmospheric drying, with widespread and frequent extreme VPD events (>30 days/month) during peak dry months, surpassing historical extremes. Such conditions significantly threaten agricultural productivity and ecosystem stability, highlighting the urgent need for sustainable land management and effective climate mitigation policies in the Amazon.