# Historical deforestation drives strong rainfall decline across the southern Amazon basin

## TL;DR

Deforestation in the southern Amazon has caused a significant drop in rainfall, more than what climate models predict.

## Contribution

The study reveals that deforestation has a stronger impact on southern Amazon rainfall than previously modeled.

## Key findings

- Deforestation in the southern Amazon caused an 8-11% decline in annual precipitation from 1980-2019.
- Deforestation suppresses forest-sourced moisture and increases atmospheric stability, reducing rainfall.
- Climate models underestimate the sensitivity of precipitation to deforestation in the region.

## Abstract

The Amazon forest has recently experienced substantial human-induced loss of forest cover. However, the extent to which such historical deforestation has altered regional observed precipitation through inter-regional atmospheric moisture transport remains unclear. Here, we combine satellite observations and an atmospheric moisture tracking model to quantify these feedbacks over the past four decades (1980-2019). We identify a contrasting northern increase and southern decrease dipole trend in observed precipitation across the Amazon basin. The pronounced reduction in precipitation for the southern Amazon basin reaches up to 3.9-5.4 mm yr-1 per year, resulting in an 8-11% decline in annual precipitation across the observation period. We discover that this reduction in precipitation is primarily (52-72%) related to widespread deforestation in the southern basin and upwind regions over South America. Deforestation substantially suppresses forest-sourced moisture, increases atmospheric stability and moisture outflow, leading to precipitation reduction. We also find that climate models substantially underestimate the sensitivity of precipitation to deforestation, implying that the Amazon forest is at risk of major loss much sooner than previously projected.

The authors find that historical deforestation has substantially altered regional observed precipitation over the southern Amazon basin through inter-regional atmospheric moisture transport, which is underestimated in current climate models.