Decreasing Rainfall and Increasing Drought: Why is this Happening in the Amazon?

Heavy rainfall is currently occurring in many parts of India, leading to flood situations in states like Uttar Pradesh, Punjab, Haryana, and Delhi. While this torrential rain in India is causing problems, recent research sheds light on why rainfall is gradually decreasing in the Amazon rainforest. The Amazon, the world’s largest tropical forest, spans across nine South American countries. A recent study reveals a decline in rainfall over time, with a reduction of approximately 21 millimeters during the dry season each year between 1985 and 2020. The study, published in Nature Communications, examines the causes of this declining rainfall, investigating the roles of both global warming and deforestation. Research led by Marco Franco and Luiz Augusto Toledo Machado from the University of Sao Paulo, studied land use and atmospheric data over 35 years in the Brazilian Legal Amazon region. Statistical models were employed to assess the impact of global warming versus deforestation on the decreasing rainfall. The research indicated that deforestation is the primary driver of this decline, accounting for approximately three-quarters of the reduction in rainfall since the mid-1980s. Global warming contributed to about one-sixth of the decrease. Deforestation resulted in a 15.8 mm reduction in dry season rainfall, accounting for 74.5% of the total decrease, and contributed to a 0.39°C increase in maximum daily temperature during the dry season. The Amazon’s trees play a crucial role in the climate, with billions of trees drawing water from the ground and releasing it into the air through transpiration, which generates over 40% of the region’s rainfall. Deforestation disrupts this cycle, and each 1% loss of forest leads to a reduction of approximately 3 mm of rainfall annually. The research also highlights how deforestation is altering the South American monsoon, increasing the risk of drought in Brazil’s central and southeastern regions. The Amazon experienced record-breaking droughts in 2023 and 2024, disrupting river transport and straining hydropower. The most significant changes in rainfall and temperature occur when 10-40% of the forest is destroyed, indicating that initial deforestation has a major impact on the weather. If deforestation continues at the current rate, dry season rainfall could decrease by another 7 mm and temperatures could rise by 0.6°C by 2035, threatening the Amazon’s biodiversity and the communities that depend on it. Approximately 13.2% of the original Amazon forest has been lost due to deforestation and other causes. While deforestation in the Brazilian Amazon decreased by 30.6% in 2024, the lowest level in the last nine years, over 4.6 million hectares of primary forest were burned in 2024, exceeding the average annual loss of the past decade.