Tropical rainforests, among Earth's most powerful carbon storage systems, can flip into carbon-releasing engines during El Niño events, new research shows. The Amazon alone holds roughly 123 billion tons of carbon, more than any other land ecosystem on the planet. This balance hangs precariously in the balance.
During El Niño years, warmer ocean temperatures trigger drought conditions across tropical regions. Reduced rainfall stresses trees, suppresses photosynthesis, and increases tree mortality. When forests die back, they stop absorbing CO₂ and begin releasing stored carbon through decomposition and reduced growth. The mechanism works like this: El Niño-driven heat dries soil moisture, forcing trees into survival mode. Stressed trees allocate energy to survival rather than growth. Dead wood and leaf litter decompose faster in warmer conditions, releasing carbon previously locked away.
The shift from carbon sink to carbon source creates a dangerous feedback loop. As tropical forests release carbon, atmospheric CO₂ concentrations rise, intensifying warming. Warmer conditions favor more frequent El Niño events, which trigger more droughts, which stress forests further. This amplification could accelerate climate change beyond current projections.
Climate models have long assumed tropical forests remain net carbon sinks regardless of climate stress. This research challenges that assumption. Understanding these dynamics matters because tropical forests currently offset a substantial fraction of global emissions. If they switch to net sources during extreme climate events, global carbon budgets require recalculation.
The stakes are enormous. The Amazon's potential tipping point looms as deforestation, climate warming, and El Niño cycles converge. Scientists now recognize that protecting remaining tropical forests is not just an environmental priority but a carbon accounting necessity. Future climate scenarios must account for forest carbon releases during El Niño rather than assuming continuous absorption. This represents a fundamental shift in how climate scientists model