Amazon Carbon Release Accelerating as Droughts and Storms Shorten Tree Lifespans

Satellite data has revealed something troubling about the Amazon: the forest is not renewing itself at a steady pace. Instead, droughts and violent storms are killing trees faster than they can be replaced, which means the carbon locked inside those trees is escaping into the atmosphere sooner than climate models have assumed. This acceleration, documented in a study published in Nature Climate Change, suggests that by the end of this century, the time it takes for the Amazon to cycle through its biomass could shrink by anywhere from 3 to 15 percent—depending on how much greenhouse gas humanity continues to emit.

The Amazon holds more than 60 percent of all plant matter on Earth. That carbon does not stay trapped in wood forever. When a tree dies and decays, the carbon it stored returns to the air, and the forest's ability to act as a carbon sink weakens. The research team, led by Donghai Wu and Xiangtao Xu from the South China Botanical Garden and the Chinese Academy of Sciences, working alongside researchers from Cornell University, UC Berkeley, and Brazil's National Institute for Space Research, set out to measure something that previous climate models had treated as a constant: the rate at which tropical forests renew their biomass.

For decades, scientists assumed that mature forests existed in equilibrium—when one tree died, another grew to replace it. But the Amazon is no longer in equilibrium. Tree mortality has been rising, and the forest's ability to accumulate carbon has weakened. The problem was that previous studies lacked the data to understand this shift. Forest inventories covered less than one millionth of the Amazon's surface, far too small a sample to reveal what was happening across the entire region. Some areas were accumulating carbon while others were losing it rapidly, and no one could explain why.

To build a detailed map of biomass renewal rates across the intact Amazon, the researchers combined satellite imagery from MODIS—which detects vegetation changes from space—with data from 57 ground-based forest inventory plots. They used machine learning to identify which climate and soil factors controlled the speed of biomass renewal. The results showed renewal times ranging from 24 to 80 years, with a median of 51 years. The northeastern Amazon had the longest cycles; the center and north had the shortest.

Two factors emerged as the primary drivers of faster tree death. Intense thunderstorms proved to be the single most influential climate variable, more powerful than dry air or extreme rainfall alone. Air dryness also had a clear effect: the drier the air, the sooner trees died and released their carbon. In the northwestern and southeastern Amazon, this dryness alone shortened biomass renewal by 5 to 10 years. When the researchers projected these trends forward to 2100 under two emissions scenarios—one optimistic with low emissions, one pessimistic with emissions continuing at current rates—the results diverged sharply. Under the best case, biomass renewal would accelerate by 3 percent. Under the worst case, it would accelerate by 15 percent, with the central and northern Amazon hit hardest.

The study carries important caveats. The model does not account for the possibility that trees might adapt to new climate conditions, nor does it capture what happens when drought and storms strike simultaneously. Uncertainty also remains about how much storm energy will be available in future climates according to global climate models. Still, the researchers were clear about what needs to happen next: climate models that project Earth's future must incorporate the effects of storms and atmospheric dryness. The same threat looms over temperate and subtropical forests, which also face intense thunderstorms and need better study of how wind and lightning affect them. The Amazon's carbon clock is ticking faster than anyone expected, and the models that guide climate policy need to catch up.