en.Wedoany.com Reported - A research team led by the Swiss Federal Institute of Technology Lausanne (EPFL) has found that extreme heat has exposed approximately 57 million hectares of tropical forests to temperatures exceeding the critical threshold for photosynthesis, an area larger than the land area of France. During the study period (2001–2020), this figure rose steadily from about 43 million hectares, as global warming, droughts, and heatwaves compressed the temperature margin within which trees can function efficiently.

The researchers combined satellite-derived canopy temperature measurements with existing thermal limit data for approximately 200 tree species. Once leaf temperatures exceed the critical threshold, the proteins involved in photosynthesis begin to degrade, reducing trees' capacity to absorb carbon dioxide and increasing the risk of slowed growth and mortality. The findings, published in the Proceedings of the National Academy of Sciences (PNAS), are among the first to assess tropical forest heat exposure by integrating species-level temperature limits with large-scale satellite observations.

The team projects that the area exceeding the critical temperature could expand to 83 million hectares by 2050 and 160 million hectares by 2100. Long-term heat stress could alter forest species composition, with more heat-tolerant species replacing vulnerable trees, triggering cascading effects on wildlife, carbon storage, and regional rainfall. Reduced rates of photosynthesis and water vapor release could also exacerbate warming and drought, though the research team notes that it remains difficult to determine whether forest species can adapt quickly enough to rising temperatures.