This 3.8 billion year old process also  photosynthesis is threatened global warming And this is already affecting the leaves of the trees in tropical forests , which are threatened with " massive die-off". This is revealed by a study published in Nature on Wednesday, August 23. It was carried out by American, Australian, Brazilian and British scientists. They used ground, satellite and modeling data to assess leaf condition tropical forests  around the world and their thermal limits. The result: from an average temperature of 46.7°C, their photosynthesis begins to decline seriously. Currently, about 0.01 % leaves are affected by this phenomenon. However, scientists predict a generalization if the situation does not change. "  If we do not respond to climate change and air temperatures in tropical forests increase by more than 4°C, we could see massive leaf dieback and tree mortality,  " explained the scientist responsible for the study Christopher Doughty. (Margaux Lamoulie)