A new study from the Swiss Federal Institute of Technology Lausanne finds that 57 million hectares of tropical forests are now too hot for photosynthesis. That area is larger than France. When treetop temperatures exceed the thermal safety margin, trees stop absorbing carbon dioxide effectively. This directly threatens the role of tropical forests as a major carbon sink. Projections show the affected area could reach 93 million hectares by 2050 and 160 million hectares by 2100. For carbon credit markets, this means nature based offsets tied to tropical forest conservation may become less reliable. Insurers and agricultural commodity traders also face higher risk from disrupted water cycles and more frequent droughts. The speed at which forests can adapt remains unknown, making long term climate planning harder.
