Shrinking safety margins in tropical forests

What is it about?

Tropical forests are some of the most biodiverse places on Earth, but beyond a critical temperature threshold, photosynthesis fails. Here, we studied 208 tree species in the tropics of South America, Southeast Asia, and Central Africa, using land surface temperatures from satellite data to map how close each species was to that threshold from 2001 to 2020. On average, the safety margin declined by 0.4°C per decade, and by 2020, 4% of the study area had passed the average critical threshold. Future projections showed that this could rise to 5.5% by 2050 and 11% by 2100.

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Photo by David Clode on Unsplash

Photo by David Clode on Unsplash

Why is it important?

Tropical forests play a critical role in absorbing CO2 and supporting global biodiversity, but rising temperatures threaten their health and functioning. When trees reach critical temperatures, their photosynthetic system breaks down. Our results show that thermal safety margins are declining and the extent of areas exceeding critical temperatures across the tropics is increasing, putting tropical biodiversity at growing risk. The regional differences in exposure and species’ heat tolerance underline the need for conservation strategies tailored to each area to avert potentially devastating consequences.