Tropical forests are facing increasing risks of exposure to critical temperature thresholds

Area of Science:

• Ecology
• Climate Change Biology
• Plant Physiology

Background:

• Global heat waves are increasing in frequency and intensity.
• Tropical tree species' photosynthetic activity is sensitive to temperature thresholds.
• Understanding thermal tolerance is crucial for tropical forest conservation.

Purpose of the Study:

• To assess the spatiotemporal variation in thermal safety margins (TSM) for tropical tree species.
• To quantify the decline in TSM across different tropical regions.
• To project future TSM changes under climate change scenarios.

Main Methods:

• Utilized remotely sensed surface temperature data from 2001-2020.
• Employed species distribution maps for tropical trees in South America, Southeast Asia, and Central Africa.
• Calculated thermal safety margins (critical photosynthetic temperature minus maximum canopy temperature).

Main Results:

• Observed a consistent global decline in TSM for tropical forests, averaging X°C per decade.
• South America showed the most significant TSM decline at X°C per decade.
• Areas exceeding critical temperatures for species increased significantly, with projections indicating widespread exceedance by 2070 under high emissions.

Conclusions:

• Tropical forests are experiencing a reduction in their thermal safety margins.
• Rising temperatures pose a substantial risk to tropical tree photosynthesis and survival.
• Projected future warming may lead to widespread exceedance of critical temperatures, impacting the global carbon cycle and biodiversity.