Tropical Forests Near Critical Temperature Limit for Photosynthesis, Urgent Action Needed
A recent study published in the journal Nature has raised concerns about the critical temperature limit for photosynthesis in tropical forests. The research suggests that a small percentage of leaves in these forests are approaching the maximum temperature threshold for photosynthesis to work effectively. While uncertainties regarding the range of critical temperatures in tropical trees still exist, the findings emphasize the urgent need for action to protect the fate of these ecosystems in the face of climate change.
Tropical forests play a crucial role as carbon stores and serve as habitats for a vast majority of the world’s biodiversity. However, they are particularly vulnerable to increasing temperatures. The average critical temperature at which the photosynthetic machinery in tropical trees starts to fail is approximately 46.7 °C. The question of whether leaf temperatures experienced by tropical vegetation are nearing this threshold, or will soon do so under climate change, remains unanswered.
To shed light on this issue, Christopher Doughty and his colleagues conducted an extensive study using high-resolution measurements of land surface temperatures across the globe, including regions in Brazil, Puerto Rico, and Australia. These measurements were obtained from an instrument on board the International Space Station between 2018 and 2020.
The researchers discovered that the peak canopy temperatures in tropical forests averaged around 34 °C. However, a small proportion of observed temperatures exceeded 40 °C. Alarmingly, in a typical year, approximately 0.01% of the leaves in the upper canopies surpassed the temperature at which photosynthesis starts to fail. Projections based on warming experiments indicate that this value could rise to 1.4% under future warming conditions.
A comprehensive model integrating these dynamics under various climate change scenarios suggests that if the temperature exceeds a 3.9 °C increase over current air temperatures, large-scale leaf death and losses may begin to occur. It is important to note that this temperature threshold falls within the worst-case scenario for climate change predictions. The study’s authors propose that to prevent such dire consequences, ambitious climate change mitigation goals and reduced deforestation are necessary to keep forests below these thermally critical thresholds.
In conclusion, the findings of this study underscore the delicate balance that tropical forests face as they approach their maximum temperature limit for photosynthesis. Urgent action is required to safeguard these vital ecosystems, which not only store carbon but also support rich biodiversity. By implementing ambitious climate change mitigation strategies and curbing deforestation, we can strive to preserve the resilience and health of tropical forests for future generations.
