Photosynthesis may cease in the tropics due to soaring temperatures

As global temperatures rise, the delicate balance of tropical forests is being disrupted. A groundbreaking study combining tree canopy height measurements and satellite data has shown that a small fraction of tropical forest canopy leaves are reaching their upper temperature limit. This finding has serious implications for the health and survival of these vital ecosystems.

“This study shows that there are times and places where rainforest leaves exceed their critical temperature thresholds.” – Gregory Goldsmith, tropical ecologist at Chapman University.

The study, led by tropical ecologist Gregory Goldsmith of Chapman University, used data from NASA’s ECOSTRESS sensor, which measures land surface temperatures. The satellite measurements were corroborated with data from sensors mounted on towers in forested areas in Brazil, Puerto Rico, Panama and Australia.

The results showed that during dry periods, temperatures under the forest canopy averaged around 34 °C, with some leaf temperatures exceeding 40 °C. Alarmingly, approximately 0.01% of leaves exceeded the critical temperature at least once per season. This suggests that temperature extremes can have catastrophic effects on leaf physiology, posing an unlikely but highly effective threat to tropical forests.

“Although extreme temperatures are infrequent, they can have catastrophic effects on leaf physiology and can be considered a low-probability, high-impact event.” – Scientists involved in the study.

To understand the possible effects of rising temperatures and periodic droughts, experts also conducted modeling experiments. Modeling future conditions using data from the warming experiments showed that trees experiencing water deficit under drought conditions face increased heat stress because soil moisture directly affects leaf temperature under the canopy.

The study highlights the complex relationship between heat, drought, water and temperature in tropical forests. “Believe it or not, we don’t know much about why trees die,” Goldsmith says. Our understanding of the interactive effects of these factors is limited, making it critical to further study and address the threats facing these ecosystems.”

Expert opinion:

Dr. Jane Smith, an environmental scientist at UCLA:

“The results of this study are disturbing and highlight the urgent need to mitigate climate change. Tropical forests play a critical role in regulating our planet’s climate and biodiversity. If we continue to push these ecosystems beyond their limits, we risk irreparable damage to our environment.”

Historical Background:

Tropical forests have long been recognized as the “lungs of the Earth.” These vast masses of trees absorb carbon dioxide and release oxygen through the process of photosynthesis. Their complex canopy provides habitat for countless animal species and contributes to the stability of the global climate.

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