Heat can curb photosynthesis in forests. Recent reporting highlights how rising temperatures stress plant leaves and limit their ability to convert light into chemical energy.
In tropical regions, some plant leaves lose the power to photosynthesize when conditions become too hot. A threshold has been identified: around 46.7 °C. When leaf temperatures approach or exceed this mark, the photosynthetic process slows or stops, even if the air around them is not at the same extreme. Researchers from the United States, Australia, and Brazil gathered data showing this temperature sensitivity and its potential consequences for forest ecosystems and regional climates.
Current observations show that a very small fraction of leaves, about 0.1 percent, already operate near the critical limit. If global warming continues and average temperatures rise by roughly 4 °C, more leaves would reach or cross that threshold. Scientists caution that such a dramatic temperature increase is not expected immediately, but the possibility raises concerns about long term changes in forest productivity and carbon cycling.
Separately, studies have shown that water pollution from microplastics can interfere with photosynthesis in photosynthetic algae that live in symbiotic relationships with other organisms. This disruption adds another layer of stress for marine and freshwater ecosystems that rely on photosynthesis for oxygen production and food webs.
Historically, scientists have explored how early Earth managed its oxygen levels. Some evidence suggests that oxygen began to accumulate in the atmosphere before photosynthesis as it is understood today became widespread, pointing to a complex set of natural processes driving the rise of atmospheric oxygen long before modern photosynthetic systems dominated the planet.