New research suggests that plants, traditionally seen as essential carbon sinks, may soon emit more CO₂ than they absorb due to the impacts of climate change. A recent study highlights how increasing temperatures are disrupting plants’ ability to absorb carbon and may transform them into net carbon emitters.
As climate change accelerates, scientists have uncovered a troubling shift in the role of plants in the global carbon cycle. Traditionally, plants have been seen as vital allies in combating global warming, absorbing carbon dioxide (CO₂) during photosynthesis and releasing oxygen and water vapor in the process. However, a new study reveals that rising temperatures are making it more difficult for plants to function as carbon sinks.
Key findings of the research indicate that as temperatures rise, plants lose more water through the cuticle, a waxy outer layer of the plant leaf that serves as a protective barrier. Unlike stomata, which control water loss and gas exchange, the cuticle cannot close, leading to uncontrollable water leakage. This, in turn, diminishes plants’ ability to absorb CO₂, potentially reducing their photosynthetic activity.
Under normal conditions, plants regulate their water loss and CO₂ absorption via tiny pores called stomata. However, when temperatures soar, this balance is disturbed. The increased water loss through the cuticle hampers photosynthesis and limits the plant’s capacity to absorb CO₂, which is essential for slowing down the impacts of climate change.
As a result, if global temperatures continue to rise, plants could even become sources of CO₂ emissions rather than carbon sinks. This role reversal would have profound implications for global warming, potentially accelerating the climate crisis instead of mitigating it.
Plants are not universally resistant to heat. While certain species, such as those in desert or tropical regions, may have adapted to high temperatures, the majority of plants are not built to withstand extreme heat. Studies on over 200 species in Vancouver have shown that photosynthesis begins to decline when temperatures exceed 104°F (40°C), and plants experience severe cellular breakdown when temperatures surpass 140°F (60°C).
Even with these variations in heat tolerance, a tipping point may be reached at around 86°F (30°C), where plants could start releasing more CO₂ than they absorb. This scenario paints a grim picture for future climate stability, as higher temperatures would directly challenge plants’ ability to help mitigate climate change.
The cuticle is a thin, waxy layer that covers the surface of plant leaves and stems. It serves to protect plants from environmental stressors, such as pathogens and excessive water loss. Unlike stomata, which open and close to control water loss, the cuticle remains impervious, allowing no control over water leakage. Under extreme heat, this layer becomes a significant contributor to water loss, further disrupting the plant’s carbon-absorbing capacity.
The role of the cuticle in water and carbon cycles has been underestimated in current climate models. As research continues to uncover the complex dynamics of plant resilience, it is becoming clear that the cuticle plays a far more critical role in regulating plant health and climate impact than previously thought.
This new understanding of plant biology could have major implications for future climate models and global climate policy. As temperatures rise, it is increasingly possible that plants could shift from being our allies in the fight against climate change to contributors to the problem. Immediate action to curb greenhouse gas emissions, combined with a deeper understanding of plant functions and climate resilience, will be essential to preventing this unsettling shift.
