New research presents an unexpectedly positive view on the ability of plants to absorb carbon dioxide (CO2) from human activities. However, environmental scientists stress that this should not be taken as an excuse for governments to slow their efforts in reducing carbon emissions as quickly as possible.

The research, led by Dr. Jürgen Knauer from Western Sydney University's Hawkesbury Institute for the Environment, was published in the renowned journal Science Advances. Although the findings are encouraging, the scientists involved caution that simply planting more trees or protecting existing vegetation is not a one-size-fits-all solution to climate change. The study does, however, highlight the many benefits of conserving vegetation.

“Plants absorb a significant amount of CO2 each year, helping to mitigate the harmful effects of climate change,” explains Dr. Knauer. “But how much they will continue to do so in the future has been uncertain.”

The study used an established climate model that contributes to global climate predictions, such as those made by the Intergovernmental Panel on Climate Change (IPCC). It found that when key physiological processes governing how plants conduct photosynthesis are considered, plants’ CO2 absorption could increase and continue throughout the 21st century.

Dr. Knauer elaborated: “We looked at how efficiently CO2 moves through the interior of leaves, how plants adapt to temperature changes, and how they distribute nutrients in their canopy. These three processes are crucial for a plant’s ability to ‘fix’ carbon, yet they are often neglected in many global models.”

Photosynthesis, the process by which plants convert CO2 into sugars used for growth and metabolism, acts as a natural climate change mitigator by removing carbon from the atmosphere. The increased uptake of CO2 by vegetation has driven the expansion of the land carbon sink over recent decades. However, it has remained unclear how this carbon sink would respond to more extreme future climate conditions, including higher temperatures and shifting rainfall patterns.

Scientists have long suspected that extreme climate events, such as severe droughts and heatwaves, could weaken terrestrial ecosystems' capacity to act as carbon sinks. This study, however, tested a high-emission climate scenario to examine how vegetation’s CO2 uptake would respond to global climate change until the century's end.

The researchers used several versions of their climate model, varying in how they accounted for plant physiological processes. The simplest version ignored the critical processes related to photosynthesis, while the most complex model included all three mechanisms. The findings were clear: models that incorporated a deeper understanding of plant physiology consistently predicted stronger increases in vegetation’s ability to absorb CO2. When all processes were accounted for together, the effects were even more pronounced, suggesting the real-world impact of these combined factors could be even stronger.

Assistant Professor Silvia Caldararu, from Trinity College Dublin’s School of Natural Sciences, also contributed to the research. She emphasised the importance of these findings: “Most terrestrial biosphere models used to estimate the global carbon sink are located at the simpler end of the complexity scale, meaning they either only partially account for these physiological mechanisms or ignore them altogether. This suggests that we may be underestimating the effects of climate change on vegetation and its ability to adapt. Biology, as much as physics, plays a crucial role in climate models and must be better integrated.”

Dr. Caldararu added that the study’s findings have significant implications for nature-based climate solutions such as reforestation and afforestation. These approaches could have a greater and more long-lasting impact in mitigating climate change than previously thought.

However, she stressed: “Planting trees alone will not solve all of our problems. We must reduce emissions across all sectors. Trees are not a ‘get out of jail free’ card for humanity.”