How Trees May Save Us From Runaway Carbon Emissions
In recent times atmospheric CO₂ concentrations have reached unprecedented levels, with 2024 marking the largest annual increase ever recorded, a groundbreaking international study offers a surprising ray of hope. Scientists have discovered that trees may release significantly less carbon dioxide under future climate warming than previously thought—potentially rewriting our understanding of how forests respond to global temperature rise.
The Conventional Wisdom Challenged
For decades, climate scientists have operated under a troubling assumption: as temperatures rise, trees would inevitably pump more carbon dioxide into the atmosphere, creating a dangerous feedback loop that would accelerate global warming. This grim prediction suggested that Earth’s forests—our planet’s most vital carbon sequestration systems—might transform from climate allies into climate villains.
The logic seemed sound. Trees, like all living organisms, respire to generate energy for growth, releasing CO₂ as a byproduct. Since respiration increases with temperature, a warming world should theoretically trigger more tree respiration and, consequently, more atmospheric carbon. This process, known as a positive feedback loop, threatened to create a runaway greenhouse effect where warming begets more warming.
However, new research published in Science by an international team led by scientists at Tsinghua University, including Distinguished Professor Ian Wright from Western Sydney University’s Hawkesbury Institute of the Environment, challenges this conventional wisdom with compelling evidence.
The Science of Thermal Acclimation
The breakthrough centres on a phenomenon called thermal acclimation—the remarkable ability of plants to adjust their physiological processes in response to long-term temperature changes. Unlike the immediate, short-term responses that occur within seconds, minutes, or hours, thermal acclimation operates over months, years, and decades.
“Short-term, temperature-driven changes in plant respiration rates are measured in seconds, minutes and hours,” explains Professor Wright. “Due to the quick-acting enzymatic processes in plant tissues, the changes in plant respiration are very fast and predictable. This contrasts with the long-term, temperature-driven changes in respiration rates that are measured in months, years and decades.”
The distinction is crucial. Most global ecosystem models have historically assumed that trees’ short-term temperature responses would remain constant over longer periods. The new research proves this assumption fundamentally flawed.
A Global Investigation
To test their hypothesis, the research team assembled an unprecedented global dataset of wood respiration measurements, encompassing thousands of observations across hundreds of species from field sites spanning all major climate zones. This comprehensive approach included data from Australian savannas, rainforests, and woodlands collected by Professor Wright’s team over the past decade, alongside measurements from temperate forests, tropical ecosystems, and boreal regions worldwide.
The scale and diversity of this dataset allowed researchers to examine how tree respiration varies not just with temperature, but with long-term climate conditions. What they discovered was revolutionary: trees demonstrate remarkable adaptive capacity, adjusting their respiration rates to maintain efficiency even as temperatures rise.
The Implications for Climate Modelling
The findings have profound implications for how scientists predict carbon cycle feedbacks under future climate scenarios. Professor Sandy Harrison from the University of Reading, one of the world’s leading vegetation modellers, emphasises the significance: “These findings give scientists a new approach for assessing the degree to which ecosystems around the globe can slow the rate of warming.”
Currently, forests offset approximately 25% of anthropogenic greenhouse gas emissions, absorbing roughly 16 billion metric tonnes of CO₂ annually while emitting 8.1 billion tonnes through deforestation and natural disturbances. The new research suggests this balance may be more favourable than previously calculated, with trees potentially maintaining their carbon-absorbing capacity even under warming conditions.
Real-World Validation
The study’s timing couldn’t be more relevant. Recent data from NOAA shows that atmospheric CO₂ increases have accelerated dramatically, from 0.8 parts per million annually in the 1960s to 2.6 ppm per year in the last decade. Meanwhile, 2024 was confirmed as the hottest year on record, surpassing the critical 1.5°C warming threshold.
Despite these alarming trends, the new research offers evidence that forests may be more resilient than expected. This resilience becomes particularly important as climate change intensifies extreme weather events. Professor Wright notes that “future climates are predicted to have more frequent and more intense events such as heat waves, fires, droughts and floods. We’re already seeing that play out both here in Australia and around the world.”
The Broader Context of Forest Carbon Storage
The study’s findings align with emerging research on forest carbon sequestration potential. Scientists have identified that forests in areas where trees have been removed could potentially store an additional 189 gigatonnes of carbon—equivalent to decades of current emissions. This potential, combined with the new understanding of thermal acclimation, suggests that forest conservation and restoration efforts may be even more valuable than previously estimated.
However, the researchers caution against complacency. Recent studies have shown that extreme heat and drought in 2024 significantly weakened forests’ ability to absorb CO₂. The thermal acclimation discovered in the current study may help forests adapt to gradual warming, but sudden extreme events remain a significant threat.
Looking Forward: Implications for Climate Policy
The research provides crucial insights for climate policymakers and conservation strategists. As NASA’s recent analysis of tree-planting viability suggests, understanding how forests will respond to future climate conditions is essential for developing effective mitigation strategies.
The thermal acclimation findings suggest that protecting existing forests and restoring degraded ones may be even more effective at combating climate change than previously thought. Rather than becoming carbon sources, many forests may maintain their role as carbon sinks even under warming conditions.
The Road Ahead
While the research offers hope, scientists emphasise that it doesn’t diminish the urgency of reducing greenhouse gas emissions. The thermal acclimation effect will “dampen” but not eliminate the positive feedback between warming and plant carbon emissions. Moreover, the study focused specifically on woody stem respiration—other components of forest carbon cycling, including leaf respiration and soil carbon, may respond differently to warming.
As Dr. Han Wang and lead author Han Zhang from Tsinghua University note, the research has only recently become possible due to the accumulation of sufficient global data. Continued monitoring and research will be essential to refine our understanding of how forests will respond to unprecedented climate conditions.
The discovery of thermal acclimation in tree respiration represents more than just a scientific breakthrough—it offers a glimpse of nature’s remarkable capacity for adaptation. In an era of climate uncertainty, this research reminds us that Earth’s ecosystems may possess hidden resilience that could help stabilise our changing climate. However, this resilience depends on our commitment to protecting and restoring the world’s forests, ensuring they can continue their vital role as guardians of our planet’s atmospheric balance.
As we face the challenges of the coming decades, the forests’ ability to adapt may prove crucial to maintaining the delicate equilibrium between human activity and planetary health. The question now is whether we will give them the chance to demonstrate this remarkable capacity for survival and service to the global climate system.
We’d love your questions or comments on today’s topic!
For more articles like this one, click here.
Thought for the day:
“Daring to set boundaries is about having the courage to love ourselves even when we risk disappointing others.” Brené Brown
