Peatlands, the vast, waterlogged landscapes that store immense amounts of carbon, are under a severe threat from climate change. New research reveals that under future conditions of increased temperatures and carbon dioxide levels, an extreme drought could cause these vital ecosystems to release staggering amounts of carbon, potentially undoing centuries of storage in just a few months. This shift would transform one of the world’s most effective long-term carbon sinks into a powerful new source of greenhouse gases, accelerating the very climate change that triggers the effect.
These ecosystems cover just 3% of the Earth’s land surface but hold more than 30% of all soil carbon, which is more than is stored in all the world’s forests combined. For millennia, the low-oxygen, water-saturated conditions of peatlands have preserved partially decayed plant material, locking its carbon away. The new study, published in the journal Science, warns that the stability of this massive reservoir is far from guaranteed. Researchers found that severe drought, when combined with the warmer and CO2-rich atmosphere expected in the future, could nearly triple the rate of carbon loss, wiping out between 90 and 250 years of accumulated carbon.
An Unprecedented Carbon Reservoir
Peatlands, which include bogs, fens, and marshes, are characterized by the slow accumulation of organic matter due to waterlogged conditions that inhibit decomposition. This process has made them incredibly efficient at sequestering atmospheric carbon over thousands of years. The sheer density of this carbon storage makes them a critical component of the global climate system. Their outsized role means that any disruption to their natural balance can have disproportionate consequences for the atmosphere.
These unique habitats are found across the globe, from tropical swamp forests to arctic tundra. They not only serve as a climate regulator but also provide essential ecosystem services, including water purification and flood mitigation, and they are home to specialized species of plants and animals. The stability of this vast carbon store has long been dependent on consistent moisture, but as climate change intensifies, the frequency and severity of droughts are increasing, placing these critical zones at risk.
Simulating Future Climate Stress
To understand how peatlands might respond to future climate conditions, a team of researchers utilized a sophisticated outdoor laboratory in northern Minnesota. The project, known as Spruce and Peatland Responses Under Climatic and Environmental Change (SPRUCE), is run by the Oak Ridge National Laboratory and involves a consortium of scientists. The experiment uses a series of large, open-topped chambers that resemble yurts, constructed over a natural peat bog.
A High-Tech Experimental Bog
Within these enclosures, scientists can precisely control environmental conditions to simulate various climate change scenarios. For this study, they manipulated plots by elevating temperatures by as much as 9 degrees Celsius and increasing atmospheric carbon dioxide concentrations. This setup allowed them to isolate the effects of these variables and study their combined impact on the peatland ecosystem, from the vegetation on the surface to the microbial communities deep within the soil.
An Unplanned Real-World Test
The experiment gained an unexpected and valuable dimension during an extreme drought that struck the region in the summer of 2021. This real-world weather event provided a natural test for how the simulated future climates would interact with a severe lack of moisture. The researchers observed that in the plots with elevated temperatures and CO2, the water table dropped lower and took longer to recover compared to control plots. This prolonged drying exposed deeper, older layers of peat to oxygen, dramatically accelerating decomposition and the release of carbon dioxide.
A Surprising Climate Feedback Loop
One of the most startling findings from the study was the role of elevated carbon dioxide. Scientists had previously hypothesized that increased CO2 might make ecosystems more resilient to drought by improving water use efficiency in plants, a phenomenon known as CO2 fertilization. While the team did observe that elevated CO2 alone could boost ecosystem productivity, its interaction with drought and high temperatures produced the opposite effect.
Instead of mitigating the impact of the drought, the combination of high CO2 and warmth created a more severe outcome. The research team discovered that the elevated carbon dioxide levels increased the amount of substrate and dissolved carbon in the bog. When the drought hit, this abundance of available carbon fueled a massive release of greenhouse gases. According to Yiqi Luo, a professor at Cornell University and the study’s senior author, this result was unexpected and indicates that previous models may have underestimated the vulnerability of peatlands. This finding points to a dangerous positive feedback loop, where the consequences of climate change could be even more severe than anticipated.
From Carbon Sink to Carbon Source
The study’s central conclusion is that future climate conditions could flip a switch on peatlands, transforming them from a net absorber of carbon to a significant emitter. The potential for a few dry months to erase centuries of carbon sequestration represents a critical tipping point. “We observed that these extreme drought events can wipe out hundreds of years of accumulated carbon,” Luo stated, highlighting the high stakes involved. This shift would not only neutralize a vital climate ally but turn it into an adversary, releasing ancient carbon that would further amplify global warming.
The Intergovernmental Panel on Climate Change already predicts that extreme droughts will become substantially more common in the near future, making the findings particularly urgent. Joel Kostka, a professor at Georgia Tech and a study co-author, emphasized the severity of the findings, noting that just two months of extreme drought could erase 10 to 100 years of carbon uptake. This rapid reversal underscores the need to protect these ecosystems to prevent the release of their immense carbon stores.
Urgent Need for Mitigation and Protection
The research highlights the urgent need for global efforts to mitigate climate change and protect peatlands. Bending the warming curve is essential to prevent these ecosystems from crossing a critical threshold. The findings from the SPRUCE site are being used to improve global climate models, providing a clearer picture of how these landscapes will behave as the planet warms.
Preserving and restoring the water-logged conditions of peatlands is now a critical climate action priority. These ecosystems are a silent but powerful force in the Earth’s carbon cycle, and their collapse would have cascading effects on global climate patterns. The study serves as a stark warning that the planet’s natural carbon reservoirs are not infinitely resilient and that failing to curb emissions could awaken these sleeping giants, with devastating consequences for the global climate system.
