A new study reveals that intact tropical peat swamp forests are now releasing more greenhouse gases than they absorb, even without human intervention. This finding significantly alters our understanding of these vital ecosystems and their role in climate change, particularly as land use, drought, and overall climate pressure increase.
Water Levels Drive Emissions
Researchers led by Professor Takashi Hirano of Hokkaido University tracked emissions across peat swamp forests in Indonesia, Malaysia, and neighboring regions. The team found that fluctuations in groundwater levels consistently led to a net release of warming gases, rather than long-term carbon storage. This pattern persisted across seasons and years, demonstrating that even undisturbed peatlands can become sustained sources of emissions during periods of rainfall swings and drought.
How Peat Forests Lock Up Carbon—and Why That’s Changing
Peatlands are formed by the accumulation of partially decayed plant matter—peat—in waterlogged conditions. The lack of oxygen slows decomposition, allowing carbon to remain stored for centuries. However, when water levels drop due to canals or dry spells, oxygen reaches the peat, accelerating its breakdown into carbon dioxide. The study highlights that this process is now occurring even in forests without direct drainage.
The Complicated Role of Methane
The release of greenhouse gases from peatlands isn’t limited to carbon dioxide. Microbes also produce methane in flooded conditions. Lower water levels increase carbon dioxide release, but decrease methane. The United States Environmental Protection Agency notes that methane traps significantly more heat than carbon dioxide, albeit for a shorter period. Therefore, strategies focused solely on reducing carbon dioxide by drying peatlands could inadvertently worsen the overall climate impact if methane emissions aren’t also considered.
Drainage and Drought Intensify the Problem
The research demonstrates that drainage dramatically increases greenhouse gas emissions. Drainage ditches lower groundwater, exposing peat to air and accelerating decomposition. Across the region, drainage nearly tripled total greenhouse gas emissions, while conversion to plantations or farmland increased that footprint over sixfold. Even without drainage, dry spells—like those associated with El Niño years—can lower water tables and trigger similar emissions increases, with annual output rising by approximately 16 percent during those events.
Looking Ahead
Satellite data was used to track peatland wetness across a 70,000 square mile area, providing a broad view of regional patterns. While the study acknowledges that smaller-scale drainage and farming practices may not be fully captured, the data reveals areas where maintaining high water levels could be most effective. Restoration efforts focused on rewetting drained peatlands could slow decay, and managers of plantations can raise canal gates and block ditches. Climate models suggest increased rainfall in some areas by mid-century, which could help lift groundwater levels. However, land-use decisions will ultimately determine how much carbon remains stored.
Frequently Asked Questions
What is peat?
Peat is partly decayed plant matter that accumulates in waterlogged conditions, forming a carbon-rich soil.
What role does groundwater play in peatland emissions?
Shifts in groundwater levels repeatedly tip peatlands toward releasing more warming gases than they absorb, even in intact forests.
How were these emissions measured?
Researchers tracked emissions using gas towers at 11 sites, combined with satellite rainfall records to estimate groundwater levels across a large area.
Given these findings, how might our understanding of natural carbon sinks need to be revised in light of changing climate conditions?
