Temperate wetlands lose climate-cooling capacity under warming

Area of Science:

• Environmental Science
• Climate Science
• Wetland Ecology

Background:

• Temperate inland wetlands traditionally regulate climate by sequestering carbon dioxide (CO₂) and emitting methane (CH₄).
• The net climatic impact of these opposing fluxes is uncertain, especially under anthropogenic warming, due to differences in emission magnitude and atmospheric lifetime.

Purpose of the Study:

• To estimate greenhouse gas dynamics in North American temperate inland wetlands over two centuries.
• To assess the shift in net climate effect from CO₂ sequestration and CH₄ emissions under historical and projected warming scenarios.

Main Methods:

• Combined 19,000 methane (CH₄) chamber measurements from 202 temperate inland wetlands.
• Utilized carbon burial rates from 16 dated sediment cores in North America's Prairie Pothole Region.
• Estimated greenhouse gas dynamics over a two-century timescale.

Main Results:

• Methane (CH₄) emissions increased by approximately 1.39 kg CH₄ ha⁻¹ yr⁻¹ historically.
• Projected CH₄ emissions may reach 950 kg CH₄ ha⁻¹ yr⁻¹ by 2100 under high-forcing scenarios.
• Carbon dioxide (CO₂) sequestration is expected to decline by approximately 0.3 kg CO₂ ha⁻¹ yr⁻¹.

Conclusions:

• Wetlands are shifting towards becoming persistent net CO₂-equivalent sources.
• The long-term cooling effect historically provided by wetlands is weakening.
• Anthropogenic warming is altering the net climatic role of temperate inland wetlands.