Climate change mitigation potential of wetlands and the cost-effectiveness of their restoration

August 24, 2020

"Global distribution of the studies that assessed the net carbon budget by accounting for CO2, CH4 (and aquatic lateral export when available) in filled circles and wetland restoration cost in open circles with a cross."

Taillardat et al. 2020

Although inland and coastal wetlands are highly efficient sinks of carbon dioxide, they also release methane – another carbon-containing greenhouse gas. Hence, wetlands can in some cases draw down carbon and yet have a net warming effect on the climate due to methane release. This means that restoration, protection and management of wetlands must be carefully planned in order to ensure an overall cooling effect on the climate. Currently, use of different metrics of greenhouse gas mitigation can show the same wetland to have a positive or negative effect on climate. This paper addresses this problem by using ‘switchover time’ (i.e. the age at which a wetland has a net cooling effect) to assess the effect of wetlands and their management on global temperatures.

The authors conduct a global meta-analysis of wetland carbon dynamics, showing that any wetland can have a net cooling effect, so long as it is maintained with stable emissions for a sufficient length of time. This time period is substantially shorter for coastal wetlands (median of 8.5 years) than inland wetlands (median of 263 years), leading to a need for different protection/restoration/management strategies for different wetland types.

The authors highlight three key policy-relevant findings:

Restoration of disturbed inland wetlands only has a net cooling effect over 10s to 100s of years, and so should not be included in short-term mitigation strategies, but is nonetheless essential to reduce CO2 emissions in the long-term.
Conservation of 100-1000s year old inland wetlands is a high priority for mitigation strategies, because they provide high rates of carbon sequestration and are already having a net cooling effect, as well as holding stores of carbon that are irrecoverable if released.
Coastal wetland conservation, restoration or creation is an especially cost-effective mitigation strategy, although it can only contribute enough emission savings to meet a very small proportion of global mitigation targets.

Read the paper here.