Climate change projected to set off substantial rise in methane emissions from wetlands

By the end of this century, natural methane (CH4) emissions from wetlands are projected to increase by up to 80%, compared with the beginning of the century, if no concrete actions are taken to reduce anthropogenic greenhouse gas emissions, a JRC led study finds.

With their water-drenched soils and low levels of oxygen, wetlands are breeding grounds for micro-organisms that produce methane. ©, adobe stock 2020

Rising temperatures, higher water tables, and the emergence of new wetlands due to the thawing of permafrost all contribute to swamps, marshes and bogs releasing more methane into the atmosphere.

Methane is a powerful greenhouse gas. Its global warming potential is estimated to be between 28 and 34 times higher than that of carbon dioxide (CO2).

In a paper published in Science Advances, JRC scientists produce a novel global estimate of wetland methane emissions based on observations of atmospheric methane concentrations and climate data.

Based on this analysis, they project future CH4 emissions from wetlands under different climate scenarios.  

Their results suggest that by 2100 - under a business-as-usual climate scenario, where no actions are taken to reduce anthropogenic greenhouse gas emissions - current natural CH4 emissions from wetlands may increase by 50% to 80%.

"These results highlight the importance to limit global warming below 2◦ C to avoid significant climate feedbacks driven by methane emissions from natural wetlands", JRC scientist Ernest Koffi said.

Wetlands are the single largest natural source of methane. About a third of all CH4 in the air originates from them.

With their water-drenched soils and low levels of oxygen, wetlands are advantageous breeding grounds for the micro-organisms that produce methane.

Methane production, however, is very sensitive to climate, especially the temperature and rainfall.

In the boreal regions, methane production will increase with increasing temperature due to global warming.

Furthermore, each degree of temperature rise is expected to bring about a 7 % hike in rainfall.

The study shows that any temperature increase will substantially foster wetland CH4 emissions in the colder regions, but decrease the emissions in the warmer areas, with compensatory effects between the latitudes.

In contrast, any increment of rainfall will enhance the wetland emissions in all climate regions.

In addition, as polar ice and permafrost melt, the wetland area is likely to grow.

All these effects together are projected to increase natural CH4 emissions from wetlands by 50-80% in 2100, if no actions are taken to reduce anthropogenic GHG emissions.