A long-held assumption is that climate change reduces the potential for forest soils to extract methane from the atmosphere; however, a new scientific study has revealed something surprising.

Methane is a powerful greenhouse gas which contributes to global warming. While many know carbon dioxide (CO₂) is a significant issue, methane is often talked about less. Reducing methane levels is important because, over 20 years, it traps more heat than carbon dioxide.

New research suggests that with warmer temperatures and reduced rainfall, forests could absorb higher levels of methane, which would help to tackle climate change. With the right conditions, microorganisms within forest soil can break down methane before it accumulates in the atmosphere.

Scientists from the University of Göttingen and the Baden-Württemberg Forest Research Institute (FVA) investigated methane absorption at forest sites in southwestern Germany. Their findings revealed that levels of methane absorbed by soil in their test sites increased over time and that warmer temperatures and reduced rainfall were associated with an improved uptake.

The science project took place over 24 years and examined measurements from thirteen forest sites: methane absorption by soil increased, on average, by 3% per year.

During the project, scientists analysed soil gas profiles to reveal gas concentrations at various depths beneath the ground. Air samples were collected through thin tubes installed in the soil every two weeks, and samples were analysed, which enabled the team to track changes in methane concentrations over many years. The team built a detailed picture of methane uptake across forest sites and scrutinised how it responded to changing environmental conditions.

The methane uptake was greater with reduced rainfall and higher temperatures, but with increased rainfall, it was more difficult for methane to move through soil particle gaps. This restricts the methane-consuming microorganisms' access to the gas. But in drier conditions, methane can move into the soil more readily, which enables microorganisms to break it down.

The forest soil acts as a natural sink for methane, removing it before it can contribute to warming. So, if in future, climate change matches these environmental conditions, it could strengthen what is a natural process and help regulate methane emissions. These results do not mean forest soils across the world will respond the same way, and we cannot let ourselves assume climate change is beneficial to forests.

Photo:Martin Maier