Forest soils absorb less atmospheric methane under higher temperatures because soil bacteria adapt to persistent heat. Scientists long assumed that rising global temperatures would speed up how quickly these microbes consume greenhouse gas. Instead, heat-adapted methanotrophs, which are specialized bacteria that break down methane, decrease their gas processing rates over time.
When forest soil experiences warmer annual temperatures, the resident methanotroph communities adjust their cellular activity to the continuous warmth. This biological shift works like a runner pacing themselves in hot weather by slowing down their baseline effort. As a result of this thermal adaptation, each bacterial cell oxidizes fewer methane molecules from the surrounding soil pores. However, exposing the soil to elevated methane levels experimentally reduces this thermal slowdown, allowing the bacteria to maintain higher oxidation activity.
Researchers collected soil samples from 67 forest sites across a broad temperature gradient to test long-term microbial responses. The team measured methane oxidation rates in each sample under controlled laboratory temperatures and varied gas concentrations. The tests proved that microbial methane breakdown rates consistently decrease with higher mean annual site temperatures.
Incorporating microbial thermal adaptation into climate models makes future predictions of land-based methane absorption far more accurate. Factoring in how methane concentrations alter this thermal response allows climate forecasters to refine projections of greenhouse gas accumulation across diverse forest ecosystems.