About This Project

Soil bacteria remove ~30 Mt of methane/year from the atmosphere, but this rate varies strongly with land use. We discovered that sage scrub ecosystems are a local hotspot for natural methane uptake, exceeding dataset averages by up to 1,240%. Why are these landscapes so effective at atmospheric methane removal? We will identify the causes, using our findings to develop soil amendments and management guidelines for better methane uptake in other landscapes.

Ask the Scientists

What is the context of this research?

As scientists are working to develop methane drawdown technologies, bacteria in soils are already consuming ~30% as much methane as is produced by the fossil fuel industry each year. Across hundreds of studies, land use has emerged as the strongest correlating factor of soil methane uptake rates–this highlights the potential to influence the soil methane sink through land use decisions. In our multi-year survey of California soils, we recorded the highest methane consumption rates in a coastal sage scrub landscape. We found that average rates in sage scrub locations exceeded rates in grasslands by 239%, even when sage and grassland sites were in the same location and climate. Our discovery points to a unique property of sage soils that enhances natural methane uptake. We propose to uncover the chemical or biological factor that enhances methane uptake in sage soils, and test how to apply this factor in other managed soils.

What is the significance of this project?

Methane is a potent greenhouse gas, with ~85 times as much heat-trapping potential as CO2 on a 20-year timescale. Rapidly improving global methane drawdown is a crucial goal for averting near-term climate warming. Based on our preliminary measurements, a simple soil amendment based on sage scrub soil could enhance methane uptake rates by >200%, contributing significantly to methane removal goals. 52% of U.S. land area is already managed for agricultural use, and a 200% enhancement of methane uptake across this land area alone would amount to increased methane drawdown of 2.24 Mt/yr, a ~7% improvement in the global soil methane sink.

What are the goals of the project?

We will construct experimental plots at two California field sites with adjacent sage scrub and grassland landscapes. Experimental plots will be used to test the effects of sage removal, sage planting, sage leaf litter application, and sage root application at 6-month and 12-month timepoints, alongside unaltered sage scrub and grassland control plots. We will track methane uptake for each plot, and use sequencing, metabolomics, and geochemical analyses to identify the unique factors that drive rapid methane uptake in sage scrub soils. These may include specific plant metabolites, bacterial species, or root structures.

Based on our results from this proposed research, we will develop and launch a second phase of the project to directly test the relevant soil components as soil amendments to additional experimental plots and quantify the enhancement in methane drawdown.