Six feet under, a new approach to global warming– soil mineral carbon pathway

  • The study is the first global-scale evaluation of the role soil plays in dissolved organic carbon and the minerals that help store it.
  • Comparing different ecosystems, Kramer saw that moist environments sequestered far more carbon than dry ones. In desert climates, where rain is scarce and water easily evaporates, reactive minerals retain less than 6 percent of the soil’s organic carbon. Dry forests are not much better. But wet forests can have as much as half their total carbon bound up by reactive minerals.
  • If temperatures near the surface warm, there can be less water moving through soils even if rainfall amounts stay the same or increase.

Washington State University

A researcher has found that one-fourth of the carbon held by soil is bound to minerals as far as six feet below the surface. The discovery opens a new possibility for dealing with the element as it continues to warm the Earth’s atmosphere. One hitch: Most of that carbon is concentrated deep beneath the world’s wet forests, and they won’t sequester as much as global temperatures continue to rise.

[Scientists used] new data from soils around the world to describe how water dissolves organic carbon and takes it deep into the soil, where it is physically and chemically bound to minerals. [They] estimate that this pathway is retaining about 600 billion metric tons, or gigatons, of carbon. That’s more than twice the carbon added to the atmosphere since the dawn of the Industrial Revolution.

Scientists still need to find a way to take advantage of this finding and move some of the atmosphere’s extra carbon underground, but Kramer says the soils can easily retain more. For starters, a new understanding of the pathway is “a major breakthrough” in our understanding of how carbon goes underground and stays there, he said….

…while climate change is unlikely to directly affect the deep mineral-bound carbon, it can influence the pathway by which the carbon is buried. That is because the delivery system depends on water to leach carbon from roots, fallen leaves and other organic matter near the surface and carry it deep into the soil, where it will attach to iron- and aluminum-rich minerals eager to form strong bonds.

If temperatures near the surface warm, there can be less water moving through soils even if rainfall amounts stay the same or increase.

Marc G. Kramer, Oliver A. Chadwick. Climate-driven thresholds in reactive mineral retention of soil carbon at the global scale. Nature Climate Change, 2018; DOI: 10.1038/s41558-018-0341-4