deep soils surprisingly contain a lot of CO2, but warming is bad news

Since we are children, we are taught natural cycles – the two most common cycles being the water and carbon cycle. We were taught that there was a balance in these cycles, preventing the Earth's carbon from being released into the atmosphere or completely absorbed by water and rocks.

In this period of the history of our planet, this equilibrium is disturbed by the industrial activities of humanity. The basic process is extremely simple: we emit too much carbon dioxide, at a much faster rate than it can be absorbed by natural processes. This process is well documented and its effects are also obviously serious, although the subtleties and details remain less well understood.

For example, the influence of soils remains somewhat uncertain.

<! – Username: zmescience_300x250_InContent

->

"We know less about soils on Earth than on the surface of Mars," said Marc Kramer, an associate professor of environmental chemistry at WSU Vancouver, whose work appears in the paper. Nature Climate change. "Before we can start thinking about storing carbon in the soil, we really need to understand how it does it and how likely it is to stay. This discovery highlights a major breakthrough in our understanding. "

A simple representation of the carbon cycle.

Kramer and his colleagues made the first global assessment of the role soil plays in carbon storage. They analyzed soil and climate data from the Americas, New Caledonia, Indonesia, and Europe and drew from more than 65 sites sampled at a depth of six feet from the network. National Ecological Observatories funded by the National Science Foundation. In particular, they focused on how carbon is dissolved in soils and minerals that help store it.

This allowed them to map out carbon accumulation and better understand the pathway that leads carbon to be trapped in these soils. Spoiler Alert: There is little reason to be optimistic.

The good news is that, according to this estimate, soils currently store about 600 billion gigabytes of carbon (twice as much as humanity's production since the industrial revolution). However, the bad news is that if temperatures continue to rise, this could seriously hamper the amount of carbon stored. This would occur because water is the main mechanism by which carbon dissolves in soils and even though rainfall remains unchanged, higher temperatures mean less water is entering the soil. It also helps to explain why wet soils store more carbon than dry soils.

The researchers also discovered that deeper soils store surprisingly a lot of carbon – but the storage route is largely similar. Thus, while carbon storage in the deepest parts of the soil will not be directly affected by rising temperatures, the route by which carbon is stored is changed. Essentially, this path depends on water to suck up carbon from roots, dead leaves and other organic matter, and transport it to the deeper layers, where it remains trapped. In simple terms, if there is less water, there is less carbon stored.

In general, moist forests tend to be the most productive environments because the thick layers of organic matter from which the water will leach carbon and transport it to minerals up to six feet below the surface.

"This is one of the most persistent mechanisms of carbon accumulation that we know," said Kramer.

This is not the first study to sound the alarm about the impact of soils on carbon levels. Two years ago, another study found that the soil's ability to absorb carbon had been significantly overestimated, whereas only a few months ago, soil erosion was considered a source. potential for additional carbon release into the atmosphere.

The study was published in Nature Climate change.

Enjoyed this article? Join over 40,000 subscribers to the ZME Science newsletter. Subscribe now!