Por Mauro Rebelo

Fix the soil and carbon, and many other things, will fix themselves

global carbon stocks
Global carbon storage compartments. Taken from https://www.fs.usda.gov/ccrc/topics/global-carbon

Most claims about climate change are based on a verifiable increase in CO2 in the atmosphere. This increase was substantial compared to what the Earth has experienced over the last few millennia. It is difficult to predict what changes this increase might cause, so it is a good strategy to try to mitigate and prevent an even greater increase.

The CO2 that went into the atmosphere was stored elsewhere. The image illustrating this post shows the compartments and the amount of CO2 in each of them. Most of the CO2 is in the ocean. But the second largest compartment is vegetation and soil. For most purposes, the Earth is considered a closed system. Apart from one meteor or another coming in, one rocket or another going out, the number of atoms on Earth is stable (a curious fact: Earth and Mars apparently exchange around 10g of dust a year).

I have to say that the first time I saw this data I was a little surprised. I knew that the oceans, because of the bicarbonate buffer system, had a LOT of carbon. It’s intuitive to think of forests as another huge compartment. But soil? Unless you know what soil really is. I like this explanation at the beginning of the MIT climate portal:

“Soils are partly made of decomposed plant matter. This means that they contain a lot of carbon that these plants absorbed from the atmosphere while they were alive. Especially in colder climates, where decomposition is slow, soils can store – or ‘sequester’ – this carbon for a long time.”

Like most nutrient atoms, carbon has a cycle, moving from one compartment to another driven by biotic (biological) and abiotic (physical, chemical and physicochemical) forces. The global carbon cycle is described here:

Carbon cycle.jpg
Diagram adapted from U.S. DOE, Biological and Environmental Research Information System. – http://earthobservatory.nasa.gov/Features/CarbonCycle/ Retrieved from: https://en.wikipedia.org/wiki/Carbon_cycle

While emissions from burning industrial and fossil fuels are responsible for most of the CO2 that goes into the atmosphere, land use change is the second.

“[…] converting natural ecosystems such as forests and grasslands into farmland disrupts soil structure, releasing much of the stored carbon and contributing to climate change. Over the past 12,000 years, the growth of agricultural land has released about 110 billion metric tons of carbon from the topsoil2 – roughly equivalent to 80 years of current US emissions,” says the MIT website again.

Soil recovery is a fundamental strategy for reducing the remobilization of CO2 into the atmosphere. The FAO’s Global Soil Partnership has a country-oriented global estimate of COS sequestration potential worldwide(GSOCseq) and a compendium of good practices for farmers “Recarbonizing global soils” on how to maintain SOC stocks and how to sequester CO2.

“Replenishing and protecting the world’s soil carbon reserves could help offset up to 5.5 billion tons of greenhouse gases every year.”

says Dr. Deborah Bossio, chief soil scientist at the Nature Conservancy, in an article published in Nature Sustainability.

Soil restoration is also a very cross-cutting measure that touches on several important aspects of environmental quality and sustainability: the carbon cycle, pollution control (preventing nutrient runoff and eutrophication of rivers), water quality, microbial biodiversity, food security… UN Sustainable Development Goals – SDGs.

But restoring degraded soil is no easy task!

“There are hundreds of millions of farmers around the world, most of them cultivating small plots of land. To make the most of soil-based sequestration as a climate solution, we would need many of them to change the way they farm, now and for hundreds of years into the future. This is a major social and economic challenge, and experts debate how much soil-based sequestration is really possible in the long term.”

Says the MIT website while Dr. Bossio says:

“There are many barriers now to changing our agricultural systems. One of the biggest is the disincentive to agricultural policy. There is also a lack of knowledge about how to change current practice. We tell farmers ‘just cover crops’ – but that means a farmer needs to know when to plant them, which ones to plant and how to manage them. “

It is therefore reasonable to understand the skepticism of some scientists as to whether this trend can be reversed on a global scale. But one way to do this would be to create products that help farmers change their practices. Biotechnology can help.

An article in Forbes talks about a new generation of biotech companies that claim they can turn the world’s soil into a major carbon sink, absorbing up to a quarter of annual emissions. One of these companies is Soil Carbon Co., based in Australia. They are adapting communities of microbes that live in the soil of farms to turn back the clock on human emissions while producing better crops. Its CEO Guy Hudson explains:

“We have developed microbiological seed treatments composed of microbial fungi and bacteria designed to provide benefits to plants. As the plant grows, it exudes sugars into the soil that are converted into stable soil carbon by the fungi.”

Hudson says that this solution allows the soil to quickly build up significant amounts of stable carbon, stored in small balls of soil called microaggregates, preventing the carbon from being released back into the atmosphere.