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Soil Organic Carbon: the hidden potential- new FAO report just launched

The publication was launched at the Global Symposium on Soil Organic Carbon (GSOC) held at FAO headquarters (Rome, 21-23 March 2017). It provides an overview to decision-makers and practitioners of the main scientific facts and information regarding the current knowledge and knowledge gaps on Soil Organic Carbon.

It highlights how better information and good practices may be implemented to support ending hunger, adapting to and mitigating climate change and achieving overall sustainable development.

In the presence of climate change, land degradation and biodiversity loss, soils have become one of the most vulnerable resources in the world. Soils are a major carbon reservoir containing more carbon than the atmosphere and terrestrial vegetation combined. Soil organic carbon (SOC) is dynamic, however, and anthropogenic impacts on soil can turn it into either a net sink or a net source of GHGs. Enormous scientific progress has been achieved in understanding and explaining SOC dynamics.

Yet, protection and monitoring of SOC stocks at national and global levels still face complicated challenges impeding effective on-the-ground policy design and regionally adapted implementation. After carbon enters the soil in the form of organic material from soil fauna and flora, it can persist in the soil for decades, centuries or even millennia. Eventually, SOC can be lost as CO2 or CH4 emitted back into the atmosphere, eroded soil material, or dissolved organic carbon washed into rivers and oceans. The dynamics of these processes highlight the importance of quantifying global carbon fluxes to ensure maximum benefits of SOC to human well-being, food production, and water and climate regulation.

Drylands cover approximately 430 million ha, which comprise 40 percent of the Earth’s surface (Figure 11, page 30) (FAO and ITPS, 2015). Although there is no clear boundary, drylands are considered to be areas where average rainfall is less than the potential 
moisture losses through evaporation and transpiration (FAO, 2004).

The soils of drylands are characterized by frequent water stress, low organic matter content and  low nutrient content. However, their carbon storage accounts for more than one third  of the global stock, mainly due to their large surface area and long-term SOC storage (when the soil is not degraded), rather than due to vegetation cover.

Drylands have the potential to sequester more carbon than as they are far from saturated (United Nations, 2011), but carbon storage in drylands is affected and limited by various bioclimatic elements and is slow.

Furthermore, these lands are susceptible to various types of degradation, including wind erosion, and certain management practices therefore easily result in degradation. Therefore, dryland soils need to be sustainably managed to maintain their existing SOC levels and foster their SOC sequestration potential.

A valuable, vulnerable resource

  • Carbon is sequestered underground after being "fixed" from the atmosphere via plants or organic residues and then incorporated into soils through largely natural processes.
  • Soil carbon content consists of both living and dead components, and can include both field stubble, as well as decayed materials from millennia ago.
  • This adds up to a vast reservoir of carbon, according to the report being presented at the symposium.
  • But when soil is disturbed or degraded, trapped carbon and other greenhouse gases resulting from decay are re-released back into the atmosphere.
  • This means that the Earth's soil carbon reservoir could either release massive amounts of greenhouse gases into the atmosphere, or sequester more of them, depending on the management decisions we make going forward, the report says.
  • Already, one-third of the planet's soils are degraded, leading to an enormous decrease in global soil organic carbon stocks and the release of up to 100 gigatonnes into the atmosphere.
  • Further damage to soil carbon stocks through poor soil management will hamper efforts to limit global temperature rises and avoid increased floods, droughts and other climate change impacts, warns "Soil Organic Carbon: The Hidden Potential"
  • Meanwhile, rising temperatures and an increased frequency of extreme weather events will lead to additional losses of soil organic carbon, making improvement management even more urgent.
  • Of particular concern are soils with high levels of organic content, like peatlands and temperature-vulnerable permafrost zones.
  • These "hot spots" will likely become net sources of greenhouse gas emissions in the future, barring effective interventions.
  • The main greenhouse gases emitted by soil are carbon dioxide and methane; another is nitrous oxide, whose emission is increasingly being driven by human activity in the livestock sector.

Making the most of a massive carbon sink

There are many agricultural and land management practices that can preserve and boost soil organic carbon — not only mitigating global warming but offering multiple additional benefits.

Some studies suggest that the rehabilitation of agricultural and degraded lands could remove up to 51 Gt of carbon from the atmosphere. Others estimate that adopting agricultural practices that conserve soil organic carbon can increase food production by 17.6 megatonnes per year.

Improving soil health will not only help raise local agricultural productivity, but also significantly boost the resilience of farmers and agricultural communities.

However, global adoption rates of sustainable soil management practices remain relatively low, due to financial, technical and institutional barriers as well as information and knowledge gaps.

Explore the related publications collection behind each of the terms listed here : forest soils; wetland soils; peatlands; grassland soils; dryland management; permafrost areas; carbon cycle; carbon sequestration; greenhouse gases; greenhouse soils; Environmental impact assessment; environmental monitoring;

Read the full text publication "Soil Organic Carbon: the hidden potential"

Follow FAO news story "Soil management could make or break climate change response efforts. Symposium, report shine light on critical role of terrestrial carbon sinks"