Ancient Indigenous communities likely spread ash and organic waste on the land to enhance fertility and support crop production. Now, some conservation groups like Conscious Planet are calling for countries to commit to intentionally enhancing soil carbon the world over as a key part of international climate action. As a soil carbon scientist, I’m here to explain why.
Soil is a vital component of the climate system. It is one of the largest stores of organic carbon on Earth – containing more carbon than both the atmosphere and vegetation combined. This makes soil both a climate risk and an opportunity.
While soils may not look that dynamic, they are constantly changing as they exchange carbon with the atmosphere and the plants and organisms living within them. As plants grow, their roots release organic compounds, adding carbon into the soils and exchanging it with other organisms like fungi. As plants and other organisms die, they add their organic matter to the soil, and decomposition of this material by microorganisms leads to the release of some of it as carbon dioxide and methane.
In natural conditions, these in and out flows may be well balanced, but human actions, such as deforestation and agriculture have disturbed these cycles, leading to the release of carbon dioxide and other greenhouse gases. It is estimated that past land use change and soil degradation is responsible for about 15% of the global warming caused by greenhouse gases. However, reversing this trend can increase the amount of carbon stored in soils, helping to mitigate climate change.
The slow rise of soil in climate policy
Soil first gained attention on the UN climate summit stage in 2015, when France launched the 4 per 1000 initiative during Cop21 in Paris. The idea: if global agricultural soils increased their carbon stocks by just 0.4% per year, it could offset nearly all annual greenhouse gas emissions.
While questions were subsequently raised about the feasibility of this rate of carbon gain, the target was intended as an aspirational one and the initiative has been important in putting soils on the climate and agricultural agendas. Also, putting carbon back into agricultural soils is not only about climate mitigation. Increasing the amount of organic matter, and in turn organic carbon, stored in soils means improving water holding capacity and nutrient cycling, helping to increase the sustainability and resilience of crop production and global food security.
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The 4 per 1000 initiative has had good buy-in: 41 nations have signed up as members, along with hundreds of other regions, environmental charities, research institutions and businesses. At subsequent UN climate summits, focus on soils has grown, with soil featured more heavily in land use and climate finance initiatives.
Yet in most national climate pledges, soil still appears only indirectly according to a new global analysis, with vague references to “soil health” embedded in other sectors like agriculture or adaptation, rather than as a clear mitigation strategy with explicit carbon targets.
An expert explains the meaning of nationally determined contributions or NDCs.
This gap matters because those pledges (known as nationally determined contributions) drive government actions. If soil carbon targets are not explicitly named, they probably won’t be funded or prioritised.
My group’s research has shown how important soils could be to national climate action – even for high-emitting countries with relatively little land per capita, such as the UK. Our modelling work suggested that reasonable levels of afforestation and grassland restoration could deliver up to 7% of the cuts in emissions needed by 2050 in the UK. This would be a substantial contribution, and other soil-focused actions, like the peatland restoration would deliver further emissions savings.
Healthy soil structure helps build climate resilience by reducing flood risk and storing carbon. William Edge/Shutterstock
Concrete commitments
Cop30 in Brazil – a global hotspot for both nature and agriculture – provides an excellent opportunity to ensure soils feature strongly in pledges and implementation plans.
Pledges to invest in nature will feature highly. For example, the Tropical Forests Forever Facility is a new global fund supporting tropical forest conservation. It’s important that soils are robustly considered as part of this.
While soil is a potentially powerful ally for climate mitigation and adaptation, nothing can replace rapid cuts to fossil fuel emissions. In a warming world, rising temperatures and extreme weather threaten the very ecosystems that store carbon. Our research suggests that soils can only remain a net carbon sink under optimistic climate scenarios.
Put simply, stronger and more specific soil carbon targets could help us on the road to better climate outcomes, but only if we act fast to protect soils and other carbon rich ecosystems, while cutting emissions across our economies.
