Sink or source: How soil savvy are you?

Samantha Ibbott·

From ‘cover crops’ to ‘carbon credits’ soil carbon is a hotly debated topic, but what exactly is it? How does it influence soil health and our ability to grow food? And what impact does human activity have on it? Dig deeper and discover how much you know with our quiz… 

The Earth’s soils contain around 1500 billion tonnes of carbon. This is significantly less than the oceans – the world’s largest carbon sink at 40,000 billion tonnes – but significantly more than the atmosphere (800 billion tonnes) and all plant and animal life (560 billion tonnes). Soil’s ability to store carbon, through organic matter, makes it a key player in the global carbon cycle, in which carbon is exchanged within and between the atmosphere, the oceans, and land. But what happens to this cycle when human activity interferes? And what is the EU doing about it? All will be revealed, but first, let’s take a closer look at the ground beneath our feet.

All soils are made equal.

Illustration of person with long hair, holding up two circles contain soil.

Different soils store different levels of carbon. Soil isn't just a layer of ‘dirt’. Dig a little deeper and you'll discover that it's so much more than that. The world's soils are an incredible habitat for life, playing host to more life, and more biodiversity, than almost anywhere else on earth. There are six main types of soil: peat; chalky; clay; loam; sandy; and silt. But when observing soil from a carbon perspective they can fit broadly into two categories, organic and mineral. 

A number of different soil samples, of various colours and textures.

Organic soils are generally found in wet areas, also known as peatlands. They formed through the growth of mosses and other plants in a waterlogged environment with no, or very little, decomposition of dead plant matter due to the lack of oxygen. They contain a very high share of organic matter and are therefore particularly high in carbon, making them incredibly effective carbon sinks. Soils with a carbon content, by dry weight, of over 18% are considered organic, but this can vary depending on soil type. On the flip side, they also have the potential to release a lot of carbon if disturbed. Only 3% of the EU’s agricultural soils are organic, but they are responsible for 25% of emissions - due to drainage from agriculture and related land-use practices. Drainage has historically been promoted to dry the land for conventional agricultural use or extraction, as peat was, and still is, used as fuel in many parts of Northern Europe. But this brings oxygen into the soil which unlocks the decomposition of organic matter, releasing the carbon - that has built up and been stored over thousands of years - into the atmosphere. By rewetting this land, the EU would be able to turn it into a net carbon sink, sequestering about six mega tonnes of carbon, and other greenhouse gases, per year. 

Mineral soils, on the other hand, are formed from the weathering and breaking down of rock material over millions of years, as well as the constant cycling of plant organic matter, and therefore contain much less carbon, on average 5% of their dry weight. These soils are also net emitters of carbon in the EU due to intensive land use. But these emissions are dwarfed by those from organic soils. While restoring organic matter (or carbon) in these soils is also critical for their overall health and resilience, many soil scientists have warned that this should not be considered a “climate mitigation” solution as carbon in mineral soils is easily re-emitted to the atmosphere if climatic conditions or land management practices change.  

Agricultural soils... 

Illustration of a tractor in a field, with the chemical symbol for carbon imposed over the top.

Globally, agricultural soils have lost between 25-75% of their carbon content - depending on climate, soil type (as above), and historic management. The intensification of agriculture in the last 70 years and large-scale land use changes since the 1850s, mainly for urbanisation and agricultural purposes, have massively degraded our soils. The carbon released through such activity accounts for about 23% of global anthropogenic greenhouse gas (GHG) emissions. This not only contributes to the climate crisis but also soil degradation, the reduced ability for soils to absorb and store water, and the collapse of below- and above-ground biodiversity, seriously risking our future capacity to grow food. 

Carbon farming has the potential to address these challenges whilst also securing the livelihoods of future farming generations. At the EEB, we define carbon farming as land management practices which sequester carbon whilst supporting and improving biodiversity. This includes agroecology, agroforestry, the restoration of peatlands, close-to-nature forestry, and extensive grassland management. Such practices are examples of agricultural systems which produce food in harmony with nature for the benefit of society and the natural world. In addition, such systems are more fertile and much more resilient to the existing and expected impacts of climate change, such as droughts, floods, and soil erosion which devastate ecosystems and ruin farmers’ livelihoods. Cover crops, wide crop rotations, ley cropping, reduced/low or no tillage, adding organic matter (by applying mulch or composted biowaste), introducing trees into agricultural landscapes, and integrating livestock in the rotation are all beneficial for the climate and soil health. However, fewer than 3% of EU farms have fully taken up agroecological practices. Why so few, and how could more be encouraged and enabled to do so? 

The European Commission’s proposal for a Carbon Removal Certification Framework (CRCF) presents an opportunity to change this by encouraging "sustainable carbon farming solutions, while fighting greenwashing". Although this sounds commendable at a glance, our analysis has found that the framework itself will encourage greenwashing, through the use of ‘carbon credits’.  

Carbon credits are thought to incentivise farmers to adopt carbon farming practices by providing a new income source, as businesses purchase credits to offset their own emissions. However, major concerns remain about the effectiveness of carbon credits, as many businesses ‘offset' their current emissions with cheap removals, rather than curtailing them in the first place. Such erroneous 'climate action' not only contradicts the warnings from the Intergovernmental Panel on Climate Change (the IPCC) that cutting emissions is - and must remain - the absolute priority, but they also leave the door wide open for widespread greenwashing. What’s more, land-based carbon removals are not permanent and can be released back into the atmosphere, leading to many businesses purchasing 'worthless' credits.    

 Nevertheless, the Commission's efforts to promote sustainable carbon farming is a welcome step in the right direction - towards a future EU farming system that meaningfully addresses, rather than compounds, the climate and ecological crises. 

What will happen to soils within 50 years if conventional farming practices continue? 

An hourglass filled with soil sunk into soil, with the date 2023 on the left and 2073 on the right

Unfortunately, all of the above are true, and they are all issues already. Currently, more than a third of the world's soils have degraded - as intensive agriculture turns our soils to dust or concrete – and pollution is already making its way to our dinner tables. But the IPCC estimates that soil degradation could rise to 90% if nothing is done. To give an indication of what this would mean, moderately degraded soils already produce 30% less food and store approximately half the amount of water than healthy soils. This poses a serious threat to farmers, who manage 40% of the EU's land area. 

Preserving and restoring our soils must be a priority. Not just for environmental health and climate mitigation and adaptation, but also for agricultural resilience – protection both food security and farmers and their livelihoods. Increasing carbon content in soils has many benefits, including soil fertility, water retention, and increased crop yields. And with 60 to 70% of EU soils already in poor health - costing the EU over 50 billion euros per year - we must act now. In June this year, the Commission is expected to publish a new EU Soil Health Law which, if designed with enough ambition, will give soils the same legislative protection that air, water, and marine environments have had for some time -paving the way for practices that will improve soil health, and unlocking the infinite benefits that result from healthy soils.  

Carbon farming practices can be a win-win-win solution, benefiting biodiversity and climate, and ensuring farming profitability and resilience. It's time to turn over a new leaf, embrace the solutions that already exist, and implement supportive policies that prioritise the health of our soils - for all of us, and generations to come.  

Want to learn more? Read our carbon farming policy recommendations: ‘Carbon Farming for Climate, Nature, and Farmers‘ or this META article: ‘The buzz and true potential of carbon farming‘.