Soil is the Earth’s habitat with the greatest diversity of species. One cubic meter (35 cubic feet) of the top layer of soil on average bustles with dozens of wood lice and spiders, hundreds of larvae and night crawlers, tens of thousands of mites, centipedes, and other arthropods, a million nematodes, and hundreds of billions of algae, fungi, and bacteria.

Microorganisms mineralize carbon in soil that can stay there like that for decades and even millenniums. Estimates made in 2017 assume that 680 billion metric tons (750 short tons) are stored in the top 30 centimeters (12 inches) of worldwide soil, so exceeding plant-based carbon storage (560 billion metric tons/617 short tons). On the down side, the metabolism of the microorganisms causes about 10 times more CO₂ to be released from soil into the atmosphere than the combustion of fossil energy sources releases. Whether soil binds more carbon than it emits is decisively affected by humans through the cultivation of plants, fertilization, and tillage. Recent research results have shown that forests, meadows, and pastures in Europe are currently carbon sinks whereas agrarian areas are sources.

Carbon farming, sensible or greenwashing?

Soil is an important carbon reservoir and the management thereof plays a central role in agricultural policies aimed at mitigating climate change. With the systematic build-up of humus, farmers can remove excess CO₂ from the atmosphere. An increase in humus of 0.1 percent per hectare results in five to six tons of CO₂ being absorbed by this hectare. According to simulations, two to five billion tons per year could theoretically be absorbed in soil worldwide.

In recent years, a market has developed in the EU that pays farmers who build up humus by regularly applying organic fertilizers such as manure, compost or slurry, and expanding crop rotation by growing catch crops – known as carbon farming. The idea behind it: Specialized companies measure the actual CO₂ absorption of a field and reward the farm with a premium in the form of humus certificates, which they in turn can sell on to companies that want to offset their own greenhouse gas emissions.

In principle, the approach of increasing the humus capacity of agricultural soil should be welcomed, but environmental and nature conservation associations are critical of carbon farming. This is because it is not necessarily sustainable in terms of climate conservation.

Firstly, as a result of the expected global warming, humus will decompose much faster in the future than at present. Secondly, the carbon absorbed in the soil can be released again as CO₂ at any time if this agricultural operation stops or gets reduced.

Flying soil enrichers: Using drones and electromagnetic waves, soil conditions such as moisture and nutrient content can be analyzed from the air quickly, easily, and precisely. The knowledge gained in that way helps farmers fertilize and irrigate soil in more systematic and soil-friendly ways, among other things. In addition, drones can be used for planting seeds on farmland. That’s beneficial to the soil there as well that would otherwise be compacted by tractors in conventional seed planting. The remote-controlled aircraft can be used in reforestation of degraded areas to systematically spread seeds in large fields or hard to access terrain.

In many industrial nations, about half of the areas – and counting – used for human settlement and the transportation infrastructure are sealed. In Germany, every day, an average of 55 hectares (136 acres) of soil are lost to the extension of infrastructure and areas used for human settlement. Especially in conurbations, that leads to higher air temperatures and sinking ground water levels.

In the European Union, more than 60 percent of soils are now regarded as being damaged. Causes are chemical degradation (e.g., over-fertilization), physical degradation (compaction, building development) and erosion due to wind and water. However, this percentage is controversial because in that classification just one negative indicator among many suffices to rate soils as being damaged. That’s why many soil scientists think that kind of classification is too restrictive.

One cubic meter of soil (35 cubic feet) can store up to 250 liters (66 gallons) of water. As a result, soil can mitigate effects of the climate crisis such as droughts, heavy rain, and flooding.

The AI4SoilHealth project supported by 28 partners from eleven EU countries intends to develop a digital platform enabling a comprehensive evaluation and enhancement of soil health in all of Europe by means of artificial intelligence (AI). For that purpose, until 2026, it’s planned to collect data from farms and pilot locations throughout Europe based on which a digital twin is supposed to be created. The objective is to enable the AI to provide soil users like farmers and foresters specific recommendations for actions and predictions of the future based on the digital twin, for example: What happens to soil if I change my fertilization regime? How will changes in plants affect soil health? How will soil change in 10, 20, or 30 years when farmland is turned into a forest?