ORCaSa Soil carbon

Why soil carbon matters?

Soil carbon is the umbrella term for the carbon stored in the world’s soils. It includes soil organic carbon (SOC), the quantifiable carbon component of soil organic matter (SOM), which is synonymous with all living things such as plants, nematodes, fungi and bacteria that contribute to healthy soil, and to a lesser extent, inorganic soil carbon, which consists largely of mineral forms of carbon. A study from 2014 estimated that the carbon contained in the world’s soils is three times more than that contained in aboveground biomass, such as trees and plants, and 230 times higher than current man-made emissions.

Soil’s constant flux

Soil is always in a state of change, with a never-ending cycle of giving and taking. Carbon enters the soil in two ways: through the roots of plants, which need it to grow, and through dead organic matter such as decomposing leaves. These processes lead to the creation of bioavailable nutrients, which are then taken up by microbes. These microbes either return the carbon to the atmosphere or add it to a stable carbon pool in the form of dead organisms. This cycle ensures the continued health and fertility of the soil.

Forest

Cities

Wetlands

Agricultural land

A disrupted naturel cycle

Unfortunately, this balance has been thrown off in the 21st century, with more CO2 being released into the atmosphere than is captured in the planet’s soils. Urbanisation, industrial farming, and deforestation are all taking a toll on soil ecosystems, making them less able to absorb CO2 from the air. The most carbon-rich soils are found in forests and wetlands, but cities are becoming a major contributor to soil degradation as they expand and consume green spaces.

Cities: a boon for civilisation, a blow to soil health

As the United Nations predicts that 68% of the world’s population will live in cities by 2050, it’s time to think about how our actions are affecting soil health and its ability to fight climate change.

As cities sprout and sprawl, nutrient-rich soil is removed and discarded as a waste product, wetlands are drained and vast areas of green space are compacted and paved. This not only affects soil chemistry, but also robs the soil of its resilience by making it impermeable to nutrients and water.

Food for thought…

Food production through industrial agriculture may increase soil productivity in the short term, but as we now know, it also plays a key role in undermining soil health, polluting water and contributing to climate change. We must rethink our practices to ensure a sustainable future for both ourselves and the planet.

Why it is vital to preserve and expand soil carbon?

Carbon-rich soils are a bulwark against food shortages, floods and climate change. In fact the climate depends on it. 25% of natural climate solutions rest on soil organic carbon. Simply protecting soil carbon would already contribute 40% of this amount, while the remaining 60% should consist of active strategies such as agroforestry and regenerative agriculture.

The use of high-residue cover crops and protection of wetlands are also exemplary measures to promote better carbon uptake. With the inexorable progress of the built environment, thoughtful urban planning and more green spaces that ultimately reduce the dreaded “urban heat islands” in summer must become the norm.