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Climate Change & Soil

September 2022 by Annie Tarpey

Photo by Dylan de Jonge on Unsplash

Football fields have been used as a way to communicate the rate of deforestation for years, but maybe it is time to use this analogy to make sense of another, less talked about, environmental issue; soil degradation.

If you have been to London recently, you may have seen some worrying statistics about soil publicised on the side of buses, commissioned by Conscious Planet for their #SaveSoil movement. One particularly worrying statistic making its way through the city is that one acre of soil is lost every second… so, if you like to visualise these things as football pitches, that is 1 football pitch every 1.5 seconds.

What does it mean for soil to be ‘lost’? Soil degradation refers to the physical, chemical and biological decline in soil quality or ‘health’.

Why is soil health in decline?

As with many of the earth’s processes, soil degradation can happen naturally, but it is significantly increased by human activity.

Intensive farming has an extremely negative effect on soil health; practices such as land clearance, over-grazing and excessive harvesting destroy its complex structure. Continuous livestock and machinery traffic compact the soil, reducing the volume of air pockets within, killing microorganisms and reducing the soil’s ability to absorb water. As nutrients are recycled from soil to vegetation and then back, the removal of vegetation either through forest clearance or harvesting reduces the nutrient content of the soil and therefore its ability to support the growth of new vegetation.

Urbanisation, which increases tarmac and concrete cover, also has similar effects; reduced water absorption and increases the death of microorganisms.

Why does this matter to us?

The decline in soil health will cause a myriad of issues for us, many of which are already underway. When functioning, soil is a vital component of the terrestrial ecosystem, supporting plant, animal and human health through biomass productivity, water and air quality maintenance, and the mitigation of climate change.

Soil delivers 95% of our global food supplies, so, losses of arable land will unequivocally reduce food security. Those living in the global south are the most at risk of food scarcity, with large increases in temperature and drought severity expected to exacerbate the already low soil fertility. But with the UK importing around 46% of the food we consume, this is not only an issue for those living near the equator but a very real threat to our food system. And of course, UK soils are not immune, with soil degradation already costing the UK £1.2bn a year.

Soil decline will not only affect food crops but also native vegetation. As soil fertility decreases and the optimal soil conditions for native plants (and therefore insects and animals) are lost, the landscape can become barren or taken over by invasive species that are suited to the altered conditions.

The threat to biodiversity runs deeper (quite literally) below the ground. The soil itself is teeming with life; one teaspoon of (healthy) soil can contain more organisms than there are humans living on earth. These organisms are responsible for the regulation of the carbon, nitrogen and phosphorus cycles; this feeds back into the issue of reduced crop yields and also plays a vital role in water purification.

Soil is also our natural flood mitigation system as the soil absorbs rainwater, preventing flooding. However, reduced soil quality also reduces the water holding capacity of the soil, making it less effective at preventing floods after a heavy rainfall event. Increased precipitation intensity is expected in many regions as a result of climate change, including the UK, according to the IPCC.

A complex relationship with climate change

Many of the properties and processes that allow the soil to provide these vital services and functions have complex relationships with one another, but also with the climate. Soil properties and processes are tangled together along with climatic factors in a complex knot of positive and negative feedback mechanisms.

Like oceans, soil plays a critical role in mitigating climate change – it is the second-largest carbon sink (after the ocean). The soil contains around two to three times more carbon than the atmosphere and is responsible for the removal of ~25% of fossil fuel emissions per year. However, climatic factors affecting soil processes and properties are having a huge effect on the ability of the soil to sequester and store this carbon, with a concerning convergence between the warming of the planet and degradation of the soil being the potential to turn soils from a carbon sink into a carbon source.

Increasing air temperatures will likely result in the increase of soil temperatures by around 1.5°C for every 1°C of air temperature increase. Increased temperature will likely increase soil respiration – the release of carbon dioxide as soil organisms respire. If this overtakes the rate at which carbon is taken into the soil via photosynthesis, soil carbon stocks will begin to decline. Peatlands in particular store a great amount of carbon and so have the potential to release huge amounts of CO2 into the atmosphere if this balance is disturbed. On the other hand, they also have the potential to be a great mitigator of climate change if protected.

What can we do?

While the potential impacts of climate change on soil are complex and concerning, they are not set in stone. They can be combatted, and the solutions can be simple – and start with you.

Find the Soil Association’s top five tips for how you can protect our planet’s soil here. Green-fingered or not, we can all do the last – and arguably most important – suggestion: speak out for soil. You can do this by using your Carbon Literacy and sharing what you’ve learnt here, about the critical connection between climate change and soil, with your friends, family, and colleagues.

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