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Soil home to more than half of the Earth’s species

According to a new study, 90 per cent of fungi, 85 per cent of plants, over 50 per cent of bacteria, and 59 per cent of life overall dwells in this ecosystem – double what many previously thought.

A recent analysis has found that soil – the top layer of the Earth’s crust that’s composed of a mixture of water, gases, minerals, and organic matter – is home to more than half of all life on the planet, making it the single most species-rich habitat in the world.

The study, which was published in the Proceedings of the National Academy of Sciences, is the first to tally the total number of dwellers underground, discovering that the new figure is double what was previously thought to be the case.

To come to this conclusion, researchers amassed estimates of how many fungi, plants, bacteria, and other creatures reside beneath our feet.

According to their findings, 59 per cent of all species depend on this ecosystem for their survival, including 90 per cent of fungi, 85 per cent of plants, and over 50 per cent of bacteria. At 3.8 per cent, mammals are the group least associated with soils.

‘Here, we show that soil is likely home to 59 per cent of life including everything from microbes to mammals, making it the singular most biodiverse habitat on Earth,’ reads the paper, which is a review of existing literature. The actual figure could be even higher as soils are so understudied.

What’s more important than these numbers, however, are the functions that this biodiversity performs.

The life within the soil not only helps to produce what we eat (it’s where 95 per cent of the world’s food is grown), but plays a crucial role in holding the soil together and even gives us potential sources for new antibiotics and medicines.

Soils also hold three times as much carbon as vegetation and twice as much as the atmosphere. This, as we know, is integral to soaking up the massive amounts of heat-trapping emissions that are driving our worsening ecological emergency.

With this in mind, the analysis highlights the urgent need to protect soil, which has historically been left out of wider debates about nature protections because we know so little about it, and which is under increasing threat from heat, drought, flooding, and intensive farming.

In fact, a third of the planet’s land is severely degraded and 24bn tonnes of fertile soil are lost every year through intensive farming alone, as revealed by a UN-backed study, the Global Land Outlook.

‘Soils are under enormous pressure, whether from agricultural intensification, climate change, invasive species and much more,’ says author, Dr Mark Anthony, who is an ecologist at the Swiss Federal Institute for Forest, Snow, and Landscape Research (WSL).

‘Our study shows that the diversity in soils is great and correspondingly important, so they should be given much more consideration in conservation. Organisms in soil play an outweighed impact on the balance of our planet. Their biodiversity matters because soil life affects climate change feedbacks, global food security, and even human health.’