There’s an ecosystem under your feet and it needs protection, new report says | Science

By Elizabeth Pennisi4 December 2020, 04:00

Reach out and collect some soil. In your hands there may be 5000 different kinds of creatures and as many single cells as there are humans in the globe. That random handful might contain microscopic fungi, rotting plant matter, a mustache-sized nematode munching on mushrooms, and a predatory pinhead-sized mite about to pounce on the nematode. One bacterium can repel another with a powerful antibiotic. It is a whole world of biodiversity that is often overlooked.

Today, on the eve of World Soil Day, the United Nations Food and Agriculture Organization (FAO) published its first comprehensive assessment of biodiversity in this underworld. Some 300 experts have combined their knowledge and data to describe the diversity of these organisms, the roles they play in natural and agricultural environments and the threats they face.

“Underground organisms are probably just as important, if not more important, than what is aboveground,” says Noah Fierer, a soil ecologist at the University of Colorado, Boulder, who did not contribute to the report. The report details how they stimulate crop growth and purify soil and water. Together with plant root systems, these organisms store more carbon, potentially longer, than parts of trees above ground. “Depending on how we manage the soil, it could become a help or a burden to tackle the biodiversity crisis or climate change,” says Francisco Pugnaire, soil and plant ecologist at the National Research Council’s Dry Zone Experimental Station. Spanish.

However, with every bulldozer or tractor ride, every bushfire, every oil spill, even the constant traffic of hikers along a popular path, more and more soil organisms are killed. By compiling research on these underground ecosystems and how they affect visible ones, the report’s authors hope to persuade scientists, policy makers and the general public to take steps to slow this loss.

“You can’t have Mars-like soil and expect to maintain food supplies and forests,” warns Diana Wall, a Colorado State University ecologist who contributed to the report. Current conservation efforts aren’t helping much, he adds. For example, soil biodiversity hotspots are not necessarily in the same place as biodiversity hotspots that conservationists focus on. “We are managing [conservation] from what we see on the surface, which does not necessarily correspond to what is underground. “On the contrary, Fierer says:” If you preserve the soil, you will probably preserve the entire ecosystem. “

Soil is a mix of organic material, minerals, gases and other components that provide the substrate for plant growth. About 40% of all animals find food, shelter or refuge in the soil during part of their life cycle.

Scientists mainly focused on the largest and smallest soil creatures. For centuries, nature historians have observed ants, termites, and even earthworms and moles chewing, wiggling, and making their way through soil particles, some feasting on rotting leaves and other debris and others feasting on each other. These ecosystem engineers aerate the soil and create underground passages that make the soil more suitable for other life forms. And in the past few decades, microbiologists sequencing soil DNA have discovered a surprising diversity of bacteria and fungi, which turn that litter into organic material.

But between the scales of macroscopic animals and microbes lie thousands of tiny, long-neglected creatures: the micro and mesofauna. Microscopic protists, nematodes and tardigrades inhabit the aqueous films surrounding the soil particles. Slightly larger animals up to 2 millimeters in size, such as mites, springs, and insect larvae, live in the airy pores between those particles, helping to make soil one of the most biologically diverse habitats on Earth. “How little we know [about these creatures] it’s a bit overwhelming, “says Fierer.

This diversity creates a rich and complex ecosystem that stimulates crop growth, breaks down pollutants and can act as an almost inexhaustible reservoir for carbon. Some soil organisms promote plant diversity and many have produced important compounds, from antibiotics to natural pesticides. “Without soil organisms and the activities they perform, it would be impossible for other organisms to survive,” says Stephen Wood, a soil ecologist at the Nature Conservancy.

Hidden underground, these ecosystems seemed immune to disturbances above the ground, Wood says. “For a long time, soil scientists thought that soil microorganisms were so widespread around the world that soil management would not harm them,” he explains. “We now know that soil microorganisms can be very specific to very specific habitats and species,” habitats that are rapidly disappearing as farms and cities expand.

The report lists a dozen human activities that heavily impact soil organisms. They include deforestation, intensive agriculture, acidification due to pollutants, salinization from improper irrigation, soil compaction, surface sealing, fire and erosion. “If you pave a site, you isolate an entire underground ecosystem,” says Fierer. “And it’s happening all over the world.”

Some governments and companies are making progress. Several states are considering legislation that would help protect the soil from destructive human activities. In China, the green agricultural development program works to preserve the soil by avoiding tillage and intertwining different crops to preserve biodiversity. However, “most organizations want to protect soil biodiversity as a means to an end -[to] the benefit of people and / or nature, “Wood points out.

Some researchers hope the report will encourage the protection of soil organisms for their own good. “Soil biodiversity is huge and we don’t have to destroy it without knowing what potential there is for improving sustainability,” says Mary Scholes, biogeochemist at the University of the Witwatersrand.

Fierer thinks the new valuation will also awaken a sense of wonder. “My hope is that people will look at this document and say ‘Huh, I never thought about it [soil organisms] and all the things they do for me. “”