By Elizabeth Bach, Executive Director, Global Soil Biodiversity Initiative & Sustainable Leadership Fellow at the School of Global Environmental Sustainability, Colorado State University
This blog post first appeared in the HUMANnature blog from the School of Global Environmental Sustainability, Colorado State University
As a 5-year-old, one of my favorite things to do was play in the dirt. My cousins and I would make “soup,” a mixture of soil, leaves, twigs, and some unfortunate bugs, with just enough water to easily stir. The “recipes” were endless; from which part of the yard we got the soil, the ratio of twigs to leaves, the addition of a stray earthworm or insect all contributed to different “soups.” As a kid, this play occupied my imagination for hours at a time. As an adult, the interactions of soil and organisms, dead and alive, continue to fascinate me. Just like a hearty stew, soil provides nutrients and energy to all organisms living aboveground, including people, and sustains ecosystems and humanity now and into the future. How, you ask? Well, here are 6 ways soil biodiversity sustains us!
Clockwise from top left: nematode, psuedoscorpion, burrowing owl, tardigrade. Photo credit: D. Robson, A. Murray, M. Knoth, N. Carrera.
- It’s Alive! Soil is home to ~25% of all described species on Earth. These range from microscopic nematodes and tardigrades to small psuedoscorpians and even larger animals like burrowing owls. But wait, there’s more! The majority of soil species likely have not even been described by scientists. That means soil holds numerous biological mysteries and likely supports far more than 25% of all species on Earth. Soil is a frontier for exploration and discovery, right beneath our feet.
- It grows our food! Some soil organisms people can eat directly, like mushrooms, truffles, and some insects. Other soil organisms help fruits, vegetables, and grains grow by recycling nutrients from dead plant material. All plants, including crops, need nutrients, such as nitrogen, phosphorous, and potassium, from soil. Most soils have limited reservoirs of these nutrients. But dead plants, perhaps from the previous year’s crop, retain many of these nutrients in their tissue. Soil organisms like insects, earthworms, micro-invertebrates, fungi, and bacteria break down dead plant material, releasing nutrients for new plant growth. Soil organisms are critical to recycling nutrients to grow food and support sustainable farming.
- It helps us live long and prosper! Soil organisms impact our health and lifestyles in both negative and positive ways. For example, anthrax, tapeworms, histoplasmosis, and brain encephalitis are all caused by soil organisms, including bacteria, pictured above. Valley Fever, or coccidioidomycosis, is a nasty and often deadly disease caused by the soil fungus Coccidioides immitis native in the southwest USA.
Other soil organisms can cure many diseases. In soil, all these organisms live together in a community. Some organisms have evolved defenses, such as antibiotic compounds, that can minimize disease agents. Antibiotics like penicillin, originate from soil organisms, and can combat many illnesses caused by bacteria or fungi, like pneumonia and strep throat. Soils are also a promising frontier in the development of new pharmaceuticals, which may reduce antibiotic resistance. People around the world, like the child receiving a shot in the photo above enjoy healthy lives thanks to soil organisms.
- It supports wildlife! Nutrient cycling from decomposition also supports food for wildlife that we enjoy viewing, hearing, and in some cases, hunting. Without soil biodiversity, wildlife would not have plants, fruit, and nuts to eat. Much like the effects on people, however, soil can also harbor disease organisms that can make wildlife sick, or even result in death. For example, in July 2016, anthrax, a soil bacterium, released from thawing soil in Siberia killed >1500 reindeer. That’s right, Santa’s sleigh may be running slow this year because of a soil organism!
- It filters water! As water moves through soil, soil organisms use the nutrients and minerals dissolved within it. This effectively removes excess nutrients and some pollutants before water reaches ponds, streams, lakes, rivers, etc. This is important not only for clean drinking water for animals and people (pictured above), but also for healthy fish and other aquatic organisms. In many areas of the US, there is extra nitrogen and phosphorous in surface waters, in part due to run-off of fertilizers from crop fields and lawns. When there is excess nitrogen and phosphorous in water, algae use it grow, consuming large amounts of dissolved oxygen. Reduction in dissolved oxygen can cause fish and other large aquatic organisms to suffocate, generating a “dead zone,” also known as hypoxia. The 2016 “dead zone” in the Gulf of Mexico was estimated to be about the size of Connecticut (5,898 square miles)! Soil organisms can reduce this nutrient load, and the number of algae that grow, keeping our waters oxygenated and healthy.
Soil biodiversity also helps store water in soil. Earthworms, insects, and other animals create tunnels, which allows water to flow into the soil more easily during precipitation events. In addition, soil organisms generate organic matter, made up of the byproducts of biological metabolism (think compost) that gives soils a dark color. Because soil organic matter is charged, it holds water between organic molecules, allowing soil to store more water than clay, slit, and sand particles alone.
- It recycles the air! Before plants covered our planet, cyanobacteria (pictured above) used simple carbon molecules and minerals from rocks as energy sources. This released oxygen, which eventually built up in the atmosphere to levels that could support the evolution of more microbes, plants, fungi, and animals, like us. We still rely on plants and soil organisms to maintain enough oxygen in the atmosphere for us to live. Soil organisms also cycle greenhouse gasses, which trap heat near the surface of Earth (pictured above, bottom panel).
Soil organisms can both pull greenhouse gases, like carbon dioxide, out of the atmosphere and respire carbon dioxide back into the atmosphere. When soil organisms decompose dead material, they use carbon from the tissue as an energy source. Some of that carbon is used for growth and reproduction. That carbon can stick around in soil for weeks, years, decades, or even longer. Some of the carbon is used for respiration, just like when we breath, soil organisms produce carbon dioxide. This adds up to a lot of carbon! As shown above, soils contain 2,300 gigatonnes of carbon. By comparison, respiration by soil organisms contributes only 60 gigatonnes of carbon back to the atmosphere. We can help soil organisms potentially reduce greenhouse gasses in the atmosphere through land management choices like ecosystem restoration, conservation farming practices, and increased urban green space.
Left: Legume Gliricidia growing with maize in Zambia, Right: mushrooms. Photo credit: ICRAF, D. Endico
Left: a child receives medication, Right: bacteria colonies can vary in color, shape, and texture. Photo credit: hdptcar, P. Turconi/Fondazione Istituto Insubrico di Ricerca per La Vida
Reindeer grazing. Photo from pixabay.com
Soil organisms filter excess nutrients and pollutants from water, keeping it safe for wildlife and humans. Photo credit: R. Kayser, Dept. Foreign Affairs & Trade
Cyanobacteria (top left, right) oxygenated Earth's atmosphere, Soil organisms cycle greenhouse gases like carbon dioxide (bottom). Photo credit: K. Siampouli, Futurilla, Art by MarkAC, EU Joint Research Center; Numbers calculated by US DOE, Biological & Environmental Research Information System.
Left, Mycen chlorophos, a bioluminescent fungus found in Asia, Top right, Fuligo septica is also known as “dog vomit slim mould,” Bottom right, scanning electron image of a tardigrade Photo credits: S. Axford, Stu’s Images, J. Méndez, and M.J.I. Briones
Soil organisms are truly the unsung heroes of sustainability. We need them. Wildlife needs them. Fish need them. Ecosystems need them. Soil biodiversity not only sustains life on earth, it is intrinsically fascinating. From bioluminescent fungi (pictured far left) to dog vomit slime mold (pictured top right) and adorable tardigrades (pictured bottom right) soil is home to some awesome living things. It is organisms like these that captured my adult imagination long after my “soup” making days as a kid. The best part is, it is not imaginary at all. The real world beneath our feet is astounding and essential. We all need living soil, so future generations can play and thrive in the dirt.
All images, except the reindeer, are from the Global Soil Biodiversity Atlas and available for free download (pdf) and use!