Soil is the foundation of our food web

By Jaime Clifton-Ross, Communications & Outreach Curator, National Environmental Treasure

Earth’s soil is an incredibly biodiverse habitat for many species. It’s also the foundation of our food web and a rich source for life.

Just below our feet, is a vibrant and exciting world filled with biodiversity. Home to one-quarter of all animals living on the planet, earth’s soil is habitat for countless species like mites, roundworms, springtails, earthworms, ants and insects. Scientists estimate that 1 gram of soil is home to 4,000 to 10,000 different species of microorganisms, like bacteria and archaea. Even mammals, reptiles, and amphibians spend time underground. Not to mention, that algae and fungi form incredible symbiotic networks between the living organisms that live and grow in this rich underground world (think tree communication networks).

The 5 ingredients of soil

So, what exactly is soil? Scientists describe soil as “the skin of the living world”. A healthy soil recipe is made up of 5 ingredients: minerals (clay, silt and sand), gas, water, organic matter (think decomposing plants and animals) and of course, living organisms. These soil-dwelling species are some of the hardest working engineers on our planet. While their contributions are fairly complex, in a nutshell, most spend their days feeding on decaying organic matter, decomposing this matter through their digestive systems and then releasing excess nutrients into the soil. For example, earthworms churn soil and eat materials from the soil surface like leaf litter. Once these materials pass through their digestive systems, the nutrients nourish new plants thereby rebooting the cycle of life.

While many soil-dwelling species are so tiny that humans can barely see them, they’re incredibly important for the health and vitality of our planet. And because they’re out of sight, they’re often out of mind. That’s why far less attention is paid to the incredibly biodiverse world that exists beneath our feet. Soil-dwelling creatures also have huge competition. Large mammals, like polar bears, caribou, and whales, often get all the attention when it comes to conservation because they’re considered more charismatic. Clearly, soil-dwelling invertebrates have a bit of a PR problem.

State of Knowledge of Soil Biodiversity

Fortunately, these unsung heroes of our planet are finally entering the spotlight. The State of Knowledge of Soil Biodiversity, published by the Food and Agriculture Organization of the United Nations and authored by 300 scientists (many of which are Canadian), was released in December 2020. As the first of its kind on soils, the report frames the decline of the earth’s soil health as on par with the threats we face from the climate emergency and the continued degradation of biodiversity above ground.

The report’s key messages address how soil organisms are an important part of the natural systems that take place in soil. They help produce the healthy soils we need to grow our food which means they play a huge role in preserving human well-being and the overall health of our planet. However, certain practices like intensive agriculture and deforestation, are causing them harm. That’s why scientists are calling for policies aimed at addressing soil degradation and protecting soil biodiversity. Their hope is for these policies to be integrated into every level of biodiversity protection. The report also explores how advances in scientific research have made it possible to study whole communities of organisms rather than individual species. This will help provide a holistic understanding of the soil-dwelling community and inform policies for tackling food security.

Why is soil at risk?

There are many anthropogenic threats contributing to the degradation of soil. Deforestation, for example, disrupts habitat, alters the physical properties of soil and can generally decrease the diversity of species in soil communities. Agriculture also greatly impacts the health of soil. Fertilizers and pesticides are often used to help grow food crops. However, these chemicals can kill soil organisms, which makes the food web below ground less efficient. There is a loss of organic matter and in this state, soil is at risk of wind and water erosion and can release carbon into the atmosphere.

Urbanization is also a contributor. When city infrastructure is built, we often destroy or cover up soil with buildings and artificial materials like concrete and asphalt. Referred to as soil sealing, this process can prevent plant growth and water retention. It also significantly reduces the water purification that happens in healthy soil.

Pollution is another anthropogenic threat. Microplastics, for example, can leach toxins into soil that are harmful to invertebrates like mites, roundworms, springtails and larvae. Ultimately, healthy and resilient soil needs organic matter for soil organisms to thrive and process nutrients for plant growth. Without the organic matter, soil becomes less diverse and functional.

How can we help protect our soil?

So, you’ve probably come to realize that soil is the foundation of our food web and the source for life on land. A full 95% of our food actually comes from soil and it takes a whole 100 years for 1 inch of topsoil to form. In fact, most of the processes that maintain life on earth exist in only 6 inches of soil. No joke! That’s why urgent action is needed.

So how can you help?

1. If you have a garden or balcony planter, grow a diversity of plants that are native to your area. By growing native plants, you can avoid the use of harmful chemicals including fertilizers and help nourish the soil you have.

2. Learn about the effects of industrial farming on soil and the environmental benefits of adopting a higher plant-based diet.

 3. Learn about the wonderful world of soil biodiversity by listening to our episode of What the f*** is biodiversity with Dr. Valerie Behan-Pelletier and talk about the importance of soil with your friends and family.

4. Talk about soil during public and political discussions to help integrate it into biodiversity protection strategies and policy.