Few people put much thought into the soil beneath their feet, but Loren Byrne does. A professor at Roger Williams University, Byrne is an expert on urban soil ecology, and he worries that humans are changing the structural integrity of soils in urban environments and limiting the ability of plants and animals to live in and nourish the soil.
“Soil is easily overlooked and taken for granted because it’s everywhere,” he said. “We walk all over it and think of it as dirt that we can manipulate at our will. But the secret of soil is what’s happening with soil organisms and what’s happening with their interactions below ground that help regulate our earth’s ecosystems.”
Byrne contributed a chapter about urban soils to a report, State of Knowledge of Soil Biodiversity, issued last month by the United Nations Food and Agriculture Organization. He discussed how the ecology of the soil changes as it is compacted during construction, paved over, chemically treated for lawns, and dug up and carried away.
“The main takeaway is that urbanization can potentially harm biodiversity, but our biggest current
threat is ignorance,” he said. “We don’t understand enough about soil biodiversity in urban environments, so we may not be able to manage it in ways to provide the benefits that are possible.”
Soil is the foundation for terrestrial life, according to Byrne, not only because it is the medium in which plants are grown but because it regulates the nitrogen cycle, sequesters carbon and manages the flow of water. He thinks soils are fascinating because they contain the full range of life on earth, from single-celled bacteria and fungi to animals of all varieties.
“If you’re patient enough to get down on your hands and knees and pull up some soil, you’ll see mites, springtails, isopods, millipedes, centipedes, spiders, ants, beetles,” he said. “Some of them have negative popular connotations, but ecologically, if we can see them as having value, then that will help us maintain more sustainable landscapes.
“Changing our perspectives of what these organisms are doing in the ecosystem is important,” Byrne added. “They perform beneficial functions, like decomposition. I tell my students that if it wasn’t for this whole suite of biodiversity in our soils, we’d literally be up to our necks in dead stuff.”
Although it may seem counterintuitive, Byrne said that urban soils contain the full range of biodiversity that is found in natural soils, and some research shows that they contain more organisms and a greater diversity of organisms than agricultural soils.
“A lot of urban habitat types, like lawns and little forest patches, are perennial, so they don’t face the same level of annual disturbance as agricultural fields,” he said. “And they have more organic matter in them, so that allows the food web to become more complex. Urban soils are home to a lot of organisms.”
He noted, however, that there is also a massive volume of degraded soil in urban areas that is compacted, trampled, over-fertilized, and removed and replaced with lower quality soil.
“It’s a very interesting dichotomy,” Byrne said. “There are some high-quality soils and other locations that have been severely negatively impacted where we would want to somehow improve them.”
How to improve degraded soils is the topic of Byrne’s latest research. Decompacting the soil and remediating pollution are important steps, but the key is the addition of organic matter.
“There’s been a wide diversity of organic matter sources that have been investigated, from basic garden compost to sewage sludge to bio-char, which is a burned organic matter that, when added to soil, provides good surfaces for microbes to live on,” he said. “But you have to be very careful about what you’re using and in what contexts and the source, because not all organic matter is the same.
“A lot of research has shown that adding organic matter will help remediate the soils in various ways. Organic matter holds onto water, so it helps with water issues, for instance,” Byrne added. “But in locations that are already prone to water-logging, adding organic matter could be a bad thing. So context matters. You need to be familiar with site specific issues to come up with a good management plan.”
Byrne focuses a great deal of his research attention on lawns, which he calls a “human created ecosystem.” While he noted that a lawn provides a nice place for a picnic and is better than pavement, he said installing a lawn is the least biodiverse way of improving urban landscapes.
“The goal with a lawn is often one grass species that’s bright green and isn’t growing or reproducing, which is the exact opposite of what life wants to do,” he said. “In the grand scheme of all life, a place becomes more diverse over time, it grows and reproduces, and humans are trying to stop all of that in a lawn.
“The problem isn’t so much the lawn itself as the monoculture, pesticide-managed lawn. A lot of what ecologist’s advocate is a more biodiverse lawn where we let the so-called weeds grow and let the grass grow a little taller. That’s good for the soil ecosystem because a higher variety of plants and no chemical pesticides will allow more soil organisms to thrive.”
To create a more sustainable urban landscape, Byrne advocates for what some have called freedom lawns – a mowed lawn that maintains a high diversity of grasses and weeds and good soils.
“If we can convince people that it’s more patriotic to shift to freedom lawns, it will be more sustainable,” he said. “And if we can shrink the area of lawn by creating more biodiverse habitat through shrubs and wildflowers, that’s another step toward sustainability and biodiversity.”
This article first appeared on EcoRI.org on January 21, 2021.