By Mary Gumerov, Assistant UpLift Crew Leader
I didn't expect enrolling in "Intro to Soil Science" during my undergrad at Maryland would radically change how I thought about environmental restoration.
I learned that soil isn't just a medium for plant growth—it also filters polluted water and supports billions of microbes that enrich food and is a source of our medications, including immunosuppressants, antibiotics, antifungals, anticancer, and antidepressants.
Soil is also a living organism. Just as we hold trillions of microbes in our bodies to make life possible, the soil is home to countless microbes that1 keep it healthy. A single teaspoon of soil can contain up to a billion microbes. Soil changes over time and shares the needs of other living organisms, such as air, water, and even shelter from harsh elements. It's definitely not lifeless dirt.
It can take over 100 years to form one inch of topsoil. Considering that most plants we grow require 8-10 inches, it can take 800-1,000 years to generate enough soil to support plant life, and it only takes a few episodes of heavy rain or wind to wipe out an inch or more of topsoil. According to a 2006 study published in the Journal of the Environment, Development, and Sustainability, "Soil is being swept and washed away 10 to 40 times faster than it is being replenished."
Erosion is a serious ecological threat. When soil erodes, it threatens the diversity of plants, microbes, and animals that keep our ecosystems resilient as well as releases stored carbon into the atmosphere.
Soil's ability to sequester carbon is critical in stabilizing climate change. Soil scientist Asmeret Asefaw Berhe makes it clear in her TedTalk, stating that "...Soil [is] a fundamental component of any climate change mitigation strategy...because it represents a long-term storage of carbon."
Carbon on the Earth's surface is in constant flux through plant photosynthesis and decomposition—plants breathe in CO2 and eventually die, feeding carbon-releasing microbes as they break down plant matter. But, soil scientists like Asmeret Berhe are exploring ways to trap carbon in the soil that would be resistant to microbial decomposition. "Carbon that's not degrading fast is carbon that's not going back into the atmosphere as greenhouse gases," said Berhe.
One way to store carbon is by creating biochar—charcoal made from organic matter such as wood, plant residue, and manure—and adding it as a soil amendment to improve plant growth. Biochar can be a natural by-product of forest fires or intentionally created to enhance agricultural soils. Western scientists rediscovered intensive biochar application in the 2000s in the Amazon Basin, where indigenous people used charred biomass to improve unproductive tropical soils for thousands of years
On the left is an example of terra preta soil found in the Amazon Basin. It is fertile due to indigenous communities burying charred organic matter for thousands of years. The nutrient deficient soil on the right is what’s usually found in the region.
Another method to sequester carbon is simple: plant native perennial grasses and trees. Their deep roots extend many feet downward, trapping carbon indefinitely while preventing erosion.
Besides releasing carbon, degraded soil increases stormwater runoff since rain cannot soak into the eroded ground. Runoff washes the sediments from exposed soil and settles it in streams, lakes, rivers, and reservoirs. The EPA lists sediment as the most common pollutant in waterways and annually causes $16 billion in environmental damages.
Excess sediment produces cloudy waters, inhibiting plant growth and preventing aquatic wildlife from finding food. The nutrients in sediment also contribute to deadly algae blooms that create dead zones in bodies of water.
Practicing erosion control prevents accelerating environmental degradation, but soil expertise is vital in successful restoration projects. In the case of wetlands, it plays a deciding role.
"It often takes a long time for restored wetlands to achieve the ecological benefits of natural wetlands," said Dr. Brian Needelman, professor of Soil Science at the University of Maryland and my former coach in soil classification.
He continued, "If the soils are ideal, this process can be fast," but Dr. Needelman warned, "if there are problems with the soils, it may never really happen, and the use of polluted soils can even create environmental problems."
Alongside rain forests and coral reefs, wetlands are one of the most productive ecosystems in the world. Maryland benefits from its 757,000 acres of wetlands as they regulate the destructiveness of floods by readily storing large quantities of water. In an era of extreme flooding and rain, we need our wetlands to thrive.
"Soils are the foundation for a successful environmental restoration," Dr. Needleman said, "and a primary actor in providing many of the benefits we want to achieve through restoration."
As we grapple with the devastating effects of environmental degradation, perhaps, the solution lies just below our feet.
Cited in this article:
Berhe, Asmeret Asefaw. “A climate change solution that’s right under our feet.” TED, Apr. 2019, https://www.ted.com/talks/asmeret_asefaw_berhe_a_climate_change_solution_that_s_right_under_our_feet Gumerov, Mary. “Re: Soil Activities for Kids.” Received by Dr. Brian Needelman. 10 Sep. 2021.
Pimentel, D. Soil Erosion: A Food and Environmental Threat. Environ Dev Sustain 8, 119–137 (2006). http://saveoursoils.com/userfiles/downloads/1368007451-Soil%20Erosion-David%20Pimentel.pdf
What is Sediment Pollution? Mid-America Regional Council. https://cfpub.epa.gov/npstbx/files/ksmo_sediment.pdf
Additional sources:
Biochar:
Photo sources:
Terra Preta soil: https://www.researchgate.net/figure/Example-of-dark-Terra-Petra-soils-on-the-left-compared-to-Ferralsol-on-the-right_fig4_259901709
Switch grass:http://gigapan.com/gigapans/7543
Sediment pollution: https://www.montgomerycountymd.gov/water/streams/habitat.html
Kirkpatrick Marsh: https://www.eurekalert.org/multimedia/62177