For Healthy Ecosystems, Look to the Soil

By Maria Adkins, WellKind Forestry Intern

Maria Adkins was an intern for WellKind Forestry during our spring 2022 session, exploring soil health and other environmental issues.

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When you picture a healthy ecosystem, what comes to mind? Perhaps tall trees, plentiful wildlife, or glittering streams? These are all important parts of an ecosystem, but the one aspect that is most frequently forgotten may also be the most crucial: soil. 

Soil may not seem particularly interesting, but without it, no other part of the ecosystem would be able to thrive. Nutrient-rich soil allows plants to grow and prosper, providing food and shelter for all kinds of wildlife. Healthy soil also holds on to water, helping ecosystems survive droughts and floods. But when the health of the soil is compromised, the entire ecosystem is put at risk.

The Consequences of Poor Soil

From 2012 to 2015, California suffered a record-breaking drought, caused by a combination of low precipitation and abnormally high temperatures. One study found that it was the worst drought in the last 1200 years (Griffin, 2014). As a result, millions of trees died. A study by Nature Geoscience found that the die-off was likely caused by the soil getting too dry in the deep-rooting-zone, the area from which trees extract nutrients and water (Goulden, 2019). 

Essentially, more water was evaporating from the soil than was entering it, so over the years, the deep-rooting-zone got too dry to support the trees, resulting in tree die-off at a massive scale. This affected not only the trees but all the other organisms in the ecosystem that depend on trees for food or shelter. Ecosystems are incredibly interconnected, so when one part of the ecosystem is removed, especially one as crucial as trees, all the other species are at risk of dying off too.

But this die-off is far from an isolated incident. California is already in the midst of another drought, and is again experiencing record low precipitation and extremely high temperatures (CBS News, 2021). And due to climate change, these droughts are only going to become more common. At the time of this writing, 35 U.S. states are experiencing moderate drought or worse, as are many other countries around the world (NIDIS, 2022). These regions with drought could very likely suffer a similar tree die-off, threatening ecosystems all over the globe. 

Why Soil Matters for Climate Change

While climate change certainly affects the soil, soil can also affect climate change. One study found that variability in soil moisture is responsible for 90 percent of the variation in how much carbon the land takes in each year (Humphrey, 2021). The more carbon the land takes in, the less CO2 ends up in the atmosphere, and the more moisture the soil has, the more carbon it (and the organisms that depend on it) can take in. 

However, if the soil gets too dry, it can have the opposite effect, and actually cause global temperatures to rise. This results in a vicious cycle, where global warming dries out the soil, and dry soil contributes to global warming. 

In addition to its more direct effects, however, soil health is closely related to climate change because of the plants that grow in it. Over 33 million kilograms of carbon is stored in trees every year, and the larger the tree, the more carbon it can store (Zhao, 2015). 

Large trees require large amounts of water and nutrients, so they require moist, nutrient-rich soil to grow and sequester carbon. A 2019 study found that large tree density was significantly correlated with the concentrations of phosphorus, potassium, and magnesium in the soil (Clark, 2019). The higher the concentration of nutrients, the more large trees, and the more carbon that can be sequestered.

How Can We Improve Soil Health?

Located in the Edwards Plateau of Texas, the Bamberger Ranch Preserve is one example of restoring the land’s biodiversity by starting with the soil. When J. David Bamberger first bought the ranch in 1969, the soil was dry and lacked nutrients, the result of neglect and overgrazing. Bamberger and his team realized that they needed the soil to be healthy to sustain plants and animals on their ranch, so they began by removing many of the invasive juniper trees, which were draining the soil of its nutrients.

 They then used tactics such as strategic grazing to restore the land. The feces from the cattle served as excellent fertilizer to rejuvenate the soil, and because the cattle were regularly moved around, they didn’t overgraze the land, giving it time to recover. The method worked, and today, the ranch is home to 221 species of birds, as well as tortoises, deer, bobcats, and countless other animals.

The success of the Bamberger Ranch Preserve shows us that healthy soil is key to supporting strong, diverse ecosystems. It also shows us that it is possible to restore dry, nutrient-poor soil, and that doing so is beneficial for both humans and the rest of the environment. With climate change already wreaking havoc on our ecosystems, it's time we focus on the soil to protect our biodiversity.

References

Jones, C.J. (2021, October 18). California Records Driest Year Since 1924. CBS News. https://www.cbsnews.com/news/california-drought-dry-water-year/

Clark DB, Ferraz A, Clark DA, Kellner JR, Letcher SG, Saatchi S. (2019). Diversity, distribution and dynamics of large trees across an old-growth lowland tropical rain forest landscape. PLoS ONE 14(11): e0224896. https://doi.org/10.1371/journal.pone.0224896

Goulden, M.L., Bales, R.C. (2019). California forest die-off linked to multi-year deep soil drying in 2012–2015 drought. Nat. Geosci. 12, 632–637. https://doi.org/10.1038/s41561-019-0388-5

Griffin, D., and Anchukaitis, K. J. (2014). How unusual is the 2012–2014 California drought?, Geophys. Res. Lett., 41, 9017– 9023, doi:10.1002/2014GL062433.

Humphrey, V., Berg, A., Ciais, P. et al. (2021). Soil moisture–atmosphere feedback dominates land carbon uptake variability. Nature 592, 65–69. https://doi.org/10.1038/s41586-021-03325-5

National Integrated Drought Information System. (2022, March 15). National Current Conditions. Drought.gov. https://www.drought.gov/current-conditions

National Integrated Drought Information System. (2022, March 18). Global Drought Conditions. Drought.gov. https://www.drought.gov/international

Zhao C, Sander HA. (2015). Quantifying and Mapping the Supply of and Demand for Carbon Storage and Sequestration Service from Urban Trees. PLoS ONE 10(8): e0136392. https://doi.org/10.1371/journal.pone.0136392