The Underappreciated Services of Soils

[See Appendix D: Ecosystem Services.] For this reason, the European Union provides soils with legal protection (European Union, 2007). The overarching framework directive of the European Union identifies pressures and impacts on soil quality and their protection. This includes short- and longer-term objectives and strategies to achieve them. In the United States, there is no comprehensive federal strategy dealing with all soils but rather targeted actions to reduce the impacts of poorly managed (particularly highly erosive) soils, in agricultural use (Natural Resources Conservation Service, 2020a). There is little reliable data on the health or condition of soils for most of the developed world, particularly those that have been under intensive use for hundreds of years. This lack of reliable information inhibits the development of policies to better manage soil resources (Cerriet al., 2000).

Although it is important to understand how past use has affected this essential resource, you do not need these data to appreciate the value of soils, the benefits from sound soil management, and the consequences of their neglect. You only

need to understand a few basic facts about soils and to be aware of their connection with other two essential resources–air and water.

Soils regulate surface and subsurface processes by controlling and limiting (regulating) the availability of the carbon, nitrogen, and phosphorus, thereby helping to provide balance within ecosystems. Such constraints are necessary when too much of something will disrupt ecosystems, with the imbalances potentially cascading through the environment to harm other systems. Balance permits biological systems to grow and to thrive. [Note that balance, as we are using it here, does not mean a static system with no change. We are using balance to refer to that state when systems are in equilibrium (more correctly, one would say steady state but that is a distinction for specialists in the field.] By providing these regulatory functions, soil with its position within the landscape greatly influences surface and subsurface biology and hydrology.

What makes up soils and how are they formed? There are over 18,000 soil series recognized in the United States, and several soil series can often be found in the same field. This variability can make managing the soil resource challenging (National Soil Survey Center, 1995). The quality of soils differs tremendously, starting with the material that comprises them. The material can be minerals dissolved or weathered from bedrock or sediment deposited over time by wind or water. This material is coupled with organic material from vegetation or deposited by macroorganisms and digested and processed by microorganisms.

The formation of the organic complex is the gradual bit-by-bit deposition and decomposition of dead bugs, plants, and micro- and macroorganisms. Soil formation takes thousands, if not tens of thousands of years (Millennium Ecosystem Assessment, 2003). But if we take into consideration how long it took for the chemical ingredients of soils to develop and to achieve the balance among reactive and nonreactive, biologically available and inert components, the timespan extends into hundreds of thousands if not millions of years (Birkeland et al., 2003; Burns et al,, 2003; Soil Science Society of America, 2013). How fast and how much soil is formed depends not only on the minerals that are weathered and the organic material deposited, but also on climatic conditions, particularly temperature and water availability. As we repeatedly witness, soils, water, air, and climate are interconnected in which the cycles (gears) in this complex machine turn at different speeds and thus proceed over differing timeframes.

Dig into undisturbed earth with a shovel so as to make a cross-section and you will find layers (or horizons), of different colors, textures, widths, and even smells. These layers reflect different periods of soil formation as well as the accumulated effects of deposition of organic materials, water, microbial processes, erosion, tillage, and other influences over time. These layers affect water infiltration, retention, and lateral movement. In cases when the soils have been disturbed by plowing or development, the upper layers are mixed.

What services do soils provide us? Why are these services so important to humans and to the ecosystems upon which we depend? We need soils to grow

It Ain’t Magic: Everything goes Somewhere 64

forests, grasses, and the crops that provide food, fiber, and energy. Soils help regulate the flow of water through our landscapes and sub-surfaces, storing and filtering water. The organic matter in soils acts like a sponge soaking up and holding water in place. This sponginess can make the difference between a flood event or simply high-water flow. By taking up water in pores within its matrix, soils store water helping to counteract periods without precipitation. Take, for example, peat moss that gardeners put in potting mix. That addition of extra organic matter, carbon, keeps the water in place. In addition, it allows the soils to breathe – the exchange of carbon dioxide with oxygen that is associated with plant growth. Also, by filtering what goes into the ground, soils purify water destined for ground water and aquifers. Soils buffer water, reducing its acidity.

This is important for keeping toxic substances from contaminating the biosphere and maintaining a balance between the mineral world and the biosphere. In summation, soils by holding, releasing, and purifying water are an important regulator in restoring balance to the land when events aboveground, such as floods, droughts, or perhaps climate change wreak havoc on exposed life.

Experiment 4.1: Plant beans in two pots, one containing quality topsoil and another with subsoil or sand that is largely bereft of its organic component.

Compare the growth of the beans growing in these pots. You will observe that the beans planted in the subsoil will grow slower and likely exhibit or signs of ill health such as yellowing and wilting.

Remember that soils are not inert media, such as cement or plastic mailing peanuts, but are living systems that we observe interacting withflora and fauna.

Soil microorganisms and soil insects living in soils play a critical role in processing nutrients and carbon. Carbon, nitrogen, and phosphorus cycle through soils as they play important roles in the functioning of our biosphere. Soils preform this by providing a habitat for the plethora of small vertebrates, invertebrates, and microorganisms that function as recyclers. Remember that rN and bioavailable phosphorus are naturally scarce, thus highly valuable.

Organisms evolved to use, decompose, and thereby recycle most if not all of these nutrients from deceased organisms by breaking down even the largest creature into its component parts. What was once waste is converted into temporary storage as part of soil until the above ground plants draw upon these nutrients. Thus, the health of surface plants and animals is tied with that of the soils below ground. Healthy soil, rich in microorganisms with a balance of carbon, nitrogen, and phosphorus, enables vibrant plant growth.

In addition, soils serve as a depository forgenetic diversity. If you have ever tended a garden, you know that seeds, especially seeds that are not particularly wanted in our garden soil such as weeds, are stored in the soil. Some of these can sprout decades after they were deposited (Kalamees et al., 2012). And there is more and more scientific evidence, that soil microorganisms share genetic

material with the macroorganisms, like plants, that we use and consume. The DNA stored in microorganisms may serve to replenish the biological diversity of systems depleted of biological species (Nealet al., 2020).

Living legacy

These other components of soil, which are the legacy of thousands if not millions of years of natural processes preparing the groundwork, literally, for all the higher organisms that make up our biosphere. Variations in soil help determine the subtle differences that make our planet so diverse and interesting.

Remember that hundreds of millions of years passed before life on earth could establish itself. This required the separating out and sequestering chemical elements anathema to life, such as lead, cadmium, mercury, etc., in mineral formations and then processing mineral complexes, such as silica minerals, into new complexes that would then lend themselves to life.

Remember again, that the organic world of carbon lives in a symbiotic relationship with the inorganic world, largely of silica. In early earth, silica minerals served as catalysts for organic processes. Nature built these chemical complexes of non-organic chemicals over a vast expanse of time that then enabled the evolution of our complex organic world that we take for granted today. Regard our terrestrial world representing one third of the surface of the earth, the first step in the biological conquest of land may well have been the creation of soil. The idea that earth is a living planet involving both its organic and inorganic parts is indeed not just a poetic statement but a scientific truth.