Soil is a unique resource for humanity as it is nonrenewable on a short-term basis and is difficult to revitalize after being degraded. Maintainable soil use therefore requires us to understand its boundaries and sustainability requirements without overstepping them. It’s importance to our species is demonstrated primarily through the agricultural areas of food production and the roles it plays in various natural cycles such as the carbon and nitrogen cycle. Over time, humanity’s impact on this important lithospheric element has caused negative consequences such as erosion, nutrient depletion, and, in many cases, globally decreasing rates of food insecurity.
As soil quality is degraded and destabilized, so is the degree of reliability with which it is able to produce sufficient quantities of nutritious produce. In fact, over the last 54 years, the average amount of arable land per person has decreased from 0.37 ha to .20ha due to soil erosion despite a near 200% increase in global human population size(ISRC, 2018.). According to the United Nation’s Food and Agriculture Department, if these rates were to continue, over 90% of Earth soils could become degraded to non-arable conditions by the year 2050 (Marks, 2019.). Subsequent studies by the the Intergovernmental Panel on Climate Change (IPCC) revealed that the primary driver of this acute erosion were human activities related to agricultural development.
In 2015, environmental scientist Garcia-Ruiz and his team plotted erosion rates of over 4000 globally- acquired soil samples. As shown in figure A below, land plots associated with the highest amount of degradation were found in areas associated with subsequently high rates of agricultural activity. (Ruiz, 2018.). The specific agricultural instigators such as fertilizer use can be further understood through a biospheric evaluation of soil and its systematic features.
Fig. 1 – “The highest soil erosion rates were found in relation to agricultural activities” (Ruiz, 2018.)
“Soil” is the term used for the upper part of Earth’s crust consisting of Black and dark brown materials made of organic remains, clay, and small particles of rocks. These particles can be categorized into 4 biotic and abiotic components; 1) rock particles, 2) water, 3) air, and 4) leaves and other decaying organic matter. The aggregates formed by these particles can also be broken down into three major categories; 1)silt, 2) sand, and 3 clay. As a primary component of the surface layer of Earth’s lithosphere, soil is considered as an element residing on the planet’s crust and upper mantle. The lithosphere itself consists of two main components; the oceanic lithosphere and the Continental lithosphere. Soil resides in the thicker Continental portion of the continental sphere. Its importance lies within its role as a intermediary constituent between the lithosphere and earth’s other natural spheres.
All of the earth’s natural elements can be categorized into one of four systems: the lithosphere (land & rock), the hydrosphere (water), the biosphere (living organisms) and the atmosphere (air & gases). Amongst all of earth’s other 3 spheres (the hydrosphere, the biosphere, and the atmosphere), soil’s interaction with organisms residing in the biosphere is perhaps one of the most powerful means of demonstrating its importance.
Within the biosphere, many of the earth’s primary producers and other smaller living organisms rely on processes such as decomposition and photosynthesis to survive. Photosynthesis, for example, is a primary driver of the carbon cycle as it allows members of the Plantae kingdom to transform carbon dioxide into oxygen for other animal and human uses. Soil plays an important role in this process since a portion of the carbon in the atmosphere is derived from biological reactions happening within the soil’s organic matter. Through the decay of once- living organisms via microbial decomposition, carbon dioxide is released back into the atmosphere through a process known as soil respiration. (World Soils Have Lost. 2019). This carbon dioxide is then re-consumed by plants who then convert it into organic compounds as they partake in the process a photosynthesis (Soil Resp. Science Direct).
One of the major ways soil impacts the hydrosphere is through the flow and transfer of groundwater. Groundwater is present beneath Earth’s surface in soil pores and crevices of rocks. The water itself is derived from melted snow, ice, and rain. It is important for all land-dwelling biotic organisms as the long-term moisture content it provides plants help them grow in the absence of surface water dispersal (such as long periods of time without rain). It is also one of the most important aqueous resources for humans as it provides about 50% of the US population with drinking water (What Is Groundwater. 2018). Groundwater’s ability to successfully flow through and permeate the soil involves 5 major soil characteristics; A) texture, B) organic matter, C) structure, D) root and animal activity, and E) density.
Soil texture refers to the percentages of sand clay and silt that encompass its composition. Loam, for example, is a type of soil with equal parts of clay, sand, and silt. Organic matter helps stabilize silt, sand, and clay particles in order to uphold it’s structure by permitting the successful flow of water movement between the soil’s various types of aggregates. Plant roots, animals, and insects (particularly ones that create burrows) assist in the creation of “macropores” which aid in rapid water transmission. When connected to soil’s surfaces, macropores located in dry areas with easily cracked soil help transport vital rainfall quickly down to the soil’s lowest layers, providing deeply situated roots with immediate access to water. (Wellwater.). Soil density refers to its degree of compaction and is measured by determining its “bulk”. This metric is important as it determines how fluently factors such as air and water can move through the soil’s structure. If the bulk density is too high, for example, one could therefore in for that is porosity is low and certain types of plant-based organisms maybe unable to draw water through it’s composition. One primary factor that can disrupt the delicate balance soil provides within these natural systems, however, is anthropogenic agricultural activity.
In this piece, I will discuss two primary human activities that have been proven to contribute to the degradation of soil quality in the lithosphere. These include A) construction/ societal development and B) fertilizer use associated with farming. The first of activities, anthropogenic construction projects, primarily reduce soil quality through the destruction of the natural flora and fauna present within it’s top two horizons; the O and A levels.
In order to build human societies, soil must be unearthed to make way for the construction of things such as roads, buildings, and houses. This is problematic for the biospheric features residing in the soil’s uppermost horizons such as plants and microorganisms. As this protective plant-based covering is removed, soil particulates are then exposed to the possibility of being washed/blown away to other areas, lakes, rivers, or streams. This excess build-up in reservoirs can contribute to problems like sedimentation; the overclouding of water surfaces leading to a reduced amount of sunlight reaching aquatic plants, thus decreasing their rate of survivability and damaging the degree of biodiversity within their associated ecosystems (Raffele, L., 2020). One particular incident that provides novel insight into the impacts of excessive societal development on soil quality was the Great Leap Forward initiative launched by Chinese Chairman Mao Zedong in 1958.
In an effort to expedite the rate at which China’s agrarian economy was converted to a communist society, Chairman Mao Zedong instigated a 5-year effort that involved expediting the rate at which grains and crops were harvested. By prioritizing the unregulated mass consumption of natural resources to expedite national industrialization, however, about 7% of the Chinese population starved to death and millions of others endured unmerited suffering. This mass famine was primarily due to the rapid loss of arable soil in which produce and grains could grow due to ‘deep plowing’, a seed-planting method that involves several levels of soil-horizon destruction in order to plant seeds about 20in below the ground (Thaxton, 2008). A second destructive anthropogenic tactic used in crop harvesting are fertilizer compounds associated with farming activities.
Farming is human society’s most essential method of developing the food crops on which the rest of the population subsists. Over the 10,000 years in which this convention has been practiced, the technology and methods involved in it’s environmental implementations have evolved drastically. This evolution, however, has not necessarily led to the proportionate degree protecting of soil quality that one may suspect. In fact, increases in uses of farming practices such as soil fertilization, plowing, and overgrazing have led to proportional rates of declination in regards to soil fertility and sustainability.
One common practice utilized by farmers is to add nitrogen, phosphorus, and potassium- based compounds of soil nutrients known as “fertilizers” to fields and large areas allotted for agricultural development in order to promote plant growth. Some of these fertilizers, however, increase the difficulty with which soil-bound microorganisms are able to naturally produce nutrients. Soil acidification, for example, is a negative byproduct of the overuse of nitrogen-based fertilizers. It is caused by excess nitrate that is not consumed by plants leeching away from root zones and therefore leaving hydrogen ions behind. This surplus of hydrogen ions forcefully lowers the pH of the soil and therefore increase its alkalinity-based acidity. More acidic soil environments can make it more difficult for the bacteria that release nitrogen from decomposing organic matter to function, thus destroying a major food source for the roots of the soil’s residing plants. (Gentit, R. 2018.). In fact, over the past 50 years, the process of artificial soil fertilization by humans has been so excessive that a 2001 study by Australia’s National Land and Water Resources Department concluded that about 50% of Australia’s agricultural land now has undesirable pH values less than a pH of 5.5 (NLWRA (2001)). In summary, agricultural activities carried out without significant attention paid to the extraction rates of soil-based nutrients required to sustain associated elements of earth’s natural systems could potentially lead to disastrous rates of economic and environmental instability. The health of earth’s soil should therefore be a crucial concern for both farmers and the global community who use it as a primary means of vital resource production.
Catastrophe and Contention in Rural China: Mao’s Great Leap Forward Famine and the Origins of Righteous Resistance in Da Fo Village, by Ralph Thaxton, Cambridge University Press, 2008, pp. 40–41.
Gentili, R., Ambrosini, R., Montagnani, C., Caronni, S., & Citterio, S. (2018, August 24). Effect of Soil pH on the Growth, Reproductive Investment and Pollen Allergenicity of Ambrosia artemisiifolia L. Frontiers. https://www.frontiersin.org/articles/10.3389/fpls.2018.01335/full.
Marks, Carey. “Let’s Stop Soil Erosion to Ensure a Food Secure Future.” Food and Agriculture Organization of the United Nations, 2019, www.fao.org/fao-stories/article/en/c/1192794/.
NLWRA (2001) ‘Australian Agriculture Assessment 2001, Volume 1’ (National Land and Water Resources Audit).
Raffaele, L., Bruno, L., & Sherman, D. J. (2020, March 21). Statistical characterization of sedimentation velocity of natural particles. Aeolian Research. https://www.sciencedirect.com/science/article/pii/S1875963719302010.
Ruiz, Garcia, and Et al. “Land Degradation IPCC Report.” IPCC , pp. 4–28., 2019. www.ipcc.ch/site/assets/uploads/2019/08/2e.-Chapter-4_FINAL.pdf.
“Soils and Food Security.” ISRIC, 2018. www.isric.org/utilise/global-issues/food-security.
Soil Respiration. Soil Respiration – an overview | ScienceDirect Topics. https://www.sciencedirect.com/topics/earth-and-planetary-sciences/soil-respiration.
Wellwater. http://wellwater.oregonstate.edu/sites/wellwater.oregonstate.edu/files/documents/how_soil_properties_affect_groundwater_vulnerability. (2008). http://wellwater.oregonstate.edu/sites/wellwater.oregonstate.edu/files/documents/how_soil_properties_affect_groundwater_vulnerability.
What is Groundwater. The Groundwater Foundation. https://www.groundwater.org/get-informed/basics/groundwater.html.
World’s soils have lost 133bn tonnes of carbon since the dawn of agriculture. Carbon Brief. (2019, January 24). https://www.carbonbrief.org/worlds-soils-have-lost-133bn-tonnes-of-carbon-since-the-dawn-of-agriculture.
One of my first memories of the natural world is visiting the Pony Pastures in Richmond, Virginia with my father when I was about ten years old. Perhaps the reason this particular image has remained in my mind is because it was the first time an environmental landscape provided me with a sense of awe. Before this, I had only been exposed to the small courtyard beyond the deck of my parents’ apartment. In contrast, the small yet powerful rapids were full of depth- both in sound and color. I can vividly remember processing a newfound sense of relative insignificance as I stared across the flowing river and the many ducks hosted by it’s surface. It was this memory that inspired me to return to this location for my environmental science project in October 2020.
As I stared across the gentle rapids once again on this October chilly morning, I reflected on the devastating loss humanity would suffer if natural landscapes like these disappeared from the earth entirely. A successive thought that repeatedly came to mind was the various anthropogenic causes that may lead to it’s loss. Because my project’s topic related primarily to the devastating impacts human agricultural activities have had on our planet, I specifically thought about a lesson from a past history class that made me feel particularly sad in regards to human relations with earth’s natural systems.
Although I have always been someone who advocates for environmental conservation, my awareness of the immediacy of the issue came about in my first US history course at VCU. I can intensely remember the way the early chapters of my textbook described the natural world as something early North American colonists sought to destroy in order to make way for industrial endeavors such as railroads and coal mines. Bison populations were reduced from 25 million only a few hundred by the 1800’s while some native variants of tree and plant species were almost completely decimated. As a result of this rapidly increasing rate of destruction, US President Ulysses S Grant signed the first national park protection act into law in 1872. This act spared certain reservoirs of land from the devastating effects of modernization.
After learning information like what I have presented above, I began to view the national landmarks, parks, and scenic natural landscapes that held so many of my childhood memories as survivors in a world that aimed to extinguish their presence. As a result, my adult view of the natural world has become one filled with a greater appreciation for its beauty and growing concern for its preservation for future generations rather than an entity that solely exists to be recreationally explored. Before leaving the Pony Pastures I reached down to feel the unique soil on the banks within my hands and meditated on whether it would still exist after another 50 year’s time.
Sandy Soil at Pony Pasture
Pony Pasture Rapids October 2020