Erosion can refer to either the effects of human and natural processes or the human-natural interactive processes, the latter serving here as the focus in discussing soil erosion and biodiversity loss, particularly as a result of surface water runoffs in both urban and rural environments. When humans disrupt soil creation processes, habitat fragmentation, habitat destruction, and general ecological unraveling begin in the soil gradient’s plant and animal life specific to it. Worldwide, the majority of biologists blame anthropogenic (resulting from human influence) soil erosion and biodiversity loss for the current sixth major mass extinction event in the history of planet Earth. This is the first anthropogenic mass extinction event, and it is far more rapid than any of the “Big Five” in past geologic times.
Natural Erosion and Soil Creation
In different soil gradients, a specific slow, organic and inorganic physical process of natural soil creation occurs that involves beneficial erosion. This process jockeys increasingly with a faster, human soil erosion and sheet runoff that kill plant and animal life within a soil gradient—carrying the slowly formed soil away. Thus anthropogenic soil erosion and associated biodiversity loss start in the alteration of this balance in the creation or destruction of soil and in how humans affect water dynamics.
Understanding soil creation chemically and physically is necessary if one wishes to understand and arrest the process of soil destruction. Soil creation results from a mixture of decayed organic and inorganic matter relationships, which create an all-important macro-molecular chelate arrangement of humic acids. Humic acids are a major component required for making humic substances, created via microbial degradation of once-living matter. A large number of humic molecules are hydrophobic, meaning they innately allow, in the presence of water, clumping into “water-avoiding” supramolecular nodes.
Only the acidic component of humic substances, mainly carboxylic acid, gives soil a capacity for chelation, a capacity to “store” inorganic minerals as ions without them having a strong chemical bond with anything else. Chelated inorganic ions are more readily bioavailable for plants or are sequestered away from them if they are poisons. Thus one of the most important properties of humic acid is this chelation ability to solubilize many ions into hydrophobic cations (water-avoiding, chemically positive ions). For bioavailability chelation, ions like magnesium, calcium, and iron are made available for plant absorption. For sequestering chelation, humic acid holds apart as ions many elements that otherwise would form toxic molecular salts to poison the soil without positive biological effect (like cadmium and lead). For instance, sodium and chlorine ions naturally want to combine to form a salt. Instead, in good fertile soil they are attached as separate ions to humic acids and clay—rendered harmless by chelation. Thus many good soils contain large quantities of safely chelated “salt,” held apart in ionic form from precipitating out in this way. Plant growth thrives in such “theoretically saline” soils, in many cases. In short, humic acid chelation capacities have an important dual role for living systems: They make biological uptake of nutrients possible, and they sequester poisons. Chemistry of varied humic acids has a profound influence on chelation capacities as well.
On the contrary, human soil erosion processes chemically have in common destruction of the humic acid creation process. This causes (1) loss of chelation capacity and (2) loss of water permeability and loss of soil infiltration capacities as a consequence. For agriculture, the latter can lead to (3) forced excessive watering, and in turn, a raised pH. Water as slightly alkaline (chemically positive) as well as dilutive would demote the slightly acidic (chemically negative) environment that encourages humic acid creation and would thus demote chelation action further. Such watering as a consequence can lead to (4) artificially raised water tables that can bring in external salts to precipitate from below, creating a hardpan and encouraging erosion of the drier soil above it. These four interactive soil destruction factors cause increased salt precipitation in chelated soil. This encourages a chemical and physical change toward poorer soil and less water-absorbent soil in both urban and rural areas. This primes the conditions that cause soil erosion, whether by sheet water runoff or wind.
Erosion: Just Add Water or Wind
Poor land or soil uses such as those involving deforestation, overgrazing, styles of chemical and physical agriculture (tilling), unmanaged construction activity, and urban impermeable surfaces demote humic acid formation. This leads to erosion because less humic acid means less hygroscopic soil, resulting in an innately dry soil—regardless of climate. Human-created poor soils facilitate ongoing natural water erosion and wind erosion above rates of natural soil formation. In heavily eroding water conditions, it is not water alone that erodes, but also suspended loads of abrasive particles of poor loose soil, pebbles, and boulders, which expand the power of erosion as they traverse and scrape soil surfaces. Waterborne soil erosion in these conditions is additionally a function of water speed and suspended particle dynamics.
Wind erosion occurs in areas with little or no vegetation, often in areas without sufficient rainfall. However, the common factor of a less humic-acidic hygroscopic soil facilitates wind erosion regardless of climate. One example is provided by the long-term shifting dunes in beaches or deserts, which advance to bury any plant life even when underground sources of water may be sufficient. Huge areas of western China are experiencing expanding desertification and wind-based erosion, whipped into incredible dust storms caused by mostly anthropogenic climate change. Both water and wind erosion cause further biodiversity loss from receiving water sedimentation and ecosystem damage (including fish kills).
Anthropogenic soil erosion and biodiversity loss expand from edge effects, the ecological juxtaposition between contrasting environments. Edge effects are boundaries between natural habitats and disturbances by poor land use choices. When an edge is created to a natural ecosystem and the area outside is a disturbed system, even the natural ecosystem fragment is affected for great distances inward from the edge. This edge effect area is called the “external habitat” and has a different microclimate than the residual “interior habitat.” This partially compromised external habitat starts a feedback loop process, leading to further soil erosion and microclimate change unraveling and exposing more interior habitat to further habitat destruction. For example, Amazonian areas altered by edge effects exceed the area actually cleared, and fires are more prevalent in the external habitat area as humidity drops and temperature and wind levels rise. Increased natural fire frequency from the 1990s in the Amazon, Indonesia, and the Philippines is an edge effect.
In such contexts, an ecosystem unravels toward a simpler, energy state (i.e., embedded or sequestered biomass energy). Intrusive exotic species are part of this, further causing biodiversity loss to levels of lower complexity. Exotics are hardly to blame. The blame is human soil-erosive processes that create edge effects and biodiversity loss that exotics opportunistically utilize.
Shifting Blame and Shifting Cultivation
The blame for much of the world’s soil and biodiversity erosion usually focuses on the poor—the slash-and-burn cultivators, mostly of the developing world. However, the developed world engages in transnational corporate logging, mining, export-driven grazing of cattle, and plantation agriculture linked to a war economy demoting political expression of local ecological self-interest. These factors in combination are to blame for soil and biodiversity loss, as well as for keeping such degradation in place. In short, current faulty and unsustainable developed world models and associated warfare are the larger origin of soil erosion, defoliation, and biodiversity destruction. Another example of misplaced priorities of exclusive blame (though a matter of proper concern) on peasant slash-and-burn for erosion is its false magnification by politicized developed world research institutions. Despite the largest blame for soil erosion and biodiversity loss coming from developed world developmental models, the Food and Agriculture Organization of the United Nations (FAO) assessed shifting cultivation of the last independent natives to be the main cause of deforestation—ignoring more invasive and destructive unsustainable developed world logging. The apparent discrimination and policy focus against independent shifting cultivators (whom the FAO recommend be forced to work on export economy rubber plantations) caused a confrontation between the FAO and environmental groups who saw the FAO supporting unsustainable commercial logging and plantation interests against local rights of indigenous people to be independent economically.
The lesson here is that the infrastructural and cultural adherence of more than 3 to 4 billion people (at least ambivalently) supportive of developed world political economic models and commodity choices is far more dangerous to soil erosion and biological diversity than the estimated mere 250 million people subsisting on slash-and-burn. Instead of nomadic slash-and-burn sustenance-minded shifting cultivation villages, it is the expansion of permanent agricultural monocropping techniques—particularly in export frameworks of high herbicide/pesticide commodities, mining pollution, transnational corporate logging, and tree plantations—that has led to more soil erosion and biodiversity loss. Massive export-oriented sheep and cattle herding, for instance, led to soil erosion and biodiversity loss in Australia, New Zealand, the United States, and the Amazon. In less than 150 years in Australia, export-oriented monocrop agriculture in New South Wales led to clearing 90 percent of native vegetation. The same chosen agricultural strategy and chosen commodities removed 99 percent of tall grass prairie in North America in the same period, leading to extreme habitat fragmentation and massive suspended loads (sediment) flowing down the Mississippi River. In the past 50 years, erosion has been affecting even oceans, with more than 60 massive dead zones of deoxygenated ocean water appearing off the littorals of the developed world. In short, organizing developmental paradigms of more locally attenuated human-environmental commodity relationships to maintain local natural soil gradient formation processes and to maintain soil infiltration are two generalized goals common to addressing soil erosion and biodiversity loss. There are already many land use techniques developed in urban and rural areas to allow for quick sedimentation and decreased water speed. Wider goals are to demote contexts that allow suspended loads or soil destruction in the first place—by altering agricultural and construction practices to mitigate loosened soil or heavy watering. There are frameworks of urban water handling and agricultural water and soil handling already developed to allow for more water infiltration, less (sometimes zero) soil tilling, and elimination of chemical pesticides and herbicides.
Integrating ecological relationships into urban infrastructural relations and making rural extraction sustainable by encouraging soil-creating human activities instead of soil destruction are both crucial. This seems to be the only route to demote the massive soil erosion and biodiversity loss that follow soil gradients. Comparatively, soil and biodiversity survive with human societies, or all will fall together.
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