Desertification is a type of land degradation in drylands in which biological productivity is lost due to natural processes or induced by human activities whereby fertile areas become arid. It is the spread of arid areas caused by a variety of factors, such as overexploitation of soil as a result of human activity and the effects of climate change. Geographic areas most affected include the Sahel region in Africa, the Gobi Desert and Mongolia in Asia as well as parts of South America. Drylands occupy approximately 40–41% of Earth's land area and are home to more than 2 billion people.
Erosion is the action of surface processes that removes soil, rock, or dissolved material from one location on the Earth's crust and then transports it to another location where it is deposited. Erosion is distinct from weathering which involves no movement. Removal of rock or soil as clastic sediment is referred to as physical or mechanical erosion; this contrasts with chemical erosion, where soil or rock material is removed from an area by dissolution. Eroded sediment or solutes may be transported just a few millimetres, or for thousands of kilometres.
Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support the life of plants and soil organisms. Some scientific definitions distinguish dirt from soil by restricting the former term specifically to displaced soil.
Soil erosion is the denudation or wearing away of the upper layer of soil. It is a form of soil degradation. This natural process is caused by the dynamic activity of erosive agents, that is, water, ice (glaciers), snow, air (wind), plants, and animals. In accordance with these agents, erosion is sometimes divided into water erosion, glacial erosion, snow erosion, wind (aeolian) erosion, zoogenic erosion and anthropogenic erosion such as tillage erosion. Soil erosion may be a slow process that continues relatively unnoticed, or it may occur at an alarming rate causing a serious loss of topsoil. The loss of soil from farmland may be reflected in reduced crop production potential, lower surface water quality and damaged drainage networks. Soil erosion could also cause sinkholes.
Soil formation, also known as pedogenesis, is the process of soil genesis as regulated by the effects of place, environment, and history. Biogeochemical processes act to both create and destroy order (anisotropy) within soils. These alterations lead to the development of layers, termed soil horizons, distinguished by differences in color, structure, texture, and chemistry. These features occur in patterns of soil type distribution, forming in response to differences in soil forming factors.
Topsoil is the upper layer of soil. It has the highest concentration of organic matter and microorganisms and is where most of the Earth's biological soil activity occurs.
Dryland farming and dry farming encompass specific agricultural techniques for the non-irrigated cultivation of crops. Dryland farming is associated with drylands, areas characterized by a cool wet season followed by a warm dry season. They are also associated with arid conditions, areas prone to drought and those having scarce water resources.
Land degradation is a process in which the value of the biophysical environment is affected by a combination of human-induced processes acting upon the land. It is viewed as any change or disturbance to the land perceived to be deleterious or undesirable. Natural hazards are excluded as a cause; however human activities can indirectly affect phenomena such as floods and bush fires.
Contour bunding or contour farming or contour ploughing is the farming practice of plowing and/or planting across a slope following its elevation contour lines. These contour lines create a water break which reduces the formation of rills and gullies during times of heavy precipitation, allowing more time for the water to settle into the soil. In contour plowing, the ruts made by the plow run perpendicular rather than parallel to the slopes, generally furrows that curve around the land and are level. This method is also known for preventing tillage erosion. Tillage erosion is the soil movement and erosion by tilling a given plot of land. A similar practice is contour bunding where stones are placed around the contours of slopes. Contour ploughing has been proved to reduce fertilizer loss, power and time consumption, and wear on machines, as well as to increase crop yields and reduces soil erosion.
Soil conservation is the prevention of loss of the topmost layer of the soil from erosion or prevention of reduced fertility caused by over usage, acidification, salinization or other chemical soil contamination.
Biological soil crusts are communities of living organisms on the soil surface in arid and semi-arid ecosystems. They are found throughout the world with varying species composition and cover depending on topography, soil characteristics, climate, plant community, microhabitats, and disturbance regimes. Biological soil crusts perform important ecological roles including carbon fixation, nitrogen fixation and soil stabilization; they alter soil albedo and water relations and affect germination and nutrient levels in vascular plants. They can be damaged by fire, recreational activity, grazing and other disturbances and can require long time periods to recover composition and function. Biological soil crusts are also known as biocrusts or as cryptogamic, microbiotic, microphytic, or cryptobiotic soils.
Hydrophobic soil is a soil whose particles repel water. The layer of hydrophobicity is commonly found at or a few centimeters below the surface, parallel to the soil profile. This layer can vary in thickness and abundance and is typically covered by a layer of ash or burned soil.
Phototrophic biofilms are microbial communities generally comprising both phototrophic microorganisms, which use light as their energy source, and chemoheterotrophs. Thick laminated multilayered phototrophic biofilms are usually referred to as microbial mats or phototrophic mats. These organisms, which can be prokaryotic or eukaryotic organisms like bacteria, cyanobacteria, fungi, and microalgae, make up diverse microbial communities that are affixed in a mucous matrix, or film. These biofilms occur on contact surfaces in a range of terrestrial and aquatic environments. The formation of biofilms is a complex process and is dependent upon the availability of light as well as the relationships between the microorganisms. Biofilms serve a variety of roles in aquatic, terrestrial, and extreme environments; these roles include functions which are both beneficial and detrimental to the environment. In addition to these natural roles, phototrophic biofilms have also been adapted for applications such as crop production and protection, bioremediation, and wastewater treatment.
The land imprinter is a no-till device for establishing grass cover in arid environments and deserts. The imprinter consists of a metal roller, with steel angles welded to the surface in various configurations. The angled teeth of the imprinter cut through weeds and brush to form a mulch, while the teeth press seeds of grasses and other plants into the soil. The imprints remain stable for approximately two years. During that time, imprints funnel water toward seedlings, protect them from wind, and concentrate nutrients for plant growth.
Andrew Warren is a British physical geographer. He is Emeritus Professor of Geography at University College London, UK.
Chrysopogon nigritanus, more widely known by the taxonomic synonym Vetiveria nigritana, or the common name black vetivergrass, is a perennial grass species of the family Poaceae and therefore is also a monocotyledon. More specifically, Vetiveria nigritana is a very thick and tall type of grass that is deeply rooted within the ground and is usually used to protect crops and deter soil erosion. Vetiveria nigritana is also a native species to Africa and is most commonly seen in Nigeria, Northern Africa, Eastern Africa and tropical parts of Southern Africa. In addition, the plant, like other vetiver grasses, has been used in these regions due to its extreme drought tolerance, ability to grow in infertile soil and the fact that it can live under complete submergence. In fact, Vetiveria nigritana can thrive in a very diverse range of environmental and climatic conditions.
Soil compaction, also known as soil structure degradation, is the increase of bulk density or decrease in porosity of soil due to externally or internally applied loads. Compaction can adversely affect nearly all physical, chemical and biological properties and functions of soil. Together with soil erosion, it is regarded as the "costliest and most serious environmental problem caused by conventional agriculture."
Soil regeneration, as a particular form of ecological regeneration within the field of restoration ecology, is creating new soil and rejuvenating soil health by: minimizing the loss of topsoil, retaining more carbon than is depleted, boosting biodiversity, and maintaining proper water and nutrient cycling. This has many benefits, such as: soil sequestration of carbon in response to a growing threat of climate change, a reduced risk of soil erosion, and increased overall soil resilience.
Soil carbon sponge is porous, well-aggregated soil in good health, better able to absorb and retain water. Australian microbiologist and climatologist, Walter Jehne, articulated the concept of the soil carbon sponge in his 2017 paper, Regenerate Earth, connecting soil carbon with a restored water cycle able induce planetary cooling through evaporative cooling and higher reflectance of denser green vegetation. Cooling from increased cloud formation is another benefit of soil regeneration anticipated by Jehne.
Desertification in Africa is a form of land degradation that involves the conversion of productive land into desert or arid areas. This issue is a pressing environmental concern that poses a significant threat to the livelihoods of millions of people in Africa who depend on the land for subsistence. Geographical and environmental studies have recently coined the term desertification. Desertification is the process by which a piece of land becomes a desert, as the word desert implies. The loss or destruction of the biological potential of the land is referred to as desertification. It reduces or eliminates the potential for plant and animal production on the land and is a component of the widespread ecosystem degradation. Additionally, the term desertification is specifically used to describe the deterioration of the world's drylands, or its arid, semi-arid, and sub-humid climates. These regions may be far from the so-called natural or climatic deserts, but they still experience irregular water stress due to their low and variable rainfall. They are especially susceptible to damage from excessive human land use pressure. The causes of desertification are a combination of natural and human factors, with climate change exacerbating the problem. Despite this, there is a common misconception that desertification in Africa is solely the result of natural causes like climate change and soil erosion. In reality, human activities like deforestation, overgrazing, and unsustainable agricultural practices contribute significantly to the issue. Another misconception is that, desertification is irreversible, and that degraded land will forever remain barren wastelands. However, it is possible to restore degraded land through sustainable land management practices like reforestation and soil conservation. A 10.3 million km2 area, or 34.2% of the continent's surface, is at risk of desertification. If the deserts are taken into account, the affected and potentially affected area is roughly 16.5 million km2 or 54.6% of all of Africa. 5.7 percent of the continent's surface is made up of very severe regions, 16.2 percent by severe regions, and 12.3 percent by moderate to mild regions.
