Desertification

 Desertification is land degradation in arid, semi-arid and drysub-humid areas resulting from various factors, including climatic variations and human activities..  It can be influenced by climate trends, but is mainly a result of human activities, including agriculture, overgrazing, over consumption of groundwater, and diversion of water from rivers for human consumption in urbanization and industrialization processes.

Desertification became well known in the 1930’s when drought, overgrazing and poor farming practices turned part of the great plains of the United States into the “dust bowl”. While improved land and water management practices have prevented that disaster from occurring again, many areas of the world are still threatened by this phenomenon to this day.¹

Desertification Vulnerability Map

Source: http://soils.usda.gov/use/worldsoils...ex/desert.html. Author: USDA. Permission: Fair Use

Areas Threatened

Roughly 47 percent of the worlds land area can be categorized as arid land.² This means that over half the globe is threatened by desertification, with semi-arid lands bordering deserts being the most vulnerable as so-called “transition areas” between deserts and cultivatable land contain some of the most fragile eco-systems on earth. Arid land is home to almost one-third of the world’s population, indicating that millions are affected by this problem every year. Already, 10-20 percent of the worlds arid land has been degraded by the process of desertification, and future degradation affects some of the world’s poorest, most subsistent populations.³

Specifically, these eco-systems are fragile because the rate of rainfall is less than the potential for water evaporation or transpiration (absorption) by plants to occur. This means that poor agricultural practices, over-irrigation and over-consumption of water by local populations can rob these areas of critical soil moisture. Decreases in plant cover (due to overgrazing, unsustainable farming practices such as slash and burn, etc.) also mean less root system’s to hold soil together, further exacerbating the encroachment of desert into the area. Without these natural protections, soil can completely dry out or be consumed by surrounding desert, eliminating soil nutrients making the area un-cultivatable.

Causes

Agricultural practices which over-use water, over-deplete soil nutrients and eliminate natural plant cover contribute to desertification. Diverting too much aquifer water to population centers is a significant cause because groundwater loses its ability to recharge. Over-grazing is a problem around the globe and contributes to loss of important plant cover. While droughts can contribute notably to this problem, they are not in-and-of themselves a cause. Human activity considerably alters the natural expansion/shrinking of the worlds deserts, creating many desertified areas which naturally would have recovered from drought.⁴

Harms

Without proper soil moisture and nutrient levels, the productive capability of land is drastically diminished. This can further or even cause crop failure and famine. It also leads to a loss of biodiversity, most worryingly in areas with endemic plant life (that only exists in that area, risking permanent extinction). Additionally, desertification can intensify drought and make areas uninhabitable.

Studies have estimated that desertification could drive 50 to 700 million people to migrate by 2050. These numbers pose great challenges from a human rights standpoint as water and food shortages lead to conflicts and regional instability. Environmentally, such large scale displacements exacerbate problems with overharvesting and poor agricultural practices. ⁵As a result of climate change driven temperature and sea level increases, decreases in precipitation and increased occurrence of extreme weather effects, the spread and effects of desertification are compounded. Desertification contributes to climate change, and may become irreversible because of climate change. Increased weather extremes such as drought and heavy rains as a result of climate change will lead to further land degradation.

Mitigation

Terracing

Source: http://4.bp.blogspot.com/_zzB_LTb_7g.../terracing.gifPermission: Fair Use.

Generally speaking, desertification can only be mitigated or even reversed if the human causes associated with the process are stopped. This does not guarantee full (or speedy) revitalization, but can promote some noticeable recovery. Examples of strategies to mitigate desertification include terracing (planting in leveled “terraces”, promoting slower water runoff and greater water absorption by soil), altering agricultural use patterns, planting trees and other plants, increasing water conservation in local population centers, etc.⁶

Improved land use practices in dryland and degraded lands offer potential for climate change mitigation. Drylands account for 36% of the total carbon stock of terrestrial ecosystems. Despite its low plant biomass per unit area of 60 tonnes per hectare compared to the 100-180 tonnes per hectare in other terrestrial systems, there is substantial potential for soil carbon sequestration given its large surface area and high degradation of its soils. Management of cropland and grazing land and the restoration of degraded and cultivated organic soils present the greatest potential for carbon reduction, while livestock and rice field management have greatest potential for nitrous oxide reductions.⁷⁸