Desertification

Overview

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Desertification is a natural or human induced process in which fertile land becomes irreversibly desert. The resulting loss of plant life leads to a decrease in overall bio productivity.[1] Barren soil becomes more susceptible to erosion and more vulnerable to evaporation and higher temperatures. The cause of this process is most often attributed to anthropogenic climate change, but a multitude of factors influence desertification. [2] Rapid desertification is expected to have drastic environmental, economic and political consequences.

Figure 1. Human Induced Desertification[6]

Causes

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Desertification is most attributable to human activity and climate change. According to scientists, poorly managed livestock herds has led to overgrazing of grasslands. In addition, the expansion of agriculture and deforestation have decreased overall natural vegetation. In turn, loss of vegetation has led to a host of problems resulting in the degradation of land. The change from fully grassed lands to scattered shrubbery leaves land bare and susceptible to erosion. Unprotected soil surfaces are also prone to salinization by evaporation and water logging. [3] Nutrients are washed away, fauna dies from lack of nutrients or washes away as well. Scientists have identified several driving forces behind desertification. It is contended that a combination of multiple factors are at play. [2] Leading causes include:

• Agricultural activities
  

  Figure 2: Leading causes of desertification [2]
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• Infrastructure extension
• Wood extraction and related activities
• Increased aridity
• Demographic factors
• Economic factors
• Technological factors
• Climatic factors
• Policy and institutional factors
• Cultural factors

Effects

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Desertification is expected to affect irrigated croplands negatively. Of the over 2 million square kilometers of irrigated croplands, more than 60% is located in drylands, with 30% of this land considered severely degraded. [1] Biological productivity of degraded land will drop significantly due to accumulation of salts in this soil. Without water to wash away accumulated salts they will remain in the soil, transforming the soil’s quality as farmland. Rangelands are also susceptible to degradation via desertification. Grazing animals often leave land barren of vegetation, exposing soil to wind and erosion. Preferential grazing may also alter plant communities. [3]

Prevention and Reversal

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There are many techniques for the prevention and reversal of desertification. Many of these methods rely heavily on the availability and usage of water. Some look to reforestation as a means of re-greening deserts. Studies have indicated that extended wet periods can reverse historical environmental regimes. [4]

A long-term study in the Qubqi Desert (Inner Mongolia) has tested the artificial inoculation of soil with cyanobacteria to stimulate plant growth. Cyanobacteria are known to stabilize soils by enriching available nutrients and increasing moisture content. Results from the study indicate that through the use of cyanobacteria almost all native plant species can be regrown in an area that has undergone desertification. [7]

Cyanobacteria as a method of reversal [8]

Holistic Management: Mexico:Before and After [5]

One of the most controversial proposals comes from Allan Savory, founder of the Savory Institute. Savory proposes a holistic approach to reversing desertification, relying on, not avoiding, livestock to re-green. Savory theorizes that through proper management, agriculture can be employed in a way to mimic nature and farmers can use sustainable farming to prevent further degradation.[5]

Desertification has become an increasingly alarming problem in Nigeria. To combat the effects of desertification, a major project was launched in 2007 titled "The Great Green Wall". Through the efforts of this project it is hoped that over 8,000 km of greenery will be restored to Africa. What initially began as an idea to plant a wall of trees has slowly evolved over time to incorporate more of a mosaic approach. Aside from just planting trees the project aims to return to responsible land use. By 2030, organizers hope to restore 100 million hectares of degraded land, sequester 250 million tons of carbon and create 10 million jobs.

References

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[1] Rafferty, J. P., and S. L. Pimm. 2019, March 22. Desertification. Encyclopædia Britannica, inc. https://www.britannica.com/science/desertification.

[2] Geist, H. J., and E. F. Lambin. 2004. Dynamic Causal Patterns of Desertification. BioScience 54:817.

[3] Huang, J., H. Yu, X. Guan, G. Wang, and R. Guo. 2015. Accelerated dryland expansion under climate change. Nature Climate Change 6:166–171.

[4] Peters, D. P. C., J. Yao, O. E. Sala, and J. P. Anderson. 2011. Directional climate change and potential reversal of desertification in arid and semiarid ecosystems. Global Change Biology 18:151–163.

[5] Holistic Management. https://www.savory.global/holistic-management/.

[6] Natural Resources Conservation Service. (n.d.). . https://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/use/worldsoils/?cid=nrcs142p2_054004.

[7] Lan, S. et al. 2014. Artificially Accelerating the Reversal of Desertification: Cyanobacterial Inoculation Facilitates the Succession of Vegetation Communities. Environmental Science & Technology 2014 48 (1), 307-315.

[8] Rossi, F. et al. 2016. Cyanobacterial inoculation (cyanobacterisation): Perspectives for the development of a standardized multifunctional technology for soil fertilization and desertification reversal. Earth-Science Reviews. Volume 171, August 2017, 28-43.