Desertification

Overview

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Desertification is a natural or human induced process in which fertile land becomes desert irreversibly. The resulting loss of plant life leads to a decrease in overall biological productivity. [1] Barren soil becomes more susceptible to erosion and increasingly 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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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]
  .
• Infrastructure extension
• Wood extraction and related activities
• Increased aridity
• Demographic factors
• Economic factors
• Technological factors
• Climatic factors
• Policy and institutional factors
• Cultural factors

Desertification is mostly attributed to human activity and climate change. Climate change has led to an increase in extreme weather events such as droughts and forest fires, which both contribute heavily to desertification. [10] Climate change has also led to an increase in global temperatures. These warmer climates have increased rates of evaporation which speed up the process of desertification. [11] In addition, the expansion of agriculture and deforestation have decreased overall natural vegetation. Increased food demand due to population growth has led to the expansion of agriculture, which decreases vegetation through: overgrazing by livestock, improper use of fertilizers, and the irresponsible cultivation of land. [11] Deforestation reduces the biodiversity of an area and its overall vegetation, which makes the soil more susceptible to erosion due to the loss of tree roots binding the soil together. [10] In turn, loss of vegetation has led to a host of problems resulting in the degradation of land. Unprotected soil surfaces are also prone to salinization by evaporation and water logging. [3] Nutrients are washed away, leading to the death of fauna. Fauna is also washed away.

Effects

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Desertification is expected to negatively affect irrigated croplands. 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. [9]

The Great Green Wall [9]

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.

[9] Successes. https://www.greatgreenwall.org/results.

[10] McSweeney, Robert. “Explainer: Desertification and the Role of Climate Change.” Carbon Brief, 2 Sept. 2020, https://www.carbonbrief.org/explainer-desertification-and-the-role-of-climate-change.

[11] Reese, April. “What's behind Desertification?” PRB, 1 Feb. 2001, https://www.prb.org/resources/whats-behind-desertification/.