Author Archives: smorton

The Green Wall of……Grazers?!

Desertification is a process of land degradation whereby environments become increasingly arid and loose productivity over time [2]. Desertification occurs when land surfaces are transformed by human activities, including overgrazing, deforestation, surface land mining, and poor irrigation techniques. Desertification in the Sahel region of Africa is mainly attributed to an increase in human activity and their grazing livestock.

For a long time it was thought that the major factor causing desertification was the over grazing of livestock. This led to strict land use policies and a shift from livestock and wildlife coexisting on the landscape to a complete separation in an attempt to curb the effects of desertification. Wildlife became increasingly concentrated on nature reserves and due to land fragmentation, livestock was held on smaller land plots [4]. Yet it seemed as though the land began to get drier each year with less and less vegetation returning.

As the seriousness of desertification began to reach a global stage, many suggestions have been made as to how to stop such a process. One idea is to grow a wall of trees that stretches across the entire southern boundary of the Sahara desert, known as the Great Green Wall [3]. The idea being that setting up a natural barrier to desertification would reduce wind speed, stabilize the soil and increase soil humidity, halting or even reversing the process. Mainly due to a lack of global support as well as little local representation, the Great Green Wall has been a slow process. This initiative has also been contested as it could lead to unforeseen problems down the road. Concerns regarding water use are most often cited; the Sahel region is an arid landscape and there may not be enough water to grow such a large wall of trees [3].

If restricting grazing only makes things worse and no one is willing to spearhead a large intervention event such as the Great Green Wall, what can be done? One solution that has been proposed is to not restrict grazing but rather release it. Using livestock to mimic the grazing behaviors once carried out by native herds, which have since been reduced due to human encroachment and land fragmentation, would encourage natural turnover of grasslands and sustain a healthy environment [1]. How does this happen? Desertification occurring in arid lands sees seasonal changes in the environment with a hot dry season and a wet growing season. Grass grows really fast during the wet season, but as things become drier the plant biomass above ground dies. These dead plants need to decay biologically and quickly so that new plants can grow during the next season. However, when large herds of grazers are absent, the dead material shifts from rapid biological decay to gradual breakdown through oxidation and weathering. This leads to dead plant material blocking light from reaching the soil and prevents new plant growth. If there is enough rain, grasslands shift to shrubs and trees, but when rainwater is scarce, they shift to bare, generally algae-covered soil and small woody bushes. As space between plants increases, the effectiveness of rainfall decreases. Rain that soaks into the soil evaporates back out. Or, in the case of extreme rain, most of the water runs off, causing flooding. Using large herds in combination with planned grazing patterns to mimic natural cycles will eventually start to restore the land and allow for it to become self-sustaining.

 

-Scott Morton

 

 

Works Cited:

  1. Savory, Allan (1983). The Savory Grazing Method or Holistic Resource Management. Rangelands. 5(4)
  2. http://earthobservatory.nasa.gov/Features/Desertification/
  3. O’Connor, D. and Ford, J. (2014). Increasing the Effectiveness of the “Great Green Wall” as an Adaptation to the Effects of Climate Change and Desertification in the Sahel. Sustainability. 6:7142-7154.
  4. Hobbs et al. (2008). Fragmentation of rangelands: Implications for humans, animals, and landscapes. Global Environmental Change-Human and Policy Dimensions. 18: 776-785.