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Desertification and the sahel The human – biosphere link

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1 Desertification and the sahel The human – biosphere link
Desertification Web Poster - Brook Hill & Michael Jordan Climate & Society Fall 2009

2 WHAT is desertification? Defeating the myth of “the marching desert”
. WHAT is desertification? Defeating the myth of “the marching desert”

3 THE myth The myth of the “marching desert" (Forse 1989).
Desertification is not the movement of an “advancing desert.” As stated by in the Bulletin of the American Meteorological Society: The image of a “living environment becoming sterile and barren…is not an accurate picture (Nicholson 1994a).” While this image is not wholly incorrect, it is an oversimplification for a phenomenon affecting ecosystems in semi-arid regions across the world.

4 WHAT is Desertification? defining the term
Desertification is a process of severe land degradation. There are several main factors that can cause this degradation, but they all work together in a reinforcing system ultimately turning many productive drylands into expanses incapable of supporting a lively ecosystem. The effect is often localized and can occur over long periods of time as well as relatively small spans in light of other natural occurring phenomena.

5 Where and WHO? The Sahel belt: desertification made significant
Desertification is perhaps one of the greatest life and biosphere altering phenomena in contemporary history, particularly affecting the Sahel belt. The Sahel belt runs through 10 countries: Senegal, Mauritania, Mali, Burkina Faso, Niger, Nigeria, Chad, Sudan, Eritrea and Cape Verde Islands. This belt was historically a region of agricultural prosperity and economic dependability, however, this situation has changed.

6 Why should we care? Population of Sahel belt: over 50 million…and growing! In the Sahel “…production in severely eroded plots averaged 21 percent less than production in normal or slightly eroded soils.” Soil is critical to life in the Sahel belt, yet a quarter of soil degradation comes from agricultural activities” (Warren 1996).

7 Fertile Soil: the critical resource in the sahel belt
In the Sahel “…production in severely eroded plots averaged 21 percent less than production in normal or slightly eroded soils.” Soil is critical to life in the Sahel belt, yet a quarter of soil degradation comes from agricultural activities. (Warren 1996). Its roots lie in societal changes like increasing population, sedentarization of indigenous nomadic peoples, breakdown of traditional market and livelihood systems, introduction of new and inappropriate technology in the affected regions, and, in general, bad strategies of land management.” Fertile Soil: the critical resource in the sahel belt

Through collected data and conclusions of reputable experts, this paper makes the claim that human-induced components of desertification significantly reinforce biophysical phenomena causing desertification in the Sahel. This paper argues that there are severe impacts to the biosphere and is ability to sustain human life due to desertification and proposes possible solutions to this significant and impending threat to life sustainability in the Sahel belt.

9 The biophysical factors:
Key in causing desertification in the Sahel: Climate change: SST’s and warming Rain variability:  As a result of prolonged drought, fertile top soil became exposed and vulnerable to periods of intense rainfall variability and deteriorated from lack of organic matter and water resources; causing desertification. Soil erosion: degradation of productivity which threatens sustainability.

10 Sea surface Temperatures and desertification
In Dr. Held’s, et. al Simulation of Sahel drought in the 20th and 21st centuries (2005) his climate models suggest that there has been an “anthropogenic drying trend in this region, due partly to increased aerosol loading and partly to increased greenhouse gases, and that the observed 20th century record is a superposition of this drying trend and large internal variability” (Held, et al. 2005). In addition, Dr. Held’s, et al. models provide evidence that Sea Surface Temperature warming, through increase in global warming due to greenhouse gases, affects rainfall variability in the Sahel thus making it a biophysical factor for desertification reinforced and accelerated through human activity.

11 The human factor: At issue is direct human reinforcement through acceleration or deceleration of biophysical phenomena such as soil erosion, land degradation, and agricultural practices. Over-cultivation is a significant cause of desertification for it reduces soil fertility (a quickly changing variable) and reinforces a cyclic decline in crop yield (a slowly changing variable). As detailed by The Center for International Earth Science Information Network (CIESIN) at Columbia University, The most commonly cited forms of unsustainable land use are over-cultivation, overgrazing, deforestation, and poor irrigation practices. Let us examine each of these significant causes individually. Additionally, the variables used to judge desertification need to be addressed individually as they indicate desertification at different rates and are effects of the human-biosphere link in different proportions depending on the micro-ecosystem.

12 Effect of desertification on albedo

13 The link between albedo and desertification
Land surface albedo products for land surface and climate modeling (Löw et al.) support the claim that “progressive removal of vegetation cover changes the surface albedo (the degree to which the land surface reflects the sun's energy) and can also reduce atmospheric humidity, which in turn affects cloud formation and precipitation” (SEDAC/CIEN 2009).

14 Move from causes to impact
We as humans are interdependent on the bio-sphere and its many micro-ecosystems. We support, rely upon, and are affected by the biosphere as much as we affect it. This type of interdependency can have positive outcomes, such as environmental sustainability and development, but it can also have potentially life and biosphere altering results. This is no truer than in the Sahel belt.

15 The Impacts of Desertification
Continued degradation of soil negatively affects the ability of Sahelian farmers to grow crops, results in less grazing land for livestock, and can have considerable impacts for people that live not only, but near, the degraded areas. Decreased soil productivity Less grazing land for livestock cause livestock populations to decrease Negative economic growth Environmental side effects

16 Soil Degradation and Lost Productivity
Soil degradation decreases the productivity of soil which is a serious threat to food security in the Sahel. productivity loss past 6.6% 21st century will be approximately 14.5% (Lal, 2001). Population growing 3% annualy Degraded land has decreased livestocks food supply lowering population in Gourma regoin of Mali by 80% between .

17 Effects of Lost Productivity on the Economy of Affected Countries
Decreased agricultural and livestock production threatens to shrink already fragile economies of Sahelian nations. Over 50% of Sahelian populations work in agriculture or livestock herding. 40 per cent of the GDP for those countries (qtd in Kandji). One Sahelian country could loose 20% of its GDP in future.

18 Impacts on the Enviroment of Surrounding Areas
Desertification and it’s the decreased production that comes with it has many non-economic effects on people living outside the affected areas. flooding, reduced water quality, sedimentation in rivers and lakes. increased numbers of dust storms,. (UNCCD, fact sheet 3). forced mass exodus of people from effected areas to urban areas. overcrowding, increased unemployment, and stress on social services

19 Rainwater Use Efficency
Using rainfall more efficiently could be an effective way to mitigate the effects of and land degradation its self 20 to 40% rainfall lost as run largest contributor to dryness (Kandji et all, 25) sub- Saharan Africa water use efficiencies 5%-15%. East Africa is 20% > United States similar climate, efficiency 50% - soil management (2003).

20 Methods of Increasing Efficency
Hedgerow systems and stone lines are promising ways to limit run off in fields because they provide a barrier to run off. greater the number of stone lines increases water infiltration improving yields (Kandji et all). Stroosnidjer wrote that in Kenya where hedgerow systems were used infiltration increased and run off decreased (2003). Another way to mitigate the effects of desertification is through planting trees in and around fields where crops are being grown. agroforestry. promotes diversified and sustainable crop production, additional source of income for Sahelian farmers (Kandji et all). Agro forestry is a practical and simple way to improve productivity in the Sahel.

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