A Brief Analysi
Environ
is of the Saha
Created
nments of th
Indiana Univ
Dr
Ap
ara Desert Re
by: Joseph P
e Tropics – G
versity – India
r. Rick Bein
pril 11, 2007
egion in North
Perry
Geography G4
anapolis
hern Africa
421
Introduction:
The Sahara Desert spans over 9,000,000 km2 of North Africa, and is the second‐largest desert in the world apart from the continent of Antarctica. Overall it is one of the least populated regions of the African continent; however, there are several groups of people who have settled and adapted to the harsh climates of the region. There are seven countries that make up the geographical region of Northern Africa, they are: Algeria, Egypt, Libya, Morocco, Sudan, Tunisia, and Western Sahara; however, several other countries can be considered part of this as well because they also have land located within the Sahara, these countries are: Chad, Djibouti, Ethiopia, Eritrea, Mali, Mauritania, and Niger.
The fourteen countries listed above are the focus of this research paper and I will concentrate on key factors in the region. These factors include a brief history, human impact, climate data, population data, and my conclusion, with thoughts on the future of the desert. I have spent a considerable amount of time compiling various data related to one of the world’s greatest environmental masterpieces. It is my hope at the conclusion of this document readers will gain a better understanding of the Sahara, and will have a starting point for further research into the content presented.
Brief History:
Scientists believe the Sahara was formed about seven million years ago; “In the Sahara region, the age of onset of the desert condition has been uncertain until now. Here we report on the discovery of 7,000,000‐year‐old eolian dune deposits from the northern Chad Basin. This geological archive is the oldest known evidence for desert occurrence in the Sahara.” (Schuster 2006) Since its formation the climate has been relatively unchanged; however the boundary has changed several times over the past hundred‐thousand years due to climate fluctuations, such as monsoons, and the various ice ages throughout Earth’s history.
Human Impact:
As with any environmental system humans have the ability to change the course of nature thus affecting the natural evolution of a species or biome. Recently scientists have begun studying how humans are affecting the desert and perhaps causing expansion of its boundaries. The process in which a desert expands either by human influence or climate changes is called ‘desertification’ and is defined as;
“Desertification is the impoverishment of terrestrial ecosystems under the impact of man. It is the process of deterioration in these ecosystems that can be measured by reduced productivity of desirable plants, undesirable alterations in the biomass and the diversity of the micro and macro fauna and flora, accelerated soil deterioration, and increased hazards for human occupancy.” (Goudie 68/2000)
One example of human influence for the expansion of the desert occurred in a study done in 1975 by Lamprey; he attempted to measure the advance of the Sahara in vegetation zones in the Sudan. Lamprey’s research revealed the desert did expand by about 90 to 100 kilometers between 1958 and 1975, or an average of 5.5 kilometers per year. (Goudie 69/2000)
The image below was taken from The Human Impact on the Natural Environment and is a representation of the study by Lamprey. (Goudie 70/2000)
Goudie goes on to state there is difficulty in determining if this study is true because of lack of remotely sensed data from the time, as well as evidence contradicting this study. “On the basis of analysis of remotely sensed data and ground observation, Helldén (1985) found sparse evidence that this had in fact happened. One problem is that there may be very substantial fluctuations in the biomass production from year to year. This has been revealed by meteorological satellite observations of green biomass production levels on the south side of the Sahara.” (Goudie 69/2000) This occurrence of vegetation shifts would be typical of the history of the desert over the past several thousands of years, which is why it is very difficult to prove one way or another; such is the case with any global changes because the time needed for an accurate study often takes at least two or more human lifetimes.
An expansion of the concept of desertification is called ‘irreversible desertization’ essentially stating that recovery is slow and very limited. Goudie points to a study by Le Houérou done in 1977 in Tunisia; “In Southern Tunisia, tracks made by tanks and wheeled vehicles of Allied and Axis armies are still apparent
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The greatest amount of rain seen in any given year is about 8cm for the entire region; however, that number can be as high as 17cm in the southern regions, or as low as one‐half of a centimeter in the northern areas, excluding the Mediterranean Coast. I have created this map, using ArcGIS, showing an image overlay of the desert region, as you can see there is very little vegetation in most areas, except to the south and along rivers and coastlines.
There are a few key factors allowing the desert to maintain its climate and land features, two of these factors are the Intertropical Convergence Zone and the Hadley Circulation; these phenomenons are described in this passage from a case study in the book: Sub‐Saharan Africa, An Environmental History by Gregory Maddox. “The climate has been governed by the Intertropical Convergence Zone (ITCZ), which also governs the monsoons. As the ITCZ moves north, it brings rain with it during the Northern Hemisphere summer. When it returns south, high pressure builds up over the Sahara, and arid conditions return. This shift is generally caused by the Hadley Circulation of warm, moist air rising at the equator, cooling, and then falling back to the Earth away from the equator coupled with the Earth tilting on its axis while rotating around the Sun. Annual and short‐term shifts in the northern extent of the monsoon result from changes in sea surface temperature in the surrounding oceans. Global temperature changes determine longer‐term shifts. During warmer epochs, the Hadley Circulation takes warmer air farther north and south from the equator. The increase in the amount of moisture in the air means that more rain reaches farther north in the Sahara. During cooler epochs, the circulation is more constricted, the air dries, and the Sahara expands.” (Maddox 172/2006)
I have created the map on the next page showing the boundaries of the Intertropical Convergence Zone; as you can see, during the winter months (blue) the ITCZ drops down below the Sahara; whereas in the summer months (red) it is located directly over the desert.
Another way for showing climate data in the world ecosystems is the Köppen Climate Classification System. The Köppen system was developed in Germany by a climatologist named Wladimir Köppen between 1900 and 1936. The Köppen system uses a series of letters to represent various climate types throughout the world. According to the Köppen system, the Sahara Desert fits into the classification of BWh: Dry/Arid (Hot) – Low Latitude Desert. (McKnight 2000/212)
Köpper Classification for Sahara Desert BWh: Dry/Arid (Hot) ‐ Low Latitude Desert
• Evaporation exceeds precipitation • On average precipitation is less than
half of potential evaporation • Usually lower latitude, hot desert
climate • Mean average temperature is over
18C°, frost absent or infrequent winter • Locations:
• Northern Mexico/Southwestern United States/Baja California
• Northern Africa/Saudi Arabia/Iran/Western India
• Central/Western Australia • Southern and Western Africa
Map adapted from: http://www3.shastacollege.edu/dscollon/images/Maps‐Images/world_climate_map.jpg
Population Data:
Population data in the Sahara region is difficult to gather prior to the year 1950; however, there have been recent additions to the data between 1950 and 2005. Generally throughout the area the population is made up of a younger generation, specifically under the age of ten years old. The primary factor for having such a young population is because in less‐developed countries children are seen as assets because these countries are primarily an agrarian society where young labor forces are essential.
The opposite end of this would be countries like the United States, or European Nations where people have fewer children because they are a liability (monetarily, physically, etc) until adulthood. The primary method for obtaining an overall view of population age distribution is through the use of a population pyramid, which separates people by age group and shows the portion of the population they occupy. Rubenstein discusses the population pyramid stating, “The shape of a pyramid is determined primarily by the crude birth rate in the community. A country in state 2 of the demographic transition, with a high CBR, has a relatively large number of young children, making the base of the population pyramid very broad. On the other hand, a country in stage 4, with a relatively large number of older people, has a graph with a wider top that looks more like a rectangle than a pyramid.” (Rubenstein 68/1999)
I have created a population pyramid for the countries of the Sahara Desert region of Northern Africa being reviewed in this report. The data is from a census done in 2005 by the United States Census and can be found in the International Data Base (IDB) on their website.
The population pyramids on the next page compare data from what I consider to be more developed and less developed countries in this region. The two countries being compared are Egypt, which has a somewhat modern society, and Sudan, which still has a more agricultural society with little industry.
30.00 20.00 10.00 0.00 10.00 20.00 30.00
0 ‐ 4
10 ‐ 14
20 ‐ 24
30 ‐ 34
40 ‐ 44
50 ‐ 54
60 ‐ 64
70 ‐ 74
80 +
Population in Millions
Age of Pup
ulation
Population Pyramid of Northern Africa 2005Male Female
As you can see, Egypt begins to take on a more rounded pyramid shape signifying they are entering into a more industrialized society where children would be seen as more of a liability. Sudan still maintains a pyramid shape where the greatest amount of population growth is below the age of ten years old, signifying a greater demand for children.
6.00 4.00 2.00 0.00 2.00 4.00 6.00
0 ‐ 4
10 ‐ 14
20 ‐ 24
30 ‐ 34
40 ‐ 44
50 ‐ 54
60 ‐ 64
70 ‐ 74
80 +
Population in Millions
Age of Pup
ulation
Population Pyramid of Egypt 2005Male Female
4.00 3.00 2.00 1.00 0.00 1.00 2.00 3.00 4.00
0 ‐ 4
10 ‐ 14
20 ‐ 24
30 ‐ 34
40 ‐ 44
50 ‐ 54
60 ‐ 64
70 ‐ 74
80 +
Population in Millions
Age of Pup
ulation
Population Pyramid of Sudan 2005Male Female
As Rubenstein discussed above, the primary method for determining the population distribution in a pyramid is the Crude Birth Rate of a given population. This leads me to demographic transition, which is the next portion of population analysis that can be utilized for determining information about a given population over a period of time. Demographic transition relies on Crude Birth Rate (CBR), Crude Death Rate (CDR), Net Increase Rate % (NIR), or Growth Rate (GR), and total population of the region being surveyed. Before discussing the demographic transition of the Sahara Desert, I feel it necessary to give brief definitions of the topics used.
• CBR – The number of births in a given year for every 1,000 persons. • CDR – The number of deaths in a given year for every 1,000 persons. • NIR % – Difference between the CBR & CDR, calculated as a percent. [(CBR – CDR) = NIR]/100 • GR – Difference between the CBR & CDR. [(CBR – CDR) = NIR] x 1000 = GR • Population – It the total number of people living in a given geographic area.
Knowing this information allows for the calculation of the demographic makeup of a given region over a period of years. With this information the researcher is able to break the population down to stages of demographic development. These stages of development allow us to understand what type of society (agricultural, industrial, post industrial) is being shown for a given area. The stages of transition according to Rubenstein are Stages 1 – 4 and are defined below. (Rubenstein 64‐66/1999)
• Stage One – Low growth of population; crude birth and death rates vary from year to year. • Stage Two – High growth of population; crude birth remains similar to stage one, crude death
rate drops significantly causing the net increase to rise rapidly. • Stage Three – Moderate growth of population; crude birth rate drops sharply, crude death rate
begins to drop at a much slower rate, overall population increases rapidly, but natural increase rate slows.
• Stage Four – Low growth; crude birth and death rates become almost equal, natural increase rate approaches zero, population increase slows.
Stages in demographic transition will not be the same for each region of the world, because not every region develops at the same rate as others due to various circumstances; such as, health related concerns, war, industrialization, and internal or external influence. The demographic transition scale on the next page is a reflection of the region from 1950 projected to 2050.
The final method for population analysis I am going to discuss is the Guttman Scalogram Technique. According to Trochim, “The purpose of Guttman scaling is to establish a one‐dimensional continuum for a concept you wish to measure.” (Trochim 2006) The scalogram, in this case, uses socio‐economic factors commonly associated with more developed countries to determine whether the country is developed or underdeveloped. I have chosen to use access to clean sanitary sewer systems (SS), gross domestic product (GDP), and literacy rate (LR) to determine the development status of this region.
Country % Pop. w/Sanitary
Sewer Access Per Capita GDP
2006 USD Literacy Rate (% above 15yo)
Algeria 90.5% $ 7,700 69.9% Chad 30.0% $ 1,500 25.7% Djibouti 41.0% $ 1,000 65.5% Egypt 70.0% $ 4,200 71.4% Eritrea 18.5% $ 1,000 56.7% Ethiopia 11.5% $ 1,000 42.7% Libya 96.5% $ 12,700 82.6% Mali 48.5% $ 1,200 19.0% Mauritania 36.5% $ 2,600 51.2% Morocco 57.0% $ 4,400 50.7% Niger 23.5% $ 1,000 14.4% Sudan 37.0% $ 2,300 61.1% Tunisia 76.0% $ 8,600 74.3% Western Sahara n/a n/a n/a Total Average 49.0% $ 3,785 52.7%
0
50
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0
100
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1950 ‐ 1955 1970 ‐ 1975 1987 1995 2005 2025 2050
Avg. Pop
ulation x 10
000
Per 1
,000
Pop
ulation
Demographic Transition ‐ Sahara Region of Africa
CBR CDR GR Population
Stage 3Stage 2 Stage 4
Scale of Degree of Development ‐ Northern Africa
Country More Developed (1) Less Developed (0) SS GDP LR SS GDP LR Total Algeria X X X 3 Chad X X X 0 Djibouti X X X 1 Egypt X X X 3 Eritrea X X X 1 Ethiopia X X X 0 Libya X X X 3 Mali X X X 0 Mauritania X X X 0 Morocco X X X 2 Niger X X X 0 Sudan X X X 1 Tunisia X X X 3
Western Sahara n/a Source Data: CIA World Fact book https://www.cia.gov/cia/publications/factbook/countrylisting.html
Total numbers range from 0 to 3, where the higher number represents a more developed country. Algeria, Egypt, Libya, and Tunisia rank as the most developed countries using the criteria surveyed for this study. These countries have established governmental systems and policies, economic production, and higher literacy rates, all of which lead to the higher total score. The location of the ‘X’ is determined by taking a total average of the data in each category; data falling below the average will receive an ‘X’ in the less developed section, whereas data higher than the average will receive an ‘X’ in the more developed section.
Conclusion:
For all its majesty the Sahara is one of the most brutal climates on Earth; “Do not regret the passing of the camel and the caravan. The Sahara has changed, but it remains a desert without compromise, the world in its extreme. There is no place as dry and hot and hostile. There are few places as huge and as wild.” (Langewiesche Pg. 3/1996)
It is my belief the environment will remain unchanged over the next few decades with only mild expansion of the desert; however, it should be noted that human influence and/or global warming may alter the normal progression. The demographic transition shows most of the region just entering stage 4, which will most likely continue to occur over the next 25 years. One of the biggest issues with the population will be the AIDS epidemic continuing to spread at a high rate in the region unless adequate measures are taken to control its advance.
Appendix:
024681012141618
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Climograph ‐ Sebha, Libya
Average Amount of Rain (cm)
Average Temperature (C°)
024681012141618
13.514
14.515
15.516
16.517
17.518
18.5
Climograph ‐ Addis Ababa, Ethiopia
Average Amount of Rain (cm)
Average Temperature (C°)
024681012141618
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Climograph ‐ Luxor, Egypt
Average Amount of Rain (cm)
Average Temperature (C°)
024681012141618
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40°
Climograph ‐ Kidal, Mali
Average Amount of Rain (cm)
Average Temperature (C°)
Bibliographic Reference:
Goudie, Andrew. The Human Impact on the Natural Environment MIT Press, Cambridge, MA, 2000
Maddox, Gregory H. Sub‐Saharan Africa – An Environmental History ABC‐CLIO, Santa Barbara, CA, 2006
McKnight, Tom L. & Hess, Darrel. Climate Zones and Types: The Köppen System, Physical Geography: A Landscape Appreciation Prentice Hall, Upper Saddle River, NJ, 2000
Rubenstein, James. The Cultural Landscape – An Introduction to Human Geography Prentice Hall, Upper Saddle River, NJ 1999
Schuster, Mathieu. The Age of the Sahara Desert Science Magazine, Vol. 311, Pg. 821, February 10, 2006
Trochim, William M.K. Guttman Scaling Research Methods Knowledgebase, website, http://www.socialresearchmethods.net, 2006
United States Census. International Database (IDB) Population Pyramids Website, http://www.census.gov/ipc/www/idbpyr.html, August 24, 2006