|Diversity, Globalization, and the Ways of Nature (IDRC, 1995, 234 p.)|
|10. Africa in the 21st Century: Sunrise or sunset?|
Africas history has produced effects on the environment that cannot be found in other areas of the world. As the cradle of humanity, ecosystems adapted to human presence and human technologies as they evolved. This is probably one of the reasons why such a wide array of large mammats is found in Africa, compared with other continents, which were occupied by humans at a later stage.
Preagricultural human occupation had effects on the environment. Hunter-gatherers and fishing cultures overhunted some species, overcollected or artificially dispersed seeds, and burned forests, bush, and herbaceous ecosystems for hunting or other purposes, deliberately or accidentally modifing the environment.
Farming and the domestication of animals introduced additional changes. Some species (cattle, goats, sheep, camels, etc.) were tamed for their meat, milk, leather, and other by-products; some were tamed as helpers or companions (cats and dogs).
Agriculture required the clearing of land for cultivation. After growing several crops and depleting the sons, the fields were abandoned and new ones opened. In many cases, after many slash-and-burn cycles, the original forest ecosystem was converted to secondary savanna, made up of a herbaceous cover and few bushes and trees (Figure 3).
Gradually, savanna ecosystems and associated cultures reached a sort of equilibrium; grassy areas with low soil fertility were used for grazing and the best soils were used for farming. In these savanna environments, two different cultures developed in close association, almost of a symbiotic nature: nomadic shepherds, such as the present-day Fulani and Peul in the Sudan and Sahel and the Masai in eastern Africa, and sedentary farmers, such as the Bambara in Mali.
Figure 3. The ecozones of Africa.
There are more humid forest areas that remained untouched, mainly because of the lack of crop species adapted to this type of environment and the presence of deadly diseases, such as sleeping sickness. The first forest dwellers, such as the Pygmies of the Congo region, based their survival on hunting, fishing, and gathering; farming was only a secondary activity. They were (and still are) nomadic and became very well adapted to the forest environment. With the development of appropriate crop species, more sedentary cultures began to encroach on forest areas. The approach of both of these cultural groups tended to preserve most of the original components of the forest ecosystem. Although there was some impact, mainly through selective gathering or overgathering, or artificial spreading of some species and varieties, the forest structure remained unchanged, with several tree strata, dense undergrowth, rich genetic diversity, and its strong effect on hydrodynamics, preventing runoff and soil erosion.
European settlers promoted or imposed the development of plantations, which gradually encroached on many forested areas. As a result, forests receded to a fraction of their former area. This progress was increased when pest control, antibiotics, and vaccines were developed to overcome the disease hazard. Now, forested areas in Africa cover less than 20% of their former area and soil erosion is widespread.
A different problem occurred in semi-arid and arid lands where rain-fed agriculture was impossible without some form of irrigation. By and large, steppe and desert cultures were based on the herding of sheep, goats, and camels. The potential for environmental degradation by these peri-desertic groups was limited to the proximity of water holes, which were few and often far apart. Sheep and goats require water almost daily, and camels once a week; therefore, herds could not be driven much beyond 2 to 4 days travel to the next water holes or places where water containers could be stored. As a result, most of the steppe and the savanna ecosystems remained relatively untouched. Natural springs are rare in semi-arid and arid areas; therefore, most water holes were hand-excavated in wadi (arid river valleys) or plains in alluvial or related eolian sediments. Wells were dug wherever the depth to good-quality water was less than 30 to 40 metres.
Several technological developments changed this situation. First, new hydrogeologic techniques, such as drilling and geophysical logging allowed identification and exploitation of much deeper and sometimes better-quality, higher yielding aquifers. Second, the development of new types of mechanical pumps permitted larger volumes of groundwater to be extracted over shorter periods. Finally, the spread of motor vehicles made possible the transportation of water from wells to drier areas. As a result of these developments and the influence of a culture that based prestige on possession of the largest number of animals, herds and herders rapidly increased.
These were the main causes of increased desertification in the Sahelian and peri-Saharan regions. Widespread overgrazing took place and, in a few decades, the southern boundary of the Sahara advanced southward by tens or even hundreds of kilometres. As a result of the new water resources, the density of people and livestock increased considerably (from 5 to 15 people per square kilometre). In 1985, overstocking had been estimated at 22% in the Sudan (Pearce et al. 1990) and similar figures seem to be common in all the cattle-raising areas of the Sudanese and Sahelian regions. Even during rainy years, the vegetation near the wells was heavily damaged. When the drought of 1973-1975 struck, the cattle ate everything. Even trees were stripped of their branches, and thousands of animals died. Because of the drought, the plants did not regenerate and an acute famine followed. A well-meant development assistance program, which had not considered all aspects of the problem, introduced a technical element that inappropriately changed traditional cultural and production patterns that were well adapted to the local environment.
The development of large cities throughout the steppe, savanna, and forested legions and the rising price of fuel have caused an increase in the amount of wood cut for use as fuel for cooking, industrial ovens, and other purposes. The final result of this has been the retreat of forests farther and farther away from urbanized areas. This process can be observed throughout the continent; even in oil-producing countries, wood is widely used for domestic and other purposes. In 1983, it was estimated that, at 43 million cubic metres, the annual consumption of fuelwood and charcoal in the Sudan represented more than 90% of the total production of wood country-wide (Pearce et al. 1990). Similar figures are reported from Mali, Niger, and other countries in the Sudanese and Sahelian regions.
Another cause of environmental degradation in Africa relates to the construction of poorly designed hydro projects, especially irrigation and storage systems and hydroelectric dams. One of the prime examples of failure was the Lake Chad irrigation system built in the 1970s (see Chapter 7). This project was planned without considering the climatological regime, which is characterized by regular cycles of drought and flood. The many millions of dollars spent on the project have resulted in the construction of kilometres of useless channels that, for most of the time, remain dry. Often the negative impact of such projects could have been predicted if an independent, in-depth study had been conducted beforehand.
There are several projects in the planning stage that may entail similar or even larger risks: the Jonglei canal in the Sudd wetlands of southern Sudan; and the trans-basin transfer of water from the Congo River to the Chad basin through the Chari and several other rivers. A lack of funds, continued political instability, and a growing sense of the risks of these megaprojects have slowed the actual execution of these projects. New endeavours will probably require in-depth impact assessments, hopefully reducing the risks of repeated failures in the future.