PHYSICAL PATTERNS

The African continent is big—the second largest after Asia and about three times the size of the United States. But Africa’s great size is not matched by its surface complexity. Africa has no major mountain ranges, but it does have several high volcanic peaks, including Mount Kilimanjaro (19,324 feet [5890 meters] high; see Figure 7.1B) and Mount Kenya (17,057 feet [5199 meters] high). At their peaks, both have permanent snow and ice, though these features have shrunk dramatically due to global climate change and associated local environmental changes. More than one-fourth of the African continent is covered by the Sahara Desert, which reaches to the edge of the Mediterranean Sea.

The surface of the continent of Africa can be envisioned as a raised platform, or plateau, bordered by fairly narrow and uniform coastal lowlands. The platform slopes downward to the north; it has an upland region with several high peaks in the southeast, and lower uplands in the northwest. The steep escarpments (long, high cliffs) between plateau and coast have obstructed transportation and hindered connections to the outside world. Africa’s lengthy, uniform coastlines provide few natural harbors; Cape Town in South Africa being an exception (see Figure 7.1E).

Geologists usually place Africa at the center of the ancient supercontinent Pangaea (see Figure 1.8). As landmasses broke off from Africa and moved away—North America to the northwest, South America to the west, and India to the northeast—Africa readjusted its position only slightly. Because its shift was so small, it did not pile up long, linear mountain ranges, as did the other continents when their plates collided with one another.

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Africa continues to break apart along its eastern flank. There, the Arabian Plate has already split away and drifted to the northeast, leaving the Red Sea, which separates Africa and Asia. Another split, known as the Great Rift Valley, extends south from the Red Sea more than 2000 miles (3200 kilometers) (see Figure 7.1C). In the future, Africa is expected to split again along these rifts.

Most of sub-Saharan Africa has a tropical climate (see the Figure 7.5 map). Average temperatures generally stay above 64°F (18°C) year-round everywhere except at the more temperate southern tip of the continent and in the cooler upland zones (hills, mountains, high plateaus). Seasonal climates in Africa differ more by the amount of rainfall than by temperature.

Most rainfall comes to Africa by way of the intertropical convergence zone (ITCZ), a band of atmospheric currents that circle the globe roughly around the equator (see the inset map in Figure 7.5). At the ITCZ, warm winds converge from both the north and the south and push against each other. This causes the air to rise, cool, and release moisture in the form of rain. The rainfall produced by the ITCZ is most abundant in Africa near the equator, where dense tropical rainforests flourish in places such as the Congo Basin (see Figure 7.5A, D).

The ITCZ shifts north and south seasonally, generally following the area of Earth’s surface that has the highest average temperature at any given time. Thus, during the height of summer in the Southern Hemisphere in January, the ITCZ might bring rain far enough south to water the dry grasslands, or steppes, of Botswana. During the height of summer in the Northern Hemisphere in August, the ITCZ brings rain as far north as the southern fringes of the Sahara, to the area called the Sahel, a band of arid grassland 200 to 400 miles (320 to 640 kilometers) wide that runs east-west along the southern edge of the Sahara (see the Figure 7.5 map). At roughly 30 ° N latitude (the Sahara) and 30 ° S latitude (the Namib and Kalahari deserts), the air, which has dried out during its passage, descends, forming a subtropical high-pressure zone that shuts out lighter, warmer, moister air. As a result of this system (which is in no way precise), deserts tend to be found in Africa (and on other continents) in these zones about 30 degrees north and south of the equator.

The tropical wet climates that support equatorial rain forests are bordered on the north, east, and south by seasonally wet/dry subtropical woodlands (see Figure 7.5B). These give way to moist tropical savannas or steppes, where tall grasses and trees intermingle in a semiarid environment. These tropical wet, wet/dry, and steppe climates have provided suitable land for different types of agriculture for thousands of years, but the amount of moisture available in each of these climates can vary greatly, in cycles that are decades long. Farther to the north and south lie the true desert zones of the Sahara, the Namib, and the Kalahari (see Figure 7.5C). This banded pattern of African ecosystems is modified in many areas by elevation and wind patterns.

Without mountain ranges to block them, wind patterns can have a strong effect on climate in Africa. Winds blowing north along the east coast keep ITCZ-related rainfall away from the Horn of Africa, the triangular peninsula that juts out from northeastern Africa below the Red Sea. As a consequence, the Horn of Africa is one of the driest parts of the continent. Along the west coast of the Namib Desert, moist air from the Atlantic is blocked from moving over the desert by cold air above the northward-flowing water of the Benguela Current. Like the cool Peru Current off South America, the Benguela is an oceanic current that is chilled by its passage past Antarctica. Rich in nutrients, it supports a major fishery along the west coast of Africa (see the Figure 7.5 map).

Sub-Saharan Africa contributes to CO₂ emissions and potential climate change primarily through deforestation. Trees absorb CO₂ as they photosynthesize, thus removing carbon from the air and storing it as biomass, a process known as carbon sequestration. When trees are burned or when they decompose after they die, they release the stored CO₂ into the atmosphere. Because of this, deforestation is a major contributor to carbon buildup in the atmosphere and ultimately to climate change.

African countries lead the world in the rate of deforestation, the percentage of total forest area lost. Of the eight countries that had the world’s highest rates of deforestation between 1990 and 2005, six are in sub-Saharan Africa (Burundi, Togo, Nigeria, Benin, Uganda, and Ghana). This deforestation constitutes a major human environmental impact across the region (Figure 7.6). The countries that have the most emissions from deforestation are Brazil and Indonesia, but Nigeria and Congo (Kinshasa) have the third and fourth most, respectively. 168. PLAN TO CLEAR-CUT UGANDAN FOREST RESERVE FOR GROWING SUGARCANE SPARKS CONTROVERSY

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The story of Silas Siakor and Ellen Johnson-Sirleaf illustrates how, like many other countries in this region, Liberia is still in the process of building strong political institutions that can extract and use the country’s resources sustainably and for the benefit of its citizens.

Most of Africa’s deforestation is driven by the growing demand for farmland and fuelwood, although logging by international timber companies is also increasing. Africans use wood (or charcoal made from wood) to supply nearly all their domestic energy (see Figure 7.6A, B). Wood remains the cheapest fuel available, in part because of African traditions that consider forests to be a free resource held in common. Even in Nigeria, a major oil producer, most people use fuelwood because they cannot afford petroleum products. Not only are charcoal prices rising across the region as the forests disappear, but the smoke from the charcoal is causing asthma and other respiratory problems, as well as creating greenhouse gases.

In Maputo, the capital of Mozambique, a group of small-scale farmers are engaged in a for-profit project that combines new technology with traditional crops to create a sustainable fuel and food preparation system. The goal is to shift the 1.2 million inhabitants of Maputo from relying on charcoal—made from the disappearing old-growth forests in the north of the country—to using ethanol made from the roots of the cassava plant grown by the farmers on their own land. Newly developed small, metal cook-stoves run on the cassava-based ethanol.

The multifaceted stove/ethanol/cassava pilot project in Maputo is funded by four American firms that hope to replicate it elsewhere around the world. Their goal is to save the forests, relieve fuel shortages, halt rising fuelwood prices, and alleviate air pollution. Other benefits include improving food security, since cassava is a major food crop in Africa, and creating local small businesses that can convert cassava into ethanol and build the innovative cookstoves.

Elsewhere, African governments that are trying to slow deforestation are encouraging agroforestry—the farming of economically useful trees in conjunction with the usual subsistence and cash crops. Using the farmed trees for fuel and construction helps reduce dependence on old-growth forests and can provide income through the sale of farmed wood. For example, by practicing agroforestry on the fringes of the Sahel, a family in Mali can produce fuelwood, fencing and building materials, medicinal products, and food—all on the same piece of land. This would double what could be earned from a single crop or from animal herding. However, critics caution that agroforestry sometimes introduces invasive species, nonnative plants that threaten many African ecosystems by out-competing indigenous species.

Agricultural systems in Africa are undergoing a rapid transition from subsistence farming to commercial farming. Unfortunately, this change is happening at a time when the advantages of traditional agriculture are just beginning to be appreciated. The social and environmental effects of turning rapidly to commercial production are not fully understood at this point, especially given the as-yet little-known ecological impacts of climate change.

Traditional Agriculture Most sub-Saharan Africans practice subsistence agriculture—farming that provides food for only the farmer’s family—usually on small farms of about 2 to 10 acres (1 to 4 hectares). Most subsistence farmers also practice mixed agriculture, which involves raising a diverse array of crops and a few animals as livestock. Many also fish, hunt, herd, and gather some of their food from forest or grassland areas. The wide variety of food produced means that the cuisine of Africa is also varied (Figure 7.7).

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To maintain soil quality in a tropical wet or wet/dry climate, subsistence farmers have for generations used shifting cultivation, in which small patches of forest are cleared, with the detritus either burned or left to decay. The clearings are cultivated with a wide variety of plants for 2 or 3 years and then are abandoned and left to regrow. After a few decades, the soil naturally replenishes its organic matter and nutrients and is ready to be cultivated again. However, when fallow periods are reduced, as is happening in many rural areas that have increasingly high population densities, the soil can become degraded.

These traditional, subsistence, mixed, and shifting cultivation food-acquisition techniques have advantages and disadvantages in the present era of climate change. All of these closely related forms of agriculture provide a diverse array of strategies for coping with the changes in temperature and rainfall that climate change may bring. As in many other parts of sub-Saharan Africa, traditional farmers in Nigeria (usually women) grow complex tropical gardens, often with 50 or more species of plants. Some of the plants can handle drought, while others can withstand intense rain or heat.

However, the subsistence nature of most African farming can also leave families without much cash. If harvests are too low to provide surplus that can be sold, and hunting and gathering fail to provide supplementary food for the family, there may not be enough money to buy food. While such situations can lead to famine, it is important to note that the most serious famines in Africa have occurred not because of low harvests but rather because of political instability that disrupts economies and food growing and distribution systems. 162. FELLOWSHIP PROGRAM AIMS TO OPEN DOORS FOR AFRICAN WOMEN IN AGRICULTURAL RESEARCH

Commercial Agriculture Much of Africa is now shifting over to commercial agriculture, in which crops are grown deliberately for cash rather than solely as food for the farm family. This type of production also has advantages and disadvantages with respect to climate change. If harvests are good and prices for crops are adequate, farmers can earn enough cash to get them through a year or two of poor harvests. Having some cash income can also allow poor families to invest in other means of earning a living, such as opening a grinding mill to help process other farmers’ harvests or building a stone oven to bake neighbors’ bread for a fee.

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However, some of the most common commercial crops, such as peanuts, cacao beans (used for making chocolate), rice, tea, and coffee, are often less adapted to environments outside their native range (Figure 7.8D). They are more likely to produce smaller yields if temperatures increase or water becomes scarce. Moreover, to maximize profits, these crops are often grown in large fields containing only a single plant species. This can leave crops vulnerable to pests; if crops fail, farmers have no other garden foods to rely on. The potential for commercial agriculture to help farmers adapt to the uncertainties of global climate change is also limited by the instability of prices for commercial crops. Prices can rise or fall dramatically from year to year because of overproduction or crop failures both in Africa and abroad.

Commercial agriculture—whether small scale and locally managed, or large scale and owned and operated by international corporations (agribusiness)—often requires permanently cleared fields. Because soil fertility declines rapidly once the trees are removed, however, commercial crops in the tropics are more likely to fail even under ideal climatic conditions. Chemical fertilizers can compensate for this loss, but are often too expensive for ordinary farmers, and may lose their effectiveness when used repeatedly. Moreover, rains almost always wash much of the fertilizer into nearby waterways, thus polluting them. This may ultimately hurt farmers and fishers by spoiling drinking water and reducing the quantity of available fish, which are important sources of protein for rural people.

These aspects of commercial agricultural systems make them a risky choice even under the most ideal climatic conditions, let alone in the hotter and more drought-prone environments that climate change may bring. Foreign agricultural “experts” who often push commercial systems can be woefully ignorant of local conditions and the value of local cultivation techniques. In Nigeria, for example, women grow most of the food for family consumption and are guardians of the knowledge that makes Nigeria’s traditional farming systems work. However, women are rarely included or even consulted by the foreign experts who promote commercial agricultural development projects. At best, women are employed as field laborers. Consequently, diverse subsistence agricultural systems based on numerous plant species and deep knowledge about the agriculture have been replaced by less stable commercial systems that are based on a single plant species and that do not take into account the skills and knowledge base of women.

Recently, agricultural scientists have begun to recognize past mistakes and have been trying to incorporate the traditional knowledge of African farmers, female and male, into commercial agriculture systems. For example, scientists at Nigeria’s International Institute for Tropical Agriculture are developing cultivation systems that, like traditional systems, use many species of plants that help each other cope with varying climatic conditions. Most of these systems are designed for both subsistence and commercial agriculture, and so can give families both a stable food supply and cash to help them ride out crop failures and pay school fees for their children (see Figure 7.8C).

Water Resources, Irrigation, and Water Management Alternatives Although sub-Saharan Africa has a large wet tropical zone, much of the region is seasonally dry (see the Figure 7.5 map). Freshwater shortages are expected to increase, as is the number of refugees (see Figure 7.8A). In water-deficit conditions, many people look to irrigation to provide more stability for agricultural systems (see Figure 7.6D).

New Groundwater Discoveries Is there sufficient groundwater in Africa? Until recently, the answer was a resounding no. However, a recent comprehensive review and quantitative mapping of all available data on groundwater for the African continent (Figure 7.9) revealed that the quantity of groundwater (water naturally stored in aquifers as many as 5000 years ago, during wetter climate conditions) was nearly 100 times that of previous estimates. In many cases, the water was close enough to the surface to be accessed via inexpensive bore well pumps. This does not mean that Africa suddenly has an inexhaustible supply of water. Nor does it mean that it will be easy to get this water to the people who need it. The largest reservoirs of groundwater are in lightly populated areas (such as North Africa and Botswana; see Figure 7.1A). The most heavily populated country, Nigeria, has only a relatively small supply of groundwater. Nonetheless, this news on groundwater resources is welcome because climate change is likely to reduce precipitation in irregular and unpredictable patterns across the continent, and because per capita water use is likely to expand exponentially as this region develops economically (see Chapter 1).

New Large- and Small-Scale Irrigation Projects Government officials continue to favor large-scale irrigation projects to address the need for increased food supplies in the face of current and future water scarcity. Africa has a number of major rivers—the Nile, the Congo, the Zambezi, and the Limpopo—and climate change will affect all of them. Here we focus on the Niger, one of Africa’s most important rivers, which flows through several very different ecological zones.

The Niger rises in the tropical wet Guinea Highlands and carries summer floodwaters northeast into the normally arid lowlands of Mali and Niger (see the Figure 7.5 map and Figure 7.6C, D). There the waters spread out into lakes and streams that nourish wetlands. For a few months of the year (June through September), the wetlands ensure the livelihoods of millions of fishers, farmers, and pastoralists. These people share the territory in carefully synchronized patterns of land use that have survived for millennia. Wetlands along the Niger produce 8 times more plant matter per acre than the average wheat field does. They provide seasonal pasture for millions of domesticated animals, and serve as an important habitat for wildlife.

The governments of Mali and Niger now want to dam the Niger River and channel its water into irrigated agribusiness projects that they hope will help feed the more than 26 million people in both countries. However, the dams would forever change the seasonal rise and fall of the river. The irrigation systems may also pose a threat to human health. Systems that rely on surface storage not only lose a great deal of water through evaporation and leakage, but the standing pools of water they create often breed mosquitoes that spread tropical diseases such as malaria, and harbor the snails that host schistosomiasis, a debilitating parasite that enters the skin of humans who spend time standing in still water to fish or do other chores.

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Many smaller-scale alternatives are available. In some parts of Senegal, for example, farmers are using hand- or foot-powered pumps to bring water from rivers or ponds directly to the individual plants that need it. This is in some ways a more modern version of traditional African irrigation practices whereby water is delivered directly to the roots of the plants by human, often female, water brigades. Smaller-scale projects provide the same protection against drought that larger systems offer, but they are much cheaper and simpler to operate for small farmers. They also avoid the social dislocation and ecological disruption of larger projects. Already used successfully for 153 years, these low-tech pumps will help farmers adjust to the drier conditions that may come with climate change.

Herding and Desertification Herding, or pastoralism, is practiced by millions of Africans, primarily in savannas, on desert margins, and in the mixture of grass and shrubs called open bush. Herders live off the milk, meat, and hides of their animals. They typically circulate seasonally through wide areas, taking their animals to available pasturelands and trading with settled farmers for grain, vegetables, and other necessities.

Many traditional herding areas in Africa are now undergoing desertification, the process by which arid conditions spread to areas that were previously moist (see Chapter 6). This drying out is often the result of the loss of native vegetation; traditional herding may be partially to blame, but economic development schemes that encourage cattle raising are also at fault. Cattle need more water and forage than do traditional herding animals and therefore place greater stress on native grasslands than goats or camels do. Agricultural intensification in the Sahel also contributes to desertification, as scarce water resources are diverted to irrigation, leaving dry, vegetation-less soils exposed to wind erosion.

Over the last century, desertification has shifted the Sahel to the south. For example, the World Geographic Atlas in 1953 showed Lake Chad situated in a forest well south of the southern edge of the Sahel. By 1998, the Sahara itself was encroaching on Lake Chad (see the Figure 7.5 map) and the lake had shrunk to a tenth of the area it occupied in 1953.

Africa’s world-renowned wildlife faces multiple threats from both human and natural forces, all of which could become more severe with increases in global climate change. The Intergovernmental Panel on Climate Change, a body of scientists tasked by the United Nations with assessing scientific information relevant to understanding climate change, estimates that 25 to 40 percent of the species in Africa’s national parks may become endangered as a result of climate change.

Wildlife managers are developing new management techniques to help animals survive. For example, one of the greatest wildlife spectacles on the planet took a tragic turn in 2007. The annual 1800-mile-long (2900-kilometer-long) natural migration of more than a million wildebeests, zebras, and gazelles in Kenya’s Maasai Mara game reserve requires animals to traverse the Mara River. In the best of times, this is a difficult migration that usually results in roughly a thousand animals drowning. In the past, the park’s managers have taken a hands-off approach to the migration, considering the losses normal. However, in 2007, extremely heavy rains, possibly related to global climate change, swelled the Mara River to record levels. When the animals tried to cross, 15,000 drowned (see Figure 7.8B). Park managers are now taking a more active role in helping the migrating animals cope with unusual climatic conditions that may worsen with climate change. This may involve stopping animals from attempting a river crossing or directing them to a safer crossing. 169. PROTECTING NATURE IN GUINEA COLLIDES WITH HUMAN NEEDS

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Farmers’ dependence on hunting wild game (bushmeat) for part of their food and income is already a major threat to wildlife in much of Africa. For example, farmers who need food or extra income are killing endangered species such as gorillas, chimpanzees, and especially elephants in record numbers (Figure 7.10C). If crop harvests are diminished by global climate change, many farmers will become even more dependent on bushmeat and on income from selling contraband, such as ivory. The threat to wild populations of various species has led to calls to expand and establish new protected areas for wildlife.

Africa’s national parks constitute one-third of the world’s preserved national parkland. The parks are struggling to deal with poaching (illegal hunting) within the park boundaries by members of surrounding communities. Poaching is often fueled by demand outside Africa for exotic animal parts (tusks, hooves, penises) as medicines and aphrodisiacs, especially in Asia, where efforts to educate consumers about the damage done by their purchases are only beginning. In 2011, the western black rhino was declared extinct, due largely to poaching driven by demand for its horns by practitioners of Chinese medicine.

Some parks are now using profits from ecotourism to fund development in nearby communities that previously depended in part on poaching. For example, in 1985, wildlife poaching threatened the animal population in Zambia’s Kasanka National Park. Park managers decided to generate employment for the villagers through tourism-related activities. They built tourist lodges and wildlife-viewing infrastructure and started cottage industries to make products to sell to the tourists. Funding also goes to local clinics and schools, and students are included in research projects within the park. Local farmers have expanded into alternative livelihoods, such as beekeeping and agroforestry. Today, poaching in Kasanka is rare, its wildlife populations are booming, tourism is growing, and local communities have an ongoing stake in the park’s success. Sub-Saharan Africa’s rich array of animals has long played an economic role in daily life. Three species are discussed in Figure 7.10.

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