Human-Environment Interaction Desertification of the Sahel ► The Sahel in Arabic means “shore of the desert.” ► It is a narrow band of dry grassland that runs east to west on the southern edge of the Sahara. ► Since the 1960s, the desert has spread into this band of dry grassland. Desertification of the Sahel Desertification of the Sahel ► This shift of the desert is called desertification, which is an expansion of dry conditions to moist areas that are next to deserts. Desertification of the Sahel ►Human Causes Overgrazing of Desertification Farming Increasing Population Desertification of the Sahel ► Farming increases this process. When farmers clear land to plant crops, they expose the soil to the wind, which can cause erosion. In addition, irrigation increases salt levels which prevent the growth of vegetation. Desertification of the Sahel Animated Clip Desertification of the Sahel ► Food and water shortages lead to malnutrition, famine, disease and high death rates. Desertification of the Sahel Harming the Environment in Nigeria ► Another environmental issue has to do with the discovery of oil in Nigeria in 1956. Rich oil deposits in the Niger Delta made Nigeria one of Africa’s wealthiest countries. Harming the Environment in Nigeria ► The damage caused by foreign oil companies and the Nigerian government has been severe. More than 4,000 oil spills have been recorded in Nigeria over the past four decades. Shell oil spill in Nigeria in 2004. Harming the Environment in Nigeria ► Cleanup operations have been slow ► Oil spills have caused fires, acid rain, massive deposits of soot ► Resulted in high rates of respiratory disease Controlling the Nile Egypt has always depended on the water of the Nile River. The two main tributaries of the Nile River are the White Nile and the Blue Nile. Lake Victoria is the source of the White Nile and the Blue Nile. The Nile River has a total length of 4,160 miles from source to sea – the longest river in the world. Controlling the Nile Sahara Desert The fertile areas surrounding the Nile River Controlling the Nile ► Throughout history, Egyptians have experienced cycles of floods and droughts. Controlling the Nile ► To solve these problems, they built the Aswan High Dam, which was completed in 1970. The dam gives farmers a regular supply of water. Facts • The Aswan High Dam is 2.2 miles long and 354 feet high. • The Soviet Union helped the Egyptian government to build the dam. • The Aswan High Dam has 12 turbines which generate over 10 billion kilowatts of electricity every year. • Construction started on the dam in 1960 and it was completed in 1971. • 30,000 Egyptian people worked day and night to build the Aswan High Dam. • Lake Nasser was created behind the Aswan High Dam. It is the largest artificial lake in the World (348 miles in length). It is named after the former President of Egypt. Controlling the Nile The Advantages of the Aswan Dam Controlling the Nile Electricity for homes and industry: Generators in the dam are used to generate electricity that is taken to homes and industries by pylons. Pylons Aluminium and copper smelting industry Controlling the Nile Flood control: Control of flooding is carried out by the dam. By keeping so much water back in Lake Nasser, the River Nile rarely floods the surrounding farmland any more. Controlling the Nile New farmland created: The act of keeping back the water from the River Nile has lowered its level, effectively creating new farmland by the river sides. This is also less prone to flooding. Controlling the Nile Irrigation water for nearby farmland: Development of irrigation channels from Lake Nasser, takes water from the reservoir to the nearby desert to make farmland for watering crops. The electricity pumps the water there. Controlling the Nile Fish stocks in Lake Nasser: Also creates tourism via game fishing. Fish live in the lake and can be fished more easily by those fishermen who used to fish in the River Nile. This improves their livelihoods and fish stocks can be replaced more easily. Controlling the Nile The Disadvantages of the Aswan Dam Controlling the Nile ► Because of the dam, the Nile River no longer deposits its rich silt on the farmland. Controlling the Nile Water-borne diseases increase: As the water in both the reservoir and irrigation channels is contained and, in a lot of places, static, this promotes the build-up of water snails which carry the disease bilharzia. Many other diseases also increase as they are not 'flushed away' by the flow of the River Nile. Controlling the Nile ► Now, farmers must rely on expensive artificial fertilizer to enrich the soil. Controlling the Nile Land lost from flooding of Lake Nasser: Although there were some land gains from the building of the dam, there were much more losses behind the dam where the land was flooded to make the reservoir of Lake Nasser. Many people were moved and made homeless as well as losing their farmland. The temples of Abu Simnel had to be moved. New Location Old Location Controlling the Nile Evaporation from Lake Nasser is very high: This is an extremely hot area of the world. Evaporation from Lake Nasser is very high as a consequence and this means a lot of water is lost. Controlling the Nile ► Water pollutants – treating municipal water can often be too expensive for the more impoverished areas along the Nile. Unfortunately, these cities dump polluted water, containing human waste, back into the Nile untreated. This causes disease to spread. Controlling the Nile ► Also, year-round irrigation has resulted in a rising water table in Egypt. As a result, salts from deep in the earth have decreased the fertility of the soil.