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Geography Lecture #4 - October 15 - 22 2013.docx

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Geography 1400F/G
Anthony Weis

Desertification -Sahel region has had massive famines and even in West Africa there was a famine that affected 20 million people, this was in 2012 -East Africa famine 2011 -Economist – talks about repeated cycles of food insecurities to man -Sahel is permanent region of crisis. Why is region so food insecure???? These are very current problems -how does nutrition crisis differ from famine? Answer: Nutrition crisis is the caused by the earth. Like seasonal dries -famine isn’t something that suddenly emerges -Episodic crisis – acute outbreaks of famine -Covert famine - stunts their development, saps their strength and cripples their immune systems. FAO argues there is a covert famine with us all the time -enough food in world to feed it 1.5 times -sub-Saharan Africa is place of famine, food insecurity and hunger -undernourished – lack of protein and vitamins ingested (vitamin deficiency in children and adults, children more so) -in last decade sub Saharan countries have been growing considerably Why is the climate in this area so seasonal? Climate isn’t necessarily determining the problems in the might be something else -this area was a region that was home to very significant empires at the civilization levels, great agricultural hearths on the planet, large ancient cities and innovation -even though area is very seasonal climate/arid and dry it was once home to very large mammals (other parts of Africa are known for its large mammals and predators now) -subtropical high zones are areas of descending warm and dry air (controls desert regions) at 30d north and south of ITCZ. The ITCZ controls where the dry lands are and semi-tropical regions -shape of continents and large ocean masses affect the climate and itcz…land masses heat up and cool down much quicker than oceans (oceans heat up and cool down at much greater depth and retain heat for much longer like a solar battery) -the land heats up Africa the most during January (most intense insulation) -Africa is 4x size of the USA -ITCZ moves north in July (our summer) and this is the rainy season. But the Sahal isn’t getting as much rain any more across large areas of the region -ITCZ does stretch into the Sahara but it reaches more south in parts of West Africa (based on lines of pure latitude), but by the time the ITCZ reaches the Sahara all the ocean rain has been dropped. In January there is a dip in the ITCZ (this is because of the ocean thermal battery and the drying effect of Harmattan winds blowing across Arabian and the Sahara – warm and very dusty winds). Wind are from the north east -ITCZ are driving story of rainfall and the dry season (continents also complicate the situation) -rainfall is heaviest in eastern parts of Africa – rains of Indian ocean -Sahel we have relatively stable temperatures but precipitation is mostly concentrated within a few months -WHY IS THERE A WIGGLE (average daily temperatures drops) DURING PERIOD OF RAINFALL? They relate, the ITCZ is bringing the rains and more cloud cover therefore temperature is a bit lower than rainy season. The cloud cover is re-radiating some of the insolation of the sun. -equatorial Africa we see a very constant temperature, average insulation doesn’t change very much and rainfall is heavy most of the year like the amazon. Limited seasonality -in south of Africa there is a very different story than Sahel -Sahel stretches 4800km east-west (and varies north to south by 500-800km) – Sahel is Arabic word for shore. The shore is of the Sahara desert. The shape of desert relates to shape of continent -for millennia principal trade routes weren’t around the ocean but the OCEAN OF THE SAHARA -Sahel is a transition region, tropical step, grasslands, vast lands and characterized by widely spaced trees and shrubs (also varies, and no consistent bioregion north (dry) and south (moister)) -grasslands south are more continuous (more north it is the complete opposite) -the region has extreme seasonality (so the story goes) and the trees look like ours, the deciduous trees lose their leaves and go into hibernation. As you move further north these trees and shrubs spread out further since there is less water in the wet season. INCREDIBLE SEASONALITY OF MOISTURE and vegetation has to deal with this change, so there is plant limitability to grow since there isn’t water for a long period of time….PLANT ADAPTATIONS -Potential evapotranspiration – a term that reflects, if you add up all the potential evaporation (all of it) and all the potential transpiration from plants, if the plants demands for moisture were met, this region of world, it would have a very high potent capacity in the world, meaning there is much more moisture dependence of plants in this part of world than what is provided. It forces plants to adapt in a number of ways. It collects water very well when it arrives (deep root system compared to amazon). Shrubs will have huge radial root systems. They hold moisture very well (leaves are very waxy and inhibit transpiration). Another important adaptation of this reason (in regards to seasonality) is fire, since there are natural fires that go to very dry regions. Fire is naturally made and manmade. Small farmers and pastoralists set the fires. Pastoralists set these fires (in semi-arid regions) is to control distribution of plants, to remove woody plants and keep plants and grasses…remove tree life vegetation. Farmer’s burn crops to remove crop stubble and ease process of cultivation -as you move north there is less moisture and vegetative cover (more sparsely of trees and grasslands). Life and greenness comes for a very limited amount of time and then they go dormant for a long period of time. Climate reduces rainfall and makes the region drier -when heavy rains do come, ITCZ moves north and produces a significant amount of erosion (Since grasslands are already overgrazed). As grasslands shrink, animals and human populations implode -Landscape is very prone to wind erosion – AEOLIAN PROCESS. Wind is constantly transporting sand, silt and micro-biota (also important material like iron oxides). Since wind is moving so fast it is transporting more material. Where there is less vegetation the wind is faster. Dust from Sahara makes its way to the Americas. The dead air area impacts the wind speed. It makes it a vicious cycle -dead air layer can protect soil from wind erosion -Sahel is the green belt, and vegetation protects soil during rainy season and dry season by preventing soil erosion th CONTINUING NEXT LECTURE (STARTED ON 15 ) -Sahel is hyper-arid (like Sahara) and semi-arid (more humid areas) -Desertification is problem haunting many of worlds dry-lands – affects human population around world and relates to food insecurity in the Sahel -Desertification – loss of lands biological productivity, caused by humans and anthropogenic climate change. ¼ of world’s dry lands may become deserts or have some degree of desertification -loss of vegetation produces more Aeolian winds, degraded top soil, water erosion, and soil density -salinization is another threat to biological productivity in dry lands (most acute in Sahel region). Salinization is a result of over irrigation. As plants transpire salt is left behind. -desertification is essentially irreparable on human time scale (but only on geological time scale) -Sahel – one of poorest region world, very arid and seasonal climate -Sahel is highest agrarian region - is a society that depends on agriculture as its primary means for support and sustenance. Sub-Saharan Africa and south Asia– 60% of population is agrarian. A lot of food import dependence. Dependence on world market as well -Why is region so poor, so much crime, hunger and malnourishment? It is mostly climate and environment. th -Environmental determinism (accepted term and explanation in geography in early 20 century) – the environment determines society and economy ALSO the view that the physical environment sets limits on human environment. THEORY HAS BEEN DEBUNKED, but some of the theory still pertains to today -Jeffrey Sachs says environmental determinism plays out in the fact that Africa is very land locked THOMA MALTHUS (British aristocrat) - neo-Malthusian is another factor - generally refers to people with the same basic concerns as Malthus, who advocate for population control programs, to ensure resources for current and future populations. It is essentially a carrying capacity of the region -Sahel has 4x more people than it had a half century ago Thomas argued that all plagues and wars are caused by humans over reproducing (no- empirical basis) Malthusian theory - theory that population increase would outpace increases in the means of subsistence -Paul Ehrlich – population bomb. He said that human reproduction is the cause of environmental degradation -beginning of 20 century population was around 1 billion now it is over 7 billion -future of human race dependent upon containing population bomb in developing world -population grows fastest in poorest regions -Desertification – population boom and livestock boom (like goats have grown by factor of 2-3x) -animals are grazing land in different ways (correlation between overgrazing and desertification) -ways livestock moves across land has changed in the last century (more desertification) Immanuel Wallerstein – most influential social scientists of second half of 20 century and establis
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