The physical settings in which African social and economic systems have evolved are diverse, and distinctive in many ways. The key elements include:

1. Climate
   1. Unlike temperate zones where growing seasons primarily reflect changes in temperature, Africa's rhythms of life reflect rainfall (i.e. moisture) as the "limiting" factor.
   2. Africa has a bimodal climate based around a summer wet season and a winter dry season (summer is June-September above and equator and December-March below the equator). In fact, Africa's swings between dry and wet seasons are the most pronounced of any of the continents.
   3. The convergence of the anticyclonic and trade winds create a zone of turbulence around the equator known as the Inter-Tropical Convergence Zone (ITCZ). The ITCZ moves north and south of the equator in summer months, bringing the bimodal patterns of rainfall.
   4. Annual variations in the ITCZ movement produces Africa's distinctive seasonality. In years with El Nino effects the ITCZ may not reach its full extensions north and south, thus causing drought in those zones.
   5. Africa has had much long-term variation in temperature and moisture. Deserts have expanded and contracted over time. Last major Sahara wet phase ended in 2500 B.C. effecting the movement of desert peoples east to the Nile Valley and, perhaps, accounting for the flourishing of Egyptian civilization.
   6. The seasonal movements of moisture has historically produced rhythms to human life as pastoralists an their livestock follow the greening of savanna grasses and water supply. Farmers adjust their planting times and crops to accommodate the wet/dry patterns, and animals travel to new sources of food.
   7. Along the East African coast the seasonal shifts in monsoon winds have determined the movement of small sailing vessels (dhows) that carried people and trade goods to and from the Persian Gulf, the Indian sub-continent, and South East Asia.


2. Hydrography (movement of water on the land)
   1. Major river systems support local transport, allow irrigation, and provide food: Nile, Niger, Zambezi, Congo.
   2. East Africa Great Lakes extend along Rift Valley have allowed dense human settlement by enhancing food supply and transport.
   3. Action of water on land has caused erosion and redeposition of soils that make river flood plains agriculturally productive.


3. Soils and Geology
   1. Africa's soils are old and in tropical temperatures are easily leached, losing fertility easily.
   2. Farmer's response has been to develop shifting agriculture by the use of systematic fallowing to allow fertility to regenerate. System called citamene in Zambia.
   3. Volcanic soils in highland areas of Kenya, Ethiopia, Rwanda, Cameroon are agriculturally productive and allow dense human populations to settle there.


4. Vegetation Types
   1. Rainforest (Africa's rainforest zones tend to be less biodiverse than other such zones around the world, a result of the protracted dry historical phases
   2. Savanna
   3. Sahel (from the Arabic for "coast") is the area immediately south of the Sahara desert
   4. Afro-Alpine, highland zones where high elevation reduces temperature and promotes a distinctive habitat.
   5. The action of rainfall and temperature over time promotes a dynamism between vegetation types (forest and savanna, savanna and desert) and human activities (pastoralism vs. agriculture), population density, and patterns of trade.


5. Fauna
   1. Africa's diversity of landscapes and habitats promotes endemism (historical development of distinctive species)
   2. In many cases, however, the long-term shifts from wet to dry and back again has forced many species to adapt to both conditions and promotes the spread of common species across broad zones rather than locally distinctive types.


6. Disease (see Topic #6)



7. Historical Epochs defined by World Trade and Political Developments
   1. 1500-1875 Mercantile Period in which circulation of global trade tied Africa to Atlantic and Indian Ocean trading systems. Key Africa participation was:
      1. Indian Ocean currents and monsoonal winds allow trade, bringing goods and peoples to East African coast: cloves, cattle, sugar cane, bananas, Islam, merchant capital.
      2. Atlantic and East African slave trade that extracted Africans as labor but also created an African cultural diaspora in the New World and Near East
      3. Expanded trade contacts (the "Columbian Exchange") that brought new food crops from the New World that became the foundation of African food systems and, later, cash crops. These included maize, cassava, groundnuts, cocoa, beans, pineapple, etc.
   2. 1875-1960 Age of Imperialism in which European industrial growth and military dominance allowed them to control most of Africa directly as colonial possessions. In macro environmental terms Age ofIimperialism and colonialism resulted in:
      1. Accelerated introduction of new species of economic plants, invasive species, diseases.
      2. Political ecology of external control over natural resources
      3. Accelerated urbanization/urban footprint on landscapes
      4. Arrival of European settlers in particular areas (Kenyan highlands, Zimbabwe, Portuguese territories of Angola and Mozambique, Algeria, South Africa)
      5. See Topic #17 for impact of colonial policy on conservation
   3. Post-colonial period and Globalization
      1. Engagement of Africa with multi-lateral aid (U.N., World Bank, IMF, UNEP)
      2. International commodity markets for raw materials, agricultural products, and natural resources (forest products, such as pharmaceuticals)
      3. Dams, water resources, energy related to above (see Topic #18).
      4. Global policies affected by development narratives and mythic ideas about Africans peoples and natural resources (see Topic #3).