The African farmer is affected by climate, vegetation and soils

Climate Similar climatic patterns north and south of equator Equatorial, tropical wet and dry, desert, and Mediterranean climates Differ in terms temperature, rainfall, and evaporation.

Temperatures high throughout Mean annual temp. ranges from 15 to 33 C (59 to 91 F) Highest temp. not at the equator –Continuous cloud cover and moisture protect against the sun's rays.

Temperatures Fairly constant at equator Fluctuates farther north or south of equator daily and annually Mali--averages 30 deg. C Congo (Zaire) averages 25 deg. C

Difference between means for the coolest and warmest months Big difference Algeria Small difference Congo

Day-time highs and night-time lows Algeria: large variation Congo: small variation

Rainfall distribution More critical than temperature ranges Explained by the Inter- tropical Convergence Zone

Inter-tropical Convergence Zone (I.T.C.Z.) Low pressure zone near equator Trade winds converge, accumulate, air ascends causes rain

I.T.C.Z. Not stationary Oscillates between 20 degrees north and 25 degrees south. Irregular and unpredictable

Direct correlation between the I.T.C.Z. and rainfall patterns. January-- I.T.C.Z. rainfall at Equator and south

July-- I.T.C.Z. shifts; rainfall is north of equator.

Only equatorial zone receives rain throughout the year Both rainbelts overlap About 8% of Africa, the Congo (Zaire) Basin and the coast of West Africa, receive >1600 mm of rain annually

50% of the continent is arid or semi-arid Agriculture is constrained by water availability in over half of Africa

Africa has a negative water balance Evaporation> rainfall, leads to water deficits –Evaporation is high because of high temp. and radiation. Only Equatorial Africa has water surplus

I.T.C.Z. is important for the African farmer I.T.C.Z. causes distinct dry season except in equatorial areas

Length of the dry season – months just North and South of Equator – up to months further away

Farming and food production determined by Length of the dry relative to the wet season

Lengthy Dry Seasons Proper storage systems become part of the food production cycle

Rains a crucial period for the farmer Farming in a restricted rainy season Planting and weeding in a short period of time High labor demands

Local traditional varieties Are adapted to –Rainfall conditions –Plant diseases and pests

Local traditional varieties Evolved over thousands of years Some were domesticated in the area

Crops domesticated in West Africa millet sorghum okra watermelon fluted pumpkin kola (coca cola ) cotton sesame

Crops domesticated in Ethiopia Coffee Teff Enset Cress Castor (castor oil)

Rainfall variability is high The smaller total amount, the higher the variability

Other factors in climate Warm or cold ocean currents High plateau of East Africa The Great Escarpments Cold fronts from Antarctica Thunderstorms in equatorial Africa

Regional distortions The Mediterranean climate –Northern and Southern Africa The Sahara desert –Brought about by dry air masses coming from Arabia

VEGETATION Correlates strongly with rainfall patterns Dry conditions -- desert-like vegetation Semi-arid conditions--steppe

VEGETATION Sub-humid conditions--savannas Wet conditions-- forests and rainforests

Vegetation Continuum rainforest-forest--savanna--steppe--desert No true boundaries exist

From the equator to the desert Fewer and smaller trees Increased grassland-like vegetation Decreased diversity of species

Vegetation zones resemble north and south of equator Rainforests cover only 8- 10% Africa-- continent of savannas and deserts

Rainforests Poor soils Nutrients recycled

Destruction of rainforests Rapid Large amounts cleared yearly

Savannas Between forests, steppes, and deserts

Nearer to the equator Trees dominate grasses Woodland savanna

Further north or south of the equator-- a distinct dry season Savanna grasslands Woodland savanna

Characteristics of savanna Herbivores (rhinoceros, elephants and giraffes) predators (lions)

Characteristics of savanna areas Baobab trees (girths of 30 feet +) Huge bodies of granite

Steppe Transition zone between savannas and deserts Narrow bands on either side of the savanna.

Semi-arid conditions e.g., Kalahari Desert Sparse vegetation Plants-- extremely scrubby Thorn trees

Under extreme conditions Cactus and aloe, growing in almost bare soils. Vegetation- a function of climate and soils.

Steppes: extensive livestock grazing Drier areas used by pastoralists

Agriculturalists occupy wetter areas Competition between the two groups for best land

Rainfall variability and drought High in the between savannas and deserts Above-average alternates with low rainfall Produces droughts

1970s: Sahel area (West Africa) 1980s: Ethiopia 1990s Southern Africa, Horn of Africa Southern Africa Massive crop failures Famine and starvation (people and livestock)

1/3 of Africa taken up by three main deserts Sahara, 1/4 of the land mass of the continent Namib Kalahari, a semi-arid region rather than true desert

Desert proper Areas receiving less than 250 mm of rain per year Little vegetation Daily temp. fluctuate > 35 C (95 F) Seasonal av. temp. > 40 C (104 F)