Reading: Drought
Drought
Smith Ch 12
Drought
A slow-acting, often long-term hazard Geographically widespread and territorially large
Niger, 1983
African Sahel Famine 1984-5
Followed 16 dry years from 1968 onwards 2/3 of Africa is dryland, 70% of its dryland farming areas are degraded
Drought
MDCs:
Drought is costly, but not deadly
LDCs:
Drought is frequently deadly food supplies are fragile, malnutrition is "normal", the poor can be killed quickly in famine
Drought
Most famine deaths in sub-Saharan Africa
Mid 1980s African Drought
Affected 20 countries, 150 million people 30 million in urgent need of food aid 10 million refugees seeking food and water 100,000 to 250,00 deaths
Africa
Current drought conditions in southern Africa
14 million in 6 countries face starvation Botswana refusing food aid from US and EU:
fears about genetically modified food.
Victoria Falls, Dry Season
Ethiopia
Drought and war brought famine in 1984
1 million deaths in Ethiopia
Now in Ethiopia
6 million require food aid, 15 million face starvation by the end of 2002 10% of government revenues spent on foreign debt repayments Will require 200 million tonnes of food aid
1984 Ethiopian Famine
Australia 1979-83 Drought
No-one died of famine Several died in bushfires Drought affected
50% of farms 60% of livestock economic hardship permanent environmental damage?
Drought
Effects are relative
Drought for a wheat farmer may not affect livestock farms Balance of moisture and evaporation Long-term drought management can reduce vulnerability
Meteorological Drought
Shortfall of precipitation Link between precipitation and useful moisture is indirect
Hydrological Drought
Reduction of stream-flow or groundwater levels Important impacts on urban areas Reduces available reserves of accessible water
1971 Frostproof Florida
Agricultural Drought
Reduction in soil moisture available for plant growth Reduced crop growth and output
Summer Drought in Toronto
Lawns absorb 1/2 of domestic water consumption Most water pumped from Lake Ontario Drought increases demand for water To reduce demand:
better conservation increase cost
Agricultural Drought
Australia 1982 drought
Wheat production down 37%, Livestock slaughtered
USA 1988 drought
31% drop in corn yield, 1/3 of crop destroyed Losses of $4.7 billion USD World grain reserve drops to 288 million tonnes or 63 days supply
US Corn Belt Drought 1988
Agricultural Drought
Southern Africa 1990-2
30-80% harvest failure 86 million people affected over 7 million km2
Agricultural NE Drought
Brazil 1985
1 million men abandon farms, head to cities to seek work
Fleeing famine in Ethiopia, 1984
Famine Drought
Drought a physical hazard Famine a cultural hazard Famine sometimes found in extreme agricultural drought conditions. Most deaths in famine are from disease, lack of access to clean water
Physical Causes
Drought more likely in drier climates
low annual precipitation high variability rains unreliable
July
October
Wet/Dry Seasons, Thailand
Thailand Dry season
US Great Plains
Dry to semiarid climate
Major droughts every 20 years or so
1890s, 1910s, 1930s, 1950s
US-Canada Dust Bowl 1930s
Cyclical drought Botched dry-farming techniques Depressed economy
Palliser's Triangle
Destroying Grassland 1900
Oxbow SK
Saskatchewan 1930s
Saskachewan 1930s
70% contraction in Provincial revenues Mass emigration of Saskatchewaners to BC
Swift Current SK
Sahel
Rainfall low (100 mm to 800 mm p.a.)
declines northwards
Rainfall reliability variable
becomes less reliable northwards
Rainfall highly seasonal
80% falls in July-August
Rain in Nigeria
Niger River, Mali
Sahel
Desertification
immediate economic needs force overgrazing demand for firewood destroys tree-cover land degradation
Physical Causes
Risk of African and other tropical droughts increased by El Nino Global atmospheric and ocean circulation rhythms involved Dust storms and dry soils alter albedo
may accentuate drought
Broken Hill dust storm
Asian dust over California
Dust Storm, Canary Islands
Human Causes
Land...