View
220
Download
0
Category
Preview:
Citation preview
Drought
Drought
• Reading: 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 Drought
• NE 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 semi-arid 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 degradation due to population pressure– 90% of Africa’s energy needs come from wood– Urban shadow denuded of trees around most
cities
China’s Great Leap Forward
• Mao’s efforts at a crash programme of industrialization and forced collectivization – disrupted rural life and
food-producing systems– mild drought in northern
China
China’s Great Leap Forward
• 20-30 million died of starvation 1959-61
• End of Mao’s economic leadership– Mao tried to regain
control via the Cultural Revolution ...
Senegal
• Senegalese change habits when they move to the city– Eat more rice: demands water– Cook, heat with Charcoal not wood: stresses
the forests
• Increases pressure on the water-resources
Human Causes
• Role of colonialism and global trading system?
Assignment 2
• Due date 28 November
• To get it back– Provide a stamped, addressed envelope with
sufficient postage– collect it during Dr Anderson’s office hours
next term
Exam
• Wednesday December 11, 3:30-5:30 p.m. Curtis Lecture Hall D
• Format:– Choice of essay questions, do two in 2 hours
Recommended