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