Drought: Causes, Impacts & Responses

A Slow-Burning Hazard

A drought is unlike a cyclone or earthquake: there is no single moment of impact. It begins quietly with low rainfall, deepens as soils dry out, and only becomes a crisis after months or years — by which time crops have failed, reservoirs have shrunk and food prices have surged. Drought is the most expensive natural hazard for global agriculture and one of the hardest to define, because what counts as ‘dry’ depends on what a place is used to. The Lake District seeing 600 mm of rain a year would be a severe drought; East Anglia seeing 600 mm is a normal year; the Sahel seeing 600 mm is a disaster only if it usually receives 800 mm.

Arid Environments vs Drought

An arid environment is one that is permanently dry — the Sahara, Atacama and central Australia receive less than 250 mm of rainfall a year as a baseline. Plants, animals and people adapt to that baseline. Drought is different: it is a temporary shortfall below normal rainfall, and it can hit even rainy places. The 2018 UK drought saw lawns brown, reservoirs drop and harvests fall by a quarter despite rainfall returning later that year. Confusing the two leads to weak exam answers — arid is a climate type, drought is an event.

Causes of Drought

Drought has three families of cause. Meteorological droughts begin when rainfall drops far below normal — typically because of shifts in the global circulation, sinking dry air at 30° latitude (where the Hadley cell descends), or warm-water/cool-water flips in the Pacific known as El Niño and La Niña. El Niño years drought-stress eastern Australia and southern Africa; La Niña tends to bring drought to the southern USA. Hydrological drought follows when rivers, reservoirs and groundwater stay low even after rain returns — aquifers can take decades to recharge. Human causes include over-extraction for agriculture (the Aral Sea has shrunk to 10% of its 1960 size from cotton irrigation), unsustainable dam-building upstream (the Mekong’s lower flow has been hit by Chinese dams), and large-scale deforestation that breaks the cycle of evaporation and rainfall (the Amazon basin sees longer dry seasons after forest loss).

Why Droughts Are Hazardous

Droughts kill mainly through food and water shortages, not directly. Crop failure cuts farmer incomes and triggers food price spikes that hit the urban poor. Livestock die when grassland fails. Water rationing closes industries that need cooling water (power stations, paper mills). Wildfires become routine in tinder-dry vegetation: the 2019–20 Australian Black Summer fires, fuelled by the worst drought in centuries, killed 33 people, three billion animals and burnt 18 million hectares. Long droughts can drive permanent migration, as the Dust Bowl did in 1930s America when 2.5 million people abandoned the Great Plains.

Australia 2017–19 (Developed-Country Drought)

Eastern Australia experienced its driest period on record between 2017 and 2019. The Murray-Darling river system — which feeds 40% of Australia’s farms — ran near-dry; some towns reported reservoirs below 5% capacity. Sheep numbers crashed; wheat exports halved. The economic loss was estimated at AU$8 billion. Yet death tolls remained low because Australia is wealthy: water trucks were sent to towns; emergency loans propped up farms; psychological support services treated rural depression. The federal government released AU$7 billion in drought funding. The drought also triggered the Black Summer wildfires that followed in late 2019.

Ethiopia 2015–16 (Developing-Country Drought)

A severe El Niño triggered Ethiopia’s worst drought in 50 years. Around 10.2 million people needed food aid; over 400,000 children faced acute malnutrition; livestock losses ran into millions. The economic loss was harder to absorb than Australia’s: Ethiopia’s GDP per capita is about $1,000, agriculture employs 70% of the workforce, and many rural households had no insurance or savings. International appeals raised $700 million in emergency aid — less than half what the UN said was needed. Long-term responses included a Productive Safety Net Programme that pays the rural poor to build small dams, terraces and water-harvesting systems.