Causes & Impacts of Drought (Cambridge (CIE) IGCSE Environmental Management): Revision Note

Causes of drought

• Key features of a drought

  • It is based on local climate conditions, so what is normal in one place may be drought in another

  • It develops slowly compared with hazards like cyclones or floods

  • It affects both surface water (rivers, lakes) and groundwater (aquifers)

• Droughts develop when the natural water cycle is disrupted for long periods

• A drought is not simply 'no rain', but means that water levels have fallen below what people, crops and ecosystems need

Lack of rain

• This is the most direct cause of a drought

• Rainfall may decrease due to:

  • Shifts in weather patterns that move rain-bearing winds away

  • Changes in monsoon timing

  • High-pressure systems that block clouds and prevent rainfall

  • Areas with dry seasons or unreliable rainy periods, such as parts of Africa, Asia and Australia, are more likely to experience repeated droughts

• The effects of prolonged lack of rain include:

  • Shrinking rivers and lakes

  • Soil becomes dry and cracked

  • Plants and crops cannot grow

  • Aquifers are not replenished

• Even a few weeks of below-normal rainfall can trigger early drought symptoms

Climate change

• Climate change increases the frequency and severity of droughts

• Links between climate change and drought include:

  • Higher global temperatures increase evaporation from soil, plants, and water bodies

  • Moisture is lost faster than rain can replace it

  • More extreme weather means rainfall becomes unreliable

    • Some places get sudden floods and rainfall one year

    • But suffer long dry spells in between storms or almost no rainfall the next year

  • Warmer oceans disrupt wind patterns and monsoons

• As climate change accelerates, droughts are becoming longer and affecting more regions worldwide

• Hotter climates are also linked to more heatwaves, which dry out vegetation and water stores even faster

Impact of drought

• Drought affects ecosystems, agriculture, infrastructure and health

• Impacts build over time, creating wide-ranging problems such as food becoming harder to grow, habitats drying out and wildfires becoming more frequent, which can last long after the drought ends

Water sources dry up

• This is often the first visible sign of drought

  • Rivers, lakes, ponds and wetlands shrink

  • Groundwater levels fall because aquifers are not being recharged

  • Wells run dry, especially in rural communities

  • Hydroelectric power stations may stop functioning

  • Communities face water shortages for drinking, washing and farming

  • Wildlife is affected because animals cannot find enough water to survive

Loss of crops, livestock and habitats

• Crops

  • Soil becomes too dry for planting

  • Young plants wither

  • Yields drop sharply

• Livestock

  • Lack of grass and fodder

  • Animals weaken and die due to heat stress or dehydration

• Habitats

  • Wetlands decline

  • Forests lose vegetation cover

  • Wildlife has less food and water

• This leads to loss of income for farmers and reduced biodiversity

Soil erosion

• Soil erosion reduces future farming productivity and damages natural ecosystems

• Dry soil becomes loose and fragile

• Why drought causes erosion

  • Without vegetation, soil is not anchored

  • Wind easily blows dry soil away

  • Sudden rainstorms wash away unprotected topsoil

• Once fertile land becomes less productive, it is part of a feedback loop that worsens drought impacts

Desertification

• Long-term drought can turn fertile land into desert-like conditions

• Desertification means

  • The land becomes more like a desert

  • Soil loses nutrients and structure

  • Plants cannot recover

  • Rainwater runs off instead of soaking in

• Desertification expands dry, sandy areas and reduces the amount of land available for farming

• Human activities like overgrazing or deforestation accelerate this process

• Communities living in these regions face long-term loss of resources and may be forced to migrate

Death of organisms

• Plants die from lack of water

• Fish and aquatic species die as rivers and lakes disappear

• Wildlife perishes from starvation and dehydration

• Some species migrate; others cannot

• Whole food chains can collapse if drought continues for long periods

• This reduces biodiversity and disrupts food webs

Famine

• Drought can trigger severe food shortages

• Why famine occurs

  • Crop failure reduces local food availability

  • Livestock losses reduce milk and meat supply

  • Food prices rise sharply

  • Vulnerable communities cannot afford food

• Famines are increasingly common in regions with repeated droughts, such as East Africa

Increased risk of wildfires

• Dry vegetation becomes highly flammable

• Wildfires spread easily because

  • Plants and grasses dry out

  • High temperatures increase ignition risk

  • Wind spreads flames quickly

• Wildfires damage forests, settlements and wildlife habitats

• Smoke from wildfires also harms air quality and human health

Decrease in air quality

• Drought creates polluted air conditions

• Reasons

  • Dust storms become more frequent

  • Smoke from wildfires fills the air

  • Dry soil particles reduce visibility

• This worsens respiratory conditions such as asthma, especially in children and the elderly

• Animals also struggle to breathe in smoky or dusty environments

Financial losses

• Economic impacts spread across many sectors

  • Farmers lose income from failed crops

  • Governments spend money on food aid and water supplies

  • Businesses suffer because water-dependent industries close

  • Tourism declines in affected regions

• National economies can be severely weakened by long droughts

• Rebuilding damaged land and restoring water supplies can be extremely costly

Human health

• Drought affects health in both direct and indirect ways

• Droughts can leave long-term health challenges even after rainfall returns

• Examples include:

  • Dehydration and heat exhaustion

  • Malnutrition due to food shortages

  • Water-related diseases increase as clean water becomes scarce

  • Dust and smoke worsen respiratory illnesses

  • Mental health impacts from stress and displacement

• Heat-related illnesses such as heatstroke become more common as climate change worsens