Impacts of Unsustainable Agriculture (Cambridge (CIE) IGCSE Environmental Management): Revision Note

Overproduction of food & food wastage

• Unsustainable agriculture involves farming practices that:

  • Damage the environment

  • Reduce the land’s ability to produce food in the future

• This often happens when farming focuses on short-term yield rather than long-term soil, water and ecosystem health

• It impacts both people and the environment, often leading to long-term problems such as:

  • Soil degradation

  • Pollution

  • Food insecurity

Food wastage

• Producing more food than is needed can lead to large amounts of waste

  • Surplus crops may rot in storage or be thrown away if they cannot be sold

• Wasting food means wasting the energy, water and land used to grow it

  • This increases the environmental footprint of agriculture

• Overproduction may encourage farmers to expand farmland, causing more deforestation or habitat destruction

Food shortages, cash crops & biofuel crops

• Growing cash crops such as coffee, cotton, soya beans and palm oil can replace food crops

  • Farmers earn more money from cash crops than from staple foods

• Replacing food crops can lead to local food shortages

  • Communities may rely on food imports, making them more vulnerable to price rises

• Growing biofuel crops (e.g. maize, sugarcane) reduces the land available for food

  • This can push up food prices, making basic foods unaffordable for low-income communities

Mismanagement of irrigation

• Mismanagement of irrigation can damage soil and reduce long-term productivity

Soil erosion

• Over-irrigation can wash away topsoil, the most fertile layer

  • This removes essential nutrients and organic matter

Salinisation

• In hot climates, repeated irrigation leaves salt deposits behind

  • Salt builds up in the soil, making it harder for plants to absorb water

Waterlogging

• Poor drainage can cause soil to become waterlogged

  • Roots lack oxygen and crops may die or grow poorly

Overuse of pesticides

Pesticide resistance

• Overusing pesticides can cause pests to develop resistance

  • Pests then survive pesticide treatments and become harder to control

Pest resurgence

• Killing natural predators may cause pest numbers to increase rapidly

  • Leads to greater crop damage

• For example, if insecticides kill ladybirds, which normally eat aphids, the aphid population can surge, causing more damage to crops

Impacts on pollinators

• Pesticides harm pollinators such as bees

  • Fewer pollinators means lower pollination rates and reduced crop yields

Overuse of fertilisers

Leaching into water sources

• Excess fertiliser can be washed into rivers and lakes

  • This causes pollution of drinking water sources

Nutrient enrichment

• Extra nutrients (especially nitrates and phosphates) cause rapid plant and algae growth in water

Eutrophication

• Algae form a thick layer on the water surface

  • This blocks sunlight and reduces oxygen in the water

  • Aquatic animals die, harming ecosystems

Soil nutrient exhaustion

• Growing crops repeatedly without replenishing nutrients exhausts organic content and inorganic ions

  • Soil becomes less fertile over time

• Poor soils reduce crop yields and may require more fertiliser, creating an unsustainable cycle

Removal of natural vegetation

Deforestation

• Clearing forests for farmland reduces biodiversity and destroys habitats

  • Soil loses erosion protection from tree roots and cover by tree canopies

Overcultivation

• Growing crops continuously, without sufficient rest periods between crop harvests, weakens soil structure

  • Makes soil more prone to erosion

Overgrazing

• Animals eat vegetation faster than it can regrow

  • Bare soil becomes exposed to wind and water erosion

Monoculture & intensification

• Monoculture refers to growing a single crop species over a large area for many seasons

  • Reduces biodiversity because only one plant species is present

  • Pests and diseases spread more easily because all plants are genetically similar

  • Can lead to faster nutrient depletion, as the same crop removes the same nutrients every year

  • Farmers may rely more on fertilisers and pesticides to maintain yields

• Intensification refers to high-input farming that uses lots of machinery, fertilisers, pesticides and irrigation

  • Produces high yields in the short term, but can cause soil degradation over time

  • Heavy use of fertilisers may lead to pollution of rivers and lakes

  • Frequent pesticide use harms beneficial insects, reduces biodiversity and can lead to resistance

Soil erosion

Loss of topsoil

• Unsustainable farming practices can remove topsoil, the uppermost and most fertile layer

  • Topsoil contains the highest levels of nutrients and organic matter

  • Losing topsoil reduces the soil’s ability to hold water and support plant roots

  • Rebuilding topsoil takes decades, making erosion a long-term problem

Loss of nutrients

• When soil erodes, it carries away essential nutrients like nitrogen, phosphorus and potassium

  • This reduces crop growth and lowers yields

• Farmers may add more fertilisers to replace lost nutrients

  • Increases farming costs and risk of nutrient pollution

  • Can make farming less sustainable in the long term