3.5 Impact of Agriculture

2026 Syllabus Objectives

By the end of these notes, you should be able to:

  1. Describe and explain the impact of agricultural practices on the environment and people.
  2. Cover all key examples: overuse of insecticides and herbicides; overuse of fertilisers; mismanagement of irrigation causing salinisation and waterlogging; overproduction and waste; exhaustion of mineral ion content; soil erosion; cash crops replacing food crops.

Main Content

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Agriculture — the practice of growing crops and raising animals for food — feeds billions of people around the world. However, many modern farming methods cause serious damage to the environment and to communities. Understanding these impacts is essential for managing agriculture sustainably.

1. Overuse of Insecticides and Herbicides

Insecticides are chemicals sprayed on crops to kill insects that eat or damage them. Herbicides are chemicals used to kill weeds — unwanted plants that compete with crops for water, light, and nutrients.

When these chemicals are used in excess, they cause widespread harm:

  • Harm to non-target organisms: Insecticides do not only kill pest insects. They also kill beneficial insects like bees, which are vital for pollinating crops and wild plants. Without pollinators, many plants cannot reproduce.
  • Bioaccumulation and biomagnification: Some insecticides, such as DDT, do not break down easily in the environment. They build up inside the bodies of organisms over time — this is called bioaccumulation. As animals eat other animals, the concentration of the chemical gets stronger and stronger up the food chain — this is called biomagnification. Top predators such as birds of prey end up with very high concentrations of these chemicals in their bodies, which can kill them or prevent them from reproducing.
  • Water pollution: Rain washes insecticides and herbicides off farm fields and into streams, rivers, and lakes. This pollutes drinking water and kills aquatic life such as fish and invertebrates (small water animals without backbones).
  • Soil damage: These chemicals can kill microorganisms (tiny living things) in the soil that are essential for breaking down dead material and recycling nutrients. This reduces soil health over time.
  • Herbicide resistance: When herbicides are overused, some weeds survive and pass on their resistance to their offspring. Over time, "superweeds" develop that are very difficult to control, forcing farmers to use even more chemicals.
  • Human health: People living near sprayed fields or farm workers who handle these chemicals regularly can develop serious health problems, including respiratory (breathing) issues, poisoning, and in some cases cancer.

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