Pesticides - Danger to Wildlife

Another recently realised danger to wildlife in many parts of the world has come from the development of more effective pesticides. As agriculture became more efficient so the need to control crop pests also became more urgent, and the agricultural chemists have devoted a great deal of their time and energy to synthesising compounds to meet this need.

In the early 1960s it became clear that a certain group of chlorinated hydrocarbons, notably aldrin, dieldrin and heptachlor, which are undoubtedly extremely effective in controlling pests, are proving increasingly harmful to many wild animals. Their great disadvantage, it was discovered, was that whereas most other pesticides were fairly rapidly destroyed when they fell on the ground, the above three pesticides persisted in the soil for years, and tended to accumulate (bioaccumulation) since each year's spraying reinforced the persisting residues from previous years.