1) Various types of are employed to promote the growth of crop plants needed to feed the ever-increasing human population. Some of these chemicals have disruptive side-effects on food .
2) If a pesticide is non-biodegradable it tends to increase in along a food chain and affect the final seriously or even fatally.
3) Repeated use of a pesticide often leads to the emergence of strains of the pest that cause as much damage as before.
4) Destruction by a chemical of one or more members of an ecosystem's interdependent community results in loss of and leads to within that ecosystem.
5) is the enrichment of an aquatic environment by nutrients such as nitrate and . It is increased to unnaturally high levels by excess fertiliser or sewage passing into waterways and disturbing the cycle.
6) Algal occur in ecosystems when excessive quantities of nitrate become available. Death of the cells and their decomposition by causes environmental degradation.
7) Disposal of inadequately treated sewage into a waterway leads to serious problems. which has been adequately treated still presents human society with the problem of finding a suitable site for its safe especially if the community is densely populated.
8) Supplies of drinking water may be contaminated by from excessive or ill-timed use of on farmland.
9) The rising demand for energy by the increasing human population (especially in industrialised societies) is met largely by the combustion of . This is causing the concentration of carbon dioxide in the Earth's atmosphere to increase.
10) Human activities are also causing the concentrations of and CFC's in the atmosphere to increase.
11) Carbon dioxide, methane and CFC's are called gases because they trap heat coming from the Earth's surface and keep the planet warm. This effect is essential to life.
12) Evidence suggests that global warming may increase in the future to well in excess of desirable levels. It is thought that this could lead to a rise in , disturbance of world , disruption of agriculture and of many forms of wildlife.