discuss on the undesirable effects of chemical control of pests and weeds and the excessive use of chemical fertilizers

In the modern agriculture, farmers widely use pesticide, weeds killer and chemical fertilizers in order to obtain a greater yield. Although we have to solve the food problem of the non-stop grow population, wide uses of chemicals will bring us undesirable effects such as pollutions and harms to health.

We concern the water pollution first, referring to the addition of undesirable materials into aquatic bodies. This may cause physical, chemical or biological changes in water, leading to different harmful effects on organisms or making water sources unsuitable for use. Many aquatic organisms have been killed and the sources of drinking water have also been deteriorated. Overuse of fertilizer and pesticide will bring us water pollution since rest of they will accumulate on the soil after irrigation and strong rainfall. The chemicals will be washed away toward to the river then to the sea. Prolong washing the chemicals into the ocean will cause serious water pollution. And it will also increase the growth of algae which will block the sunlight pass through the sea, influencing the photosynthetic rate so the oxygen content in the sea.

Moreover, intensive use of pesticides and herbicides in agriculture greatly interfere the ecosystems in two ways. Firstly, most pests have enemies, which prey upon them. The pesticides may decrease the efficiency of these predators as agents that control pest populations. Secondly, pesticides may extensively eliminate the pests. This may result in deprivation of the only food source of the pest’s enemies and eventually remove them from the ecosystems. In both situations, the pests may proliferate in such an extent that they can no longer be controlled in the ecosystem. The herbicides will keep the lawn weed-free. This eliminates interspecific competition and greatly reduces the diversity of species. Frequent use of pesticides may promote the development of new strains of pests which are resistant to these chemicals which will allow the growth of super pest. As a result, it will be more and more difficult to control the new strains of pests. In fact, many insecticides that are effectively in the past are no longer useful nowadays. Chemicals maybe toxic to the organisms or affect their reproductive success. Many of them cannot be excreted, accumulating in the body of the organisms and be passed from one trophic level to another one. Usually the consumers in higher trophic levels are feed on a large number of smaller organisms at lower trophic levels Therefore, large amount of toxins stay inside those organisms and damage to human health if we take in those kinds of organisms. Soil destruction will also happen since chemical fertilizers used instead of organic one. The soil becomes lack of humus or organic matter, and thus the water retaining ability is greatly reduced. As a result, the soil becomes compact and less suitable for crop growth.

The chemical will severely harm our health and some of them are even fatal. We have to wash the vegetable clearly and cook them thoughtfully in order to ensure that all the fertilizer on the vegetable are washed away.