Pesticide application has been responsible for great increases in UK farm yields over the past fifty years (Ecology and Conservation, Fred Webber, 1994). Also Farmers can now protect their crops. Some crops can now be grown in areas or times of the year when before they could not be grown because of the presence of a successful pest, weed or disease (Food, Farming and the Environment, Damian Allen and Gareth Williams, 1997).
The fact is that without the use of pesticides the global food production would fall drastically to a point at which it was too low to feed the world’s population. Leading to large-scale starvation.
There are, however, problems attached to the uses of pesticides. Although some pesticides break down in the environment quickly, such as herbicides that break down rapidly and are only poisonous when ingested at high concentrations thus cause problems very occasionally, others do not.
For example fungicides can be important pollutants. Many of them contain either Copper or Mercury, as fungi are very sensitive to these two elements. Mercury is toxic to humans. Cases have arisen, for instance in Japan, where people have died as a result of eating fish and molluscs, which had accumulated high concentrations of Mercury (Advanced Biology, Michael Roberts etal, 2000).
In addition, some insecticides are not broken down completely or very quickly once they have been applied. They remain in the environment for a long time this is known as persistence. When insecticides are not broken down they may persist in food chains. As the chemicals pass from one trophic level to another, they become concentrated, particularly in fat deposits of top carnivores such as birds of prey. This is called bioaccumulation. The effect may be quite dramatic, as with DDT, which is now found in virtually all animal tissue, in every food chain, and even the Antarctic snow (Food, Farming and the Environment, Damian Allen and Gareth Williams, 1997). However thanks to its use, millions of people survived who would other wise have died of malaria or starvation (Biology: Principles and Processes, Michael Roberts etal, 1993).
Pesticides are chemicals that are manufactured specifically to be toxic. When they are released into the environment, for example by spraying, they can cause accidental death to humans, pets and domestic animals. This is called direct killing. There are approximately 150 deaths a year in the USA from insecticides, and thousands each year in developing countries due to warnings on labels not being read or interpreted properly.
Some members within a species of pest are genetically less susceptible and may survive to pass on their resistance to the next generation. This could lead to the development of significant pest resistance. Most insects have rapid reproduction rates, so the evolution of resistance can be quite quick.
Another difficulty is pest replacement, or secondary pest outbreak. This occurs where crops become affected by another pest species. Once one pest species that is not affected by the insecticide may become a pest (Food, Farming and the Environment, Damian Allen and Gareth Williams, 1997). This is shown in the diagram below.
This situation can often lead to a farmer becoming locked into an expensive cycle, being forced to spray more frequently and more extensively than was originally intended because natural predators of the pest have been wiped out (Ecology and Conservation, Fred Webber, 1994).
In conclusion, pesticides are vital in order to increase global food production to meet the demand of the human population. This increases crop productivity has saved millions of people from starvation particularly in developing countries. The problem, however is that pesticides can be introduced into the environment with little knowledge of theirs effects on harmless or helpful organisms within the ecosystem. This can lead to ‘bioaccumulation’, ‘pest resistance’ and or ‘pest replacement’. Coupled with the potential dangerous miss use of pesticides leading to so called ‘direct killing’, the use of pesticides has to seriously considered. Therefore it is my view that a compromise must be taken. Pesticides must be used in order to increase crop yield to a necessary amount. However, their effects must be well researched and their use must be responsibly controlled to prevent damage to the environment, ecosystem and human health. The use of pesticides is being regulated by introduction of new laws. In the UK, the law on the sale and use of pesticides was made stricter by the Food and Environment Act 1985 and the Control of Pesticide Regulations 1986 (Food, Farming and the Environment, Damian Allen and Gareth Williams, 1997).
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Food, Farming and the Environment
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Pest Control and It’s Ecology
Michael Roberts, Michael Reiss, Grace Monger
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Michael Roberts, Michael Reiss, Grace Monger
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Ecology
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Fred Webber
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Ecology and Conservation
publisher