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Problems with Pesticides

Pesticides cause many problems including genetic resistance, ecosystem disruption, pesticide persistence, and pesticide mobility in the environment

Genetic Resistance is resistance to a pesticide that occurs after the prior generation has survived it.  Prolonged usage of a pesticide on a pest results in natural selection leaving only those with resistance to reproduce.  Eventually, a new generation is created, all that have inherited resistance to the pesticide.  To combat this resistance, as time goes on farmers must use more pesticide in larger dosages to kill of the resistant pests.  This means the cost of applying the pesticide increases while the effectiveness decreases, also known as the Pesticide Treadmill.

 

Ecosystem Disruption is when use of pesticides actually results in the creation of new pests, or turning minor pests into major pests.  When a pesticide is used, it may kill of the natural predators, parasites, or competitors of a certain pest, which allows for that pests population to rebound.  For example, an outbreak of a scale insect pest occurred only after spraying lemon trees with DDT.

 

A pesticide is Persistent if it natural decomposers such as bacteria cannot degrade them due to their synthetic and unnatural chemical structures.  When these pesticides are not metabolized or broken down, they build up in large concentrations in an organism’s body, which is known as Bioaccumulation.  Since there is no loss of pesticide from trophic level to trophic level, but a loss in energy according to the 10% rule, organisms at higher levels must eat more organisms containing the pesticide to get the energy needed to live.  This increase in pesticide concentration as the pesticide passes through successive levels of the trophic pyramid is called Biological Magnification.  As the pesticide accumulates in higher trophic levels, it becomes toxic and can harm or kill the organism.

 

Mobility in the environment is a problem because pesticides tend to move away from where they were applied and often accumulate in bodies of water where they were washed up.  The fishes in these ponds and lakes can suffer and die from accumulated pesticides.  It is also harmful for humans because pesticides can drain through the soil and into ground water supplies.  They can also travel long distances by wind and wind up in the air we breathe.

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