The use of pesticides in farming is an important issue to environmental scientists. Farmers encounter many different pests that can damage their crops, and each kind of pest requires different chemical compounds to kill it.
The use of pesticides isn’t new, but these days most of the pesticides farmers use are synthetic rather than organic, or natural. Scientists create synthetic pesticides in a laboratory and can engineer them specifically to target a particular problem pest. While this control seems like a good thing, it results in a never-ending battle between farmers and pests and the need to constantly develop new chemical formulas.
The pesticide treadmill
Agricultural pests, like all other organisms, strive to survive. When farmers expose them to a chemical compound that’s designed to kill them, a few of them invariably survive to reproduce. As a result, the next generation is likely to be resistant to the deadly chemical (after all, their parents had some genetic mutation that allowed them to survive).
Thus begins a cycle some environmental scientists call the pesticide treadmill: As farmers and pesticide producers work harder to control pests, they create pests that are harder to control. The pesticide treadmill starts with the development of a new and powerful pesticide, but once it starts, it never ends. Here’s how the cycle goes:
Chemists create Pesticide A, which is extremely effective at killing pests.
Farmers apply the pesticide to their crops.
Most pests die, but a few survive and reproduce.
A new generation of pests that aren’t affected by Pesticide A is born.
Farmers apply Pesticide A with little or no result now that the pests are resistant.
Chemists create a newer, more powerful compound, Pesticide B.
The cycle repeats itself over and over again.
The pesticide treadmill leads to increasing costs for farmers, who have to purchase new pesticide formulas every year or risk losing their crops. Plus, each generation of pests is increasingly more difficult to kill, meaning that the pesticides chemists develop to kill the new pests must be even more potent than the last ones.
Spreading pesticide poisons in the environment
Not all pesticides are manmade. Some, such as botanical extracts and oils, are naturally occurring compounds. Naturally occurring pesticides are still extremely toxic and can affect both the humans and the pests that are exposed to them. However, naturally occurring pesticide compounds eventually break down and recycle back through the ecosystem, whereas manmade compounds often do not.
Scientists categorize synthetic or manmade pesticides according to their chemical structure. Here are a few of the most common types and the effects they have on their environment and the living things in it:
Organophosphates: Organophosphates are the most common and widely used synthetic pesticides. Organophosphate compounds break down eventually, but they’re highly toxic for the first few days after they’re applied. These chemicals are related to the nerve gases used in World War II, and they can result in severe damage to the nervous system (brain) of animals, including humans.
Chlorinated hydrocarbons: Chlorinated hydrocarbons are also called organochlorines. These compounds don’t easily break down and, therefore, remain in the environment long after farmers apply them to their cropland. Chlorinated hydrocarbon compounds, such as the commonly used Atrazine, have been linked to cancer, are considered an endocrine disruptor, and are banned in Europe.
Inorganic pesticides: Inorganic pesticides are chemical compounds that don’t include carbon molecules. Inorganic pesticides usually contain toxic elements, such as mercury and arsenic. These elements remain in the soil and ecosystem long after they’ve been applied to crops and enter the food chain.
Dangerous organic compounds that remain in the environment without breaking down are called persistent organic pollutants or POPs. (In this case, the term organic simply means that these compounds are built of carbon molecules, which is different from the use of the word organic to describe food.)
POPs, such as those found in the synthetic pesticides in the preceding list, exist for years, even decades, in lethal amounts. They remain in the soil or are washed into water supplies or groundwater, where they circulate into every corner of the environment. Some of them even evaporate into the atmosphere and then rain down into a completely different environment, far from the farmlands they were originally applied to.
POPs are particularly dangerous to animals and humans because they can accumulate in living organisms (through a process called bioaccumulation) or become increasingly concentrated up the food chain (a process called biomagnification).
