Pesticides are chemicals used to eliminate or control a variety of agricultural pests that can damage crops and livestock and reduce farm productivity. The most commonly applied pesticides are insecticides (to kill insects), herbicides (to kill weeds), rodenticides (to kill rodents), and fungicides (to control fungi, mold, and mildew).
Pesticides and the Environment
According to Cornell entomologist David Pimentel, “It has been estimated that only 0.1% of applied pesticides reach the target pests, leaving the bulk of the pesticides (99.9%) to impact the environment. Harmful environmental impacts of pesticide use include:
– Loss of biodiversity
– Elimination of key species (e.g., bees)
– Water pollution
– Soil contamination
– Pest resistance, resulting in the need for increased application of pesticides, or formulation of alternate pesticides.
Sources of Agricultural Pesticides
Pesticides became common after the second World War as part of the war effort was scientific research into a way to end hunger, i.e. pesticides and the increasing productivity and availability of food production with their help. Currently an estimated 3.2 million tons of pesticides are used each year.
Pesticides are wasted in environments where the farmer has little knowledge or care for the detrimental effects of the pesticides. Without regulations and enforcements these pesticides can easily be spread farther than their intended area. This is especially common in developing countries. With misuse the pesticides can easily be picked up by the rainwater and washed into the streams as runoff.
Cross-Over Transport of Agricultural Pesticides
Pesticides can be transported to humans or other organisms in a variety of ways. It is near to impossible for the pesticide to only affect its targeted crop.
-Wind is one transportation method. The wind picks up the pesticides and can blow them onto other farms or into rivers.
-It can be absorbed into the soil and then taken up by other organisms or can contaminate the surface and groundwater that run over/through it.
– Pesticides are then absorbed by the plants which is detrimental to the growth of the plants.
– That which is not absorbed usually remains on the surface and flows into streams as surface runoff. It is dissolved into the water and then can be taken in by plants and animals. The streams would then be considered a reservoir of pesticides with a relatively high abundance level.
Pesticides frequently enter the world’s surface and groundwater through either point source (direct locations where excess pesticides spill, or non-point sources, where the pesticides enter the streams through wind flow, precipitation, runoff, and leaching. These pesticides can accumulate in a surface water source such as a lake, stream, or pond, they can also leach down and become integrated into the groundwater reserves such as reservoirs.
Pesticides enter the food chain through the direct application of the substance to the plants themselves by humans. Once they are absorbed by the plants or animals which eat the plants they become residue. There are maximum residue levels for crops and animals. They can also be taken in when an organism takes in the water which contains the runoff and dissolved pesticides. This can be further extended to the human who eats the fish. An easier way for humans to ingest pesticides is directly through contaminated drinking water from those polluted streams.
Pesticides and Animal Feed
Approximately 80% of the corn and 22% of the wheat produced in the US every year is used for animal feed, while 30 million tons of US-produced soy meal is consumed annually as livestock feed. FThis grain is grown by intensive industrial farming operations that use large amounts of pesticides and other inputs, and often rely on genetically engineered crop varieties. Common genetic modifications include plants that are bred to contain insecticides within their genetic makeup (e.g. corn) or to withstand direct application of herbicides (e.g.,glyphosate resistant soybeans).
In addition to causing environmental damage, when grain is grown with pesticides and then fed to livestock, pesticide residues can accumulate in the animals’ fatty tissue and milk. Pesticides, such as arsenic compounds, are also included in livestock feed to control intestinal parasites and other pests.