Fertilizers and pesticides both have definite pros and cons associated with their use. Both types of chemical tend to increase yields, and thus make a significant difference in food production, particularly in countries that struggle periodically with famines. On the other hand, they both can cause water pollution when erosion carries the chemicals off of farms along with eroded soils after each rainfall. There is also concern by some authorities that pesticides pose a risk, not only to nontarget animal and plant species, but to humans as well.
Positive Effects of Fertilizers
There is no doubt that fertilizers increase yields of crops around the world. Use of modern fertilizers exploded after World War II. New, ammonia-based fertilizers also fed the process of specialization that was occurring in agriculture. Farmers rotated crops less, which led more quickly to soil exhaustion. Norman Borlaug, the father of the 1960s Green Revolution, which vastly expanded food production and helped stave off world hunger, has argued that modern farming, including the use of fertilizers and herbicides, could “double or triple food production” in Africa. Increased yields also reduce the need for conversion of wild lands to agriculture, contributing to the conservation of biodiversity.
Negative Effects of Pesticides
The downside of fertilizers is that some portion inevitably washes into waterways along with eroded sediments. This nonpoint source runoff occurs nationwide, and the nitrogen fertilizer finds its way into rivers, lakes and the ocean where it causes eutrophication and "dead zones" that kill aquatic life. Eutrophication is a process whereby nitrogen feeds an algal bloom, but when the short-lived algae die, decomposing bacteria then consume most of the available oxygen, suffocating aquatic life. Additionally, use of artificial fertilizers in place of animal or “green” manure--cover crops plowed into the soil--eventually can deplete soils of organic matter, making them lose their ability to hold water and more subject to erosion.
Positive Effects of Pesticides
According to the National Institute of Environmental Health Sciences, the term pesticide includes chemicals used to control insects, fungi and weeds. Pesticides serve many functions, some of which are more essential to society than others. Pesticides can prevent crop failure, control invasive plants, or promote a uniformly green lawn. Some pesticides reduce blemishes on fruit and vegetables, ensuring that a greater proportion of the crop is marketable.
Negative Effects of Pesticides
According to the National Institute of Environmental Health Sciences, pesticides have as yet incompletely understood effects on humans. Most people are exposed to a certain level of pesticides. Farmers who experience routine exposure to pesticides have exhibited neurological symptoms such as headache and hand tremors. Children, in particular, may be more susceptible to negative effects resulting from pesticide exposure. Pesticide runoff can have devastating effects on nontarget organisms as well. For example, roundup, an extremely common herbicide used in agriculture, is highly toxic to fish and amphibians. The National Coalition for Pesticide-Free Lawns says, "Of 30 commonly used lawn pesticides, 19 are linked with cancer or carcinogencity, 13 are linked with birth defects, 21 with reproductive effects, 26 with liver or kidney damage, 15 with neurotoxicity, and 11 with disruption of the endocrine system."