Environmental Engineering Reference
In-Depth Information
• Many pesticides are toxic, especially in large amounts, and can harm humans and wildlife (see Chapter
6).
• Runoff from sites where pesticides are used contaminates water sources.
• Pesticides are expensive to use.
• Many pesticides are nonspecific and kill more than just the targeted organisms.
• Organism loss can alter entire ecosystems.
Pests evolve and develop genetic resistance to pesticides over time. When a pesticide is applied, most of the
targeted organisms die, but some survive. The ones that survive then reproduce, passing on the genes that al-
lowed them to survive. Over several generations, a population develops increasing resistance to the pesticide,
forcing the use of more powerful pesticides to target these organisms. This creates a perpetual cycle of organ-
isms developing resistance to pesticides and humans increasing our use of different and more powerful chemic-
als to control the pests.
Some pesticides have proven extremely harmful to the environment and to humans. For example, DDT (di-
chlorodiphenyltrichloroethane) was used as a pesticide in the United States until 1973, when it was banned due
to its detrimental effects on the nervous systems of humans and wildlife. Some countries still use it, though, to
control mosquitos and prevent the transmission of malaria.
Increasingly, farmers are exploring alternatives to synthetic pesticides, including oils from trees and plants,
such as mint, clove, and rosemary. Also, farmers are using certain pesticides in a more targeted way for specif-
ic pests, resulting in less overall ecosystem destruction.
Integrated Pest Management
Another way to address the issue of pest control involves using more than one technique in a process known as
integrated pest management.
This process uses knowledge about the pest's life cycle and environmental in-
teractions, with other control methods such as biological control, crop rotation, and chemicals when necessary.
The goal of IPM is to reduce pest impact while also reducing pesticide use.
Livestock and Feedlots
Raising livestock is widely considered to be another essential part of feeding the human population.
Livestock
includes cows, chickens, pigs, goats, sheep, and other domesticated animals raised for profit. Commonly, an-
imals such as cows are kept on large expanses of land to graze for a period of time until they are sold to feed-
lots.
Feedlots,
also called factory farms or concentrated animal feeding operations, are areas where livestock
are fed foods high in energy to fatten them up before market. Feedlots require less land per cow and are a more
efficient way of meeting the meat consumption needs of a large population. Also, the manure produced by
feedlot animals is frequently used as fertilizer for farms.
Negative aspects of feedlots include potential contamination of water sources from runoff containing waste
products and the increased potential for the spread of disease among animals in close contact, which necessit-
ates use of antibiotics. This industry is monitored by states and federally by the Environmental Protection
Agency, to help minimize the environmental impact.
The "Rangelands" section of this chapter discusses the environmental impacts of livestock agriculture on ran-
gelands.
