Environmental Science Chapter 7

We have accomplished this goal by utilizing more fossil fuels, water for irrigation, fertilizers, pesticides, land, and productive crop varieties.

low-income Americans. most likely to purchase cheap foods that are high in calories but low in nutrients, leading to overnutrition and obesity.

seed banks. We store as many types of seeds as possible in seed banks in order to assure that we will have diversity of food in the future.

Varieties contain genes that, through conventional breeding, might confer resistance to disease. "Seed banks" have increased worldwide to provide a gene-reserve hedge against the possibility of major crop plants being decimated due to the evolution of a new pest or environmental change.

The Green Revolution has led to a decrease in the diversity of our crops. Recall that our food supply is now largely dependent on 15 crop species and 8 livestock species.

a 100-acre field, all of which is planted with the same variety of corn

Green Revolution. technological advances including pesticides and bioengineering of food helped to increase food production to keep up with a growing population.

monocultures. contain all the same crop over large expanses. When the diversity of crops decreases, crops tend to be less protected against blights and pests.

The dark, crumbly material that is formed from decomposition of organic material is called "humus."

The O or organic horizon contains the remains of stems and leaves that are broken down by microarthropods, bacteria, and fungi to release minerals and make humus.

The A horizon is also known as the topsoil. Along with the O horizon, this is the horizon that is lost during erosion.

This is a false statement regarding the soil of the rainforest. If the forest were not suitable for forest growth, then there would be no tropical rainforests.

Over time, when soil is not dealt with sustainably it can lose its productivity and decline in quality.

Vegetation protects the soil from direct impacts by rainfall, and the roots hold the soil in place.

The removal of native prairie plants. The plants would have held the soil in place. Strong winds blew the topsoil away, blackening rain and snow as far away as New York City.

Overgrazing, along with overcultivation, deforestation, and erosion, can result in the loss of productivity in dry areas.

crop rotation. By alternating between normal crops and those that are able to fix nitrogen (the legumes), crop rotation can help to replenish soil nutrients.

contour farming. prevents the formation of gullies, slows runoff, and helps capture soil.

Many of the erosion control measures discussed in the chapter are designed to prevent the problems caused by planting large areas in a single crop.

The CRP pays farmers not to grow crops on land that is not well suited for crop production. Rather than have people farm on land that will erode, the CRP pays farmers to let the land return to grassland or other semi-natural state that protects and build the soil and serves as habitat for wildlife.

salinization. In dry areas, crops that are frequently irrigated tend to have water evaporate from the surface quickly, either leaving salts behind or drawing salts up from lower soil horizons.

pests can evolve defenses against pesticides. Organisms that can reproduce quickly will be screened down to a few that are genetically equipped to resist the chemical used against them. These remaining few will then reproduce in large numbers. The same process applies to bacterial resistance against antibiotics.

Greenbelts can provide predator insects, spiders, and birds to control certain pests; crop rotation prevents the buildup of one specific pest; no-till farming conserves soil; and certain chemicals with a short environmental half-life can be used as well.

Weevils were introduced into Lake Victoria to help eradicate the invasive water hyacinth. These weevils are a biological control agent.

biocontrol. This method uses living organisms that attack pests to control them. Integrated pest management may involve biocontrol along with other methods (such as frugal use of pesticides) to control pests.

Soybeans contain high levels of protein and are used to feed both humans and animals bred for human consumption. They can be genetically modified with more than one desirable trait, and over 90% of the soybean crop grown in the United States is genetically modified.

precautionary principle. generally states that we should take no action until we understand the consequences of doing it. The U.S. government ignored the possible effects of GM crops to seize the "commercial moment" and allowed GMOs to be widely grown.

U.S. citizens have largely accepted the GM crops on the market. There seems to be little concern about GM foods in the United States. People in the United States do not realize that so much of their food has been genetically modified.

genetically modifying plants. Recombinant DNA technology involves patching together DNA from multiple organisms to produce a crop with certain desirable traits.

a vegetarian diet. As you eat food from organisms at higher tropic levels, lesser percentages of solar energy are put to use; therefore, eating from the lowest trophic levels (directly from plants) will make the most use of the sun's energy.

feedlots. huge warehouses or pens designed to deliver energy-rich food to animals living at extremely high densities. Nearly half of the world's pork and most of its poultry come from feedlots.

incredibly energy-efficient compared to harvesting fish from open waters. Aquaculture can produce up to 1000 times more fish per unit of area than the open ocean!

Consumers pay farmers ahead of time for a weekly delivery of in-season produce. n a CSA program, farmers get a guaranteed income up front that they can use to invest in their crops.

synthetic fertilizers, insecticides, or herbicides. This is how organic farming differs from industrial farming.