Name: ______Date: ______Period:_____
Unit 2: Earth’s Land Resources
Section 3: Agriculture
Essential Questions: How do we use bio-engineering and technology in agriculture? What are some methods used to maintain agricultural sustainability?
In our last section, we learned that agriculture began about 10,000 years ago in the area called the Fertile Crescent. Before that, humans were nomadic, hunting and gathering their food. Warming temperatures eventually allowed humans to settle down to plant seeds and raise livestock.
I. History of Agriculture
A. Development of Agriculture
Everything you eat and all the natural fabrics you wear are products of agriculture. If you don’t run a farm, then you rely on people who do. During most of the human species’ 200,000-year existence, we have been hunter-gatherers. However, about 10,000 years ago when the climate began to warm, we begin to see evidence of agriculture in Middle Eastern Asia and the area now known as China. Agriculture is the science of farming, including cultivation of the soil for the growing of crops and the rearing of animals to provide food and other products.
Agriculture probably began when hunter-gatherers brought wild fruits, grains, and nuts back to their camps. Some of these foods fell to the ground, were thrown away, or were eaten but had seeds that passed through someone’s digestive system. When a plant grew from these seeds, humans began to realize that they could guide this process and grow their own food using the seeds they selected from wild ones.
B. Selective Breeding and Settlement
Our ancestors then began planting seeds only from those plants whose fruit they liked the most. These were the beginnings of artificial selection, or selective breeding. Selective breeding is when one chooses to grow plants or breed animals from the healthiest and most productive of their stock. Selective breeding has resulted in all the food crops and livestock that feed you everyday.
Once our ancestors learned to cultivate crops, they began to build more permanent settlements, often near water sources. The need to harvest more crops kept them settled, and once they were settled, it made sense to plat more crops. They also began to raise animals as livestock. As populations in the settlements increased, so did the need to continue and expand agriculture. Eventually, the ability to grow excess food enabled some people to live away from the farm, leading to the development of professional specialties, commerce, technology, cities, social classes, and political organization (governments). Agriculture brought us the civilization we know today.
C. Traditional Agriculture
Until the Industrial Revolution of the 1800’s, the work of cultivating, harvesting, storing, and distributing crops everywhere was performed by humans and animal muscle power, along with hand tools and non-motorized machines such as plows. This biologically powered agriculture is known as traditional agriculture. This type of agriculture does not require fossil fuels.
II. Industrial Agriculture
The Industrial Revolution introduced large-scale mechanization and fossil-fuel engines to agriculture just as it did to industry. Farmers could replace their horses and oxen with faster, more powerful, and more efficient means of harvesting, processing, and transporting crops.
The mid-1900’s saw another expansion of farming technology encouraged by the devastation of the Dust Bowl and wartime needs. There were irrigation improvements and the introduction of synthetic fertilizers. There was also the introduction of chemical pesticides, which reduced competition from weeds and the loss of crops to pests. Since the soil was more productive, and fewer crops were lost to pests, yield increased. Yield is the amount of a crop produced in a given area.
A. The Rise of Industrial Agriculture
Industrial agriculture produces huge amounts of crops and livestock. It is also known as high-input agriculture, since it relies on people to “put in” enormous quantities of energy, water, and chemicals. Today, industrial agriculture is practiced on more than 25% of the world’s croplands and on most of the croplands in the United States.
Because it uses large machinery and chemicals that are customized for a specific crop, to be the most efficient, industrial agriculture requires large areas be planted with a single crop, or monoculture. The planting of crops in monocultures makes planting and harvesting more efficient and can thereby increases harvests. However, monocultures have drawbacks as well. Large monocultures reduce biodiversity over large areas, because far fewer wild organisms are able to live in monocultures than in their native habitats or in more diverse plantings. Moreover, since all the plants in a monoculture are genetically similar, they are vulnerable to the same diseases and pests. For this reason, monocultures carry the risk of catastrophic crop failure.
B. The Green Revolution
In the mid to late 1900’s, the desire for more and better food for the world’s growing population led to the green revolution, in which agricultural scientists from developed nations introduced new technology, crop varieties, and farming practices to the developing world.
1. Technology – The technology sharing began in the 1940’s, when U.S. scientist Norman Borlaug introduced Mexico’s farmers to a specially bred strain of wheat. It produced large seed heads, was short enough to avoid wind damage, resisted diseases, and produced high yields. Within two decades Mexico had tripled its wheat production – in fact, it had surplus wheat it could export. Soon many developing nations were increasing their crop yields using selectively bred wheat, rice, corn, and other crops from developed nations.
Along with new strains of crops, developing nations also imported new methods of industrial agriculture from developed nations including heavy machinery. Intensive agriculture of this sort saved millions in India and Pakistan from starvation in the 1970s and eventually turned these nations into net exporters of grain.
2. Environmental Effects – The green revolution has saved millions of lives, its technology comes at a high energy cost, however. Between 1900 and 2008, the energy used by agriculture increased by 7000%! On the positive side, the higher productivity of already-cultivated land preserved some ecosystems since less additional land needed to be cleared for crops. For example, between 1961 and 2008, food production rose by 150% and population 100%, while converted for agriculture increased only 10%. So the green revolution has prevented some deforestation and habitat loss and preserved the biodiversity of some ecosystems.
On the negative side, the intensive application of water, inorganic fertilizers, and pesticides has worsened erosion, salinization, desertification, eutrophication, and pollution. In addition, the use of fossil fuels to produce fertilizer and pesticides or to run farm equipment has increased air pollution and contributed to global warming.
So the green revolution has saved human lives, but there have been environmental costs. The need to maintain this life-saving productivity while limiting environmental damage has led to attempts at more-sustainable agriculture.
III. Pests
We call an organism a pest when it damages plants that are valuable to us, such as crops. We call a plant a weed when it competes with our plants. As you see, these are subjective terms based on our economic interests. Since the beginning of agriculture, the pests that eat our crops and the weeds that compete with them have taken advantage of the way we cluster plants in agricultural fields. In a monoculture, a population of a pest adapted to the plant can chew through entire fields. From the viewpoint of a pest adapted to feed on corn, for example, a cornfield is an all-you-eat buffet!
A. Chemical Pesticides
To prevent crop losses from pests and weeds, people have developed thousands of chemical pesticides. About 400 million kilograms of active ingredients from pesticides are applied each year in the United States alone. Usage in developed nations has leveled off, but continues to grow in developing nations.
The ability of a pesticide to reduce a pest population often declines over time as the population evolves resistance to it. Recall that natural selection occurs within populations when individuals vary in their traits. Because populations of insects and microorganisms in farm fields are huge, it is likely that some individuals have genes that give them immunity to a given pesticide. So even if a pesticide application kills 99.9% of the insects in a field, 1 in 10,000 survives. As those surviving individuals mate, they pass on the resistant genes to the next generation. Eventually, the percentage of pests affected by the pesticide begins to decrease until the pesticide becomes completely ineffective. As a result, industrial chemists are caught up in an “evolutionary arms race” with the pests they battle, racing to increase the toxicity of pesticides while the pests continue to evolve resistance.
B. Biological Pest Control
Because of pesticide resistance and health risks from some pesticides, agricultural scientists increasingly battle pests and weeds with organisms that eat or infect them. This strategy is called biological pest control. For example, parasitoid wasps are natural enemies of many caterpillars. These wasps lay eggs on a caterpillar, eventually killing it. Some successful biological pest control efforts have led to steep reductions in pesticide use.
There are serious risks to consider with biological pest control. In some cases, it requires the introduction of an organism from another ecosystem. Unfortunately, this means that no one can know for certain in advance what affects the biological pest control organism might have. In some cases, these introduced organisms have become invasive and harmed non-target organisms - organisms other than the pests. If a non-target organism is harmed, the damage may be permanent because halting biological pest control is far more difficult than stopping the application of a pesticide. Because of such concerns, researchers study biological pest control proposals carefully before putting them into action and government regulators must approve those proposals.
C. Integrated Pest Management
Since both pesticides and biological pest control both have their drawbacks, agricultural scientists and farmers have developed more complex strategies that combine the most-useful aspects of each. In integrated pest management (IPM), different techniques are combined to achieve the most effective long-term pest reduction. IPM may include biological pest control, close monitoring of populations, habitat alteration, crop rotation, reduced soil tillage, mechanical pest removal, and chemical pesticides.
IV. Pollinators
Pests are such a major problem in agriculture that it is easy to fall into a habit of thinking of all insects as destructive. But in fact, most insects are harmless to agriculture and are essential to the reproduction of many crops.
A. Pollination
Pollination is the process by which male sex cells of a plant (pollen) fertilize female sex cells of a plant. Without pollination, plants cannot reproduce sexually. Plants such as conifer trees and grasses are pollinated by pollen carried on the wind that by chance lands on the female parts of their species. Plants with showy flowers, however, are typically pollinated by animals, such as insects, hummingbirds, and bats. These animals are called pollinators.
Pollinators are among the most vital, yet least appreciated, factors in agriculture. When pollinators feed on flower nectar, they collect pollen on their bodies and take it to the next flower, which might then be fertilized. Corn and wheat are wind-pollinated, but there are about 800 other species of cultivated plants that rely on bees or other animals for pollination, such as most fruit species.
B. Declining Pollinators
Unfortunately, pollinator populations have been declining since the use of pesticides became popular. Preserving the biodiversity of native pollinators is especially important because our most common domesticated pollinator, the honeybee, is declining sharply. North American farmers regularly hire beekeepers to bring whole colonies of this introduced bee into their fields when it is time to pollinate crops. Honeybees pollinate more than 100 crops, which together make up 1/3 of the U.S. diet. Scientists are racing to discover why, starting in 2006, entire hives began dying off for an unknown reason. Farmers and scientists call this complete loss of a hive “colony collapse disorder.”
C. Pollinator Conservation
Farmers and homeowners can help maintain populations of insect pollinators, such as bees, by reducing or eliminating pesticide use. Otherwise, they risk killing the “good” bugs along with the “bad” bugs. Pest control measures that target specific pests, such as pheromone traps, are pollinator-safe alternatives to pesticides.
Section 3 Review Questions
1. What happened to the climate of the Earth that allowed humans to begin farming?
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2. “The first people to begin farming probably did so by accident.” Describe what is meant by this statement. ______
3. What agricultural practice results in healthier and more productive crops with each generation? ______
4. Describe the major differences between traditional agriculture and industrial agriculture. ______
5. What two events encouraged the expansion of agricultural technology during the mid 1900’s? ______
6. Why is industrial agriculture considered to be “high-input”?
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7. What is one advantage of growing a monoculture crop?
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8. What is one disadvantage of growing a monoculture crop?
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9. Which 3 countries mentioned in the notes were saved from mass starvation because of industrial agriculture techniques from developed nations?
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10. Describe one positive environmental effect that came from industrialized agriculture. ______
11. Describe one negative environmental effect that came from industrialized agriculture.
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12. Explain how a species could be considered a pest to one farmer, but just another bug to another farmer. ______
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13. Explain why a certain pesticide loses effectiveness over time.
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14. What is the biggest problem to consider when planning to introduce a new biological pest control species into a new environment? ______
15. True or False: All insects are harmful to crops. ______
16. Name 3 different types/species of pollinator.
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17. Which type of crop typically relies on pollinators and not the wind to reproduce?
a. conifers b. corn c. grasses d. fruits
18. What is the name we give to a colony of bees that has died suddenly and without a specific cause? ______
19. What two things can gardeners do (or not do) to help maintain pollinator populations? ______
Section 3 Vocabulary