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Agriculture LESSON 3 Guiding Question: How has evolved?

• Discuss the beginnings of agriculture. Reading Strategy As you read, fill in a main idea and • Explain the importance of industrial agriculture and details chart. List the main ideas of the lesson in the left col- the . umn. In the right column, note important details about each • Identify different types of control. main idea. • Explain the importance of pollinators to agriculture. Vocabulary traditional agriculture, yield, industrial agriculture, green revolution, biological , integrated pest management (IPM), pollinator

Can you imagine having to hunt and gather your own food every day? Can you imagine life without cotton? That was life 15,000 years ago. Agriculture arose only about 10,000 years ago. Many aspects of human 12.3 LESSON PLAN PREVIEW civilization began about the same time. That is probably not a coinci- Inquiry Students investigate dence. Walking around all day hunting and gathering didn’t leave much agricultural advances through- time for creating art or new technology! out history. Real World Students find ex- amples of chemical use Development of Agriculture in their environment. Agriculture began about 10,000 years ago, when a warmer Differentiated Instruction climate enabled humans to plant seeds and raise . English language learners study word parts to understand the Everything you eat and all the natural fabrics you wear are products of terms pollination and pollinators. agriculture. If you don’t run a , you rely on people who do. But agri- 12.3 RESOURCES culture is a relatively new development in human history. In Your Neighborhood Activity, Local During most of the human species’ 200,000-year existence, we have Planting Conditions • Map It Online • been hunter-gatherers, depending on wild plants and animals for our Lesson 12.3 Worksheets • Lesson 12.3 food and fiber. Then about 10,000 years ago, the climate warmed follow- Assessment • Chapter 12 Overview ing an ice age. In the warmer climate, plants grew better. People in the Presentation Middle East, , and other areas began to grow plants from seed and to raise animals. Figure 12 Early Farming Tools The blades in this photo were used to Agriculture probably began when hunter-gatherers harvest crops about 5000 years ago. 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. The plants that grew from these seeds likely produced fruits larger and tastier than most, because they came from seeds of fruits that people had selected. As these plants bred with others nearby that shared those characteristics, they produced new generations of plants with large and tasty fruits. You can see more details of the evolution of agriculture in Figure 13 on the next page.

Soil and Agriculture 365 Eastern wheat rice United Fertile States Crescent China Sahel

sunower New Guinea Mesoamerica sorghum West Ethiopia Africa bananas Amazonia co ee corn squash Andes

potato Origins of agriculture Independent origin Possible independent origin

Data from syntheses in Diamond, J. 1997. Guns, germs, and steel. : W.W. Norton; and Goudie, A. 2000. The human impact, 5th ed. Cambridge, MA: MIT Press.

Figure 13 Beginnings of Agriculture Agriculture agriculture independently are colored green. In areas colored originated independently in multiple locations as different blue, it is not known whether people invented agriculture cultures selectively bred plants and animals from wild independently or adopted it from other cultures. The map also species. Areas where people are thought to have invented shows a few of the crops farmed in each region.

Selective Breeding and Settlement Eventually, people realized they could control what they grew. Our ancestors then began planting Map it seeds only from those plants whose fruit they liked the most. These were Origins of Agriculture the beginnings of artificial selection, orselective breeding. Selective breed- The earliest widely accepted ing has resulted in all the food crops and livestock that feed you every day. evidence of agriculture is from Once our ancestors learned to cultivate crops, they began to build the Fertile Crescent region of the more permanent settlements, often near water sources. The need to Middle East. Refer to Figure 13 harvest their crops kept them settled, and once they were settled, it made as you answer the questions that sense to plant more crops. They also began to raise animals as livestock. follow. Increased populations resulted from settlement and more-reliable food 1. Interpret Maps According to supply and reinforced the need for both. Eventually, the ability to grow the map, in what four areas did excess food enabled some people to live away from the farm, leading to agriculture most likely arise the development of professional specialties, commerce, technology, cities, independently? social classes, and political organization. Agriculture ultimately brought us the civilization we know today. 2. Interpret Maps In which part of the world were coffee crops Traditional Agriculture Until the Industrial Revolution of the first planted? 1800s, the work of cultivating, harvesting, storing, and distributing crops 3. Infer Two large rivers, the everywhere was performed by human and animal muscle power, along Tigris and Euphrates, run with hand tools and non-motorized machines such as plows. This biologi- through the Fertile Crescent. cally powered agriculture is known as traditional agriculture. Traditional How did those rivers help make agriculture may use teams of worker animals and use and it a good place for agriculture? organic fertilizer, but it does not require fossil fuels.

366 Lesson 3 Industrial Agriculture Industrial agriculture and the green revolution have saved mil- lions of people from starvation.

The Industrial Revolution introduced large-scale mechanization and fossil-fuel engines to agriculture just as it did to industry. could replace their horses and oxen with faster, more powerful, and more effi- cient means of harvesting, processing, and transporting crops. In addition to the efficient farm machinery that resulted from the Industrial Revolution, other changes to agriculture came in the mid- 1900s. Many of these were reactions to the Dust Bowl of the 1930s and/or based on wartime technology. There were irrigation improvements and the introduction of synthetic fertilizers. There was also the introduc- tion of chemical , which reduced from and the loss of crops to pests. Because 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.

The Rise of Industrial Agriculture Mechanized farming technol- ogy, the fossil fuels it runs on, manufactured chemicals, and irrigation all allow for industrial agriculture. Industrial agriculture produces huge amounts of crops and livestock. It is also known as high-input agriculture because it relies on people to “put in” enormous quantities of energy, water, and chemicals. Today, industrial agriculture is practiced on more than 25 percent of the world’s croplands and on most of the croplands in the . Because it uses large machinery and chemicals that are customized for a specific crop, to be most efficient, industrial agriculture requires that large areas be planted with a single crop, in a . You can see a ANSWERS monoculture in Figure 14. The planting of crops in makes Map It planting and harvesting more efficient and can thereby increase harvests. 1. Mesoamerica, the Andes, the Fer- However, monocultures have drawbacks as well. Large monocultures tile Crescent, China reduce over large areas, because far fewer wild organisms 2. Ethiopia are able to live in monocultures than in their native or in more- 3. They supply water. diverse plantings. Moreover, because all the plants in a monoculture are Reading Checkpoint Sample genetically similar, they are vulnerable to the same diseases and pests. For answer: Advantage: efficiency; this reason, monocultures carry the risk of catastrophic crop failure. disadvantage: possible catastrophic crop failure because all the plants are Reading Describe one advantage and one disadvantage of a vulnerable to the same diseases and Checkpoint monoculture. pests

Figure 14 Monoculture Most crop production in developed nations comes from monocultures such as this cornfield in Texas. Planting crops in large, uniform fields greatly improves the efficiency of planting and harvesting. Unfortunately, it also decreases biodiversity and makes crops susceptible to pests that have adapted to feed on that crop. The Green Revolution In the mid- to late 1900s, 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. (Green in this context implies “covered with plants” rather than “environmen- tally friendly.”) ▶ Technology The technology sharing began in the 1940s, when U.S. scientist Norman Borlaug introduced Mexico’s farmers to a specially bred strain of wheat (Figure 15). 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 increas- ing their crop yields using selectively bred strains of 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. Developing nations began applying large amounts of synthetic fertilizers and chemical pesticides on their fields, liber- ally irrigating crops, and using heavy equipment powered by fos- Figure 15 The Green Revolution sil fuels. Intensive agriculture of this sort saved millions in India Norman Borlaug, the “Father of the Green Revolution,” holds the wheat and Pakistan from starvation in the 1970s and eventually turned variety he bred that launched the these nations into net exporters of grain. green revolution. The high-yielding, disease-resistant wheat saved many ▶ Environmental Effects The green revolution has saved people in developing nations from millions of lives. Its technology comes at a high energy cost, starvation. however. Between 1900 and 2008, the energy used by agricul- BIG QUESTION ture increased by 7000 percent! On the positive side, the higher productivity of already-cultivated land preserved some ecosys- How can we balance our growing demand for food with our need to tems, because less additional land needed to be cleared for crops. protect the environment? Between 1961 and 2008, food production rose 150 percent and Perspective Have students work population rose 100 percent, while area converted for agriculture in pairs. Have each pair write one increased only 10 percent. So the green revolution has prevented paragraph that evaluates how the some deforestation and loss and preserved the biodiver- green revolution affected our ability sity of some ecosystems. to meet the growing need for food. Then, have students write a second On the negative side, the intensive application of water, inor- paragraph that evaluates how the ganic fertilizers, and pesticides has worsened erosion, saliniza- green revolution affected human- tion, desertification, eutrophication, and pollution. In addition, ity’s impact on land and soil. Have the use of fossil fuels to produce fertilizer and pesticides and to students share their completed paragraphs with the class. 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 ANSWERS maintain this life-saving productivity while limiting environ- Reading Checkpoint Sample mental damage has led to attempts at more-sustainable agricul- answer: The green revolution ture. You will read more about these in the next lesson. introduced new technologies, crop varieties, and farming practices to Reading Describe the green revolution in your own words. Checkpoint developing nations.

368 Lesson 3 Pests Chemical pesticides, biological pest control, and integrated pest management can all effectively protect crops from pests.

What are pests? What are weeds? We call an organism a pest when it dam- ages plants that are valuable to us, such as crops. We call a plant a when it competes with our plants. As you see, these are subjective terms based on our economic interests. Since the beginnings of agriculture, the pests that eat our crops and the weeds that compete with them have taken advantage of the ways we cluster plants in agricultural fields. In a mon- oculture, a population of a pest adapted to that 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-can-eat buffet.

Chemical Pesticides To prevent crop losses from pests and weeds, people have developed thousands of chemical pesticides. Roughly 400 million kilograms (900 million pounds) of active ingredients from conventional pesticides are applied in the United States each year. Three quarters of this amount is applied on agricultural land. Since 1960, pes- ticide use has risen fourfold worldwide. Usage in developed nations has leveled off in the past two decades, but it continues to rise in the develop- ing world. 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 the populations of and in farm fields are huge, it is likely that some individuals have that give them immunity to a given pesticide. So even if a kills 99.99 percent Figure 16 Biological Pest Control of the insects in a field, 1 in 10,000 survives. If an survives because Tomato hornworms are large cater­ it is genetically resistant to a pesticide and it passes the resistance trait to pillars that can destroy a tomato crop its offspring, the trait will become more common in the population. As a very quickly. Here you can see the small white of a on a larger and larger proportion of the insects in the population become resis- hornworm. When the eggs hatch, the tant to the pesticide, the chemical becomes less and less effective on that larvae will feed on the till it population. As a result, industrial chemists are caught up in an “evolution- dies—possibly saving a tomato plant! ary arms race” with the pests they battle, racing to increase the toxicity of pesticides while the pests continue to develop resistance.

Biological Pest Control Because of and health risks from some pesticides, agricultural scientists increasingly battle pests and weeds with organisms that eat or infect them. This strategy is calledbiological pest control. For example, parasitoid are natural enemies of many . These wasps lay eggs on a caterpillar. The larvae that hatch from the eggs feed on the caterpillar, eventually killing it (Figure 16). Some successful biological pest control efforts have led to steep reductions in pesticide use.

Soil and Agriculture 369 Find Out More

▶ Bt A widespread modern biological pest control effort is the use of Find Out thuringiensis (Bt). Bt is a naturally occurring soil bacterium that More produces a that kills many caterpillars and the larvae of some and . Farmers have used the natural pesticidal activity of this bac- Contact your local division of the terium to their advantage by spraying spores of it on their crops. When USDA and ask if an introduced used correctly, Bt can protect crops from pest-related losses. predator or parasite has ever been used to control a pest in your area. If ▶ Introduced Predators and Parasites In some cases, biological pest so, what was the result? If not, ask if control requires the introduction of an organism from a different eco- they would ever consider doing so. system. Unfortunately, this means that no one can know for certain in advance what effects the biological pest control organism might have. In some cases, biological pest control organisms have become invasive and ANSWERS harmed nontarget organisms—organisms other than the pests. Find Out More Answers will vary. ▶ Benefits and Costs If biological pest control works as planned, it can Students’ responses should indicate that they have contacted the local be a permanent solution that requires no maintenance and is environ- division of the USDA to learn about mentally harmless. However, like all invasive species, invasive biological introduced predators or parasites. pest control organisms can have wide-ranging ecological and economic Reading Checkpoint No one impacts, as did the in Figure 17. And if nontarget organisms knows what effects the predator are harmed, the damage may be permanent because halting biological or parasite will have on nontarget pest control is far more difficult than stopping the application of a pesti- organisms because they have never lived in the same ecosystem before. cide. Because of such concerns, researchers study biological pest control proposals carefully before putting them into action, and government regulators must approve those proposals. But there is never a surefire way of knowing in advance whether a biological pest control program will work as planned. Reading What is one risk of introducing a predator or parasite from a Checkpoint different ecosystem?

Figure 17 Risks of Biological Pest Control Cactus moth larvae eat the pads of prickly pear cactus. The story of the cactus moth is one of both great success and environmental destruction. The cactus moth was imported from Argentina to in the 1920s to control prickly pear cactus that was invading rangeland. Within just a few years, millions of hectares of rangeland were free of the cactus. Following the cactus moth’s success in Australia, it was introduced in other nations. Unfortunately, cactus introduced to Caribbean islands spread to and ate many rare native cacti there. If these moths spread to Mexico and the southwestern United States, they could destroy the many native and economically important species of prickly pear there. Biologist Colothdian Tate (inset) has worked to prevent this ecological disaster.

370 Lesson 3 Integrated Pest Management Because both chemical and biologi- cal pest control approaches 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), dif- ferent techniques are combined to achieve the most effective long-term pest reduction. IPM may include biological pest control, close monitor- ing of populations, habitat alteration, , reduced soil tillage, mechanical pest removal, and chemical pesticides. In recent decades, IPM has become popular in many parts of the world. Indonesia is an important example. Indonesia’s government had financially supported chemical pesticide use for years, but its scientists came to understand that the pesticides were actually making the pest problems worse. Pesticides were killing the natural predators of the brown plant-hopper, an insect that devastated rice fields as its population exploded. Concluding that supporting pesticide use was costing money, causing pollution, and decreasing yields, in 1986, the Indonesian govern- ment acted. It banned imports of 57 pesticides, slashed financial support for pesticide use, and encouraged IPM. Within four years, Indonesia’s pesticide production fell to less than half its 1986 level, pesticide imports fell to one third, and financial support for them was phased out, saving $179 million annually. After these actions, rice yields rose 13 percent. Pollinators Insects and other animals are essential to the reproduction of Figure 18 Pollinators Many many crops. agricultural crops depend on insects to pollinate them. Our food supply, therefore, depends partly on Pests are such a major problem in agriculture that it is easy to fall into a conservation of these vital animals. habit of thinking of all insects as destructive. But in fact, most insects are such as these apple blossoms harmless to agriculture, and some are essential. have shapes and sweet scents that advertise to pollinators such as Pollination Pollination is the process by which male sex cells honeybees. of a plant () fertilize female sex cells of a plant. Without pollination, plants cannot reproduce sexually. Plants such as conifer trees and grasses are pollinated by pollen grains car- ried on the wind. These plants are fertilized when, by chance, pollen grains land on the female parts of other plants 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 agri- culture. When pollinators feed on nectar, they collect pollen on their bodies and take it to the next flower, which might then be fertilized. Our important grain crops, such as corn and wheat, are wind-pollinated, but many other crops, such as fruits, depend on insects for pollination (Figure 18). The most complete survey to date lists 800 species of cultivated plants that rely on and other insects for pollination.

Soil and Agriculture 371 Declining Pollinators Unfortunately, pollinator populations have declined. One example is the alkali , a native pollina- tor of Utah, Nevada, and other dry areas of western . Alkali bees are a major pollinator of , which is a very important livestock feed and . When pesticide use rose in the mid- 1900s, alkali bee populations plummeted, and alfalfa yields fell, threatening both crop and livestock agriculture. Farmers have changed the way they use pesticides in alkali bee habitat, but alkali bees are now extinct in many of their former breeding areas. Preserving the biodiversity of native pollinators is especially important because our most common domesticated pollinator, the honeybee, is declining Figure 19 Pollinator-Safe Gardening sharply. North American farmers regu- Japanese beetles can destroy rosebushes larly hire beekeepers to bring colonies of this introduced bee to very quickly. The canister (inset) contains a their fields when it is time to pollinate crops. Honeybees pollinate pheromone (chemical signal) that attracts only Japanese beetles, destroying them and more than 100 crops, which together make up one third of the U.S. conserving pollinators while protecting diet. In recent years, two accidentally introduced parasites have rosebushes. swept through honeybee populations, destroying hives. In addi- tion, starting in 2006, entire hives began dying off for an unknown reason. Scientists are racing to discover the reasons for this myste- rious syndrome, which is called , before it threatens our food supply.

Pollinator Conservation Farmers and homeowners can help maintain populations of insect pollinators, such as bees, by reduc- ANSWERS ing or eliminating pesticide use. Otherwise, they risk killing the Lesson 3 Assessment For answers “good” bugs along with the “bad” bugs. Pest control measures that to the Lesson 3 Assessment, see page target specific pests, such as the pheromone trap inFigure 19, are A–18 at the back of the book. pollinator-safe alternatives to pesticides.

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1. Communicate Write a paragraph describing 4. Review How are pollinators important to crop when and how agriculture likely began. End with a agriculture? description of the beginnings of selective breeding. 5. Suppose that you were 2. Infer How have industrial agriculture and the the resource manager for a national wildlife green revolution affected the world’s population? with a pest problem. You have been told that you 3. Compare and Contrast How do (a) chemical can import predators of the pest from Asia to begin pesticides, (b) biological control, and (c) integrated a biological pest control program. What three pest management protect crops from pests? questions would you ask before you began that program?

372 Lesson 3