Understanding Our Environment

Transcription

1 Understanding Our Environment When someone mentions the term environment, some people think of a beautiful scene, such as a stream flowing through a wilderness area or a rain forest canopy alive with blooming flowers and howling monkeys. You might not think of your backyard or neighborhood as part of the environment. In fact, the environment is everything around us. It includes the natural world as well as things produced by humans. But the environment is also more than what you can see it is a complex web of relationships that connects us with the world we live in. What Is Environmental Science? There is a growing need to understand the environment as a whole, including both its biological and physical features. A wide variety of people contribute to this understanding of the environment, including high school students. In the 1990s, students from Keene High School in Figure 1.1 studied dwarf wedge mussels in the Ashuelot River of New Hampshire. The mussels, which were once abundant in the river, were in danger of disappearing, and the students wanted to know why. The students tested water samples from different parts of the river, conducted experiments, and asked questions. The students efforts were highly praised and widely recognized. More importantly, their work contributed to an ongoing community effort that still works toward the preservation of the endangered dwarf wedge mussel. The students work is just one example of a field called environmental science, the study of the environment that includes the physical, biological, and social sciences. Section 1 Objectives Define environmental science, and compare environmental science with ecology. List the five major fields of study that contribute to environmental science. Describe the major environmental effects of huntergatherers, the agricultural revolution, and the Industrial Revolution. Distinguish between renewable and nonrenewable resources. Classify environmental problems into three major categories. Key Terms environmental science ecology agriculture natural resource pollution biodiversity Figure 1.1 Student Scientists These students are counting the dwarf wedge mussels in part of the Ashuelot River. Chapter 1: Science and the Environment 5

2 Figure 1.2 Environmental Scientists Scientists from a variety of fields use different methods to study how humans interact with and impact the environment. Connect to HISTORY Rachel Carson Alarmed by the increasing levels of pesticides and other chemicals in the environment, biologist Rachel Carson published Silent Spring in Carson imagined a spring morning that was silent because the birds and frogs were dead after being poisoned by pesticides. Carson s carefully researched book was enthusiastically received by the public and was read by many other scientists, as well as policy makers and politicians. However, many people in the chemical industry saw Silent Spring as a threat to their pesticide sales and launched a $250,000 campaign to discredit Carson. Carson s research prevailed, although she died in 1964 unaware that the book she had written was instrumental in the birth of the modern environmental movement. Check for Understanding Compare How is ecology related to environmental science? The Goals of Environmental Science Environmental scientists have found that the environment is influenced by people and that people are influenced by the environment. A major goal of many environmental scientists is to understand and solve environmental problems. To address this goal, environmental scientists study two main types of interactions between humans and the environment. One area of study focuses on how we use natural resources, such as water and plants. The other area of study focuses on how our actions alter our environment. Environmental scientists must gather and analyze information from many different disciplines. Even though environmental scientists want to solve environmental problems, they are not the same as environmentalists. Scientists study the environment to accurately describe environmental systems and determine how they work. Scientists also can use data and mathematical models to predict how systems might change under different scenarios. It is up to the public, special interest groups, and politicians to make decisions about how to manage the environment. Environmentalism is a social movement that seeks to protect the environment and, because we all depend on the environment, people. Many Fields of Study Environmental science is an interdisciplinary science, which means it involves many fields of study. Ecology is the study of how living things interact with each other and with their nonliving environment. Chemistry helps us understand how organic matter is transformed and the nature of pollutants. Geology helps us model how water and air move around the globe. Botany and zoology provide information needed to preserve species. Paleontology, the study of fossils, helps us understand how Earth s climate has changed in the past. Using such information about the past can help us predict how future climate changes could affect life on Earth. Often, teams of environmental scientists work together to understand and solve environmental problems. Studying the environment also involves studying human populations. Environmental scientists may use the social sciences, which include economics, law, politics, and geography. Social sciences can help us answer questions such as How does human migration from rural to urban areas affect the local environment? Or how can economic incentives change people s decisions to protect the environment? Figure 1.3 lists some of the major fields of study that contribute to the study of environmental science. Matt Meadows 6 Unit 1: Introduction to Environmental Science

3 Figure 1.3 Major Fields of Study That Contribute to Environmental Science Biology is the study of living organi sms. Zoology is the study of animals. Botany is the study of plants. Microbiology is the study of microorganisms. Ecology is the study of how organisms interact with their environment and each other. Earth science is the study of Earth s nonliving systems and the planet as a whole. Physics is the study of matter and energy. Chemistry is the study of chemicals and their interactions. Social sciences are the study of human populations. Geology is the study of Earth s surface, interior processes, and history. Paleontology is the study of fossils and ancient life. Climatology is the study of Earth s atmosphere and climate. Hydrology is the study of Earth s water resources. Engineering is the science by which matter and energy are made useful to humans in structures, machines, and products. Biochemistry is the study of the chemistry of living things. Geochemistry, a branch of geology, is the study of the chemistry of materials such as rocks, soil, and water. Geography is the study of the relationship between human populations and Earth s features. Anthropology is the study of the interactions of the biological, cultural, geographical, and historical aspects of humankind. Sociology is the study of human population dynamics and statistics. Douglas Faulkner/Photo Researchers, Inc. Chapter 1: Science and the Environment 7

4 Figure 1.4 Environmental Science and Public Life Scientists at a conference discuss climate change. Students study the movements of box turtles. Figure 1.5 Change Three hundred years ago, Manhattan was a very different place. This painting shows an area where Native Americans hunted and fished. Scientists as Citizens, Citizens as Scientists Governments, businesses, and communities recognize that studying our environment is vital to maintaining a healthy and productive society. Thus, environmental scientists are often asked to share their research with the world. Figure 1.4 shows scientists meeting to discuss climate change at a United Nations conference. Often, the observations of nonscientists are the first step toward addressing an environmental problem. For example, middle-school students first noticed the appearance of deformed frogs in Minnesota lakes. Similarly, the students at Dublin Scioto High School in Ohio, shown in Figure 1.4, have studied the habitat of endangered box turtles. A habitat is a place where an organism usually lives. The students wanted to find out how the turtles live and what factors affect their nesting and hibernation sites in their habitat. The students tracked and mapped the turtles movements, measured atmospheric conditions, and analyzed soil samples. These efforts are important because the box turtle habitat is threatened. The students have presented their findings to city planners, in an effort to protect the most sensitive turtle habitats. Our Environment Through Time Wherever humans have hunted, grown food, or settled, they have changed the environment. For example, the land where New York City now stands was once an area where Native Americans hunted game and gathered food, as shown in Figure 1.5. The environmental change that has occurred on Manhattan Island over the past 300 years is immense, yet this period of time is just a blink in human history. (b) North Wind Picture Archives; (tr) Courtesy of Gardner Watkins; (tl) Xu Jinquan/Xinhua Press/Corbis 8 Unit 1: Introduction to Environmental Science

5 Hunter-Gatherers For most of human history, people were hunter-gatherers, or people who obtain food by collecting plants and by hunting wild animals or scavenging their remains. Early hunter-gatherer groups were small, and they migrated from place to place as different types of food became available at different times of the year. Even today there are hunter-gatherer societies in the Amazon rain forests of South America and in New Guinea, as shown in Figure 1.6. Hunter-gatherers affected their environment in many ways. For example, some Native American tribes hunted bison that live in grasslands. The tribes set fires to burn the prairies and prevent the growth of trees. This kept the prairies as open grassland where the tribes could hunt bison. In North America, rapid climate changes and overhunting by huntergatherers may have contributed to the disappearance of some species of large mammals. These species include giant sloths, giant bison, mastodons, cave bears, and saber-toothed cats. Large piles of bones have been found where meat was possibly stored during the winter. In Australia and New Zealand, hunter-gatherers caused the extinction of many large species of mammals and birds. ECOFACT The Fall of Troy Environmental problems are nothing new. Nearly 3,000 years ago, the Greek poet Homer wrote about the ancient seaport of Troy, which was located beneath a wooded hillside. The Trojans cut down all the trees on the surrounding hills. Without trees to hold the soil in place, rain washed the soil into the harbor. So much silt accumulated in the harbor that large ships could not enter and Troy s economy collapsed. Today, the ruins of Troy are several miles from the sea. Check for Understanding Identify Name two ways that huntergatherers affected their environment. Figure 1.6 Hunter-Gatherers This modern hunter-gatherer group lives in New Guinea, a tropical island off the north coast of Australia. David Gillison Chapter 1: Science and the Environment 9

6 FieldStudy Go to Appendix B to find the field study Measure Up. The Agricultural Revolution Eventually many hunter-gatherer groups began to collect the seeds of the plants they gathered and to domesticate some of the animals in their environment. Agriculture is the practice of growing, breeding, and caring for plants and animals that are used for food, clothing, housing, transportation, and other purposes. The practice of agriculture started in many different parts of the world over 10,000 years ago. This change had such a dramatic impact on human societies and their environment that it is often called the neolithic agricultural revolution. The agricultural revolution allowed human populations to grow at an unprecedented rate. An area of land can support up to 100 times as many people by farming as it can by hunting and gathering. As populations grew, they began to concentrate in smaller areas. These changes placed increased pressure on local environments. The agricultural revolution also changed the food we eat. The plants we grow and eat today are descended from wild plants. During harvest season, farmers collected seeds from plants that exhibited the qualities they desired. The seeds of plants with large kernels or sweet and nutritious flesh were planted and harvested again. Over the course of many generations, the domesticated plants became very different from their wild ancestors. For example, the grass shown in Figure 1.7 may be related to the grass from which corn was bred. As grasslands, forests, and wetlands were replaced with farmland, habitats were destroyed. Slash-and-burn agriculture, shown in Figure 1.7, is one of the earliest ways by which land was converted to farmland. Replacing forest with farmland on a large scale caused soil loss, floods, and water shortages. In addition, much of this converted land was farmed poorly and is no longer fertile. The loss of fertile farmland had far-reaching effects. For example, the early civilizations of the Tigris-Euphrates River basin collapsed, in part, because the overworked soil became infertile through salt contamination. Figure 1.7 The Agricultural Revolution This grass, called Eastern gama grass, is thought to be a relative of the modern corn plant. Native Americans may have selectively bred a grass like this to produce corn. For thousands of years humans have burned forests to create fields for agriculture. In this photo, a rain forest in Thailand is being cleared for farming. (bl) A. Murray/University of Florida; (br) Still Pictures 10 Unit 1: Introduction to Environmental Science

7 Figure 1.8 Industrial Revolution During much of the Industrial Revolution, few limits were placed on the air pollution caused by burning fossil fuels. Locomotives such as these were powered by burning coal. Quality of Life The invention of computers has improved the ways that people work, learn, communicate, and entertain themselves. (tl) Lambert/Archive Photos/PictureQuest/Getty Images; (tr) Color Blind Images/Blend Images/Getty Images The Industrial Revolution For about 2.5 million years the tools of human societies were powered mainly by humans or animals. This pattern changed in the middle of the 1700s with the Industrial Revolution, which involved a shift from energy sources, such as animal muscle and running water, to fossil fuels, such as coal and oil. The increased use of fossil fuels and machines, such as the steam engines shown in Figure 1.8, changed society and greatly increased the efficiency of agriculture, industry, and transportation. During the Industrial Revolution, the large-scale production of goods in factories became less expensive than the local production of goods. Machinery reduced the amount of land and human labor needed for farming. As fewer people grew their own food, populations in urban areas steadily grew. Fossil fuels and motorized vehicles allowed food and other goods to be transported cheaply across great distances. Improving Quality of Life The Industrial Revolution introduced many positive changes. Inventions such as the light bulb greatly improved our quality of life. Agricultural productivity increased, and sanitation, nutrition, and medical care vastly improved. Technologies such as the telephone and the portable computer, shown in Figure 1.8, enabled people to work and communicate more easily from any location. Yet with all of these advances, the Industrial Revolution introduced many new environmental problems. In the 1900s, modern societies began to use artificial substances in place of raw animal and plant products. Plastics and many other artificial ma terials have made life easier. However, we now understand some of the environmental problems they present. Much of environmental science is concerned with the problems associated with the Industrial Revolution. Check for Understanding Identify Identify three ways that the Industrial Revolution changed society. Chapter 1: Science and the Environment 11

8 Spaceship Earth Figure 1.9 Space This photograph was taken in 1968 by the crew of Apollo 8. Photographs such as this helped people realize the uniqueness of the planet we share. Earth, shown from space in Figure 1.9, has been compared to a ship traveling through space, unable to dispose of waste or take on new supplies as it travels. Earth is essentially a closed system the only thing that enters Earth s atmosphere in large amounts is energy from the sun, and the only thing that leaves in large amounts is heat. A closed system has potential problems. Some resources are limited, and as the population grows, the resources will be used. In a closed system there is also the chance that we will produce wastes more quickly than we can dispose of them. Although Earth can be thought of as a complete system, envi ronmental problems can occur on different scales: local, regional, or global. For example, your community may be discussing where to build a new landfill, or local developers may be arguing with environmentalists about the importance of a rare bird or insect. On a regional level, the drinking water in your area may be affected by a polluted river hundreds of miles away. Other environmental problems are global. For example, carbon dioxide released in one part of the world can contribute to climate change around the globe. CASESTUDY Dam Removal on the Penobscot River The Penobscot River, Maine The watershed of the Penobscot River is the largest in Maine, and the major streams extend over 8,800 km (about 5,500 miles). Historically, the Penobscot was home to abundant fish and other wildlife. For example, more than 100,000 salmon per year migrated for reproduction from the ocean to this watershed. Salmon and ten other species of migratory fish enriched the watershed and provided food and cultural value for the Wabanaki people, who occupied the area continuously for more than 9,000 years. European settlement of the area brought construction of many dams to provide power for mills and eventually to produce electricity. In the past few decades all commercial 12 Unit 1: Introduction to Environmental Science fisheries have been lost and the Penobscot population of salmon was listed under the Endangered Species Act in Scientists determined that the primary cause of decline is obstruction of fishes migratory paths by dams. Dams reduce the environmental benefits of a freerunning river in many ways. These benefits include food, recreation, cultural enrichment, and clean water. Varying depths and currents that come with natural flow create diverse habitats that promote diverse wildlife. Periods of fast flow remove silt from gravel beds, which is necessary for many aquatic insects. These insects are food for fish. Many species of fish need sand or gravel to reproduce. Normal river flow helps rivers recover from pollution, and coastal ocean ecosystems are productive because rivers deliver nutrients from land to ocean. These benefits of natural river flow have been revealed by the work of many environmental scientists. The Penobscot River Restoration Trust To reconcile the benefits and costs of dams, the Penobscot River Restoration Project brought together a wide variety of groups to develop a plan that is now being implemented. NASA Dams on rivers help to produce much-needed electricity without continuously burning fossil fuels. These benefits, however, are accompanied by some environmental, economic, and social costs. The large geographic areas of watersheds (the land area that drains into a river) and the diverse mix of interest groups present challenges to making fair and sustainable decisions about hydropower. How can the right balance be achieved?

9 Population Growth: A Local Pressure Figure 1.10 One reason many environmental problems are so pressing today is that the agricultural revolution and the Industrial Revolution allowed the human population to grow much faster than it had ever grown before. The development of modern medicine and sanitation also helped increase the human population. As shown in Figure 1.10, the human population almost quadrupled during the 20th century. Producing enough food for such a large population has environmental consequences. Many of the environmental problems that affect us today, such as habitat destruction and pesticide pollution, are the result of feeding the world in the 20th century. Other problems, like climate change, are the result of filling the demand for goods and transportation of so many people. World Population The size of the WorldÊPopulation:Ê 1600Ð2010 Population (in billions) There are many different predictions of population growth for the future. But most scientists think that the human population will almost double in the 21st century before it will begin to stabilize. We can expect that the pressure on the environment will continue to increase as the human population and its need for food and resources grow. human population in 2010 was nearly 14 times larger than it was in Year Source:ÊU.S.ÊCensusÊBureau,Ê InternationalÊDatabase Edwin Remsberg/Alamy Images The Penobscot River, Maine These groups include a hydropower company, the Penobscot Indian Nation (a part of the Wabanaki people), seven conservation groups, and government agencies at the state and federal levels. As part of the plan, hydropower levels will be maintained, but two dams closest to the mouth of the river will be removed, construction of a bypass for migratory fish will occur at a third dam, and passages will be built for fish at four more dams. These actions will be monitored by Maine and Federal agencies. Most importantly, the Penobscot River Restoration Trust was formed to promote continued collaboration and oversight for all the participating groups. Increased access to proper habitat and improved water quality should allow populations of many migratory fishes to grow from no more than 2,000 today to millions of fish! This will revitalize the Penobscot Indian Nation s culture and traditions and will promote sustainable economic development of communities within the watershed. The story of the Penobscot River is an example of how environmental science and public action work together to solve environmental problems. Good science revealed the causes for decline, needs for ecological Critical Thinking restoration, and the engineering solutions to implement large-scale projects. Science will continue to be applied to evaluate the recovery of wildlife, and many groups with different interests working together will ensure the long-term health of the river and local communities. Critical Thinking 1. Analyzing Processes Why was the Penobscot River Restoration Trust formed? 2. Analyzing Relationships Describe how environmental science helped the Trust decide that some dams should be removed. Chapter 1: Science and the Environment 13

10 QUICKLAB Classifying Resources Procedure 1. You and a partner will be given a small container of objects by your teacher. 2. Working separately, you should each create a data table with the headings, Renewable and Nonrenewable. 3. Without speaking, each of you should look at the objects and decide in which of the two categories they belong. 4. When you are both finished, compare your choices. Discuss any differences, explaining why you placed objects in a particular category. 5. Participate in a class discussion about what resources the objects represent and why they are considered renewable or nonrenewable. Analysis 1. Why are resources like air and water considered to be at risk, even though they are considered renewable? 2. Select one resource and hypothesize what side effects might occur if that resource is depleted. What Are Our Main Environmental Problems? You may feel as though the world has an unlimited variety of environmental problems. But many environmental problems fall into three categories: resource depletion, pollution, or loss of biodiversity. Resource Depletion Any natural material that is used by humans is called a natural resource. Natural resources can be classified as renewable or nonrenewable, as shown in Figure A renewable resource is a resource that can be replaced relatively quickly by natural processes. Fresh water, air, soil, trees, and crops are all resources that can be renewed. Energy from the sun is also a renewable resource. A nonrenewable resource is a resource that forms at a much slower rate than the rate that it is consumed. The most common nonrenewable resources are minerals and fossil fuels. Once a nonrenewable resource is used up, it may take millions of years to replenish it. Resources are said to be depleted when a large fraction of the resource has been used up. Figure 1.11 shows a mine where copper, a nonrenewable resource, is removed from the Earth s crust. Some renewable resources can also be depleted. For example, if trees are harvested faster than they can grow naturally in an area, deforestation will result. Pollution With the Industrial Revolution, societies began producing wastes faster than the wastes could be disposed of. The wastes accumulate and cause pollution. Pollution is an undesired change in air, water, or soil that adversely affects the health, survival, or activities of humans or other organisms. Air pollution levels in Mexico City, as shown in Figure 1.12, are dangerously high, mostly because of car exhaust and industrial pollutants. Biode gradable pollutants can be broken down by natural processes. These pollutants include things such as human sewage and food wastes. Figure 1.11 Resources More than 12 million tons of copper have been mined from the Bingham mine in Utah. Once all of the copper that can be profitably extracted is used up, the copper in this mine will be depleted. Renewable and Nonrenewable Resources Renewable energy from the sun water wood soil air Nonrenewable metals such as iron, aluminum, and copper nonmetallic ma terials such as salt, sand, and clay fossil fuels Gene Ahrens/Bruce Coleman, Inc./Photoshot 14 Unit 1: Introduction to Environmental Science

11 Biodegradable pollutants are a problem when they accumulate faster than they can be broken down. Nonbiodegradable pollutants, such as mercury, lead, and some types of plastic, cannot be broken down by natural processes. Because such pollutants do not break down easily, they can build to dangerous levels in the environment. Because carbon dioxide is generally not harmful to people s health we breathe it out when we exhale people often don t think of it as a pollutant. But the huge amounts of CO 2 being released from the burning of fossil fuels are increasing the amount in the atmosphere and changing the climate. Because of this undesirable effect, it may be considered pollution in some forms. Because climate change is a global problem that affects many other environmental problems, many scientists believe that it is the most pressing environmental issue. Figure 1.12 Air Pollution The problem of air pollution in Mexico City is compounded because the city is located in a valley that traps air pollutants. (cr) Nature Source/Photo Researchers, Inc; (tr) SPL/Photo Researchers, Inc. Loss of Biodiversity The term biodiversity refers to the number and variety of species that live in an area. Earth has been home to hundreds of millions of species. Only a fraction of those species are alive today. Extinction is a natural process, and several large-scale extinctions, or mass extinctions, have occurred through Earth s history. Scientists believe that the pace of extinctions occurring today matches that of mass extinctions in the past. Why should we be concerned about the modern extinction of individual species? The organisms that share the world with us can be considered natural resources. We depend on other organisms for food, for the oxygen we breathe, and for many other things. A species that is extinct is gone forever, so a species can be considered a nonrenewable resource. Scientists think that if current rates of extinction continue, it may cause problems for human populations in the future because the loss of too many species may cause significant disruption in ecosystems. If this happens, many of the services ecosystems provide to people may be lost. Many people also argue that all species have potential economic, ecological, scientific, aesthetic, and recrea tional value, so it is important to preserve them. Figure 1.13 Loss of Biodiversity The Tasmanian tiger, native to Australia and the island of Tasmania, was declared extinct in Section 1 Formative Assessment Reviewing Main Ideas 1. Describe the two main types of interactions that environmental scientists study. Give an example of each. 2. Describe the major environmental effects of the agricultural revolution and the Industrial Revolution. 3. Explain how environmental problems can be local, regional, or global. Give one example of each. 4. Explain why environmental science is an interdisciplinary science. Critical Thinking 5. Making Comparisons What is the difference between environmental science and ecology? 6. Making Inferences Fossil fuels are said to be nonrenewable resources, yet they are produced by the Earth over millions of years. By what time frame are they considered nonrenewable? Write a paragraph that explains your answer. Chapter 1: Science and the Environment 15