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The only popular study guide available on environmental science
This new Wiley Self-Teaching Guide introduces learners to all the basics of environmental science, from air pollution to the water cycle, covering both natural systems and human impacts on the environment. Using quick quizzes and self-tests to reinforce key concepts, Environmental Science walks students through this interdisciplinary topic with clarity and thoroughness. With 125 photographs and illustrations, this ...
The only popular study guide available on environmental science
This new Wiley Self-Teaching Guide introduces learners to all the basics of environmental science, from air pollution to the water cycle, covering both natural systems and human impacts on the environment. Using quick quizzes and self-tests to reinforce key concepts, Environmental Science walks students through this interdisciplinary topic with clarity and thoroughness. With 125 photographs and illustrations, this book is a unique and valuable resource for anyone interested in learning more about-and in preserving-our green home.
We speak for Earth. -Carl Sagan
In this chapter you will learn about:
the field of environmental science;
the features and characteristics that make Earth unique;
the geosphere, atmosphere, hydrosphere, biosphere, ecosphere, and technosphere; and
the materials and processes of the solid Earth.
The Environment and Environmental Science
Once upon a time, the term environment just meant "surroundings." It was used in reference to the physical world separate from ourselves-rocks, soil, air, and water. People gradually came to realize that the organisms that inhabit the physical world-the enormous variety of plants, animals, and microorganisms on this planet, including humans-are an integral part of the environment. It doesn't make sense to define environment without recognizing the fundamental importance of interactivity among organisms, and between organisms and their surroundings. Therefore, we can define environment to include all of the components, characteristics, and conditions in the natural world that influence organisms, as well as the interactions between and among organisms and the natural world. This definition encompasses the physical-chemical-geologic surroundings of an organism, as well as the other biologic inhabitants of the neighborhood. It implies that there is a range ofpossible interactions among the various components of the environment, both biotic (living) and abiotic (nonliving).
Our conceptual understanding of the environment continues to evolve, reflecting the emerging understanding that humans, too, are an integral part. We influence the physical world and other organisms; in turn, we are influenced by them. Therefore, more recent definitions of environment incorporate social, cultural, and economic factors in addition to the components of the natural, biophysical world. For example, human technology is affected by the natural environment through the availability or scarcity of natural resources. Technology, in turn, has profound and sometimes devastating impacts on the natural environment. Understanding the technosphere-the built, manufactured, industrialized, and domesticated aspects of the world-is fundamental to our understanding and successful management of the environment.
Environmental science, the focus of this book, is an interdisciplinary combination of basic sciences applied to the study of the environment. By one relatively early definition, environmental science includes "all of nature we perceive or can observe ... a composite of Earth, Sun, sea, and atmosphere, their interactions, and the hazards they present" (from the U.S. Environmental Science Services Administration, 1968). Environmental science draws its fundamental principles from a number of basic scientific disciplines, particularly biology, geology, chemistry, and physics. These and other scientific disciplines, including hydrology, climatology, oceanography, soil science, statistics, and meteorology, are applied to the study of the environment and contribute to our understanding of this complex planet we inhabit.
Environmental science is a multifaceted discipline, but the study of the environment extends well beyond the realm of science. People are the de facto managers of this planet. We manage the environment-our impacts on the environment, as well as its impacts on human society-through our laws, policies, writings, and other human systems. We draw from disciplines as diverse as philosophy, literature, economics, political science, sociology, management, geography, history, anthropology, art, and even psychology. The application of these disciplines to the environment has given rise to such fields as environmental law, environmental economics, environmental management, and environmental ethics. Although these are not scientific disciplines, they are fundamental to our understanding of the environment.
How would you modify the definition of environment stated above so that it takes into consideration human technology and its interactions with the natural environment?
Answer: One possible definition is that environment encompasses the natural physical, chemical, biologic, and geologic aspects and conditions that influence and are influenced by organisms, including humans; the interactions among them; and social, cultural, and economic factors that influence and are influenced by the natural world. Does this definition include everything that you think it should?
Why do you think it is important to be precise and thorough in defining the concept of environment? ________________
Answer: One reason is that the term environment is often used in a legal context, where the wording must be very precise. Another reason for being careful and thorough is that how we define environment reflects, in part, how we view ourselves in relation to other organisms and to the natural world. The impacts of technologic developments on the natural environment sometimes result in degradation of the social or cultural environment; these need to be included in our definition so that they will be taken into consideration when we undertake activities that may alter the natural environment.
Hot Topics in Environmental Science
If you were to take a poll in which you asked citizens of North America and Europe to name the most pressing environmental issues today, you would likely find significant regional variations. People in the northeastern United States and southern Canada might have concerns about the health of the Great Lakes. In the Northwest, people might have concerns about deforestation in old-growth forests. In the Midwest and dry Southwest, the availability of abundant water and the depletion of groundwater supplies might be of concern. People in Western Europe might be most worried about the effects of acid rain on forests and lakes. Some concerns would be common to all regions, including climatic change, the ozone hole, loss of biodiversity, health impacts of air pollution, toxic contaminants in natural waters, overpopulation, energy shortages, and municipal garbage. These are widespread or even global problems that are part of the legacy of industrialization. Throughout this book, we will be looking at the science that underlies these and other environmental problems.
What are the most pressing environmental issues facing your local neighborhood, city, or region? How do they differ from the environmental issues in other regions, and how are they similar? How do your local concerns differ from global environmental issues?
If you were to conduct the same poll in a less economically developed country, perhaps in South America, Asia, or Africa, the list of pressing environmental issues might be quite different. The environmental concerns of people in the developing world tend to be more local, more immediate, and relate more directly to daily survival. The list might include land degradation and its impact on food production; lack of clean water for drinking, washing, and cooking; and the lack of fuel wood and other energy sources for cooking. Today almost 2 billion of the world's poorest people lack access to sanitation facilities and wastewater treatment. Approximately 1 billion people do not have access to clean water, and almost 1 billion people are chronically hungry. These problems threaten people's survival; they are part of the legacy of poverty. Some of them are not strictly environmental problems-there are underlying political, social, and economic causes-but the impacts of environmental degradation on human health and well-being are immediate, local, and severe in the developing world.
Until fairly recently, most developing countries were not particularly interested in entering the international dialogue about dealing with problems like ozone depletion or global warming. Why? It's partly an issue of responsibility and blame; some of our current global environmental problems were caused-or were at least initiated-by industrialization in wealthier nations. It's also partly because people in developing countries are simply too busy dealing with the immediate problems of daily survival and with getting food, water, and other basic services to people in need. Now, however, it is widely recognized that regardless of the cause everyone in the world is potentially at risk from the impacts of environmental degradation. All nations and all people bear a common responsibility to deal with these problems.
A concept that has become familiar in international dialogues about global environmental issues is the idea of common but differentiated responsibility of nations. What do you think it means? ________________
Answer: Common but differentiated responsibility refers to the concept that all nations must bear responsibility for dealing with global environmental problems, but different nations have different capacities and resources with which to respond to these problems.
Welcome to Our World
Now that we have covered some basic terminology and concepts, let's begin our study of the environment by taking a look at the planet itself. Earth is one of nine planets in our solar system-the Sun and the group of objects orbiting around it, which originated as a system approximately 4.6 billion years ago. The solar system also includes more than sixty moons, a vast number of asteroids, millions of comets, and innumerable floating fragments of rock and dust. The objects in our solar system move through space in smooth, regular orbits held in place by gravitational attraction. The planets, asteroids, and comets orbit the Sun, and the moons orbit the planets (Figure 1.1).
The planets can be separated into two groups on the basis of their characteristics and distances from the Sun. The innermost planets-Mercury, Venus, Earth, and Mars-are small, rocky, and relatively dense. These planets are similar in size and chemical composition. They are called terrestrial planets because they resemble Terra ("Earth" in Latin). With the exception of Pluto, the outer or jovian planets-Jupiter, Saturn, Uranus, and Neptune-are much larger than the terrestrial planets but much less dense, with very thick atmospheres of hydrogen, helium, and other gases. You can learn more about the solar system by reading Astronomy: A Self-Teaching Guide, by Dinah L. Moche ( John Wiley & Sons, 2004).
The terrestrial planets have many things in common beyond their small sizes, rocky compositions, and positions close to the Sun. They have all been subjected to volcanic activity and intense meteorite impact cratering. They have all been hot and, indeed, partially molten at some time early in their histories. During this partially molten period, the terrestrial planets separated into layers of differing chemical composition: a relatively thin, low-density, rocky crust on the outside; a metallic, high-density core in the center; and a rocky mantle in between. This separation process happened to all of the terrestrial planets, including Earth. In the context of environmental science, the physical Earth-distinct from the organisms that inhabit it-is referred to as the geosphere. The term geosphere is used in reference to the planet and the whole physical environment-the atmosphere, the hydrosphere, and the solid Earth.
What are the four terrestrial planets, and why are they given this name? ________________
Answer: Mercury, Venus, Earth, and Mars. They are all similar to Earth (Terra).
What Makes Earth Unique?
In spite of the similarities among the terrestrial planets, the history and specific characteristics of Earth are different enough from those of the other terrestrial planets to make this planet habitable. If you look at a photograph of Earth taken from space, you immediately notice the blue-and-white atmosphere, an envelope of gases dominated by nitrogen, oxygen, argon, and water vapor, with traces of other gases. Other planets have atmospheres, but no other planet in the solar system has an atmosphere of this particular chemical composition.
The atmosphere contains clouds of condensed water vapor that form because water evaporates from the hydrosphere, another unique feature. The hydrosphere ("watery sphere") consists of the oceans, lakes, and streams; underground water; and snow and ice. Planets farther from the Sun are too cold for liquid water to exist on their surfaces; planets closer to the Sun are so hot that any surface water evaporated long ago. Only Earth has just the right surface temperature to have liquid water, ice, and water vapor in its hydrosphere.
Another unique feature of Earth is the biosphere, the "living sphere." The biosphere comprises innumerable living things, large and small, which belong to millions of different species, as well as recently dead plants and animals that have not yet completely decomposed. The ecosphere is the physical environment that permits or facilitates the existence of the biosphere. On Earth, the ecosphere extends from the deepest valleys and the bottom of the ocean to the tops of the highest mountains and well into the lower part of the atmosphere. Even the great polar ice sheets host a variety of life forms. Although many new planets have been discovered orbiting distant stars that seem similar to our own Sun, we don't yet know of another planet that offers an ecosphere or hosts a biosphere.
The nature of Earth's solid surface is also special; it is covered by an irregular blanket of loose debris called regolith (from the Greek rhegos, meaning "blanket"). Earth's regolith forms as a result of weathering, the continuous chemical alteration and mechanical breakdown of surface materials through exposure to the atmosphere, hydrosphere, and biosphere. The weathered, broken-down materials are picked up by moving wind, water, and ice, carried downhill under the influence of gravity, and eventually deposited. Weathering and the transport of weathered materials together comprise the process of erosion, which is part of the global rock cycle (Figure 1.2). Soil, mud in river valleys, sand in the desert, rock fragments, and other unconsolidated debris are all part of the regolith. Some other planets and planetary bodies are blanketed by loose, fragmented material, but in those cases the fragmentation has been caused primarily by the endless pounding of meteorite impacts. Earth's regolith is unique because it forms as a result of complex interactions of physical, chemical, and biologic processes, usually involving water. It is also unique because it teems with life; most plants and animals live on or in the regolith or in the hydrosphere.
Why does Earth have an ecosphere, whereas all other known planets do not? ________________
Answer: A combination of just the right size and composition (especially the presence of water) and optimal distance from the Sun make the surface conditions on Earth perfectly suited for hosting life.
Earth, Inside and Out
Earth, like the other terrestrial planets, is composed primarily of rock, a naturally formed, solid, coherent aggregate. The basic building blocks of rocks are minerals-naturally occurring, inorganic elements or chemical compounds that have specific chemical compositions, orderly internal atomic structures, and characteristic physical properties. Geology is the scientific study of these and other Earth materials and processes. If you are interested in learning more about the science of the Earth, you can read Geology: A Self-Teaching Guide, by Barbara Murck (John Wiley & Sons, 2001).
Three basic families of rocks are recognized. They are:
1. sedimentary rocks, which form as a result of the deposition, consolidation, and cementation of unconsolidated rock and mineral fragments (sediment) in low-temperature and low-pressure conditions near Earth's surface;
2. igneous rocks, which solidify from molten rock (magma or lava) on the surface (volcanic rocks) or deep underground (plutonic rocks); and
3. metamorphic rocks, which are rocks that have been altered as a result of exposure to very high pressures and/or temperatures.
Excerpted from Environmental Science by Barbara W. Murck Excerpted by permission.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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A Note to the Reader.
1. Our Unique Planet.
2. The Interactive Earth.
3. The Hydrosphere and the Atmosphere.
4. The Biosphere: Life on Earth.
5. Earth’s Major Ecosystems.
6. Habitat and Biodiversity.
7. People, Population, and Resources.
8. Living Resources I: Forests, Wildlife, and Fisheries.
9. Living Resources II: Soils and Agriculture.
10. Mineral Resources.
11. Energy Resources.
12. Water Resources.
13. Water Pollution and Soil Pollution.
14. Air Pollution.
15. Cities and Waste Management.
16. Global Change.
Appendix 1: Units and Conversions.
Appendix 2: Some Great Environmental Science Web Sites.
Appendix 3: Soil Classifications.