Key Concepts

After completing this chapter, you will be able to:

1. Define environmental science and distinguish it from related fields such as environmental studies, ecology, and geography.
2. Explain the complexity of the universe through a hierarchical framework that includes consideration of Earth, life, and ecosystems at various scales.
3. Identify key principles of the ecosystem approach to conserving natural resources.
4. Describe how environmental stressors and disturbances can affect species and ecosystems.
5. Explain the history of human cultural evolution in terms of an increasing ability to cope with environmental constraints on the availability of natural resources and other aspects of economic development.
6. List at least three ways in which humans directly influence environmental conditions.
7. Identify four broad classes of environmental values.
8. Describe five important worldviews.
9. Understand the diverse issues of the environmental crisis by classifying them into three categories, and give several examples within each of them.
10. Discuss the environmental effects of humans as a function of two major influences: increases of population and intensification of lifestyle (per-capita effects).
11. Explain the differences between economic growth and ecologically sustainable development.

Environmental Science and Its Context

Every one of us is sustained by various kinds of natural resources – such as food, materials, and energy that are harvested or otherwise extracted from the environment. Our need for those resources is absolute – we cannot survive without them. Moreover, the same is true of all other species; every organism is a component of an ecosystem that provides the means of subsistence.

Collectively, the needs and activities of people comprise a human economy. That economy operates at various scales, ranging from an individual person, to a family, to communities such as towns and cities, nation-states (such as the U.S.), and ultimately the global human enterprise. While an enormous (and rapidly growing) number of people are supported by the global economy, a lot of environmental damage is also being caused. The most important of the damages are the depletion of vital natural resources, various kinds of pollution (including climate change), and widespread destruction of natural habitats to the extent that the survival of many of the natural ecosystems and species of Earth are at grave risk (Image 1.1).

Image 1.1. Planet Earth. Earth is the third closest planet to the Sun, and it is the only place in the universe that is definitely known to sustain life and ecosystems. Other than sunlight, the natural resources needed to sustain the human economy are restricted to the limited amounts that can be extracted on Earth. This image of the Western Hemisphere was taken from a distance of 35-thousand km from the surface of Earth. Source: R. Stöckli, N. El Saleous, and M. Jentoft-Nilsen, NASA GSFC. 

These issues are of vital importance to all people, and to all life on the planet. Their subject matter provides the context for a wide-ranging field of knowledge called environmental studies, an extremely broad field of knowledge that examines the scientific, social, and cultural aspects of environmental issues. As such, the subject matter of environmental studies engages all forms of understanding that are relevant to identifying, understanding, and resolving environmental problems. Within that context, environmental science examines the science-related implications of environmental issues (this is explained in more detail in the following section). The subject matter of environmental science is the focus of this book.

Issues related to environmental problems are extremely diverse and they interact in myriad ways. Despite this complexity, environmental issues can be studied by aggregating them into three broad categories:

1. The causes and consequences of the rapidly increasing human population.
2. The use and depletion of natural resources.
3. Damage caused by pollution and disturbances, including the endangerment of biodiversity.

These are extremely big issues – their sustainable resolution poses great challenges to people and their economy at all scales. Nevertheless, it is important to understand that the study of environmental issues should not be regarded as being a gloomy task of understanding awful problems – rather, the major goal is to identify problems and find practical ways to repair them and prevent others from occurring. These are worthwhile and necessary actions that represent real progress towards an ecologically sustainable economy. As such, people who understand and work towards the resolution of environmental problems can achieve high levels of satisfaction with their contribution, which is something that helps to make life worth living.

Typical questions that might be examined in environmental science include the following:

1. How large is the human population likely to be in the U.S., or on Earth, in 50 or 200 years?
2. How can the use of fossil fuels be integrated into a sustainable economy, in view of the fact that they are non-renewable resources that do not regenerate?
3. How can we harvest renewable resources (which do have the potential to regenerate) in ways that do not degrade their stocks, such as cod along the Atlantic Coast, wild salmon in Alaska, wheat and other grains in the Central Great Plains, and forest resources across the country?
4. What ecological damages are caused by various kinds of pollution, such as acid rain, ozone, pesticides, and sulfur dioxide, and how can these effects be prevented or repaired?
5. Are human influences affecting global climate, and if so, what are the causes and consequences of this effect?
6. Where and how quickly are species and natural habitats becoming endangered or extinct, and how can these calamities be prevented?

Specialists examining these and other questions related to environmental issues may come from many specific areas of study, each of which is referred to as a discipline. However, the various ways of understanding each issue may be integrated into comprehensive studies of the subject matter – this is why environmental studies is referred to as an interdisciplinary field. For environmental science, the most relevant of the disciplinary subjects are atmospheric science, biology, chemistry, computer science, ecology, geography, geology, mathematics, medical science, oceanography, physics, and statistics. The field of environmental studies includes more emphasis on the political, economic, and social aspects related to the environment. This is illustrated in Figure 1.1, which suggests that all fields of scientific knowledge are relevant to understanding the causes, consequences, and resolution of environmental problems.

Figure 1.1. The Interdisciplinary Nature of Environmental Studies. Environmental studies has an interdisciplinary character. All scientific disciplines are relevant to the identification and resolution of environmental issues. However, the work requires an interdisciplinary approach that engages many disciplines in a coordinated manner. This integration is suggested by the overlaps among the disciplinary fields. Environmental studies broadens the field of environmental science as it includes more emphasis on the political, economic, and social aspects related to the environment.

Of all of the academic disciplines, ecology is the most relevant to environmental science, and in fact the terms are often confused. Ecology may be defined simply as the study of the relationships of organisms with their environment. Ecology is itself a highly interdisciplinary field of study – it mostly involves biology, but knowledge of chemistry, computer science, mathematics, physics, geology, and other fields is also important. Geography is another interdisciplinary field that is central to environmental science. Geography can be simply defined as the study of natural features of Earth’s surface, including climate, soil, topography, and vegetation, as well as intersections with the human economy. Obviously, ecology and geography are closely related fields.

Increasing numbers of scientists are studying human (or anthropogenic) influences on ecosystems, occurring as a result of pollution, disturbances, and other stressors. Examples of the major subject areas are:

1. The extraction, processing, and use of non-renewable resources, such as fossil fuels and metals, in ways that do not cause unacceptable environmental damage, while also moderating their depletion to some possible degree (for example, by re-cycling certain materials).
2. The harvesting and management of biological resources, such as those in agriculture, fisheries, and forestry, in ways that allow them to fully regenerate so their stocks can be sustained into the future.
3. The growth of renewable sources of energy, such as the various forms of solar energy (including biomass fuels, hydroelectricity, photovoltaics, and wind), as a way of replacing non-renewable fossil fuels and thereby making the energy economy more sustainable.
4. The prevention and repair of ecological damages, such as those related to endangered biodiversity, degraded land or water, and the management of greenhouse gases.

An environmental scientist is a generalist who uses science-related knowledge relevant to environmental quality, such as air or water chemistry, climate modelling, or the ecological effects of pollution. Several historically prominent environmental scientists from the United States include Aldo Leopold, a forester, ecologist, and philosopher who pioneered wildlife management and environmental ethics, as well as Rachel Carson, a marine biologist and author whose book, Silent Spring, brought environmental concerns to a widespread audience for the first time. Some contemporary influential environmental scientists include: E.O. Wilson, one of the world’s leading experts on ants, a major contributor to sociobiology, and a collaborating developer of the theory of island biogeography; James Hansen, a climatologist and director of the Program on Climate Science, Awareness, and Solutions of the Earth Institute at Columbia University who also provided congressional testimony on climate change and global warming; Susan Solomon, an atmospheric chemist who has worked at the National Oceanic and Atmospheric Administration and the Earth Systems Research Laboratory where she developed the hypothesis that the ozone layer hole was due to human contributions of chlorofluorocarbons (CFCs); and Sylvia Earle, an oceanographer who has dedicated her life to marine exploration, research, and conservation.

Another group of people, known as environmentalists, is also involved with these sorts of issues, especially in relation to advocacy. This involves taking a strong public stance on a particular environmental issue, in terms of the need to address the problem. John Muir is a classic example of the beginnings of American environmentalism, whose naturalism and conservationism resulted in the protection of Yosemite Valley and Sequoia Forest as National Parks, and co-founded the organization the Sierra Club. Marjory Stoneman Douglas is another well-known American environmentalist, whose activism prevented the drainage of the Everglades and its protection and recognition as an essential natural artifact. In the face of global crises, environmentalism is a global movement with many influential figures from across demographics. For example, Vandana Shiva is an Indian physicist by training who has worked to highlight the negative impacts of conventional agriculture on ecosystems, in an effort to restore food sovereignty for communities. Additionally, in the past decade young people have increasingly become more involved in such causes to become prominent figures. At 15 years old, Greta Thunberg’s weekly school strikes for climate action rapidly caught the world’s attention. She addressed the United Nations Climate Change Conference that same year—continuing her weekly protests into the next year where she sailed to the United Nations 2019 Climate Action Summit to proclaim in front of the world’s leaders, “how dare you,” for their lack of climate action. However, any person can be called an environmentalist if they care about the quality of the environment and work towards changes that would help to resolve the issue. Environmentalists may work as individuals, and they often pursue their advocacy through non-governmental organizations (NGOs).

Earth, Life, and Ecosystems

The universe consists of billions of billions of stars and probably an even larger number of associated planets. Our Earth is one particular planet, located within a seemingly ordinary solar system, which consists of the Sun, eight planets, three “dwarf” planets, and additional orbiting bodies, such as asteroids and comets. Earth is the third closest planet to the sun, orbiting that medium-sized star every 365 days at an average distance of 149 million kilometers, and revolving on its own axis every 24 hours. Earth is a spherical body with a diameter of 12,700 kilometers. About 70% of its surface is covered with liquid water, and the remaining terrestrial area of exposed land and rock is covered mostly with vegetation. With so much of its surface covered with water, one might wonder why our planet was not named “Water” instead of “Earth.” The most singularly exceptional characteristic of Earth is the fact that certain qualities of its environment have led to the genesis and subsequent evolution of organisms and ecosystems. These favorable environmental factors include aspects of Earth’s chemistry, surface temperature, and strength of gravity.

The beginning of life occurred about 3.5 billion years ago, only 1 billion years following the origin of Earth during the formation of the solar system. It is not exactly known how life first evolved from inanimate matter, although it is believed to have been a spontaneous event. In other words, the genesis of life happened naturally, as a direct result of appropriate physical and chemical conditions.

Aside from the musings of science fiction, Earth is celebrated as the only place in the universe that is known to sustain life and its associated ecological processes. Of course, this observation simply reflects our present state of knowledge. We do not actually know that organisms do not exist elsewhere – only that life or its signals have not yet been discovered anywhere else in the universe. In fact, many scientists believe that because of the extraordinary diversity of environments that must exist among the innumerable planets of the multitudinous solar systems of the universe, it is likely that life forms have developed elsewhere. Nevertheless, the fact remains that Earth is the only planet definitely known to support organisms and ecosystems. This makes Earth an extraordinarily special place. We can consider the universe at various hierarchical levels (Figure 1.2). The scale ranges from the extremely small, such as subatomic particles and photons, to the fantastically large, such as galaxies and, ultimately, the universe.

Figure 1.2. Hierarchical Ecological Organization. Source: “Ecological levels” by Siyavula Education is licensed under CC BY 2.0.

Life on Earth occupies intermediate levels of this hierarchy. The realm of ecology encompasses the following levels:

1. Individual organisms, which are living entities that are genetically and physically discrete.
2. Populations, or individuals of the same species that occur together in time and space.
3. Communities, or populations of various species, also co-occurring at the same time and place.
4. Landscapes and seascapes (collectively, these are ecoscapes), which are spatial integrations of various communities over large areas.
5. Biosphere in its entirety, which is composed of all life and ecosystems on Earth.

Species and Ecosystems

A species is defined as individuals and populations that can potentially interbreed and produce fertile offspring (see Chapter 6). The word ecosystem is a generic term that is used to describe one or more communities of organisms that are interacting with their environment as a defined unit. As such, ecosystems can be organized in a hierarchy – they may range from small units occurring in discrete microhabitats (such as an aquatic ecosystem contained within a pitcher plant or in a garden surrounded by pavement) to much larger scales (such as a landscape or seascape). Even the biosphere can be viewed as being a single ecosystem.

Ecological interpretations of the natural world consider the web-like connections among the many components of ecosystems in a holistic manner. This ecosystem approach does not view the system as a random grouping of individuals, populations, species, communities, and environments. Rather, it confirms all of these as being intrinsically connected and mutually dependent, although in varying degrees, and also as having emergent properties (In Detail 1.1).

An important ecological principle is that all species are sustained by environmental resources: the “goods and services” that are provided by their ecosystem. All organisms require specific necessities of life, such as inorganic nutrients, food, and habitat with particular biological and physical qualities. Green plants, for example, need access to an adequate supply of moisture, inorganic nutrients (such as nitrate and phosphate), sunlight, and space. Animals require suitable foods of plant or animal biomass (organic matter), along with habitat requirements that differ for each species.

It is important to understand that humans are no different in this respect from other species. Although this dependence may not always seem to be immediately apparent as we live our daily lives, we nevertheless depend on environmental resources such as food, energy, shelter, and water to sustain ourselves and our larger economies.

It follows that the development and growth of individual people, their populations, and their societies and cultures are limited to some degree by environmental factors. Examples of such constraints include excessively cold or dry climatic conditions, mountainous or otherwise inhospitable terrain, and other factors that influence food production by agriculture or hunting.

However, humans are often able to favorably manipulate their environmental circumstances. For example, crop productivity may be increased by irrigating agricultural land, by applying fertilizer, or by managing pests. In fact, humans are enormously more capable of overcoming their environmental constraints than any other species. This ability is a distinguishing characteristic of our species.

The human species is labelled by the scientific term Homo sapiens, a two-word name (or binomial) that is Latin for “wise man.” Indeed, humans are the most intelligent of all the species, with an enormous cognitive ability (that is, an aptitude for solving problems). When humans and their societies perceive an environmental constraint, such as a scarcity of resources, they often have been able to understand the limiting factors and to then use insight and tools to manipulate the environment accordingly. The clever solutions have generally involved management of the environment or other species to the benefit of humans, or the development of social systems and technologies that allow a more efficient exploitation of natural resources.

Humans are not the only species that can cope with ecological constraints in clever ways. A few other species have learned to use rudimentary tools to exploit the resources of their environment more efficiently. For example, the woodpecker finch of the Galapagos Islands uses cactus spines to pry its food of insects out of fissures in bark and rotting wood. Chimpanzees modify twigs and use them to extract termites, a favorite food, from termite mounds. Egyptian vultures pick up stones in their beak and drop them on ostrich eggs, breaking them and allowing access to the rich food inside.

Although other species have developed behavioral changes that allow more efficient exploitation of their environment, none have approached the number and variety of innovations developed by humans. Moreover, no other species has developed a cumulative expertise for exploiting such a broad range of resources. And no other species has managed to spread these adaptive capabilities as extensively as humans have, in an increasingly global culture. Unfortunately, humans also have developed an unparalleled ability to degrade resources and ecosystems and to cause the extinction of other species. The intense damage caused by humans and our economy is, of course, a major element of the subject matter of environmental science.

Stressors and Responses

The development and productivity of organisms, populations, communities, and ecosystems are naturally constrained by environmental factors. These constraints can be viewed as being environmental stressors. For example, an individual plant may be stressed by inadequate nutrition, perhaps because of infertile soil or competition with nearby plants for scarce resources. Less-than-optimal access to nutrients, water, or sunlight results in physiological stress, which causes the plant to be less productive than it is genetically capable of being. One result of this stress–response relationship is that the plant may develop relatively few seeds during its lifetime. Because reproductive (and evolutionary) success is related to the number of progeny an organism produces to carry on its genetic lineage, the realized success of this individual plant is less than its potential.

Similarly, the development and productivity of an animal (including any human) are constrained by the environmental conditions under which it lives. For instance, an individual may have to deal with stresses caused by food shortage or by difficult interactions with other animals through predation, parasitism, or competition for scarce resources.

The most benign or least stressful natural environments are characterized by conditions in which factors such as moisture, nutrients, and temperature are not unduly constraining, while disturbances associated with disease, wildfire, windstorm, or other cataclysms are rare. These kinds of relatively benevolent conditions allow the most complex and biodiverse ecosystems to develop, namely old-growth rainforest and coral reefs. Other environments, however, are characterized by conditions that are more stressful, which therefore limits their development to less complex ecosystems, such as prairie, tundra, or desert.

All ecosystems are dynamic, in the sense that they change profoundly, and quite naturally, over time. Many ecosystems are especially dynamic, in that they regularly experience large changes in their species, amounts of biomass, and rates of productivity and nutrient cycling. For example, ecosystems that occur in seasonal climates usually have a discrete growing season, which is followed by a dormant period when little or no growth occurs. To varying degrees, most of the natural ecosystems of the United States are seasonally dynamic: a warm growing season is followed by a cold dormant period when little to no plant productivity or growth occurs. Animals may survive the hard times of winter by migrating, hibernating, or feeding on plant biomass remaining from the previous growing season.

Ecosystems that have recently been affected by a disturbance (an episode of destruction) are particularly dynamic because they are undergoing a process of ecological recovery known as succession. Succession occurs in response to changes associated with natural disturbances such as a wildfire, windstorm, or insect or disease epidemic. These cataclysmic stressors kill many of the dominant organisms in an ecosystem, creating opportunities for relatively short-lived species, which may dominate the earlier years of the post-disturbance recovery. Succession also occurs after anthropogenic disturbances, such as a deliberately lit wildfire or a clear-cut of mature timber.

The dynamics of natural disturbances can be far-reaching, in some cases affecting extensive landscapes. For example, in most years, millions of hectares of forest in the western U.S. are disturbed by wildfires. Typically, most of these pine forests have evolved to be maintained by regular low-intensity fires, but, due to human-imposed fire suppression and climate change, understory vegetation and dead trees build up without being regularly burned, providing additional fuel for wildfires. Additionally, climate change causes earlier snowmelt, a longer feeding season for insects to kill trees, and hotter and drier conditions for the fuel to burn, resulting in the high-intensity fires that spread to other vulnerable ecosystems or destroy communities at greater rates than they can recover. An even more extensive cataclysm ended about 12,000 years ago, when glaciation covered parts of North America with enormous ice sheets up to several kilometers thick. However, disturbances can also be local in scale. For example, the death of a large tree within an otherwise intact forest creates a local zone of damage, referred to as a microdisturbance. This small-scale disturbance induces a local succession of vigorously growing plants that attempt to achieve individual success by occupying the newly available gap in the forest canopy.

Even highly stable ecosystems such as tropical rainforest and communities of deep regions of the oceans change inexorably over time. Although catastrophic disturbances may affect those stable ecosystems, they are rare under natural conditions. Nevertheless, as with all ecosystems, these stable types are influenced by pervasive changes in climate and by other long-term dynamics, such as evolution.

In fact, natural environmental and ecological changes have caused the extinction of almost all of the species that have ever lived on Earth since life began about 3.5 billion years ago. Many of the extinctions occurred because particular species could not cope with the stresses of changes in climate or in biological interactions such as competition, disease, or predation. However, many of the extinctions appear to have occurred synchronously (at about the same time) and were presumably caused by an unpredictable catastrophe, such as a meteorite colliding with the Earth. (See Chapter 7 and 14 for descriptions of natural extinctions and those caused by human influences.)

Environmental stressors and disturbances have always been an important, natural context for life on Earth. So, too, have been the resulting ecological responses, including changes in species and the dynamics of their communities and ecosystems.

Human Activities are Environmental Stressors

These days, of course, ecosystems are influenced not just by “natural” environmental stressors. In many situations, anthropogenic influences have become the most important constraining influence on the productivity of species and on ecosystems more generally. These direct and indirect influences have intensified enormously in modern times (Image 1.6).

Image 1.6. Urban Sprawl. Places where people live, work, grow food, and harvest natural resources are affected by many kinds of anthropogenic stressors. These result in ecosystems that are not very natural in character, such as the pavement and grassy edges of the urbans sprawl of Los Angeles. Source: “Urban Sprawl — Los Angeles” by ATIS547 is licensed under CC BY-NC-SA 2.0.

Humans affect ecosystems and species in three direct ways: (a) by harvesting valuable biomass, such as trees and hunted animals; (b) by causing damage through pollution; and (c) by converting natural ecosystems into land-uses for the purposes of agriculture, industry, or urbanization.

These actions also engender many indirect effects. For example, the harvesting of trees alters the habitat conditions for the diversity of plants, animals, and microorganisms that require forested habitat, thereby affecting their populations. At the same time, timber harvesting indirectly changes functional properties of the landscape, such as erosion, productivity, and the quantity of water flowing in streams. Both the direct and indirect effects of humans on ecosystems are important.

Humans have always left “footprints” in nature – to some degree, they have always influenced the ecosystems of which they were a component. During most of the more than 100,000 years of evolution of modern Homo sapiens, that ecological footprint was relatively shallow. This was because the capability of humans for exploiting their environment was not much different from that of other similarly abundant, large animals. However, during the cultural evolution of humans, the ecological changes associated with our activities progressively intensified. This process of cultural evolution has been characterized by the discovery and use of increasingly more sophisticated methods, tools, and social organizations to secure resources by exploiting the environment and other species.

Certain innovations occurring during the cultural evolution of humans represented particularly large increases in capability. Because of their great influence on human success, these advances are referred to as “revolutions.” The following are examples of early technological revolutions:

• The discovery of ways of making improved weapons for hunting animals
• Domestication of the dog, which also greatly facilitated hunting
• Domestication of fire, which provided warmth and allowed for cooked, more digestible foods
• Ways of cultivating and domesticating plants and livestock, which resulted in huge increases in food availability
• Techniques for working raw metals into tools, which were much better than those made of wood, stone, or bone

The rate of new discoveries has increased enormously over time. More recent technological revolutions include the following:

• Methods of using machines and energy to perform work previously done by humans or draught animals
• Further advances in the domestication and cultivation of plants and animals
• Discoveries in medicine and sanitation
• Extraordinary strides in communications and information-processing technologies

These and other revolutionary innovations all led to substantial increases in the ability of humans to exploit the resources of their environment and to achieve population growth (Chapter 10). Unfortunately, enhanced exploitation has rarely been accompanied by the development of a compensating ethic that encourages conservation of the resources needed for survival. Even early hunting societies of more than about 10,000 years ago appear to have caused the extinction of species that were hunted too effectively (Chapter 14).

The diverse effects of human activities on environmental quality are vital issues, and they will be examined in detail in later chapters. For now, we emphasize the message that intense environmental stress associated with diverse human activities has become the major factor causing ecological changes on Earth. Many of the changes are degrading the ability of the environment and ecosystems to sustain humans and their economies. Anthropogenic activities are also causing enormous damage to natural ecosystems, including to habitats needed to support most other species.

In fact, the environmental and ecological damage caused by humans has become so severe that an appropriate metaphor for the human enterprise may be that of a malignancy, or cancer. This is a sobering image. It is useful to dwell on it so that its meaning does not escape our understanding. Humans and their activities are endangering species and natural ecosystems on such a tremendous scale and rate that the integrity of Earth’s life-support systems is at risk.

From an ecological perspective, the pace and intensity of these changes is staggering. Moreover, the damage will become substantially worse before corrective actions are (hopefully) undertaken to reverse the damage and allow an ecologically sustainable human enterprise to become possible. From a pessimistic standpoint, however, it may prove to be beyond the capability of human societies to act effectively to fix the damage and to design and implement solutions for sustainability.

These are, of course, only opinions, albeit the informed views of many environmental specialists. Anticipating the future is always uncertain, and things may turn out to be less grim than is now commonly predicted. For example, we might be wrong about the availability of key resources needed to sustain future generations of humans. Still, the clear indications from recent patterns of change are that the environmental crisis is severe and that it will worsen in the foreseeable future.

But not all this damage is inevitable. There is sincere hope and expectation that human societies will yet make appropriate adjustments and will choose to pursue options that are more sustainable than many of those now being followed. In fact, no other outcome could be considered acceptable.

Ethics and Worldviews

The choices that people make can influence environmental quality in many ways– affecting the availability of resources, causing pollution, and causing species and natural ecosystems to become endangered. Decisions influencing environmental quality are influenced by two types of considerations: knowledge and ethics.

Knowledge refers to information and understanding about the natural world, and ethics refers to the perception of right and wrong and the appropriate behavior of people toward each other, other species, and nature. Of course, people may choose to interact with the environment and ecosystems in various ways. On the one hand, knowledge provides guidance about the consequences of alternative choices, including damage that might be caused and actions that could be taken to avoid that effect. On the other hand, ethics provides guidance about which alternative actions should be favored or even allowed to occur.

Because modern humans have enormous power to utilize and damage the environment, the influence of knowledge and ethics on choices is a vital consideration. And we can choose among various alternatives. For example, individual people can decide whether to have children, purchase an automobile, or eat meat, while society can choose whether to allow the hunting of whales, clear-cutting of forests, or construction of nuclear-power plants. All of these options have implications for environmental quality.

Perceptions of value (of merit or importance) also profoundly influence how the consequences of human actions are interpreted. Environmental values can be divided into two broad classes: utilitarian and intrinsic.

1. Utilitarian value (also known as instrumental value) is based on the known importance of something to the welfare of people (see also the discussion of the anthropocentric world view, below). Accordingly, components of the environment and ecosystems are considered important only if they are resources necessary to sustain humans—that is, if they bestow economic benefits, provide livelihoods, and contribute to the life-support system. In effect, people harvest materials from nature because they have utilitarian value. These necessities include water, timber, fish and animals hunted in wild places, and agricultural crops grown in managed ecosystems.
   • Ecological values are somewhat broader utilitarian values—they are based on the needs of humans, but also on those of other species and natural ecosystems. Ecological values often take a longer-term view.
   • Aesthetic values are also utilitarian but are based on an appreciation of beauty, but they are subjective and influenced by cultural perspectives. For instance, environmental aesthetics might value natural wilderness over human-dominated ecosystems, free-living whales over whale meat, and large standing trees over toilet paper. On the other hand, aesthetics that are heavily influenced by more anthropogenic considerations might result in the opposite preferences. Maintaining aesthetic values can provide substantial cultural, social, psychological, and economic benefits.
2. Intrinsic value is based on the belief that components of the natural environment (such as species and natural ecosystems) have inherent value and a right to exist, regardless of any positive, negative, or neutral relationships with humans. Under this system, it would be wrong for people to treat other creatures cruelly, to take actions that cause natural entities to become endangered or extinct, or to fail to prevent such occurrences.

As was noted previously, ethics concerns the perception of right and wrong and the values and rules that should govern human conduct. Clearly, ethics of all kinds depend upon the values that people believe are important. Environmental ethics deal with the responsibilities of present humans to both future generations and other species to ensure that the world will continue to function in an ecologically healthy way, and to provide adequate resources and livelihoods (this is also a key aspect of sustainable development; see the last section of this chapter). The environmental values described above underlie this system of ethics. Applying environmental ethics often means analyzing and balancing standards that may conflict, because aesthetic, ecological, intrinsic, and utilitarian values rarely all coincide.

There is also tension between ethical considerations that are individualistic and those that are holistic. For example, animal-rights activists are highly concerned with issues involving the treatment of individual organisms. Ecologists, however, are typically more concerned with holistic values, such as a population, species, or ecosystem. As such, an ecologist might advocate a cull of overabundant deer in a park in order to favor the survival of populations of endangered plants, whereas that action might be resisted by an animal-rights activist.

Values and ethics, in turn, support larger systems known as worldviews. A worldview is a comprehensive philosophy of human life and the universe, and of the relationship between people and the natural world. Worldviews include traditional religions, philosophies, and science, as well as other belief systems. In an environmental context, generally important worldviews are known as anthropocentric, biocentric, and ecocentric, while the frontier and sustainability worldviews are more related to the use of resources.

The anthropocentric worldview considers humans as being at the center of moral consideration. People are viewed as being more worthy than any other species and as uniquely disconnected from the rest of nature. Therefore, the anthropocentric worldview judges the importance and worthiness of everything, including other species and ecosystems, in terms of the implications for human welfare.

The biocentric worldview focuses on living entities and considers all species (and individuals) as having intrinsic value. Humans are considered a unique and special species, but not as being more worthy than other species. As such, the biocentric world view rejects discrimination against other species, or speciesism (a term similar to racism or sexism).

The ecocentric worldview considers the direct and indirect connections among species within ecosystems to be invaluable. It also includes consideration for non-living entities, such as rocks, soil, and water. It incorporates the biocentric worldview but goes well beyond it by stressing the importance of interdependent ecological functions, such as productivity and nutrient cycling.

Image 1.7. Ecological Impacts of Fossil Fuel Energy. The ecological impacts of fossil fuel extraction and combustion, such as from the coal strip mine pictured above, include destruction of vegetation and topsoil, contamination of surface and ground water, and atmospheric pollution. However, the combustion of fossil fuels yields a high-quality energy source. People with anthropocentric vs. ecocentric worldviews may differ in their support of this type of resource extraction and use. Source: “Garzweiler.strip.mine” by Ekem is licensed under CC BY-SA 3.0.

The frontier worldview asserts that humans have a right to exploit nature by consuming natural resources in boundless quantities. This worldview claims that people are superior and have a right to exploit nature. Moreover, the supply of resources to sustain humans is considered to be limitless, because new stocks can always be found, or substitutes discovered. The consumption of resources is considered to be good because it enables economies to grow. Nations and individuals should be allowed to consume resources aggressively, as long as no people are hurt in the process.

The sustainability worldview acknowledges that humans must have access to vital resources, but the exploitation of those necessities should be governed by appropriate ecological, intrinsic, and aesthetic values. The sustainability worldview can assume various forms. The spaceship worldview is quite anthropocentric. It focuses only on sustaining resources needed by people, and it assumes that humans can exert a great degree of control over natural processes and can safely pilot “spaceship Earth.” In contrast, ecological sustainability is more ecocentric. It considers people within an ecological context and focuses on sustaining all components of Earth’s life-support system by preventing human actions that would degrade them. In an ecologically sustainable economy, natural goods and services should be utilized only in ways that do not compromise their future availability and do not endanger the survival of species or natural ecosystems.

The attitudes of people and their societies toward other species, natural ecosystems, and resources have enormous implications for environmental quality. Extraordinary damages have been legitimized by attitudes based on a belief in the inalienable right of humans to harvest whatever they desire from nature, without consideration of pollution, threats to species, or the availability of resources for future generations. Clearly, one of the keys to resolving the environmental crisis is to achieve a widespread adoption of ecocentric and ecological sustainability world views.

The Environmental Crisis

The modern environmental crisis encompasses many issues. In large part, however, we can classify the issues into three categories: population, resources, and environmental quality. In essence, these topics are what this book is about. However, the core of their subject areas is the following:

• Population

In 2020, the human population numbered more than 7.68 billion, including about 330 million in the United States. At the global level, the human population has been increasing because of the excess of birth rates over death rates. The recent explosive population growth, and the poverty of so many people, is a root cause of much of the environmental crisis. Directly or indirectly, large population increases result in extensive deforestation, expanding deserts, land degradation by erosion, shortages of water, change in regional and global climate, endangerment and extinction of species, and other great environmental problems. Considered together, these damages represent changes in the character of the biosphere that are as cataclysmic as major geological events, such as glaciation. We will discuss the human population in more detail in Chapter 10.

• Resources

Two kinds of natural resources can be distinguished. A non-renewable resource is present in a finite quantity. As these resources are extracted from the environment, in a process referred to as mining, their stocks are inexorably diminished and so are available in increasingly smaller quantities for future generations. Non-renewable resources include metals and fossil fuels such as petroleum and coal. In contrast, a renewable resource can regenerate after harvesting, and if managed suitably, can provide a supply that is sustainable forever. However, to be renewable, the ability of the resource to regenerate cannot be compromised by excessive harvesting or inappropriate management practices. Examples of renewable resources include freshwater, the biomass of trees and agricultural plants and livestock, and hunted animals such as fish and deer. Ultimately, a sustainable economy must be supported by renewable resources. Too often, however, potentially renewable resources are not used responsibly, which impairs their renewal and represents a type of mining. The subject area of natural resources is examined in detail in Chapters 11, 12, and 18.

• Environmental Quality

This subject area deals with anthropogenic pollution and disturbances and their effects on people, their economies, other species, and natural ecosystems. Pollution may be caused by gases emitted by power plants and vehicles, pesticides, or heated water discharged into lakes. Examples of disturbance include clear-cutting, fishing, and forest fires. The consequences of pollution and disturbance for biodiversity, climate change, resource availability, risks to human health, and other aspects of environmental quality are examined in Chapters 13, 14, and 19 to 28.

Environmental Impacts of Humans

In a general sense, the cumulative impact of humans on the biosphere is a function of two major factors: (1) the size of the population and (2) the per-capita (per-person) environmental impact. The human population varies greatly among and within countries, as does the per-capita impact, which depends on the kind and degree of economic development that has occurred.

Paul Ehrlich, an American ecologist, has expressed this simple relationship using an “impact formula,” as follows: I = P × A × T, where:

• I is the total environmental impact of a human population
• P is the population size
• A is an estimate of the per-capita affluence in terms of resource use
• T is the degree of technological development of the economy, on a per-capita basis

Calculations based on this simple IPAT formula show that affluent, technological societies have a much larger per-capita environmental impact than do poorer ones.

How does the U.S.’s impact on the environment compare with that of more populous countries, such as China and India? We can examine this question by looking at two simple indicators of the environmental impact of both individual people and national economies: (a) the size of the human population, (b) the use of energy and (c) gross domestic product (GDP, or the annual value of all goods and services produced by a country). The use of energy is a helpful environmental indicator because power is needed to carry out virtually all activities in a modern society, including driving vehicles, heating or cooling buildings, manufacturing industrial products, and running computers. GDP represents all of the economic activities in a country, each of which results in some degree of environmental impact.

One of the major influences on the environmental impact of any human population is the number of people (the population size). The United States has a much smaller population (326.8 million) compared to China (1.415 billion) and India (1.354 billion; Figure 1.3).

Figure 1.3. Population Growth Between 1800 to 2019 for Selected Countries. Source: visualization by OurWorldinData.org is licensed under CC BY 4.0. Data from Gapminder, HYDE & UN Population Division (2019).

However, on a per-person basis, people living in the U.S. and Canada have much larger environmental impacts than do those living in China or India, as indicated by both per-capita energy use (Figure 1.4) and per-capita GDP (Figure 1.5). This difference is an inevitable consequence of the prosperous nature of the lifestyle of North Americans and other wealthier people, which on a per-capita basis is achieved by consuming relatively large amounts of natural resources and energy, while generating a great deal of waste materials. Sometimes this environmental effect of a wealthier population is referred to as “affluenza” (Image 1.8).

Figure 1.4. Fossil Fuel Consumption Per Capita (MWh) for Selected Countries in 2019. The environmental impacts of countries, and of their individual citizens, can be compared using simple indicators, such as the use of energy and the gross domestic product. Source: visualization by OurWorldinData.org is licensed under CC BY. Data from BP Statistical Review of World Energy.

Figure 1.5. GDP Per Capita by Country (US$) in 2017. The environmental impacts of countries, and of their individual citizens, can be compared using simple indicators, such as the use of energy and the gross domestic product. Source: visualization by OurWorldinData.org is licensed under CC BY. Data from the World Bank.

These observations drive home the fact that the environmental impact of any human population is a function of both (a) the number of people and (b) the per-person environmental impact. Because of this context, relatively wealthy countries like Canada and the U.S. have much larger environmental impacts than might be predicted based only on the size of their population. On the other hand, the environmental impacts of poorer countries are smaller than might be predicted based on their population. We can conclude that the environmental crisis is due to both overpopulation and excessive resource consumption.

Image 1.8. Modern Consumerism. Modern consumerism results in huge demands for material and energy resources to build and run homes and to manufacture and operate machines and other goods. In an environmental context, this is sometimes referred to as “affluenza.” Source: B. Freedman.

Ecologically Sustainable Development

Sustainable development refers to development of an economic system that uses natural resources in ways that do not deplete them or otherwise compromise their availability to future generations. In this sense, the present human economy is clearly non-sustainable. The reason for this bold assertion is that the present economy achieves rapid economic growth through vigorous depletion of both non-renewable and renewable resources (see Chapters 11, 12, 18). Economic growth and development are different phenomena. Economic growth refers to increases in the size of an economy because of expansions of both population and per-capita resource use. This growth is typically achieved by increasing the consumption of natural resources, particularly non-renewable ones, such as fossil fuels and metals. The rapid use results in an aggressive depletion of vital non-renewable resources, and even renewable ones. For example, former U.S. president Donald Trump intended to open up the Arctic National Wildlife Refuge for oil drilling by auctioning leases early in 2021. This action would have threatened the already fragile Arctic ecosystem and indigenous ancestral lands, while perpetuating the negative effects of climate change by further investing into fossil fuel extraction. While this action never came to fruition due to pushback from the general public and many state governments, it would have encouraged short-term economic growth at the expense of environmental degradation. In contrast, a comparable scale of investment in renewable energy initiatives, such as wind or solar power, or in energy conservation, would contribute more towards sustainable development.

Almost all national economies have been growing rapidly in recent times. Moreover, most politicians, economic planners, and business people hope for additional growth of economic activity, in order to generate more wealth and to provide a better life for citizens. At the same time, however, most leaders of society have publicly affirmed their support of sustainable development. However, they are confusing sustainable development with “sustainable economic growth.” Unfortunately, continuous economic growth is not sustainable because there are well-known limits due to finite stocks of natural resources, as well as a limited ability of the biosphere to absorb wastes and ecological damage without suffering irreversible degradation. This limit is a fundamental principle of ecological economics.

Economic development is quite different from economic growth. Development implies a progressively improving efficiency in the use of materials and energy, a process that reflects socio-economic evolution toward a more sustainable economy. Within that context, so-called developed countries have a relatively well-organized economic infrastructure and a high average per-capita income (because of their latter characteristic, they may also be referred to as high-income countries). Examples include Canada, the United States, Japan, countries of western Europe, and Australia. In contrast, less-developed or low-income countries have much less economic infrastructure and low per-capita earnings. Examples include Afghanistan, Bolivia, Myanmar, and Zimbabwe. A third group is comprised of rapidly developing or middle-income countries, such as Brazil, Chile, China, India, Malaysia, Russia, and Thailand.

A sustainable economy must be fundamentally supported by the wise use of renewable resources, meaning they are not used more quickly than their rate of regeneration. For these reasons, the term sustainable development should refer only to progress being made toward a sustainable economic system. Progress in sustainable development involves the following sorts of desirable changes:

• Increasing efficiency of use of non-renewable resources, for example, by careful recycling of metals and by optimizing the use of energy
• Increasing use of renewable sources of energy and materials in the economy (to replace non-renewable sources)
• Improving social equity, with the ultimate goal of helping all people (and not just a privileged minority) to have reasonable access to the basic necessities and amenities of life

Despite abundant public rhetoric, our society has not yet made much progress toward true sustainability. This has happened because most actions undertaken by governments and businesses have supported economic growth, rather than sustainable development. We will further examine these issues in Chapter 11 and other parts of this book.

Sustainable development is a lofty and necessary goal for society to pursue. But if a sustainable human economy is not attained, then the non-sustainable one will run short of resources and could collapse. This would cause terrible misery for huge numbers of people and colossal damage to the biosphere.

The notion of sustainability can be further extended to that of ecologically sustainable development. This idea includes the usual aspect of sustainable development in which countries develop without depleting their essential base of natural resources, essentially by basing their economy on the wise use of renewable sources of energy and materials. Beyond that, however, an ecologically sustainable economy runs without causing an irretrievable loss of natural ecosystems or extinctions of species, while also maintaining important environmental services, such as the provision of clean air and water. Ecological sustainability is a reasonable extension of sustainability, which only focuses on the human economy. By expanding to embrace the interests of other species and natural ecosystems, ecological sustainability provides an inclusive vision for a truly harmonious enterprise of humans on planet Earth. Identifying and resolving the barriers to ecological sustainability are the fundamental objectives and subject matter of environmental studies. It provides a framework for all that we do.

Conclusions

Environmental science is a highly interdisciplinary field that is concerned with issues associated with the rapidly increasing human population, the use and diminishing stocks of natural resources, damage caused by pollution and disturbance, and effects on biodiversity and the biosphere. These are extremely important issues, but they involve complex and poorly understood systems. They also engage conflicts between direct human interests and those of other species and the natural world.

Ultimately, the design and implementation of an ecologically sustainable human economy will require a widespread adoption of new world views and cultural attitudes that are based on environmental and ecological ethics, which include consideration for the needs of future generations of people as well as other species and natural ecosystems. This will be the best way of dealing with the so-called “environmental crisis,” a modern phenomenon that is associated with rapid population growth, resource depletion, and environmental damage. This crisis is caused by the combined effects of population increase and an intensification of per-capita environmental damage.

Finally, it must be understood that the study of environmental issues is not just about the dismal task of understanding awful problems. Rather, a major part of the subject is to find ways to repair many of the damages that have been caused, and to prevent others that might yet occur. These are helpful and hopeful actions, and they represent necessary progress toward an ecologically sustainable economy.

Questions for Review

1. Define environmental science, environmental studies, and ecology. List the key disciplinary fields of knowledge that each includes.
2. Describe the hierarchical structure of the universe and list the elements that encompass the realms of biology and ecology.
3. Identify the key environmental stressors that may be affecting an ecosystem in your area (e.g., a local park). Make sure that you consider both natural and anthropogenic stressors.
4. What is the difference between morals and knowledge, and how are these conditioned by personal and societal values?
5. Explain how cultural attributes and expressions can affect the ways that people view the natural world and interact with environmental issues.

Questions for Discussion

1. Describe how you are connected with ecosystems, both through the resources that you consume (food, energy, and materials) and through your recreational activities. Which of these connections could you do without?
2. How are your personal ethical standards related to utilitarian, ecological, aesthetic, and intrinsic values? Think about your world view and discuss how it relates to the anthropocentric, biocentric, and ecocentric worldviews.
3. According to information presented in this chapter, the U.S. and Canada might be regarded as being as overpopulated as India and China. Do you believe this is a reasonable conclusion? Justify your answer.
4. Make a list of the most important cultural influences that have affected your own attitudes about the natural world and environmental issues.

Exploring Issues

1. You have been asked by the United Nations to devise an index of national and per-capita environmental impacts that will be used to compare various developed and less-developed countries. Until now, the United Nations has used extremely simple indicators, such as energy use and gross domestic product, but they now want to use more realistic data. How would you design better indicators? What do you think would be the most important components of the indicators, and why?

References Cited and Further Reading

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