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Overview
The book begins by exploring the need for ecological science in understanding current environmental issues and briefly discussing what ecology is and isn’t. Subsequent chapters address critical issues in conservation and show how ecological science can be applied to them. The book explores questions such as:
• What is the role of ecological science in decision making?
• What factors govern the assembly of ecosystems and determine their response to various stressors?
• How does Earth’s climate system function and determine the distribution of life on Earth?
• What factors control the size of populations?
• How does fragmentation of the landscape affect the persistence of species on the landscape?
• How does biological diversity influence ecosystem processes?
Product Details
| ISBN-13: | 9781597265980 |
|---|---|
| Publisher: | Island Press |
| Publication date: | 03/19/2013 |
| Series: | Foundations of Contemporary Environmental Studies Series |
| Sold by: | Barnes & Noble |
| Format: | eBook |
| Pages: | 184 |
| File size: | 4 MB |
About the Author
Oswald J. Schmitz is a professor in the Yale School of Forestry and Environmental Studies. His research examines how the nature and strength of species interactions in ecosystems determine patterns in biodiversity and ecosystem function.
Read an Excerpt
Ecology and Ecosystem Conservation
By Oswald J. Schmitz
ISLAND PRESS
Copyright © 2007 Oswald J. SchmitzAll rights reserved.
ISBN: 978-1-59726-598-0
CHAPTER 1
Ecosystem Conservation: The Need for Ecological Science
IT IS BECOMING INCREASINGLY IMPOSSIBLE TO TALK ABOUT HUMANS' RELATIONSHIP to nature without mentioning ecology. More and more, this particular field of science is being called upon to play a leading role in illuminating and solving environmental problems. So much so that the environmental historian Donald Worster suggests that the twenty-first century might well be called the "Age of Ecology" (Worster 1994).
In the post–World War II era, ecological science has played a prominent role in identifying the cause of major environmental problems and motivating consequent policy to mitigate them. Rachel Carson's Silent Spring (1961) alerted us to the danger to humans and wildlife species of pesticides, which led to government regulation of chemicals in the environment. The investment of resources and brainpower to discover that phosphate pollution from households caused massive algae blooms that choke out other forms of life in major freshwater bodies (Schindler 1974) was nothing short of an ecological Manhattan project that led to the Clean Water Act. At the same time, the prospect that acid precipitation (Likens and Borman 1974), produced when sulphur and nitrous oxides from industrial and automobile emissions react and mix with atmospheric oxygen and hydrogen and rain back down, could corrode major terrestrial and aquatic ecosystems spurred tougher sulfate and nitrous emissions standards.
Ecological science successfully led to policy solutions to these problems because ecologists could easily trace the causal chain of effects: "the problems could be seen and smelled and their sources easily identified" (Speth 2004). The problems also were localized and they resonated with society because they directly jeopardized local livelihoods and well-being.
Solving other contemporary environmental problems, such as habitat fragmentation and attendant species extinctions (Simberloff and Abele 1976), has been a less successful enterprise. In this case, the solution to the problem—halting land development and massive scale resource extraction—is usually perceived as standing in the way of human enterprise and economic well being. Moreover, those most directly affected by such activity often are non-human species. And, in many cases, the direct consequences of the actions (e.g., tropical forest loss) occur in distant lands under different government regimes. In this case, the problems were "out of [immediate] sight" and so could be relegated "out of mind."
The irony in such reasoning is that we take great pains to understand how one kind of economy—the market economy—functions; and we take great pains to protect the integrity and functioning of the capital markets that drive economic progress. Society spends comparatively much less time thinking about, understanding, and protecting another major economy—the natural economy—resulting from ecosystem functions and services. Like market economies, myriad lines of dependency exist between species of producers and consumers within natural economies. Humans are not exempted from these dependencies. Any collapse in ecosystem functions, including collapse due to deforestation and fragmentation, stands to reverberate through the market economy, in turn, affecting human well being. Therefore, slogans such as "jobs versus the environment" that pit putative economic progress against measures to conserve ecosystem functions may be misguided. Ecosystems ultimately undergird and drive our economic stability.
The aim of this book is to offer insight into the link between the diversity of life—biodiversity—and the structure and functioning of ecosystems. As with the problems of the mid 1900s, the role of ecological science is central to identifying and illuminating the intricate ways that nature works. However, unlike in the past, the challenge for ecological science in discerning the causal chain of effects is becoming more difficult. But the challenge is surmountable. Meeting the challenge requires a new way of thinking about the intricate dependencies between humans and nature in society's endeavor to sustain long-term health and well being.
Human impacts are many, they are global in reach, and they often combine in synergistic or antagonistic ways at many different geographic scales. Thus, the effect of any single impact is often insidious and therefore requires decades to centuries before it becomes fully manifest. It becomes difficult to pinpoint a specific culprit for such ails as rising cancer levels, degradation of water quality, species' limb deformities, endocrine dysfunction, and many others. Answers require in-depth and critical understanding of the complex ways that species and impacts are linked.
Resolving this complexity is what makes ecological science exciting. At the same time, this complexity is what makes environmental problems ecologically "wicked problems" to solve (Ludwig et al. 2001). Murkiness about causality makes it very easy for governments to dismiss a putative cause of any one impact and therefore avoid action to solve the problem. But, is dismissing an environmental problem for lack of clear causal understanding a wise decision? Such a question cannot be answered without first having a clear understanding of the way that impacts propagate along the myriad lines of dependency within ecosystems.
This book aims to offer such understanding by conveying ecological principles that are relevant to the grand scientific questions about sustaining ecosystem functions. In identifying those questions I take some guidance from a forward-looking report produced in the early 1990s on behalf on the Ecological Society of America titled "The Sustainable Biosphere Initiative" (Lubchenco et al. 1991). This report first underscored the point that most of the environmental problems that human society faces are fundamentally ecological in nature.
In anticipation of the increasing need for ecologists to play a leading intellectual role in solving environmental problems, the authors—leading senior ecologists—developed a plan of action to assemble critical scientific knowledge required to conserve and to wisely manage global ecosystems in the twenty-first century. This report recognized that citizens, policy makers, resource managers, and leaders of business and industry routinely must make decisions concerning the exploitation of resources, but that these decisions cannot be made effectively with limited understanding of the interplay between human domination of ecosystems and impacts on ecosystem function.
According to the report, effective environmental decision-making requires better scientific understanding on three major issues at the nexus between human society and their exploitation of ecosystems:
• Global Change, which includes the ecological consequences of natural and human-caused changes in climate, soil properties, water quality, and land- and water-use patterns.
• Biological Diversity, which includes the natural basis for the distribution and abundance of species and habitats, human-caused alterations to those patterns locally as well as globally, and the link between diversity and the sustainable functioning of ecosystems.
• Sustainable Ecological Systems, which includes the response of ecological systems to exploitation and disturbances, the restoration of ecosystems, the sustainable management of ecological systems, and the interface between ecological processes and human social systems.
I deal with each of those issues consistently throughout the book. But each issue can grade into the other. For example, global change through conversion of forest land into agriculture can impact the distribution and abundance of species—biodiversity. Thus, rather than treat each issue separately, they are interwoven throughout book. The Sustainable Biosphere Initiative report also points out that in order to make effective choices and decisions about the environment in light of these issues we need to answer several big questions about ecology and ecological systems. These questions are:
1. What is the role of ecological science in decision-making?
2. What factors govern the assembly of ecosystems and determine their response to various stressors?
3. How does the earth's climate system function and determine the distribution of life on Earth?
4. What factors control the size of populations?
5. What are the population level consequences of species' life-history adaptations?
6. How does fragmentation of the landscape affect the persistence of species on the landscape?
7. How does biological diversity influence ecosystem process?
8. What ecological principles need to be considered in the design of strategies to protect biological diversity?
My aim here is to address these big research questions by structuring the narrative around example environmental problems. At the same time I will show how the questions posed in the Sustainable Biosphere Initiative document have lead to fresh ways of thinking about ecosystems that are directly relevant to solving problems, including the link between biodiversity and ecosystem functioning, valuing ecosystem services, interconnections of ecosystems across geographic scales, and emergence of ecosystem properties consequent to species sorting processes on landscapes.
I deal with each of the questions in individual chapters. The chapters highlight the latest concepts aimed at answering the big research questions. The book then closes with a final chapter that addresses the need, not only to understand ecological science, but to put that science into an ecosystem ethics perspective. It also returns to and answers the question: Is it wise for policy makers to dismiss environmental problems when their cause is uncertain?
In answering this question, I recognize that society must reconcile significant trade-offs between human health and economic welfare and the protection of natural ecosystem function. One role of ecological science, as I see it, is not to judge, but rather to illuminate the ecological consequences of different potential choices that might be made. Another role, which I also try to convey, is to engender new thinking and awareness of the looming spatial and temporal scales of our impact on nature as globalization of market economies increases the human footprint on the environment.
CHAPTER 2The Science of Ecology
ASK SOMEONE TO DESCRIBE AN ECOLOGICAL SYSTEM AND YOU MIGHT GET the response that it is a group of organisms living together in a fixed place. This is a view likely derived from the familiar elementary school science experiment in which soil, water, nutrients such as nitrogen, bacteria, worms, some plants, and perhaps some herbivores such as snails or insects are put into a hermetically sealed glass container, placed in sunlight, and then left to their own devices. Observers of this experiment always marvel that this simple ecosystem is able to maintain itself indefinitely without any kind of nutrient or species input from the outside. This is because the experiment does not merely assemble a haphazard collection of species. Rather, the experiment deliberately assembles species that together create a natural economy involving a chain of production and consumption, albeit of food energy and nutrients, but an economy nonetheless. In this economy, plants draw up water and nutrients from the soil and carbon dioxide from the air and are stimulated by sunlight to convert those different chemicals into tissue; herbivores eat that plant tissue and when old individuals die the chemical constituents of their body are broken down by worms and bacteria and are recycled back through the system. This economy functions whenever the important lines of dependency, that is the linkage between consumers and their resources and the recycling feedbacks, are sustained.
This simple container system is a powerful metaphor for the way species assemble and interact in nature. The processes of production and consumption are fundamental to sustaining the functioning of all ecological systems globally. Natural ecological systems differ from the container system in that they are comprised of vastly more species with many more interdependencies than those found in the glass container. Understanding these complex interdependencies is the fundamental purpose of that subfield of biology known as ecology.
What Is Ecology?
Ecology is a science aimed at understanding:
• The processes by which living organisms interact with each other and with the physical and chemical components of their surrounding environment.
• The way those processes lead to patterns in the geographical distribution and abundance of different kinds of organisms.
The result of the process leading to a pattern is the assembly of a natural economy. In ecology such a natural economy is formally called an ecosystem.
Ecosystems encapsulate many forms of biological diversity (also called biodiversity). Biodiversity results from a variety among individuals comprising a species owing to sex, age, and genetic differences among those individuals. It also stems from differences between species living together in a geographic location. For example, species may differ in their functional roles (e.g., plant, herbivore, carnivore) and the efficiency with which each carries out its function in different environmental conditions. Biodiversity also arises from the myriad ways that species are linked to each other in ecosystems. As a consequence of these many forms of biodiversity, there is considerable complexity underlying the structure of ecosystems. The challenge in ecology is resolving this complexity.
Resolving Ecological Complexity
One way to begin resolving complexity is to envision an ecosystem as comprised of vertical food chains in which soil nutrients are linked to plants, plants are linked to herbivores, and herbivores are linked to carnivores. Such linkages indicate that plants are consumers (predators) of soil nutrients, herbivores are consumers (predators) of plants, and carnivores are consumers (predators) of herbivores. Ecologists give such consumer-resource interactions a special name—trophic interactions. Species engaging in a particular kind of trophic interaction belong to the same trophic level of the food chain. So, for example, species engaging in herbivory belong to the herbivore trophic level, species preying on herbivores belong to the carnivore trophic level, and so on.
In addition, plant species are limited by, and thus must compete for, light and soil nutrients. Herbivore species may therefore compete for limited plant resources and carnivores may potentially compete for an even more limited number of herbivores that comprise their prey. Limiting resources and the need to compete for them can lead to ecological innovation in the way species vie for their share of resources. Thus, we can elaborate our vertical conception of an ecological system by envisioning horizontal linkages within a trophic level as species engage in various strategies to maximize consumption of particular resources.
Conceptualizing Predation and Competition
Together, the vertical chain comprised of consumer-resource links coupled with horizontal links between species at the same trophic level create a highly interconnected web of life—a food web. Individual species within this web are sandwiched between their predators, their resources, and their competitors. The easiest way to imagine the implications of such complexity is to begin by drawing food web diagrams that depict the interdependencies among species created by their linkages and the nature of each species' net effect on the other species (figure 2.1). Such an approach assumes that we can ignore the diversity of individuals within a species and understand interactions simply on the basis of a typical or average individual. This is a good staring point for conveying principles that can be later elaborated with the added complexity of variety within a species.
In the case of a consumer-resource interaction, the arrow pointing from the consumer to the resource is denoted by a minus sign and the arrow pointing from the resource to the consumer is denoted by a plus sign (figure 2.1a) called a (+/-) link. This implies that the consumer derives a net nutritional benefit (hence +) by directly feeding on the resource; and the resource, being the victim suffers a cost (hence -). If the victim is another animal, then the cost is the victim's life. If the victim is a plant, then the cost is loss of some plant tissue such as leaves or stems. (Herbivores rarely kill and consume an entire plant—leaves, flowers, stems, and roots—in the same way that carnivores kill and consume their herbivore prey.)
(Continues...)
Excerpted from Ecology and Ecosystem Conservation by Oswald J. Schmitz. Copyright © 2007 Oswald J. Schmitz. Excerpted by permission of ISLAND PRESS.
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Table of Contents
PrefaceChapter 1. Ecosystem Conservation: The Need for Ecological Science
Chapter 2. The Science of Ecology
-What is Ecology?
-Resolving Ecological Complexity
-Life as a Game
-Ecological Science: Gaining Reliable Knowledge about Ecosystems
Chapter 3. Climate-Template for Global Biodiversity
-The Physics Underlying Life on Earth
-Ecosystem Types
-Coping With with Climate
-Climate-Space
-Effects of Global Climate Change
Chapter 4. Ecological Limits and the Size of Populations
-Simple Population Growth
-Ecological Balance and Carrying Capacity
-Competitors and Predators
-Weather
-Carrying Capacity and Population Overabundance
Chapter 5. Viability of Threatened Species
-Life-Cycles and Population Dynamics
-Modeling Age-Structured Population Dynamics
-Viability of Loggerhead Sea Turtles
Chapter 6. Biodiversity and Habitat Fragmentation
-Diversity Indices
-Habitat Fragmentation and the Species-Area Relationship
-Habitat Fragmentation and Population and Community Processes
Chapter 7. The Web of Life: Connections in Space and Time
-Ecosystems in Time
-Ecosystems in Space: Linkages Across Geographic Boundaries
Chapter 8. Ecosystem Services of Biodiversity
-Diversity Begets Ecosystem Stability
-Diversity-Productivity Relations
-Crop Pollination
-Pest Control
-Invasion Resistance
Chapter 9. Protecting Biological Diversity and Ecosystem Function
-Conservation Tools
-Dynamic Landscapes
-Global Climate Change and Reshuffling of Faunas
Chapter 10. The Good of a Species: Toward a Science-Based
-Ecosystem Conservation Ethic
-Tinkering with Economies
-Ecological Science, Uncertainty, and Precaution
-Policy and Management as a Scientific Enterprise
-Questions for Discussion
References
Further Reading
Glossary
About the Author
Index