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Introduction Concern for the quality of the environment has been evident in the United States for over 100 years. One result of this concern has been the passage of laws, regulations, and treaties that require actions to preserve environmental quality or that inhibit actions detrimental to the environment. These legislative acts have caused the investment of large amounts of time, effort, and money in analyses of the possible envi- ronmental impacts of specific development projects or management decisions. For two reasons, the effectiveness of these analyses and the magnitude of resources devoted to them are controversial (Goodman, 1975; Schindler, 1976; Suter, 1981~: available scientific information is often not used effectively in their preparation, and research conducted to provide additional information is often inadequate. It is also com- monly perceived that massive studies yield predictions that are little better than those produced with much less effort, cost, and time. This report, by the Committee on Applications of Ecological Theory to En- vironmental Problems, in the Board on Basic Biology of the National Research Council's Commission on Life Sciences, deals with both prob- lems. It explores how the scientific tools of ecology can be used more effectively in dealing with a variety of environmental problems. "Ecological theory," as described in standard textbooks on ecology, is seldom applied directly to environmental problems. But ecological "knowledge" including not only theory, but also facts, observations, research results, syntheses, models, and methods of investigation has been extremely important in developing approaches to a wide range of

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2 INTRODUCTION environmental problems. This report discusses knowledge that has proved useful and how it has been used. It deals with a wide range of envi- ronmental issues, including prediction and management of environ- mental impacts, management of renewable resources, protection and restoration of species and ecosystems, control of agricultural and sil- vicultural pests, and use of generic ecological studies to promote un- derstanding of classes of environmental problems. Rather than focusing on what is wrong with the way ecology is often applied, we use suc- cessful applications to show how ecological knowledge can be valuable when used appropriately. Environmental assessment and management are based on societal goals, which are not always clearly articulated. The social effects of environ- mental changes and the way goals are developed by society are important aspects of environmental problems. Nevertheless, we treat only the bio- logical side of environmental problems, to avoid taking on an unman- ageably large task. The report does not attempt to cover all aspects of ecology. To have done so would have made our task unacceptably difficult and the report unacceptably long. We have focused on different kinds of ecological knowledge and appropriate arenas for their use, but have restricted the coverage of subjects and have not provided details of methods, except as examples or in the case studies. The subjects covered were determined by the experiences of the com- mittee members. Ecological subjects that have interfaces with chemistry, geology, and hydrology have been slighted, except in some of the case studies (e.g., Chapters 20, 21, 23, and 241. Thus, detailed discussions of such subjects as CO2 buildup, acid deposition, ecotoxicology, and the effects of complex chemical mixtures in the environment are lacking. For treatment of these important topics, the reader is referred to several recent reviews (e.g., Harshbarger and Black, in press; Maki etal., 1980; National Research Council, 1976, 1981, 1982, 1983a,b,c, 1984, in press a,b; Reif, 1984). Among the most important methods some of which have changed the scope and scale of ecological research that do not receive explicit treat- ment in this report are equations for estimating environmental partitioning of chemicals and related phenomena, such as transformations and trans- port; hazard evaluation protocols and risk assessment; validation; decision analysis; remote sensing; interpretation of photographs and satellite pho- tography; and bioassays. Some methods such as modeling, statistical analysis, and use of computers-are not discussed specifically, but appear in many of the chapters of Part I and the case studies.

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INTRODUCTION Structure 3 STRUCTURE AND AUDIENCE OF THE REPORT The report is divided into "What we know" (Part I) and "How our knowledge is applied" (Part II). Chapters 1-5 treat a number of categories of ecological knowledge and Chapters 6-10 discuss procedures and kinds of knowledge that are common to most environmental problems. Part II presents studies of 13 specific cases of environmental problem-solving. The first three chapters deal with populations of single species, inter- actions between two species, and community ecology. They focus on the kinds of information that are available and how that information might be useful in solving environmental problems. Chapter 4 discusses the flow of energy and materials through ecosystems; Chapter 5 deals with the effects of changes in time and space scales on ecological processes and products. Chapter 6 explores the benefits of treating environmental ma- nipulations as large-scale experiments so that we can learn more from them. Chapters 7 and 8 discuss biological monitoring and the management of ecological systems in the face of the substantial uncertainty associated with the behavior of those systems. Chapter 9 deals with cumulative environmental changes that result from repeated perturbations. There is increasing recognition that some of our most severe environmental problems involve the cumulative effects of many small local actions individually insignificant, but collectively cre- ating major regional and even global changes. The discussion points out the major issues associated with cumulative effects, which have only recently begun to receive serious consideration, but which present some of the most difficult challenges to decision-makers. Chapter 10 deals with procedures for application of ecological knowl- edge. It begins with a discussion of how ecology can help in concep- tualizing a problem and in devising appropriate approaches to its solution. We focus on the design of ecological studies for predicting and managing the effects of manipulations, emphasizing the importance of monitoring projects and decisions to determine their consequences. Part II discusses 13 cases chosen as instructive examples of the appli- cation of ecological knowledge to various kinds of problems. The cases were selected because the committee members and consultants who were asked for suggestions were familiar with them and believed that they would reveal the challenges of applying ecological knowledge, show the diffi- culty of predicting accurately the behavior of complex systems, and point out the substantial value of monitoring the results of manipulations. The

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4 INTRODUCTION cases were chosen to exemplify scientifically sound uses of ecological knowledge. No attempt was made to achieve comprehensive coverage; of necessity, the cases are a small sample of a large universe of potentially informative examples. Audience This report is intended for a broad audience, including: Those who prepare, receive, and use environmental evaluations and management plans. Legislators and regulators concerned with environmental issues. Teachers and students in the natural and environmental sciences. TYPES OF ECOLOGICAL KNOWLEDGE The chapters in Part I discuss the ways in which ecological knowledge has been applied in a variety of environmental problems, from the man- agement of renewable resources to the prediction of environmental im- pacts. A few common themes run through these chapters. The themes are related to the basic characteristics of ecological systems that are of fun- damental importance to understanding their responses to perturbations. Complex Linkages Because of the complex linkages between species in ecosystems, the effects of changes are often indirect. Obvious and direct influences on the objects of study are sometimes not as important as less obvious indirect influences. Problem-solvers can find it helpful to develop diagrams that show both direct and indirect influences and show the pathways through which indirect agents exert their influences (Andrewartha and Birch, 1984~. Such diagrams are accounting schemes that help to identify important environmental factors. The case studies in Part II contain many examples of indirect effects, such as the effect of DDT on birds far from sites of its application (Chapter 24) and the mobilization of mercury that results from changing the level of a lake (Chapter 211. These phenomena could not have been predicted by analyses that concentrated on direct effects. In addition, many ecological interactions are characterized by strong non- linear effects brought about by slight changes in key factors.

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INTRODUCTION Density Dependence Because environments are finite and resources might not be renewed as quickly as they are harvested, the success of individuals often depends on the number of individuals of the same and other species in their en- vironments. Often, but not always, conditions deteriorate for individuals as the numbers of individuals of the same species, predators, and parasites increase. Conversely, conditions can improve when the numbers of in- dividuals of those classes decrease. It is therefore often possible to extract much higher sustainable yields from populations than would be expected on the basis of an examination of birth, growth, and death rates in an unharvested population existing close to the limit set by environmental resources. Alternatively, high population densities in most areas could prevent individuals displaced by a perturbation from moving into other areas. Very low densities might influence the probability of finding mates, erode genetic diversity of a population, and increase the probability of its extinction. The existence of density-dependent effects does not necessarily imply that populations exist at steady densities. These effects can cause populations to fluctuate regularly or irregularly (May 1973), as did the blowflies studied by Nicholson and Bailey (1935) and the bean weevil Callosubrochus chinensis studied by Utida (1957~. Moreover, density- independent effects can often mask density-dependent ones, because they are often much larger. The Uniqueness of individuals Each individual in a sexually reproducing population is unique, as opposed to many nonliving entities (e.g., all CO2 molecules can be treated as identical). A species is composed of different age and sex classes, and genetic variation occurs within each class. Plants with open growth systems often have substantial intraindividual variability that is important for con- sumers of the plants (Whitham et al., 19841. Because of genetic variability, management practices can create selective pressures that cause genetic and thus phenotypic changes in a population that sometimes subvert the goals of the management practices (Chapter 11. Keystone Species Keystone species are those which exert influences over other members of their ecological communities out of proportion to their abundances. Keystone species can have various roles in ecological communities. For example, dominant plants are the major photosynthesizers in communities,

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6 INTRODUCTION and they also form the physical structure in which many interactions in the system take place. Keystone predators preferentially eat prey that would be competitive dominants in the absence of predation. As a result, keystone predators create conditions favorable for the existence of species that are crowded out of systems with less predation. Keystone predators have been most commonly identified among predators on sessile prey- such as plants and sessile marine invertebrates of rocky shores-that compete for space (Harper, 1969; Hurlbert and Mulla, 1981; Lubchenco, 1978; Morin, 1983; Paine, 1974; Paine and Vadas, 19691. Keystone mu- tualists are essential for survival of other members of their communities, even though the amount of resources they consume is sometimes small. Well-known examples are pollinators and frugivores, ants that patrol and protect plants, and microorganisms associated with vascular plants (Alex- ander, 1971; Gilbert, 1975; Howe, 1981; Janzen, 1966~. Because changes in the populations of keystone species can influence community dynamics in major ways, astute environmental problem-solvers are alert to keystone relationships in the communities being altered (Chapter 3~. Biological Magnification' Organisms are united through food chains, so materials taken up by prey can accumulate and become concentrated in their predators. Passage of substances through several trophic levels in a community can result in concentrations hundreds of times those initially present in the environment. The greatly magnified indirect effects of pesticides like DDT, which are metabolically stable and fat-soluble, constitute a striking case of biological magnification (Chapter 244. Population Fragmentation Human activities often change large patches of, say, forest or prairie into small patches surrounded by land devoted to other purposes (such as agriculture, forest plantations, highways, and cities). Fragmentation of habitats sets in motion processes that can cause unexpected changes in the system. Among these processes is the loss of species unable to exist in small patches (Chapter 51. An important management implication is the need to provide corridors of suitable habitat through which individuals can travel between more extensive patches of appropriate habitat. Ignoring the larger, heterogeneous environment in which local populations of in- terest are set can lead to poor management of those populations (Chapters 17 and 194.

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INTRODUCTION 7 Stability Boundaries "Stability," the tendency of ecological systems to remain in a relatively constant state, can result from several processes (Orians, 19751. Of con- cern to the manager and environmental problem-solver are the resistance of a system or a component of it to change, the speed with which it returns to its previous state when the perturbation ends, and its stability bound- aries the range over which it can be changed without leaving it unable to return to its previous state (Holling, 19731. The crossing of stability boundaries or thresholds by individual organisms can lead to large changes in their functioning. Photoperiods above a threshold might be necessary to induce a plant to flower or an animal to come into breeding condition (e.g., Farner, 1964; Salisbury and Ross, 1978; Sundararaj and Vasali, 19764. A critical minimal density of prey might be necessary for a par- ticular kind of predator to survive in an area. A specific patch size of suitable habitat might be necessary for a particular species to survive (Chapter 171. An organism might be able to withstand temperatures down to or up to a critical point, but not beyond. Stability boundaries are also important for more complex ecological systems. For example, environmental change and overharvesting can cause persistent changes in the composition of fish stocks (Dean, 1980; Gulland and Garcia, 1984; Chapters 1 and 81. Overgrazed plant communities might be resistant to invasion by new species, even if grazing ceases. These "alternate stable states" are usually less desirable from the human per- spective, but some are seen as beneficial, as when a shrub stage resistant to invasion by trees is established as a low-maintenance community along roads and powerline rights of way (Niering and Egler, 19551. Managing systems to achieve greater constancy, a common human objective, can reduce their ability to withstand perturbations. For example, the suppres- sion of spruce budworrn populations in eastern Canada through the use of insecticides achieved the intended preservation of the pulp and paper industry in the short run, but left the forests and the economy more vulnerable to outbreaks of a size and intensity that would be impossible in undisturbed forests (Holling, 19731. It is especially important for the environmental problem-solver to rec- ognize that these thresholds are sometimes not apparent until after they have been crossed. An important role of ecological knowledge is to suggest what such thresholds are likely to be. Aggregate Variables Ecologists and other scientists use aggregate variables in several ways. Typically, entities are grouped on the basis of shared characteristics. These

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8 lNrRODUCTlON might be traits shared because of common ancestry, such as the dorsal, hollow nervous system of all vertebrates; they might result from inde- pendent adaptations, as in the aggregate entity "herbivores." Ecological guilds groups of species that use common resources in similar ways- are examples of aggregates consisting of units connected by strong inter- actions. Aggregates can also be based on some composite process or product, such as productivity or biomass, that is deemed to be of theoretical or applied interest. Analysis of complex systems requires the use of aggregate variables. Aggregate variables should be designed to capture the essence of traits or processes. It is the nature of aggregate variables that they lose substantial amounts of information; but essential information should not be sacrificed. A major challenge in using ecological information to help in solving environmental problems is to delineate aggregrate variables, their prop- erties, and what will be gained and lost if they are adopted. Complexity and Uncertainty Ecological theory is most fully developed for relatively simple systems, which have relatively small numbers of interacting units. Ecology's great- est predictive success occurs in cases that involve only one or two species. That is why, for example, management of game and fish populations through regulation of hunting and fishing is often successful. Predicting the outcome of interactions among many species is much more difficult. Therefore, most environmental problem-solving entails considerable un- certainty. Wise problem-solvers learn to expect the unexpected and to develop approaches that allow them to learn as they proceed, altering their responses as they learn more about the system and avoiding irrevocable actions (Chapter 8~. Scales in Space and Time Processes and products in ecological systems are strongly influenced by differences in scale (Addicott, 1978; Andrewartha and Birch, 1954, 1984; Levin, 1974; Wiens, 1976; Chapter 5~. Large lakes are not simply smaller lakes made bigger, and a large expanse of forest is not the same as a collection of small woodlots. Patchy environments have more edges in proportion to their area than do homogeneous environments; they create dispersal problems for organisms inhabiting them, and they lead to high local extinction rates. Speciation, particularly of large organisms, requires large expanses of suitable habitat (Soule and Wilcox, 1980) larger, in fact, than most parks and reserves. Success in achieving some local goal

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INTRODUCTION 9 can set in motion processes that cause regional results opposite to those desired (Chapter 191. Populations of some species are maintained by high rates of reproduction in a small fraction of the area that they occupy; populations in the rest of the area depend on a steady supply of immigrants from sites with high reproductive rates. Evolutionary changes can cause both interacting organisms and the results of their interactions to change, often rapidly enough to be important for the environmental problem-solver (Chapter 1~. APPLICATIONS OF ECOLOGICAL KNOWLEDGE The chapters of Part I are organized in part by their ecological content. Chapters 1-5 deal with a variety of kinds of ecological knowledge, many having specific applicability to different kinds of problem-solving. Chap- ters 6-10 deal with knowledge and procedures that are more general in their applicability. We briefly summarize here the parts of the report that deal with particular kinds of application (see Table 1) so that users can more easily tap the sources of knowledge most important to them. Renewable-Resource Management Renewable-resource management refers to commercial and recreational harvesting of animals and plants. The important topics of population growth, life histories, habitat selection and other behaviors, genetics of popula- tions, and evolution in response to management are dealt with in Chapter 1. Equally important for managers are interactions between populations (Chapter 2) and energetics i.e., productivity and nutrient requirements (Chapter 41. Examples of renewable-resource management are discussed TABLE 1 Kinds of Applications of Ecological Knowledge and Where They Are Discussed Application Renewable-resource management Conservation of species Control of pests and diseases Impact assessment and prediction of effects Preservation of communities Preservation of habitat Contaminants and toxic substances Mitigation of effects of construction Restoration General applications Chapter 1,2,4, 12, 19 1-3, 5, 8, 17 1-3, 13-15, 24 6-9, 16, 21-24 3-5,8, 18,20 7-9, 17, 18,20,23 4, 7, 9, 20-22, 24 7, 10, 16, 18, 21 3-5,8, 18 6-10

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10 INTRODUCTION in detail in Chapter 12 (managing a fishery) and Chapter 19 (managing a forest). Conservation of Species Closely related to the commercial and recreational harvest of plants and animals is the protection of species that lack commercial value, but that have aesthetic value or that play important roles in ecosystems valued for other reasons. Species conservation requires knowledge of the ecology of the species (Chapter I), its interactions with other species (Chapter 2), and its relationships to its ecological community (Chapter 31. The size and shape of the available habitat and the population size of the species needed to ensure its survival for acceptably long periods are central to management decisions (Chapter 5), as is knowledge of environmental and demographic variability (Chapter 81. Application of such knowledge to the conservation of populations of spotted owls is discussed in Chapter 17. Control of Pests and Diseases The control of pests and diseases usually requires knowledge of the natural history and population characteristics of the pests and their victims (Chapter 1) and understanding of their interactions (Chapter 2) and of the ecological communities in which they occur (Chapter 31. Attempts to control pests and diseases often result in the evolution of resistance, which tends to reduce the effectiveness of the programs (Chapter 11. Cases of control are discussed in Chapter 13 (vampire bats), Chapter 14 (biological control of citrus pests), Chapter 15 (malaria vectors), and Chapter 24 (results of attempts to control insects with DDT). Impact Assessment and Prediction of Effects Predicting effects and assessing potential impacts of activities require knowledge of present conditions (Chapter 7) and of the variability inherent in nature and the uncertainties of science (Chapter 81; without such knowl- edge, effects cannot be reliably detected and the causes of change cannot be understood. Because the effects of a project can combine with effects of other projects elsewhere, and the effects of distant projects can add to the effects of the project under consideration, potential cumulative effects might require modifications in project design (Chapter 91. It is often useful to compare the situation under consideration with similar ones elsewhere and to carry out pilot studies (Chapter 61. Cases of impact assessment are

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INTRODUCTION discussed in Chapter 16 (predicting the effects of construction on a herd of caribou), Chapter 21 (predicting the effects of freshwater impound- ment), Chapter 22 (studies of the effects of ionizing radiation), Chapter 23 (studies of the effects of clearcutting), and Chapter 24 (predicting and learning the effects of the use of DDT and application of that knowledge to other cases). 11 Preservation of Communities When the management goal is the preservation of entire communities of organisms, an understanding of community ecology (Chapter 3), of productivity and nutrient cycling (Chapter 4), and of the required space and time scales (Chapter 5) is important. Natural variability in climate and community patterns will also affect preservation efforts (Chapter 81. Chapter 18 (restoration of communities of plants on derelict lands) and Chapter 20 (protecting a lake ecosystem from the effects of eutrophication) discuss examples of such applications. Preservation of Habitat The conservation of communities and species requires preservation of the habitat in which those organisms live. Monitoring both before and after efforts are initiated is necessary to determine the success of the efforts (Chapter 71. The variability of natural systems and the cumulative effects of various activities, often far from the site of concern, can strongly influence the outcome of preservation attempts (Chapters 8 and 9~. Some aspects of habitat preservation are treated in Chapters 17, 18, 20, and 23. Contaminants and Toxic Substances The pervasive and crucial issues of pollution and exposure to toxic chemicals are relatively neglected in this report, but the transport of chem- icals is discussed in Chapter 4, indicator species and biological monitoring to detect pollutants and toxic chemicals are discussed in Chapter 7, and the problem of cumulative effects (e.g., several sources of pollutants) is discussed in Chapter 9. Specific examples are presented in Chapter 20 (excess nutrients), Chapter 21 (chemistry and hydrology related to heavy metals), Chapter 22 (ionizing radiation), and Chapter 24 (persistent pes- ticides).

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12 INTRODUCTION Mitigation of Effects of Construction Mitigation of undesired side effects of projects is often economically, aesthetically, or legally motivated. If done after the project is completed, it might take the form of restoration (see below); but the best approach to mitigation is to make it unnecessary by appropriate design of the project. This requires careful planning and scoping (Chapter 10), as well as careful monitoring (Chapter 71. Chapter 16 (protecting caribou during hydro- electric development) and Chapter 21 (raising the water level of a lake) provide examples of including mitigation efforts in the design of a project; Chapter 18 (restoration of derelict land) describes mitigation of effects of projects completed many years earlier. Restoration To restore an ecosystem, one must have a goal to work toward. This requires some knowledge of previous conditions. Success in reaching the goal depends on knowledge of community structure (Chapter 3), of pro- ductivity and nutrient requirements (Chapter 4), of the space and time scales that will be needed for success (Chapter 5), and of natural variation in biotic and abiotic factors (Chapter 81. Chapter 18 describes the resto- ration of plant communities on derelict lands in Britain. General Applications Some issues, procedures, and kinds of knowledge common to most environmental problems are treated in Chapters 6-10. There is always uncertainty, both in the abiotic environment and in organisms' responses to perturbations (Chapter 8~. And there is always a need for rigorous scientific procedures and careful scoping, even when time and money are short (Chapter 10~. It is always helpful to compare the case at issue with similar ones; it is often useful to conduct pilot experiments, if feasible (Chapter 64. Potential cumulative effects are often a concern, and moni- toring is almost always necessary to ascertain current conditions, to detect variability, and to measure the effects of actions (Chapter 71. THE CASE STUDIES The objective of Part II is to show how ecological knowledge has been used in planning and carrying out problem-solving efforts, including how the knowledge has been limited and how it has had to be adapted to the

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INTRODUCTION 13 details of specific problems. The case studies are referred to repeatedly in Part I. The existence and application of scientific knowledge do not guarantee correct predictions. Ecological systems are complex, situations are often unique, and predictive ecological theories are sometimes inadequate. Nonetheless, when scientific predictions turn out to be inaccurate, the results can reveal important aspects of the limitations of even the best available scientific approaches and show the need to increase the knowl- edge base on which decision-makers depend. We selected examples to cover a wide array of types of environmental problem-solving (Table 21. In some of our cases such as those of the North Pacific halibut, the spotted owl, and the Newfoundland caribou- protection of a single species or achievement of a sustained harvest was the goal. In the malaria, red scale, and vampire bat cases, the goal was to eliminate an organism or at least to reduce it enough to render the damage it caused acceptable. Problem-solving oriented toward manipu- lating a single species can draw on general ecological knowledge, such as population dynamics and predator-prey theory, and on the results of previous efforts. As the case studies show, proper targeting of management usually requires a great deal of knowledge about the natural history of the organisms in question. Other case studies deal with problem-solving at the community level. The objective might have been the achievement of a sustained steady yield of useful products from a combination of species, as in the New Brunswick forest case, or the creation of a functioning ecological community similar to one that existed before the influence of human disturbance, as in the Lake Washington and derelict lands cases. In some cases, the purpose was to anticipate, and thereby to reduce, the undesirable impacts of a future project. For example, in the Southern Indian Lake case, the lake was altered for hydroelectric power generation, in the hope that it would not impair other uses of the lake. Still other case studies deal with projects in which the objective was to determine the impacts of practices that take place in many locations over a broad area. Some of these practices are subject to legal regulation (use of pesticides, forestry practices, and uses of nuclear energy), and case studies can help to determine what kinds of legal restraints might be properly applied to reduce unwanted consequences in natural environ- ments. As examples we have chosen the use of DDT in the United States, forest clearcutting, and the effects of nuclear radiation on ecological com- munities. In the latter two, a major objective was scientific. To ensure consistent emphasis of particular points, we adopted a general format for the presentation of case studies. The preparer of each case

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14 TABLE 2 Synopsis of Case Studies Presented in Part II INTRODUCTION Short Title Type of Case Subject Halibut (Chapter 12) Vampire Bat (Chapter 13) Red Scale (Chapter 14) Malaria (Chapter 15) Caribou (Chapter 16) Spotted Owl (Chapter 17) Derelict Lands (Chapter 18) New Brunswick Forest (Chapter 19) Renewable-resource manage- ment Pest control Pest control Disease control Impact assessment Species conservation Ecosystem restoration Renewable-resource manage- ment Lake Washington Ecosystem protection (Chapter 20) Southern Indian Lake (Chapter 21) Managing an international marine fishery Chemical control of a para- site on cattle in Central America Biological control of a pest on citrus crops in Califor- nia Experimental study of chem- ical control of a malaria vector Protecting a caribou herd during hydroelectric de- velopment Managing a regional popula tion of a rare species Restoring seminatural plant communities in mined areas Developing a model for Impact assessment long-term regional forestry management Predicting and controlling cumulative impacts of sewage effluent in an ur- ban lake Predicting impacts of raising the level of a subarctic lake Nuclear Radiation Generic ecological studies Ecological effects of nuclear (Chapter 22) radiation Forest Clearcutting Generic ecological studies Ecological effects of clear (Chapter 23) cutting forests DDT Pesticide use Ecological effects of DDT (Chapter 24) study, whether a committee member or another person intimately involved with the project, was asked to treat in sequence, if possible, the history of the study project, the major environmental problems that it posed, the types of ecological knowledge used in the project, and the role of the knowledge in determining how the problems were perceived, approached, and dealt with. Each case study is followed by a committee comment on the project's strengths and weaknesses and on the lessons that can be drawn from it for other studies of a similar nature. Our concentration on

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INTRODUCTION 15 ecological knowledge is not meant to suggest that other sources of knowl- edge were not used or were necessarily less important in dealing with the environmental problems posed; it merely reflects our specific objective of showing how ecological knowledge can be used creatively in helping to solve environmental problems. RECOMMENDATIONS This report does not attempt to provide a "cookbook" for solving environmental problems; that would be impractical. Rather, it is a guide to the process of "cooking," indicating where useful approaches to par- ticular problems can be found in the literature and suggesting how ap- propriate knowledge and skills might be integrated for dealing with complex environmental problems. The following recommendations constitute general advice to field work- ers, managers, and regulators and are intended to form the basis of sci- entifically sound but flexible environmental problem-solving. The overall approach we recommend is described in Chapter 10. Here we highlight some major recommendations that apply to most environmental problems. If followed, they should increase the probability that solutions chosen for dealing with environmental problems are imaginative and appropriate. More details can be found in the chapters referred to, including the case studies, which constitute recommendations by example. Involve scientists from the beginning. Scientists should be involved from the beginning of a project in setting goals, in identifying valued ecosystem components, and in scoping the problem (Chapter 101. Sci- entists do not determine the values attached by society to ecosystem com- ponents, but they might know which organisms have important roles in the ecosystem that are not understood or appreciated by the general public. Scientists can help to assemble information about a project site and about similar sites and projects elsewhere. They are also helpful in defining goals, because of their knowledge of potential outcomes of manipulations that might be considered. They can advise on the implications of trying to achieve particular goals, on the measurement of values, and on why seemingly compatible values might conflict. The involvement of scientists does not guarantee success, but it should increase the probability that project plans are appropriate. Treat projects as experiments. Many projects are carried out on a larger scale than scientific experiments can be. To learn the scientific and management lessons that these projects have to offer, we need to treat

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16 INTRODUCTION them as experiments (Chapter 61. Treating projects as environmental ex- periments increases the understanding of basic ecological science and allows the testing of predictions made in impact statements. Careful mon- itoring is essential to anyone who would understand the effects of projects (Chapter 7), test the predictions made in impact statements (Chapter 6), detect changes in baseline conditions (Chapter 8), and detect cumulative effects (Chapter 9~. To be most successful, monitoring should be incor- porated into the project and study plans (Chapters 7 and 101. Publish information. Many people associated with projects learn a great deal from them, but without making their knowledge available to others through publication. If the knowledge were made widely available, similar projects could be managed better and could serve as controls. The cases described in Chapters 12, 14, 15, 18-20, 22, and 23 are good examples. Set proper boundaries on projects. Setting appropriate boundaries (Chapters 5 and 9) involves matching the scale of management to the scales of ecosystems. Environmental problems that cross political bound- aries are especially difficult to deal with (e.g., Chapters 12 and 23), so the appropriate jurisdiction for management should be chosen carefully (Chapter 91. Use natural-history information. Carefully collected natural-history information can help in solving environmental problems (Chapter 1~. The success of the cases described in Chapters 12-21 depended on such in- formation; for example, the control of such pests as vampire bats (Chapter 13) and red scale (Chapter 15) was based on identifying key natural- history features of the focal organisms. Be aware of interactions. Interactions among populations and among species in communities are complex (Chapters 2-4), and they can influence the effects of perturbations. It is important to remember that the most obvious connections are not necessarily the most important. Be alert for possible cumulative elects. Small perturbations, even if individually trivial, can have important cumulative effects when they are repeated in space and time. Therefore, many projects need to be evaluated not only in isolation, but also in the context of the overall frequency of their occurrence. Similarly, when a particular environment is being stud- ied, investigators need to be alert for possible effects of activities and perturbations elsewhere (Chapter 91. Plan for heterogeneity in space and time. Environmental patchiness, variation in time, and variation in the species composition of ecological communities conspire to complicate environmental management (Chapter 51. These considerations are particularly important in harvesting popula- tions (for example, the maximal sustainable yield changes as the envi

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INTRODUCTION 17 ronment changes) and in conservation. Interpopulation variations both genetic and behavioral, can also complicate management, because of rapid evolutionary changes (e.g., Chapters 1 and 151. Prepare for uncertainty and think probabilistically. A goal of man- agement is usually to minimize uncertainty. But uncertainty is unavoidable (Chapter 8), and managers are advised to expect it and to plan for it. In addition, pretending that uncertainty is absent leads to bad planning and inflexibility. Therefore, both scientists and managers must be willing to think in terms of probabilities and to deal with them, as weather forecasters and farmers, sailors, fliers, and the general public do every day. REFERENCES Alexander, M. 1971. Microbial Ecology. John Wiley & Sons, New York. Addicott, J. F. 1978. The population dynamics of aphids on fireweed: A comparison of local populations and metapopulations. Can. J. Zool. 56:2554-2564. Andrewartha, H. G., and L. C. Birch. 1954. The Distribution and Abundance of Animals. University of Chicago Press, Chicago. Andrewartha, H. G., andL. C. Birch. 1984. The EcologicalWeb: More on the Distribution and Abundance of Animals. University of Chicago Press, Chicago. Daan, N. 1980. A review of replacement of depleted stocks by other species and the mechanisms underlying such replacement. Rapp. P-v. Reun. Cons. Int. Expl. Mer 177:4{)5- 421. Earner, D. S. 1964. The photoperiodic control of reproductive cycles in birds. Am. Sci. 52:137- 156. Gilbert, L. E. 1975. Ecological consequences of a convolved mutualism between butterflies and plants. Pp. 210-240 in L. E. Gilbert and P. H. Raven, eds. Coevolution of Animals and Plants. University of Texas Press, Austin. Goodman, D. 1975. The theory of diversity-stability relationships in ecology. Q. Rev. Biol. 50:237-266. Gulland, J. A., and S. Garcia. 1984. Observed patterns in multi-species fisheries. Pp. 155- 190 in R. M. May, ed. Exploitation of Marine Communities. Dahlem Konferenzen. Springer, Berlin. Harper, J. L. 1969. The role of predation in vegetational diversity. Pp. 48-62 in Diversity and Stability in Ecological Systems. Brookhaven Symposia in Biology 22. Brookhaven National Laboratory, Upton, N.Y. Harshberger, J. C., and J. J. Black. In press. A strategy for using fish bioassays and surveys to identify and eliminate point source environmental carcinogens. In Towards a Transboundary Monitoring Network: Proceedings of a Workshop. International Joint Commission, Washington, D.C., and Ottawa, C)nt. Holling, C. S. 1973. Resilience and stability of ecological systems. Annul Rev. Ecol. Syst. 4: 1-23. Howe, H. F. 1981. Removal of wild nutmeg (Virola suranimensis) crops by birds. Ecology 62: 1093-1106. Hurlbert, S. H., and M. S. Mulla. 1981. Impacts of mosquitofish (Gambusia Alibis) predation on plankton communities. Hydrobiologia 83:125-151.

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