7
Integrating Obstacles and Opportunities

INTRODUCTION

The previous six chapters underscore the need for integrating environmental concerns into all phases of road development and the special challenges to that integration. In this chapter, some of the barriers to integration and some ways to eliminate or lessen those barriers are discussed. As suggested in Chapter 1, integration is critical in two areas: integrating across scales of space and time and integrating ecological and social concerns. The first section in this chapter briefly summarizes how issues of scale influence the understanding and management of road ecology. The second section reviews how environmental issues can be integrated with other social concerns. The chapter concludes with a section on facilitating integration in practice and suggests some alternative approaches and considerations for developing integrative solutions.

ISSUES OF INTEGRATION ACROSS SCALES

Ecological systems self-organize across a wide range of spatial and temporal scales. They operate over spatial scales of millimeters to thousands of kilometers and temporal scales of milliseconds to millennia (see Chapter 1, Figure 1-9). The span of scales over which ecosystems operate is much larger than the span of scales evaluated in this report. In the evaluation of the ecological effects of roads and in the assessment and management options associated with those effects, the committee fo-



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Assessing and Managing the Ecological Impacts of Paved Roads 7 Integrating Obstacles and Opportunities INTRODUCTION The previous six chapters underscore the need for integrating environmental concerns into all phases of road development and the special challenges to that integration. In this chapter, some of the barriers to integration and some ways to eliminate or lessen those barriers are discussed. As suggested in Chapter 1, integration is critical in two areas: integrating across scales of space and time and integrating ecological and social concerns. The first section in this chapter briefly summarizes how issues of scale influence the understanding and management of road ecology. The second section reviews how environmental issues can be integrated with other social concerns. The chapter concludes with a section on facilitating integration in practice and suggests some alternative approaches and considerations for developing integrative solutions. ISSUES OF INTEGRATION ACROSS SCALES Ecological systems self-organize across a wide range of spatial and temporal scales. They operate over spatial scales of millimeters to thousands of kilometers and temporal scales of milliseconds to millennia (see Chapter 1, Figure 1-9). The span of scales over which ecosystems operate is much larger than the span of scales evaluated in this report. In the evaluation of the ecological effects of roads and in the assessment and management options associated with those effects, the committee fo-

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Assessing and Managing the Ecological Impacts of Paved Roads cused on spatial scales from meters to hundreds of kilometers. Temporal scales included in this report range from days to a few decades. In confronting the broad range of scales covered by ecosystems and road systems, the approach has been to divide the scales into research, assessment, and management categories. As shown in Chapter 3, most research on, and understanding of, ecological effects covers small scales—road segments and corridors. The committee has inferred effects at larger scales (disruption of landscapes and spread of exotic organisms), but few studies cover these scales. In all of these studies, bounds are established that define a discrete scale range. Studies are bounded in space (for example, meter square plots to hundreds of hectares) and time (for example, days to years), whether they are field investigations or modeling-based inquiries. As with the understanding of ecosystems, the scales for road planning, assessment, and operation are also divided; long-range transportation plans (LRTPs) cover regions and decades, and state transportation improvement plans cover road segments and years (see Chapters 3 and 6). This division of scales has its roots in theory, as described in Chapter 3; Chapter 3 also discusses cross-scale effects and their relevance to road ecology. The remainder of this chapter focuses on integrating social (including legal, institutional, and economic) and ecological issues. Scales of Law, Planning, Assessment, and Financing Federal laws apply to the lands within the United States, unless specified otherwise, and thus cover a wide range of spatial scales, from a very small scale (molecular level for water or air quality) to a national scale. State laws are restricted to the geographical extent of that specific state and may address environmental concerns in relation to roads. Even though these laws cover a conceptually wide area (the nation), the spatial scope is narrowed greatly during the planning and assessment process. For example, consideration of wetland resources is only applied to specific areas where wetland ecosystems occur. Similar restrictions are applied to endangered species consideration, generally applied to a specific population and habitat, regardless of wider distributions. Hence, there appears to be a consideration of the relationship of immediate (spatial scale) impacts on wetlands and on endangered species, but insufficient consideration of how those immediate impacts relate to impacts on a greater scale. This narrowing in scope of federal statutes requiring envi-

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Assessing and Managing the Ecological Impacts of Paved Roads ronmental considerations occurs when road projects cross state borders—that is, ecosystems cross state borders, but planning of road projects does not. One of the gaps identified by the committee is the lack of protection of ecosystem goods and services at scales larger than the road segment. A broader and consistent set of ecological concerns should be addressed to provide that protection. The current system of planning is conducted at two scales: the project level (e.g., transportation improvement program) and the regional or state (LRTP) level as detailed in Chapter 6. Project level planning addresses certain environmental issues that are required by law or policy and addresses them on restricted scales (up to watershed scales in some cases). The understanding of ecological effects is restricted in a similar manner to scales from small to intermediate (see Chapter 3). Almost no studies of ecological effects at the national scale were found in the literature, nor were national-scale data sets. Regional and state planning addresses such issues as economics and population growth but rarely addresses ecological concerns. Hence, most of the ongoing road assessment and planning ignores ecological structures and processes that occur at broad scales. Transportation-related issues at the national scale are addressed by many groups, such as the Federal Highway Administration, the American Association of State Highway and Transportation Officials, the surface transportation policy project, and nongovernmental organizations (NGOs), with few, if any, intersections with national-scale ecological issues (for example, global change, biodiversity loss, and exotic pest biota). At smaller scales (regions to municipalities), more ecological knowledge becomes integrated. This situation suggests that a better integration of transportation and ecology is needed across a wide range of scales. Deciding on an appropriate scale for assessment and management of road effects on ecological systems is problematic. Bounds are established to analyze road effects. No matter where those bounds are set, structures and processes at larger and smaller scales must be considered. There are few opportunities in the current system (from planning through project implementation) where these two scales are addressed. The key question for each assessment and monitoring effort is determining the spatial and temporal scale of interest. Assessment and planning should be redesigned to fill these gaps in scale. A multiscale approach will be required. Models and data sets

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Assessing and Managing the Ecological Impacts of Paved Roads should be developed at different scales. Ecological effects occur over wide scales and cannot be addressed solely by scaling up or down on the basis of existing information or models. Experience suggests that multiple models should be developed to deal with the cross-scale dynamics of these systems (Holling 1978, Walters 1986). INTEGRATING ECOLOGICAL CONCERNS AND SOCIAL OBJECTIVES The issues that arise in road planning, development, construction, and use are complex. One source of complexity is from the many competing ideas and agendas that exist among various people, groups, and agencies involved in these processes. These groups include governmental agencies at state, local, or federal levels, private consultants and experts, NGOs, academics, interested individuals, and the public. Recognition of the sources and nature of these perspectives can help in developing strategies to confront complexity while meeting goals of integration and streamlining. A set of processes needs to be developed to manage these complexities. The technical contributors from the list above (those concerned with understanding and evaluating environmental effects of roads and applying that understanding) are all trained in an academic discipline. A source of integration complexities arises from differences among many disciplines that underlie their practices. For example, conservationists’ ideas are rooted in understanding of ecology or biology; road engineers in mathematics and physics; planners in geography or architecture. The differences in paradigms, theories, methods, and practices among disciplines provide large gaps and problems in methods, approaches, and language. For example, ecologists or engineers can be very good at understanding and evaluating environmental effects but could be better trained at communicating to a wider audience or trained in alternative models of the realities of human behavior, organizational structures, and institutional arrangements. Another such example is when engineers or managers assume that the uncertainty of nature can be replaced by human attempts to control and stabilize ecological systems. It is not that these approaches are wrong but that they are partial and require more disciplinary integration (Gunderson and Holling 2002) and perhaps more broadened, cross-disciplinary training.

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Assessing and Managing the Ecological Impacts of Paved Roads Another type of complexity occurs when a diverse set of social values held by a myriad of groups intersect. Road planning and design engage governmental agencies, conservationists, and other stakeholder groups. Federal agencies—such as the U.S. Fish and Wildlife Service, which has responsibilities under the Endangered Species Act and the U.S. Environmental Protection Agency (EPA) and the U.S. Army Corps of Engineers (Corps), which are charged with protecting wetlands—have specific mandates that are not overlapping and can come into conflict with other governmental objectives. Many states have similar agencies that are also engaged. NGOs and even sovereign entities (Native American tribes) are becoming more involved in lobbying, planning, design, and management of roads (for example, the Nature Conservancy and the California Department of Transportation). Current efforts of assessment and planning, reviewed in Chapter 6, describe how various groups are engaged. Yet difficulties persist and protract the planning and design process because of the number and types of agencies and stakeholders involved. In addition to the number and types of competing interests, another obstacle to integration is the ways in which the groups interact and resolve differences so that actions can be taken. Differences can be resolved in a variety of ways, from discussions at workshops or public meetings to formal dispute resolution or lawsuits. The set of laws and bureaucratic structures developed to implement policy appears to generate partial solutions to a myriad of problems faced in integrating environmental concerns into all elements of road design, construction, or management. Moreover, legal and bureaucratic frameworks are set up in a way that defaults first to administrative processes and second to legal institutions to resolve conflicts. In these approaches, integration of environmental concerns with other issues can be, but is not always, achieved. Often, this deficiency occurs because of a lack of understanding about the natural systems or because of unrealistic expectations about how natural systems behave. Sometimes, partial solutions generate new ecological problems. For some controversial projects, there is a clear understanding about the natural systems that will be affected by a transportation project, but existing institutions do not provide a way to address the concern, so project opponents must select from a small number of mandatory requirements, such as clean air conformity, for their concerns to be addressed. Hence, what appears to be needed is a new type of institutional arrangement or structure that is based on an un-

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Assessing and Managing the Ecological Impacts of Paved Roads derstanding of the integrated nature of the social and ecological components of road ecology (such as step 1 in the committee’s proposed assessment framework [see Figure 6-3]). TOWARD INTEGRATIVE SOLUTIONS In this section, the committee presents some proposals for better integration of ecological concerns with all phases of road activity from planning through management. Previous authors (Forman et al. 2003, White and Ernst 2003) argue for more attention to ecological objectives and better integration of ecological and social objectives. Other authors (TRB 2002b) suggest that transportation agencies become environmental stewards and address ecological issues earlier in the planning process through improved coordination, communication, and education among the agencies. The committee suggests that integration of environmental concerns with other social objectives may be facilitated in three areas: (1) developing new institutions and institutional arrangements, (2) developing new tools and methods, and (3) developing adaptive management. Each area is discussed in the subsequent sections. New Institutions and Arrangements The committee’s review and others (TRB 2002b) suggest that transportation agencies continue to expand their roles as environmental coordinators and stewards. This expansion can be viewed as filling “institutional gaps.” Institutions are defined in this context as the set of norms and rules that people use to organize activities (Ostrom 1990). Institutional gaps occur when new problems arise that existing agency mandates do not address or when agencies recognize the need to interact in new ways with other agencies or stakeholders. Expanding the existing mandate and tasks of transportation agencies toward environmental stewardship (Executive Order 13274, September 2002) has begun. It is a bureaucratic solution, the assumption being that governmental agencies can and will evolve and adapt to the new duties. There are a number of obstacles in attempting these changes, and the history of such attempts indicates mixed success. Recent attempts to reform agencies at the state level (such as water management

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Assessing and Managing the Ecological Impacts of Paved Roads districts in Florida) suggest that it is a long and difficult process (Light et al. 1995). The Corps attempted a similar reformation (Shallat 1994). Another solution to the institutional gap is the creation of new institutions referred to as meshing organizations (Haas 1990), which would provide bridges among agencies and stakeholders that have existing relationships. These organizations may be formal or informal. One example of a formal arrangement is the tripartite model set up to manage resource issues in the Grand Canyon. Arising from an National Research Council (NRC) report (1996), three groups (the Grand Canyon Research and Monitoring Center, the Adaptive Management Work Group, and external review groups) meshed together to form the Adaptive Management Program. Forming a meshing group is one way to integrate technical and social concerns. Other institutional forms exist. They include a type of ombudsman, in which the authority to resolve and reconcile technical and social issues is given to one individual. A modification of that approach could create a panel or council to resolve issues as they arise in the planning and assessment process. Dispute resolution mechanisms could also be considered to fill institutional gaps. These types of institutions do not replace legal or scientific institutions that are in use. The new institutional forms are useful in sorting through assessments that do not require the rigor of a scientific approach to generate actions or plausible sets of actions. They also can be effective at reconciling or working around worldviews or mental models, which are often unspoken constructs that influence the way that environmental effects are perceived and managed. For example, the worldview of a real estate developer who works in downtown Atlanta might be very different from that of a conservationist who works to preserve biodiversity. There is a tension between the environmentally “negative” effects of road construction and use and the socially or economically “positive” effects of roads. Forums are needed for expression of many perspectives, so that differences can be recognized and resolutions negotiated. Other institutional configurations, such as free markets, or some versions of cost-benefit approaches exist but are unlikely to resolve the complexities outlined above. Much work over the past decade or so in the field of ecological economics has attempted to quantify the value of ecosystem goods and services. Daly (1996), Costanza et al. (1997), Odum (1996), and others have created a variety of methods to place dollar values on the natural capital of ecosystems. Their work has undoubtedly created scholarly discourse and exposed the importance of the eco-

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Assessing and Managing the Ecological Impacts of Paved Roads system goods and services that underpin but are ignored by economic institutions. Yet, few working examples that demonstrate the utility of an environmental cost-benefit approach to decision making about the environment are persuasive. One or all of these proposals for new or alternative institutional arrangements could be attempted. In the wide array of governments and stakeholders across the United States, many (and even other new) combinations could be tested. In establishing these institutions, design principles developed by Ostrom (1990), who has studied international cooperative institutions that are organized and governed by the users of common-pool resources (for example, fisheries, groundwater basins, and irrigation systems) can be applied. The author’s principles include clearly defined boundaries, provision and appropriation rules, collective choice rules, monitoring, gradual sanctioning, conflict resolution mechanisms, external recognition, and layers of nested enterprise. Her principles are useful guidelines for the design of new institutions that promote successful cooperation and achievement of social goals. New Tools and Methods Technological Developments Advances in methods and technology for establishing and managing roads have reduced and will continue to reduce some of the ecological effects of roads. For example, wildlife underpasses can successfully retain the connection among populations of animals even when a road bisects their territory. Agencies such as the Natural Resource Conservation Service now supports nurseries in 18 locales for growing seed of native plants, which can thrive in the stressful roadside conditions. Even so, entire regions do not have such native plant nurseries and still heavily use a mix of largely European plants, which have been planted along roads for decades. Other developments have attempted to improve environmental benefits associated with roads: Innovations in building materials (for example, porous pavement), design strategies (for example, for bridges and culverts), and stormwater strategies are being developed and implemented to mitigate environmental impacts of roads.

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Assessing and Managing the Ecological Impacts of Paved Roads Since 1970, 44 states and Puerto Rico have constructed over 1,600 miles of noise barriers. Highway developers are among the largest recyclers in America through remilling pavements, using fly ash in concrete, and using crumb rubber as a component of road surfaces. Over the past 11 years, $4.9 billion in enhancement projects, such as bike paths and the preservation of historic bridges and train stations, has been spent in more than 14,000 communities (AASHTO 2002a). Environmental effects of roads are greatly influenced by the surrounding socioeconomic conditions. Socioeconomic constraints and opportunities are often expressed in the use and management of roadsides. As an example of land-use constraints, roads in U.S. agricultural areas zigzag around fields. As human populations grow and change in distribution and movement patterns, roads are no longer designed to avoid fields and become linear features on the landscape. Furthermore, anticipated climate changes are likely to affect where people want to travel and where roads can be built (for example, seaside roads may be under water because of rising sea levels). Technological change might alter the effects of roads on the environment. For example, air conditioning has changed where people want to live, and the Southeast and Southwest regions of the United States have grown rapidly. Telecommuting can reduce traffic volume. Although hydrogen-based fuels introduce new environmental problems, they would also reduce water, air, and noise pollution (Ludwig et al. 1993). Hence, changes in knowledge can affect how environmental effects, as well as steps taken to mitigate them, are viewed. Several sites in the city of Seattle, Washington, provide examples of environmental improvements that can be implemented: The overpasses on Mercer Island, known as the 1-90 LIDS, are noted for their attractive dense vegetation. Freeway Park in downtown Seattle was designed to provide a bridge over Interstate 5 and connect adjoining neighborhoods (Wright 1989). Its waterfall masks traffic noise, and the gorge provides a quiet escape from city life. Using shallow-rooted trees and plants resistant to air pollution ensured the success of the park. Street edge alternatives (SEA) is a street design that uses special grading, soils, plants, and layout combined with traditional drainage

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Assessing and Managing the Ecological Impacts of Paved Roads infrastructure to reduce traffic flow and water runoff in one block of a city neighborhood. The aesthetic benefits of this design increased property values, but it is unclear whether the increase makes up for the high cost of implementing a SEA. For the most part, however, Seattle is a typical large city with all the environmental problems that accompany roads. The commitment to improved roadsides in spot locations probably arises from an interest in the environment being aesthetically appealing and in the federal listing of salmon as an endangered species; the effects of runoff on fish are a major environmental concern. New Conceptual Approaches Roads can be envisioned as a network because they form a set of interconnections. One of the origins of the mathematical theory of networks deals with the transportation problem of moving goods and services across roads. Solutions to that and other optimization problems resulted in a body of knowledge on how goods can most efficiently move across interconnections. The recent application of these ideas to road systems has led to the formation of basic principles for interpreting how road networks fit into an ecological landscape (Forman et al. 2003): The arrangement of land uses around roads determines the structure of the road network. Network arrangement and traffic flow affect the delivery of good and services. The ecological landscape in which road networks are set can be influenced by road density, network structure, traffic flow, and patterns of the ecological systems in the landscape. The landscape patterns around a road network can have intended and unintended effects on roads and traffic. The design of the road network can be made ecologically sensitive. Although the first two factors have been the focus of most road design, the last two factors call for consideration of the unintended ecological effects of roads. The spatial attributes of the road network include the number and layout of roads. Road size is important because it affects traffic flow and

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Assessing and Managing the Ecological Impacts of Paved Roads road footprint (surface space). Road density (the lane length of roads per unit area of land) is perhaps the simplest measure of road structure. Road density can influence such diverse ecological features as how far large animals move across the landscape (van Dyke et al. 1986, Mech et al. 1988) and how fast water moves into streams (Jones and Grant 1996). Hence, attributes of road networks can serve as a means to quantify the human impact on the environment. Adaptive Management This report and others (Forman et al. 2003) suggest that although much has been learned about the interactions between roads and ecosystems, much more is required. In addition to peer-reviewed published studies from academic and technical centers and summaries and syntheses by professional road groups, the committee recommends the development of other learning methods—that is, some retrospective analysis to evaluate efficacy of actions taken to avoid or mitigate ecological effects. In a sense, the approaches being applied are not solutions but rather best guesses at solutions. For example, when over- or underpasses are constructed for animal migration, there may be uncertainty about animal use, what kinds of animals will use or avoid them, and unexpected results (such as increased predation risks). Often, solutions applied in particular projects are, in effect, pilot projects to see whether and how a problem can be addressed. As noted elsewhere in the report, there is insufficient monitoring, follow-up, and reevaluation, the result being that the opportunity to learn from experience is lessened. Learning opportunities are also available from the management activities that are done throughout the country (see Chapter 4). To evaluate construction or management actions, new sets of data, types of institutions, and ways of evaluating actions need to be developed. The need for a robust set of ecological indicators is central to this activity. Examining Ecological Indicators Ecological indicators are meant to quantify the magnitude of stress, degree of exposure to stresses, and degree of ecological response to exposures (Hunsaker and Carpenter 1990, Suter 1993). They provide a

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Assessing and Managing the Ecological Impacts of Paved Roads simple and efficient method to examine the ecological composition, structure, and functioning of complex ecological systems (Karr 1981). Several ecological indicators have been proposed to measure or monitor ecological effects, and some of these indicators are applicable to road effects. Reports of the NRC (2000b), the Heinz Center (2002), and EPA (2003c) focus on indicators at the national level. The EPA framework (EPA/SAB 2002) builds on the Heinz Center report to form a checklist of factors to be considered for measurement. The journal Ecological Indicators and many scientific papers mark the growth of this field. Ecological Indicators for the Nation (NRC 2000b) evaluates indicators meant to track such factors as how land is used and the status of wildlife and other natural resources at a national level. These measures are meant to identify potential national environmental problems and evaluate the effectiveness of protective regulations and policies. The recommended indicators fall into three categories: Ecosystem status. Indicators include the types and extent of the nation’s major land cover, such as wetlands, forests, and deserts. Ecological capital. The capacity of an ecological system to maintain itself as determined by such indicators as total species, native species diversity, nutrient runoff, and soil quality. Ecosystem productivity. Ecological indicators of a system’s ability to produce oxygen and capture and store energy to support life include production capacity, carbon storage, and oxygen content in rivers, streams, and coastal areas. The NRC (2000b) report calls for indicators to be credible, understandable, quantifiable, and broadly applicable (including roads). The data upon which the indicators depend should be clear and objective. The Heinz Center (2002) report presents a plan for regular reporting on the condition and use of the nation’s lands, waters, and living resources. It identifies indicators for the nation’s ecological systems, provides information on current conditions and past trends, and illustrates the many gaps in current data on key characteristics of ecological systems at the national level. Among these indicators are physical and chemical conditions (for example, nitrogen and phosphorus storages), changes in land use (for example, aerial extent of forests and grasslands), and listing and extent of nonnative plants and animals. The EPA (2003c) report on the environment focuses on how human activities affect human health and the environment at the national level. It quantifies trends in five areas:

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Assessing and Managing the Ecological Impacts of Paved Roads Human health. Changes in diseases, human exposure to environmental pollutants, and diseases that might be related to environmental pollution. Ecological condition. A perspective of natural resources, stressors on those resources, and potential for future sustainability. Clean air. Effects of indoor and outdoor air quality on human health and ecological systems. Pure water. Drinking water, use of recreational water, and condition of water resources and the living systems that they sustain. Better protected land. Land use and activities that affect the condition of the landscape, including agricultural practices, pest management, waste management, emergency response and preparedness, and recycling. In summary, these three reports form a body of work on indicators at the national level that can be used to guide understanding of how best to measure ecological effects of roads at the scale of the entire United States. However, many of the effects of roads occur on local or intermediate scales. The use of ecological indicators relies on the assumption that the presence or absence of these indicators reflects changes occurring at various levels in the ecological hierarchy, from genes to species and ultimately to entire regions and the nation (Noon et al. 1999). The ecological system must be viewed as a moving target (Walters and Holling 1990), the system variables changing slowly and not stabilizing for a long period of time. The EPA/SAB (2002) Framework for Assessing and Reporting on Ecological Condition provides a checklist that can be used to determine whether key ecological attributes are being considered at any scale of measure. It also provides a scheme for organizing the hundreds of proposed indicators. The major thematic areas of the framework are landscape condition, biotic condition, chemical and physical characteristics, ecological processes, hydrology and geomorphology, and disturbance regimes. Because these themes are independent of spatial scale, they formed the basis for the approach adopted in this report. Several concerns constrain the use of ecological indicators as a resource management tool (Landres et al. 1988, Kelly and Harwell 1990, Noss 1990, Kremen 1992, Cairns et al. 1993, Mills et al. 1993, Noss and Cooperrider 1994, Gurney et al. 1995, Simberloff 1997). Dale and Beyeler (2001) summarized these concerns in three categories:

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Assessing and Managing the Ecological Impacts of Paved Roads Monitoring programs often depend on a small number of indicators and thus fail to consider the full complexity of the ecological system. Choice of ecological indicators is often confounded in management programs that have vague long-term goals and objectives. Management and monitoring programs often lack scientific rigor because of their failure to use a defined protocol for identifying ecological indicators. Yet, selection of appropriate indicators is key to any planning, monitoring, or management program. Identifying criteria for using indicators for analyzing and addressing road effects on ecological systems might be the best way to determine the indicators most appropriate for roads effects. Cairns et al. (1993) pointed out that ecological indicators can be used to assess the condition of the environment, to monitor trends in condition over time, to provide an early warning signal of changes in the environment, and to diagnose the cause of an environmental problem. The purpose of using ecological indicators influences the choice of which indicator is most appropriate (Slocombe 1998). Several criteria should be used to evaluate indicators. These criteria are the significance of ecological changes measured by indicators, the basis of the ecological understanding of indicators, the reliability of indicators, the quality of the indicator data, and the costs and benefits (NRC 2000b). Criteria listed for indicators are drawn from Dale and Beyeler (2001): The indicator is easily measured. “The indicator should be straightforward and relatively inexpensive to measure. The metric needs to be easy to understand, simple to apply, and provide information to managers and policymakers that is relevant, scientifically sound, easily documented and cost-effective.” The indicator is sensitive to stresses on the system. “While some indicators may respond to all dramatic changes in the system, the most useful indicator is one that displays high sensitivity to a particular and, perhaps, subtle stress, thereby serving as an early indicator of reduced system integrity.” The indicator responds to stress in a predictable manner. “The indicator response should be unambiguous and predictable even if the indicator responds to the stress by a gradual change…. Ideally there is some threshold response level at which the observable response occurs before the level of concern.”

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Assessing and Managing the Ecological Impacts of Paved Roads The indicator is anticipatory (signifies an impending change in the ecological system). “Change in the indicator should be measurable before substantial change in ecological system integrity occurs.” The indicator predicts changes that can be averted by management actions. “The value of the indicator depends on its relationship to possible changes in management actions.” The indicator has a known response to natural disturbances, anthropogenic stresses, and changes over time. “The indicator should have a well-documented reaction to both natural disturbance and to anthropogenic stresses in the system. This criterion would pertain to conditions that have been extensively studied and have a clearly established pattern of response.” The indicator has low variability in response. “Indicators that have a small range in response to particular stresses allow for changes in the response value to be better distinguished from background variability.” The indicator is integrative. “The full suite of indicators provides a measure of coverage of the key gradients across the ecological systems (e.g., soils, vegetation types, temperature, etc.).” Furthermore, information proposed to evaluate candidate indicators (see Andreasen et al. 2001) might be useful in evaluating the suite selected for a particular condition. The spatial scale of the indicator affects both the availability of relevant data and the interpretation. For example, the Heinz Center (2002) report focuses on indicators at the national level and largely demonstrates the absence of information at this scale. The committee’s analysis of data on ecological effects of roads (see Table 3-2) also reveals the paucity of data at the national scale. However, local and regional (or intermediate) scale information is more readily available and more interpretable in terms of analyzing road effects. Therefore, the committee recommends that projects designed to manage and monitor road effects should include indicators specific to the scale and concerns about the potential effects. After the goals and criteria for indictors for a specific project have been identified, the EPA/SAB (2002) framework can be used as a checklist to determine which indicators might be most useful. Perhaps the initiation of a few pilot programs that cover a wide range of spatial and temporal scales that engage relevant expertise on indicators (such as the NRC or the Heinz Center) would be a way to improve understanding of the development and application of key indica-

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Assessing and Managing the Ecological Impacts of Paved Roads tors, such as soil nutrient content, size of stream buffers, and distribution of nonnative pest organisms (plants and animals). To date, attributes of road networks are not often considered in lists of ecological indicators, but road density and the spatial arrangement of new roads or roads that are removed strongly influence the ecological implications of road networks. SUMMARY In evaluating ecological effects of roads, two areas of integration were identified. The first involves integration across scales and complexities of ecological systems. The second involves integration across multiple societal goals associated with roads. Ecological systems cover wide ranges of spatial and temporal scales. The cross-scale structure and dynamics are not always amenable to simple scaling approaches and are the source of unexpected behavior. Some road effects confine the scale of ecological effects, and other effects can increase or decrease the spatial or temporal extent of ecological processes. The complexity and cross-scale interactions in ecological systems generate problems for assessment and planning. Multiple assessments must be developed, each at different spatial and temporal scales to address key ecosystem processes and structures. Ecological concerns should be included early in the assessment and planning processes, which are context sensitive. Some components of the environment are incompatible with the existence of roads. Although great progress has been made in understanding and mitigating road effects, much more is needed. The development of a broader set of robust ecological indicators and learning-based institutions will help to facilitate understanding of the complexities in ecological systems. Complexities that arise in the dynamics of social structures used to assess, plan, construct, and manage road systems must be addressed. Better integration of the social institutions will probably require the development of new relationships among the existing institutions. Transportation agencies have an opportunity to play a key role in meshing and integrating planning and management of environmental issues. New types of institutions are needed to address the mix of socioeconomic and ecological concerns. Enhanced collaboration can be generated by new kinds of rules and groups for interactions among agencies and stakeholders.