Paul L. Angermeier

MEETING ECOLOGICAL AND SOCIETAL NEEDS FOR FRESHWATER

Human society has used freshwater from rivers, lakes, groundwater, and wetlands for many different urban, agricultural, and industrial activities, but in doing so has overlooked its value in supporting ecosystems. Freshwater is vital to human life and societal well-being, and thus its utilization for consumption, irrigation, and transport has long taken precedence over other commodities and services provided by freshwater ecosystems. However, there is growing recognition that functionally intact and biologically complex aquatic ecosystems provide many economically valuable services and long-term benefits to society. The short-term benefits include ecosystem goods and services, such as food supply, flood control, purification of human and industrial wastes, and habitat for plant and animal life—and these are costly, if not impossible, to replace. Long-term benefits include the sustained provision of those goods and services, as well as the adaptive capacity of aquatic ecosystems to respond to future environmental alterations, such as climate change. Thus, maintenance of the processes and properties that support freshwater ecosystem integrity should be included in debates over sustainable water resource allocation. The purpose of this report is to explain how the integrity of freshwater ecosystems depends upon adequate quantity, quality, timing, and temporal variability of water flow. Defining these requirements in a comprehensive but general manner provides a better foundation for their inclusion in current and future debates about allocation of water resources. In this way the needs of freshwater ecosystems can be legitimately recognized and addressed. We also recommend ways in which freshwater ecosystems can be protected, maintained, and restored. Freshwater ecosystem structure and function are tightly linked to the watershed or catchment of which they are a part. Because riverine networks, lakes, wetlands, and their connecting groundwaters, are literally the “sinks” into which landscapes drain, they are greatly influenced by terrestrial processes, including many human uses or modifications of land and water. Freshwater ecosystems, whether lakes, wetlands, or rivers, have specific requirements in terms of quantity, quality, and seasonality of their water supplies. Sustainability normally requires these systems to fluctuate within a natural range of variation. Flow regime, sediment and organic matter inputs, thermal and light characteristics, chemical and nutrient characteristics, and biotic assemblages are fundamental defining attributes of freshwater ecosystems. These attributes impart relatively unique characteristics of productivity and biodiversity to each ecosystem. The natural range of variation in each of these attributes is critical to maintaining the integrity and dynamic potential of aquatic ecosystems; therefore, management should allow for dynamic change. Piecemeal approaches cannot solve the problems confronting freshwater ecosystems. Scientific definitions of the requirements to protect and maintain aquatic ecosystems are necessary but insufficient for establishing the appropriate distribution between societal and ecosystem water needs. For scientific knowledge to be implemented science must be connected to a political agenda for sustainable development. We offer these recommendations as a beginning to redress how water is viewed and managed in the United States: (1) Frame national and regional water management policies to explicitly incorporate freshwater ecosystem needs, particularly those related to naturally variable flow regimes and to the linking of water quality with water quantity; (2) Define water resources to include watersheds, so that freshwaters are viewed within a landscape, or systems context; (3) Increase communication and education across disciplines, especially among engineers, hydrologists, economists, and ecologists to facilitate an integrated view of freshwater resources; (4) Increase restoration efforts, using well-grounded ecological principles as guidelines; (5) Maintain and protect the remaining freshwater ecosystems that have high integrity; and (6) Recognize the dependence of human society on naturally functioning ecosystems.

Biological Integrity versus Biological Diversity as Policy Directives

Two phrases — biological integrity and biological diversity—have joined the lexicon of biologists and natural resource managers during the past two decades. The importance of these phrases is demonstrated by their influence on environmental research, regulatory, and policy agendas. The concepts behind the phrases are central to strategies being developed to sustain global resources (Lubchenco et al. 1991). Unfortunately, the phrases are widely used by the media, citizens, policy makers, and some biologists without adequate attention to the concepts they embody. Precise use of the terms integrity and diversity can help set and achieve societal goals for sustaining global resources; imprecise or inappropriate use may exacerbate biotic impoverishment—the systematic decline in biological resources (Woodwell 1990).

Biological Integrity versus Biological Diversity as Policy DirectivesProtecting biotic resources

Two phrases — biological integrity and biological diversity—have joined the lexicon of biologists and natural resource managers during the past two decades. The importance of these phrases is demonstrated by their influence on environmental research, regulatory, and policy agendas. The concepts behind the phrases are central to strategies being developed to sustain global resources (Lubchenco et al. 1991). Unfortunately, the phrases are widely used by the media, citizens, policy makers, and some biologists without adequate attention to the concepts they embody. Precise use of the terms integrity and diversity can help set and achieve societal goals for sustaining global resources; imprecise or inappropriate use may exacerbate biotic impoverishment—the systematic decline in biological resources (Woodwell 1990).

Regional Applications of an Index of Biotic Integrity for Use in Water Resource Management

Abstract The index of biotic integrity (IBI) integrates 12 measures of stream fish assemblages for assessing water resource quality. Initially developed and tested in the Midwest, the IBI recently was adapted for use in western Oregon, northeastern Colorado, New England, the Appalachians of West Virginia and Virginia, and northern California. The concept also was extended to Louisiana estuaries. In regions of low species richness, the IBI proved difficult to apply and often required extensive modification. Adapting the 1BI to those regions required that metrics be replaced, deleted, or added to accommodate regional differences in fish distribution and assemblage structure and function. Frequently replaced metrics include: proportion of individuals as green sunfish (Lepomis cyanellus), proportion of individuals as insectivorous cyprinids, proportion of individuals as hybrids, and number and identity of sunfish and darter species. The proportion of individuals as top carnivore metric was often deleted. Metr...

How Much Is Enough? The Recurrent Problem of Setting Measurable Objectives in Conservation

Abstract International agreements, environmental laws, resource management agencies, and environmental nongovernmental organizations all establish objectives that define what they hope to accomplish. Unfortunately, quantitative objectives in conservation are typically set without consistency and scientific rigor. As a result, conservationists are failing to provide credible answers to the question “How much is enough?” This is a serious problem because objectives profoundly shape where and how limited conservation resources are spent, and help to create a shared vision for the future. In this article we develop guidelines to help steer conservation biologists and practitioners through the process of objective setting. We provide three case studies to highlight the practical challenges of objective setting in different social, political, and legal contexts. We also identify crucial gaps in our science, including limited knowledge of species distributions and of large-scale, long-term ecosystem dynamics, that must be filled if we hope to do better than setting conservation objectives through intuition and best guesses.

local vs. regional influences on local diversity in stream fish communities of Virginia

Local species richness is a function of many factors operating at multiple spatial and temporal scales. We examined stream fish communities from regions throughout Virginia to assess (1) the relative influence of local vs. regional factors on local species richness, (2) evidence for community saturation, and (3) scale dependency of regional influences. We defined regions at four spatial scales: major drainages, drainage-physiography units, hydrologic-physiography units, and sites. We used multiple regression to identify key correlates of local native and introduced diversity for each regional scale. Both local (e.g., microhabitat diversity) and regional (e.g., species richness) factors were correlated with local diversity; regional diversity was the most consistent correlate. Plots of local vs. regional native diversity were asymptotic for the three largest regional definitions, thereby suggesting community saturation. However, analogous plots for introduced species were not asymptotic; local introduced d...

Applying an Index of Biotic Integrity Based on Stream-Fish Communities: Considerations in Sampling and Interpretation

Abstract Physical and chemical monitoring of water bodies is relatively common. However, water resource assessment suffers from lack of integrative and reliable measures of the biotic condition of aquatic systems. This situation persists despite the fundamentally biological nature of water resource degradation. We examined three aspects of applying an index of biotic integrity (IBI) that uses attributes of fish communities to assess stream degradation: (1) relative contributions of individual metrics to the final IBI assessment; (2) effects of sampling effort on the IBI; and (3) effects of including young-of-year fish data on IBI computations. Relative contributions of individual metrics to IBI assessments varied substantially among data sets from Illinois, Ohio, and West Virginia, and variation in contributions reflected differences in ranges of metric scores and types of degradation being assessed. No metric was consistently best or worst at detecting degradation, and metrics did not appear redundant wi...

Characterizing fish community diversity across Virginia landscapes: Prerequisite for conservation

The number of community types occurring within landscapes is an important, but often unprotected, component of biological diversity. Generally applicable protocols for characterizing community diversity need to be developed to facilitate conservation. We used several multivariate techniques to analyze geographic variation in the composition of fish communities in Virginia streams. We examined relationships between community com- position and six landscape variables: drainage basin, physiography, stream order, elevation, channel slope, and map coordinates. We compared patterns at two scales (statewide and subdrainage-specific) to assess sensitivity of community classification to spatial scale. We also compared patterns based on characterizing communities by species composition vs. ecological composition. All landscape variables explained significant proportions of the variance in community composition. Statewide, they explained 32% of the variance in species composition and 48% of the variance in ecological composition. Typical commu- nities in each drainage or physiography were statistically distinctive. Communities in dif- ferent combinations of drainage, physiography, and stream size were even more distinctive, but composition was strongly spatially autocorrelated. Ecological similarity and species similarity of community pairs were strongly related, but replacement by ecologically similar species was common among drainage-physiography combinations. Landscape variables explained significant proportions of variance in community composition within selected subdrainages, but proportions were less than at the statewide scale, and the explanatory power of individual variables varied considerably among subdrainages. Community vari- ation within subdrainages appeared to be much more closely related to environmental variation than to replacement among ecologically similar species. Our results suggest that taxonomic and ecological characterizations of community com- position are complementary; both are useful in a conservation context. Landscape features such as drainage, physiography, and water body size generally may provide a basis for assessing aquatic community diversity, especially in regions where the biota is poorly known. Systematic conservation of community types would be a major advance relative to most current conservation programs, which typically focus narrowly on populations of imperiled species. More effective conservation of aquatic biodiversity will require new approaches that recognize the value of both species and assemblages, and that emphasize protection of key landscape-scale processes.

Fish Traits: A Database of Ecological and Life-history Traits of Freshwater Fishes of the United States

Abstract The need for integrated and widely accessible sources of species traits data to facilitate studies of ecology, conservation, and management has motivated development of traits databases for various taxa. In spite of the increasing number of traits-based analyses of freshwater fishes in the United States, no consolidated database of traits of this group exists publicly, and much useful information on these species is documented only in obscure sources. The largely inaccessible and unconsolidated traits information makes large-scale analysis involving many fishes and/or traits particularly challenging. We have compiled a database of > 100 traits for 809 (731 native and 78 nonnative) fish species found in freshwaters of the conterminous United States, including 37 native families and 145 native genera. The database, named Fish Traits, contains information on four major categories of traits: (1) trophic ecology; (2) body size, reproductive ecology, and life history; (3) habitat preferences; and (4) s...

Forecasting the combined effects of urbanization and climate change on stream ecosystems: from impacts to management options

Summary 1 Streams collect runoff, heat, and sediment from their watersheds, making them highly vulnerable to anthropogenic disturbances such as urbanization and climate change. Forecasting the effects of these disturbances using process‐based models is critical to identifying the form and magnitude of likely impacts. Here, we integrate a new biotic model with four previously developed physical models (downscaled climate projections, stream hydrology, geomorphology, and water temperature) to predict how stream fish growth and reproduction will most probably respond to shifts in climate and urbanization over the next several decades.2 The biotic submodel couples dynamics in fish populations and habitat suitability to predict fish assemblage composition, based on readily available biotic information (preferences for habitat, temperature, and food, and characteristics of spawning) and day‐to‐day variability in stream conditions.3 We illustrate the model using Piedmont headwater streams in the Chesapeake Bay watershed of the USA, projecting ten scenarios: Baseline (low urbanization; no on‐going construction; and present‐day climate); one Urbanization scenario (higher impervious surface, lower forest cover, significant construction activity); four future climate change scenarios [Hadley CM3 and Parallel Climate Models under medium‐high (A2) and medium‐low (B2) emissions scenarios]; and the same four climate change scenarios plus Urbanization.4 Urbanization alone depressed growth or reproduction of 8 of 39 species, while climate change alone depressed 22 to 29 species. Almost every recreationally important species (i.e. trouts, basses, sunfishes) and six of the ten currently most common species were predicted to be significantly stressed. The combined effect of climate change and urbanization on adult growth was sometimes large compared to the effect of either stressor alone. Thus, the model predicts considerable change in fish assemblage composition, including loss of diversity.5 Synthesis and applications. The interaction of climate change and urban growth may entail significant reconfiguring of headwater streams, including a loss of ecosystem structure and services, which will be more costly than climate change alone. On local scales, stakeholders cannot control climate drivers but they can mitigate stream impacts via careful land use. Therefore, to conserve stream ecosystems, we recommend that proactive measures be taken to insure against species loss or severe population declines. Delays will inevitably exacerbate the impacts of both climate change and urbanization on headwater systems.