Sustaining living rivers

Hydrobiologia 422/423: 1–14, 2000. 1 M. Jungwirth, S. Muhar & S. Schmutz (eds), Assessing the Ecological Integrity of Running Waters. © 2000 Kluwer Academic Publishers. Printed in the Netherlands. Introduction Sustaining living rivers James R. Karr1 & Ellen W. Chu2 1 University of Washington, Box 355020, Seattle, WA 98195-5020, U.S.A. 2 Northwest Environment Watch, 1402 Third Ave., Suite 1127, Seattle, WA 98101-2118, U.S.A. Key words: biological integrity, IBI, rivers, RIVPACS, urban rivers, water cycle Abstract Rivers cannot continue to meet society’s needs, or the needs of living things, if humans continue to regard river management as a purely political or engineering challenge. The flow of rivers is part of a greater flow, the planet’s water cycle, which sustains not only the flow of water but the entire web of life. Ultimately, the condition, or health, of the aquatic biota is the best means of understanding and controlling humans’ impact on the Earth’s watercourses and on the whole water cycle. Biological monitoring, especially multimetric approaches such as the index of biological integrity, acknowledges the importance of rivers’ biotic integrity and offers one of the strongest available tools for diagnosing, minimizing, and preventing river degradation. The broad perspective offered by biological evaluations stands a better chance than narrow chemical criteria or conventional measures of urban development of sustaining living rivers. One major, overwhelming reason why we are to hearth? How do we keep water clean enough to running out of water is that drink? How much waste can rivers absorb? How can we are killing the water we have. we protect homes and property from floods? Where WILLIAM A SHWORTH, Nor Any Drop to Drink, 1982 can we find more water than flows within our political boundaries? For thousands of years, but especially in the last Introduction hundred, human engineering prowess has been driven to ensure reliable supplies of water, to limit damage Humans could not live without rivers. As long as hu- from flooding, and to avoid or clean up pollution. Hu- mans have inhabited the Earth, rivers have provided man intents for water were assumed to be attainable by them with food, drink, and sites for settlement. People intensifying human control of water and watercourses. have long relied on rivers for cleaning as well as But now more than ever, water supplies are insuf- for waste removal and decomposition, not to mention ficient to meet growing demands, and flood control commerce, transportation, and recreation. And rivers infrastructure cannot control flood damage. Indeed, feed the soul; “without them we should be spiritually our efforts to tame water have heightened our vulner- as well as materially deprived” (Macdonald, 1999; ability to long-term fluctuations in climate and flow Pielou, 1998). So as agricultural, industrial, and do- patterns and even brought about the unraveling of mestic consumption of water and associated resources living aquatic systems. grows, concern about river conservation increases. Our sharp focus on political and engineering chal- Will the momentum be enough to reverse decades of lenges has led us to ignore this unraveling and the river degradation? biological challenges the collapse of living riverine For most of human history, human interactions systems brings. Many local and regional fisheries are with rivers aimed at creating or maintaining water sup- gone; many others are so contaminated with pollutants plies. These challenges were seen as both engineering that they are not safe to eat. Declining fishery or recre- and political: How can we haul water from stream ational resources are omens of a much wider crisis, 2 but too few people see them as such. Likewise, too processes that nourish them (mutation, selection, fish few people – including water scientists, engineers, and migration, biogeochemical cycles, and the water cycle policymakers it seems – see the greater flow of which itself), is crucial to retaining water supplies and all rivers are a part: the planet’s water cycle. the goods and services associated with water (Karr & Chu, 1999). By using the word integrity, the US 1972 Water Pollution Control Act Amendments (now called Don’t forget the water cycle the Clean Water Act) recognized this importance of whole hydrobiological systems: “The objective of this Every drop of water in rivers flowing across the land Act is to restore and maintain the chemical, physical, once fell to Earth from the atmosphere. Given enough and biological integrity of the Nation’s waters.” This time, every drop will return to the atmosphere as wa- perspective has been carried into the Great Lakes Wa- ter vapor. Schoolchildren learn this lesson early. But ter Quality Agreement between the United States and when schoolchildren grow up, they forget about the Canada and into the Water Framework that now guides water cycle. They begin to see rivers as ‘surface wa- the European Union. ters’ and ‘channels’ that ‘drain’ away ‘dirt’ to the sea. Still, despite progress in controlling pollution com- They see wetlands as swamps to be dried to make ing from point sources, aquatic ecosystems have con- way for progress, not as sponges that shelter aquatic tinued to decline worldwide. Altered water flows in life and control floods. They forget that groundwater dammed streams and rivers; pollution from nonpoint nourishes rivers; they think only of mining it to water sources such as cities, farms, and feedlots; destruction cities and farms. And, ignoring the ancient lesson that of habitats above and alongside rivers by development a deluge is just compensation for human sins, they or logging; and invasions by alien species have all still build walls to contain the rivers. Yet without the taken a heavy toll. endless cycle of water, human and other life on Earth For too long, people have regarded water as a would simply cease. simple fluid to be used; water unused was water Ultimately, water matters most to living things, for wasted. Consequently, water resource management is without water, the rest of our Earthly habitat could not still dominated by legal doctrines from a less crowded sustain us. The converse is that life itself, and biology, world, weak implementation of good laws, and a fo- offers the best means of telling whether our actions are cus on water chemistry (Karr, 1995). But such narrow allowing the water cycle to continue unimpaired. The views do not guarantee the well-being of aquatic life, natural transformations and flows of water support all the integrity of water and watersheds, or the continu- life, including humans, and it is living aquatic systems ity of the water cycle. Seeing water only as a fluid that provide the goods and services humans need to – even a clean fluid – protects neither water quality survive. nor the continued supply of water itself. Only protect- ing the integrity of the water cycle can protect both (Falkenmark, 1997). River biota: mark of integrity The most direct and effective measure of a water body’s integrity, and of its place in the water cycle, The biota of every watershed on Earth is the product is the status of life in the water. “Ecosystem integ- of millions of years of geological change and biolo- rity is primarily a biological concern” (Reynoldson et gical evolution; the very existence of living organisms al., 1995). Living communities reflect watershed con- represents the integration of conditions around them. ditions better than any chemical or physical measure Such a highly evolved, complex living web is the mark because they respond to the entire range of biogeo- of integrity against which we can measure degrada- chemical factors in the environment. When something tion. Living things in a water body ‘do the integral,’ alters the landscape of a river’s headwaters, life in so to speak, of every biogeochemical process that has lowland reaches feels the effects. Actions that protect shaped that water body. Understanding the interac- the biota tell us directly if we are protecting the wa- tions that keep water bodies and other places alive ter cycle. Protecting the biological integrity of water – holds the secret to sustaining water supplies for human the full range of diversity and ecological processes re- enterprise and, indeed, for sustaining all life. flecting the evolutionary and biogeographical history Retaining the biological parts of riverine ecosys- of a place – will thus protect human uses of that wa- tems (populations, species, genes), as well as the ter, whether for drinking, fishing, washing, flushing,  3 shipping, irrigating, generating electricity, or making analytical methods; (6) score sites numerically to money in countless ways. When waters no longer sup- reflect site condition; (7) define “bands,” or condi- port living things, they will no longer support human tion classes, representing degrees of degradation; and affairs (Karr & Chu, 1999). (8) furnish needed analyses for selecting high-quality areas as acquisition and conservation priorities. Despite these shared properties, the details of Biological monitoring: vital for the long term RIVPACS and IBI also differ in important ways (Table 1). IBI was first developed for use with fish More than a century ago, people recognized that hu- (Karr, 1981; Karr et al., 1986) and has subsequently man activities produced pollution harmful to the biota been adapted for use with invertebrates (Karr, 1998; (for reviews see Davis, 1995; Perry & Vanderklein, Karr & Chu, 1999). IBI can be used with algae, plank- 1996). They therefore made an effort to track the ton, and vascular plants in wetlands, streams, and extent of biological degradation; biological degrada- coastal estuaries, and the index is also being adap- tion was even considered an indicator for the presence ted for use in terrestrial environments (Bradford et al., of human activities. So began biological monitor- 1998; Karr & Chu, 1999). ing (Forbes, 1928; Kofoid, 1903, 1908; Kolkwitz & IBI and RIVPACS both classify stream segments Marrson, 1908). according to important environmental features in or- Rather than staying focused on biology, however, der to restrict comparisons to areas with equivalent water quality evaluations shifted for much of the twen- natural environmental conditions. Both RIVPACS and tieth century to the effects of chemical contaminants; IBI define a reference standard as a benchmark of a rarely were connections between chemical criteria healthy river, although how those standards are defined and ambient biotic condition documented. At the differ. RIVPACS analyses select sites of “good or same time, water quantity evaluations measured wa- fairly good quality” (Armitage et al., 1983) or that are ter volume in light of human needs or wants. Rarely, “free of serious pollution” (Wright et al., 1984). The if ever, was the whole flow of the water cycle seen focus on chemical contamination contrasts with the as limiting the quantity of water supplies or as the broader reference standards established for IBI, where environment in which water planning should be tak- reference stream segments or watersheds are chosen to ing place. Humans pushed ahead with control, not have little or no human influence from any source, not understanding. just chemical pollution. During the past two decades, life in the waters has Perhaps the most important difference between again come to the fore, and biological monitoring – de- RIVPACS and IBI is the biological information used tecting human-caused biotic changes apart from those to frame the assessment process. The early goal of occurring naturally – is again part of water managers’ RIVPACS was to improve site selection for conser- tool kits (Chovanec et al., 1995; Davis & Simon, 1995; vation (Wright et al., 1984). As a result, recognizing Hellawell, 1986; Karr, 1981, 1991; Karr & Chu, 1999; patterns of species composition was and continues to Norris & Thoms, 1999; Norris et al., 1995; Reynold- be the core of RIVPACS analyses. In contrast, IBI son et al., 1995; Rosenberg & Resh, 1993; Simon, was developed to measure river condition, or river 1999; Wright et al., 1989, 1997). health, and included development of measurements for Two major approaches to biological monitoring diagnosing causes of degradation. As a result, the bio- have emerged in the past 20 years: the river inverteb- logical signals that make up IBI analyses are broader, rate prediction and classification system (RIVPACS) including taxa richness and composition, trophic or and the index of biological integrity (IBI). The un- other aspects of ecological organization, presence and derlying principle of both is that the biota is the relative abundance of tolerant and intolerant taxa, and ultimate integrator of all human actions. The two ap- presence of diseased individuals or individuals with proaches overlap in many important ways. Both, for other anomalies (Karr, 1991; Karr & Chu, 1999). example, (1) focus on biological endpoints to define A primary goal of IBI is to define the attributes of river health; (2) use a concept of reference condition living systems that change systematically in diverse as a benchmark; (3) organize sites into classes with situations when exposed to the activity of humans. a select set of environmental characteristics; (4) as- RIVPACS emphasizes species identity and abund- sess change and degradation caused by human effects; ances. IBI searches for a broader array of biological (5) require standardized sampling, laboratory, and signals from species to higher taxa, including sys- 4 Table 1. Comparative analysis of the conceptual, sampling, and analytical characteristics of multivariate (RIVPACS) and multimetric (B-IBI) approaches to river monitoring and assessment (based on the most common current applications) RIVPACSa (multivariate) IBIb (multimetric) Site classification or Stream size, geography, substrate Geology, stream size and characterization particle size, water chemistry temperature, altitude Reference standard Sites without serious pollution Sites with little or no human (RP); other human influences influence not considered. Broader in recent applications (AR) Model foundations Multivariate associations between Empirically defined measures; environmental variables and dose–response graphs plotting species present human influence against biological response Decision criteria Species presence or absence Biological attributes such as taxa (observed vs. expected ratios) richness, relative abundance, from probabilistic models; taxa composition, tolerance sometimes tolerance measures and intolerance Microhabitat sampled Multiple (e.g., riffle, edge, pool- Riffles rock: RP). Riffles (AR) Subsampling Varies regionally and with Full samples counted application Stream applications Benthic invertebrates Benthic invertebrates, fish, algae available Data set required Extensive, hundreds of sites Fifteen to 20 sites representing a Regional foundation; some broad gradient of human smaller-scale applications disturbance; can be developed being developed locally or over larger areas Transferability Extensive data sets and new Consistency in selected measures species-specific models needed and biological responses across for each region regions Treatment of rare species Often excluded from analyses Included in analyses Sampling period RP: combined 3-season model Defined period for sampling AR: model for each season Analytical basis Species presence–absence Diverse dimensions of biological and natural history patterns Human influence Largely chemical contamination Full spectrum of human influences Diagnostic capability Not explored Moderately well developed Communication Statistical foundations difficult Simple dose–response curves Breadth of signal narrow (O/E similar to toxicology; broad ratio); pollution tolerance range of biological signal a RIVPACS (RP) developed in England and cloned as AUSRIVAS (AR) in Australia for rivers and streams, being applied in rivers in other regions. b IBI developed in midwestern United States for rivers and streams; now used internationally. Applica- tions for other habitats in use or development.  5 tematic shifts in the natural history of assemblages of such as water quality and water quantity, surface species. Because RIVPACS analyses emphasize prob- water and groundwater; ability statements about species presence, rare taxa are • stands up to scientific and legal scrutiny and is excluded from analyses; rare taxa are not excluded in actually improving the legal and regulatory ap- IBI. Finally, RIVPACS depends on large data sets for proaches used by governments to protect the pub- its multivariate models, whereas smaller data sets still lic’s interest in water resources; produce an effective IBI. • directly addresses the central call of the United These and other differences notwithstanding, both States’ Clean Water Act and the European Union’s RIVPACS and IBI have changed the way many scient- Water Framework to protect the integrity of water; ists and water managers think. Developing and testing • is simple to develop and use, demanding no ad- these integrative approaches to water resource assess- vanced technologies beyond the reach of develop- ment have provided a long-needed counterpoint to ing countries with limited financial means or of the history of monitoring chemical water quality and citizen groups seeking to understand the condition simple water quantity. of their local and regional watersheds; • defines the health of a water resource system and aids in diagnosing and identifying causes of any What is IBI? detected degradation; IBI – like the multifaceted indexes measuring eco- • enables us to identify and protect the places most nomic and human health – integrates multiple biolo- deserving of conservation (defines places where gical indicators to measure and communicate biolo- restoration is possible and practical, and guides de- gical condition, and thereby the ecological health of a velopment activities to prevent or minimize dam- river and its watershed. Much as a physician relies on age to water resources); a battery of medical tests, not just one, to diagnose ill- • provides results that can be used to assess the ness, anyone can use an IBI to diagnose the condition effectiveness of particular resource management of a water body. Connecting many previously discon- decisions and to set funding priorities; nected dimensions of water science and policy, the • extends the concept of taking multiple measures index has been tested and refined over nearly two dec- to assess health – long central in economics and ades and now provides the foundation of US federal medicine – to environmental assessments; programs for biological monitoring. An IBI based on • integrates precise biological measurements of the fish has been applied on every continent except Ant- condition of waters and their associated resources arctica; in developing as well as developed countries; into numbers and words that are easily understood and in basic science, resource management, engin- by diverse audiences; eering, public policy, legal, and community volunteer • allows us to compare the effects of single acts with arenas (Hughes & Oberdorff, 1999; Simon, 1999). An the cumulative effects of many activities; IBI based on benthic invertebrates (B-IBI) has been • permits comparisons across time and space: of applied in areas from the United States to Japan. the effects of different human activities through Based on empirically defined ‘dose-response’ re- time at the same site or of watershed condition in lationships between particular human influences and different geographic regions; the biological responses they provoke, IBI is one of • allows us to measure and compare the relative the most commonly used – “and arguably the most impacts of different human land uses, including effective” (Simon, 1999) – biological monitoring ap- recreation, farming, logging, and urbanization, proaches. IBI, along with its component metrics: and to compare such impacts with those affecting water bodies directly, such as pollution, channeliz- • tells us whether we are maintaining water bodies, ation, or dam building; water supply, and flow through the water cycle, • can be applied with a broad range of taxa, from al- along with the vital resources the water cycle gae and vascular plants to invertebrates and fishes. supports; • works in streams, rivers, lakes, wetlands, estuaries, Human activities degrade water resources by alter- and coastal marine systems; ing one or more of five principal groups of attributes: • integrates elements that conventionally have been water quality, habitat structure, flow regime, energy fragmented in water policy and decision making, source, and biotic interactions (Figure 1; Karr & Chu, 6 Figure 1. The five principal factors with some of their important chemical, physical, and biological components that are commonly altered by human actions (modified from Karr et al., 1986). 1999). IBI is an effective assessment tool because it incorporates the sensitivity of the biota itself to all five of these factors. Building a robust and effective IBI requires se- lecting measurable attributes that provide reliable and relevant signals about the biological effects of human activities. The biological attributes ultimately incor- porated into an IBI are called metrics. They are chosen because they reflect specific, predictable responses of Figure 2. The number of taxa of rock-clinging invertebrates de- organisms to changes in landscape condition. They are clined with increasing human influence in 65 west-central Japan- ese rivers (Rossano, 1996) because increasing sediment filled the sensitive to a range of physical, chemical, and bio- interstitial spaces in the gravel streambed. logical factors that alter biological systems, and they are relatively easy to measure and interpret. The index of biological integrity explicitly comprises several at- diversity of invertebrates clinging to rocks in a stream tributes of the sampled biota, including taxa richness, goes down as human activities in the landscape in- indicator groups, health of individual organisms, and crease (Figure 2; Rossano, 1996). Such relationships ecological processes (Table 2). are best discovered and deciphered with graphs. A The most important criterion for choosing a bio- multimetric IBI comprising well-chosen metrics integ- logical attribute as a metric is whether the attribute rates information from ecosystem, community, popu- responds predictably along a gradient of human in- lation, and individual levels (Karr & Chu, 1999) and fluence. Does the attribute vary systematically with clearly discriminates biological ‘signal’ – including varying degrees of human impact? In Japan, the bio- the effects of human activities – from the ‘noise’ of  7 Table 2. Sample biological attributes, in four broad categories, that might have potential as metrics. Actual monitoring protocols have proven some of these attributes effective; other attributes may work but need more testing; still others are difficult to measure or too theoretical. Ideally, an IBI should include metrics in each of these categories, but untested or inadequately tested attributes should not be incorporated into the final index (Modified from Karr & Chu, 1999) Category Demonstrated effective Need more testing Difficult to measure or too theoretical Taxa richness Total taxa richness Dominance (relative abundance Relative abundance Richness of major taxa, of most-numerous taxa) distribution, after Preston (1962) (e.g., mayflies or sunfish) Tolerance, intolerance Taxa richness of intolerant organisms Number of rare or endangered taxa Chironomid species Relative abundance of green sunfish (difficult to identify) Relative abundance of tolerant taxa Trophic structure Trophic organization, e.g., relative Productivity abundance of predators or omnivores Individual health Relative abundance of individual Contaminant levels in tissue Metabolic rate fish with deformities, lesions, or tumors (biomarkers) Relative abundance of individual chironomids with head-capsule deformities Growth rates by size or age class Other ecological Age structure of target species attributes population Table 3. Biological monitoring and assessment support the goals of many sections in the US Clean Water Act IBI in action Listing of impaired waters (§303d) The strength of IBI is its adaptability – to diverse Permitting of point-source discharges (§402) contexts and geographies and diverse environmental Nonpoint source assessment (§319) conditions, such as point-source and nonpoint pollu- Hazardous waste site assessments (§104e) Evaluation of habitat modifications (§401/404) tion or the effects of urbanization. As the index has Analysis of total maximum daily loads (TMDLs) been tested worldwide, IBI has proven more sensitive Aquatic life use designations (§305b) to human impacts than many conventional measures Reporting condition of waters (§305b) of these impacts. IBI has detected the effects of ef- Clean Lakes Program activities (§314) fluents from a bauxite plant in Guinea (Hugueny et Thermal effluent and entrainment–impingement (§316a, b) al., 1996) and from salmonid aquaculture on small Wet-weather discharge (stormwater) (§319, §402) streams in France (Oberdorff & Porcher, 1994); the ef- Water quality standards and criteria (§303c) fects of channelization and chemical effluents in small Comparative risk assessment (multiple sections) Venezuelan rivers (Gutierrez, 1994); metal and or- Watershed protection and assessments ganic pollution in central Indian rivers (Ganasan & Hughes, 1998); the cumulative effects of channeliz- ation, agricultural runoff, and urbanization in France’s Seine River basin; and the impact of diverse land uses on streams in dry west-central Mexico (Lyons et al., 1995). IBIs have been used to reflect the biological effects of chemical contamination (Figure 3) and the natural variation. Moreover, because IBI is founded impacts of human activities on a watershed or land- on empirical data, its use does not require resolution of scape scale (Figure 4). IBI has served as a framework all the higher-order theoretical debates in contempor- for reinventing biological assessments for water re- ary ecology (Miller & Ehnes, in press) or the formal source investigations (Figure 5), as a foundation for mathematical models of ecological functions. citizen water-monitoring programs (Figure 6), and to 8 Figure 3. Within stream channels, IBI fully reflects chemical contamination in diverse geographical settings, such as urban point and nonpoint pollution gradients from ‘pristine’ to ‘grossly polluted’ in Thailand, Ghana, and Brazil (Thorne & Williams, 1998). support the goals of the Clean Water Act (Table 3). (Karr et al., in press). Rivers in most cities have IBI helped to evaluate watersheds in the entire Sierra been straightened, diverted, dammed, contained, and Nevada for setting conservation priorities; it was ap- otherwise physically engineered beyond recognition. plied in a long-term evaluation of dammed streams They have been hydrologically transformed and pol- and to evaluate a relatively undisturbed stream heavily luted to the point of catching fire – all this to feed invaded by alien species (Moyle & Randall, 1998). cities’ demand for massive concentrations of water, food, energy, and raw materials. Cities also put out huge amounts of organic and synthetic garbage, fully Tracking the health of urban rivers expecting rivers to carry much of it away. As sprawl pushes beyond city centers into neighboring water- Urbanization, the concentration of more and more hu- sheds, it degrades rural watersheds and streams as mans into densely populated areas, may be the most well. Urban ecological footprints (Wackernagel & important trend influencing rivers today. In 1850 only Rees, 1996), which extend much farther than urban one metropolis boasted a population larger than 1 mil- boundaries, put tremendous pressure on rivers, dam- lion. By 1998, 326 cities had populations exceeding 1 aging them more than agriculture, logging, and other million, and 14 megalopolises had populations greater land uses. Both within and between midwestern US than 10 million (O’Meara, 1999). Globally, urban pop- watersheds, the most degraded streams (as measured ulations increase by 1 million each week, driven by by biological condition) are located in urban areas natural increase, migration from rural areas, and urban (Karr et al., 1986; see also Karr & Chu, 1999: sprawl engulfing nearby towns. In the United States, Figure 6). officially designated metropolitan areas have mush- In the face of such pressures, looking at the living roomed from 9% of the nation’s land area in 1960 to systems in urban watersheds stands a better chance of 19% (Stoel, 1999). Four out of five US citizens live protecting long-term human needs and well-being than in urban zones, over half in areas with more than a the narrower management perspectives of the past. million people. In the twenty-first century, a growing Multimetric indexes like IBI can improve both the share of people will come to measure environmental conservation and restoration of urban rivers even as quality by conditions in their cities (Stoel, 1999). they guide decision-making about development. Indeed, many US residents believe that urban en- Past urban watershed management concerned it- vironmental conditions are deteriorating, and the con- self mostly with stormwater management: managing dition of waterways is high on their list of worries  9 Figure 4. IBIs also reflect impacts of human activities on a watershed scale. For example, an IBI based on fishes declined as forest land cover declined in Wisconsin (Wang et al., 1997). Figure 5. IBI has provided the framework for reinventing biological assessments for water resource investigations, leading many US states to make such assessments central to their water resource programs (from Davis et al., 1996). 10 increased runoff during storms, a consequence of pav- ing over large segments of a basin. Little attention was directed at measuring or understanding runoff’s effects on the biological health of rivers (Roesner, 1997). Fortunately, this perspective is beginning to change, within governments and among professionals and laypersons alike. One study of Puget Sound lowland streams in some 40 watersheds near Seattle (Washington, USA) sought to identify the linkages between landscape conditions, in-stream environmental factors, and stream biota as well as to develop a set of indexes of stream qual- ity that could help minimize river degradation caused by urban development (May et al., 1997). Among the study’s elements was an examination of biological condition (expressed as a benthic IBI) with respect to Figure 6. IBI provides a powerful tool that even citizen water- the percentage of total impervious area (% TIA), a monitoring groups can use. A study in the Puget Sound lowlands (Fore et al., in press) showed volunteer efforts to be in line with measure that has been widely embraced in regulatory professional laboratory studies. Indexes based on volunteer (V) and circles because of its reputation as an integrative meas- professional (P) lab analyses were correlated with each other (P < ure of human activity. The study streams – all similar 0.01) and with disturbance (P < 0.01). in size, physiography, and the historical presence of breeding salmon populations – ranged from relatively undeveloped (2–5% TIA) to highly urbanized (60% TIA). In theory, an integrative measure of urban devel- opment should be highly correlated with a stream’s biological condition (Figure 7). Sites with little or no development should support a diversity of species and an ecological organization that reflects the history of evolutionary and biogeographic processes for that site and region; such sites have biological integrity. An in- tegrative measure of urbanization’s effects on a stream biota should show a drop in biological condition, away Figure 7. An ideal measurement of urban development (x-axis) from integrity, as urbanization intensifies. that accounts for development’s impacts on living aquatic systems The percentage of total impervious area is indeed should be tightly correlated with actual measures of a stream’s bio- correlated with declining stream health, or biological logical condition, or health (y-axis). One would expect stream health to fall way from integrity (top left) as development increased. condition as measured by B-IBI (Figure 8a). But the correlation is not tight as it is in Figure 7, suggest- ing that % TIA alone does not capture all aspects of marked effects on the biota even when urbanization is urbanization (e.g., removal of riparian vegetation) or minimal. Yet development permitting is often based on account for all its biological effects. At low levels the assumption that the correlation between biological of development (low % TIA) some streams remained condition and % TIA is direct, tight, and simple. It is healthy (B-IBI = 45–50) while others suffered (B- not. IBI = 15–20); at high development levels, biological Urban development radically alters a watershed’s condition was uniformly poor. drainage network by changing or destroying many A line through the plot’s top points (Figure 8b) small natural streams and channels and by creating illustrates what Thomson et al. (1986) term a ‘factor artificial channels across and along roads, in culverts, ceiling distribution,’ defining the best biological con- and through stormwater outfalls. The percentage of dition one can expect as a function of % TIA. The impervious area likely takes much of this hydrological scatter of points below the ceiling shows that factors transformation into account (producing the ‘ceiling’ other than % TIA are at work, and that they can have in Figure 8b), but omits other activities associated  11 Figure 8. (a) Biological condition, as measured by the benthic index of biological integrity (IBI), declines with increasing urban development expressed as the percentage of total impervious area (% TIA). The correlation is not tight, however, especially at low levels of development. (b) As indicated by the error bars at the top right, B-IBI is a statistically precise measure of biological condition; % TIA, however, does not reflect all of development’s effects on a biota, although it does set a ‘ceiling’ for the biota’s response (the distinct upper bound of the plot’s wedge shape, termed a factor ceiling distribution). (c) At low levels of imperviousness, other factors not captured in measures such as % TIA, including riparian condition or point sources of pollution, are often responsible for biological decline. (d) At intermediate levels of imperviousness, the index of biological integrity can help managers choose among a variety of potential sites for successful restoration as well as guide managers to the most successful restoration approaches at those sites. At very high levels of imperviousness, IBI can help avoid wasting resources on sites with only limited possibilities for restoration or rehabilitation. with development, such as point pollution sources or At low levels of development, some activities have rel- riparian cover. In the Puget Sound lowlands, for ex- atively little impact on stream biota, while others harm ample, watersheds with protected riparian corridors it (Figure 8c). At intermediate and high (Figure 8d) and wetlands are in better biological condition, as levels of imperviousness, IBI enables managers to measured by B-IBI, than watersheds where develop- pick and choose among a range of opportunities for ment is concentrated along streams. A stream with successful restoration or rehabilitation and to avoid effluent from an old mine seeping into it is in worse sites where expensive restoration efforts would be condition than a stream with similar levels of de- wasted. Continuing studies are identifying which de- velopment, as measured by impervious area, but no velopment activities do the most damage, ultimately abandoned mine. Similarly, sites on streams adjacent offering planners a guide for development least likely to wastewater treatment plants have lower B-IBIs than to harm streams and watersheds. streams with the same % TIA but no wastewater plant (J. Adams et al., 1999). What studies of B-IBI in urban areas has revealed What’s next? is that an index like IBI better reflects the cumulative influence of human activity on a biota than conven- Biological monitoring gets at the heart of sustaining tional measures such as % TIA. It also shows that IBI water resources because biology – more precisely, the is a better guide than % TIA for planning development. biota – is the best indicator of the health of humans’ 12 relationship with water. If we understand this rela- We have to put our basic research results – our un- tionship, we can meter our activities to ensure the derstanding of biological responses – to work in the maintenance of the planet’s life-giving water cycle. world’s watersheds. Failure to rise to this challenge Without such understanding, we are likely to continue may spell failure to keep the world’s waters alive. dealing with one problem at a time, out of the larger context. We will pile unintended consequence upon unintended consequence as we have for centuries – Acknowledgements and end up robbing the ‘watery planet’ of its most precious resource. This paper was made possible by grants from Inasmuch as the strength of IBI is its adaptability many agencies and organizations during the past 30 and utility for getting this understanding across to a years. Recently, especially important support came broad audience, the goal of future IBI work is to adapt from Washington Department of Ecology Centennial it and use it as much as possible. After all, an effective Clean Water Fund Grant No. G9400121, Environ- river IBI can be developed within the time frame and mental Protection Agency/National Science Founda- budget of a master’s thesis. IBI and other biological tion Water and Watersheds Program Grant EPA R82- monitoring tools can: 5284-010, and the Consortium for Risk Evaluation • heighten awareness that ‘it’s the biology!’ across with Stakeholder Participation (CRESP) by Depart- the broadest possible technical, scientific, and ment of Energy Cooperative Agreement #DE-FC01- management circles and among citizen groups; 95EW55084.S. Among others, Derek Booth, Stephen • speed adoption of biological monitoring by grow- Burges, and Sarah Morley contributed significantly to ing numbers of local, state, regional, federal, the understanding of urban streams. and even international organizations charged with maintaining sustainable supplies of water. References Biological monitoring as exemplified by IBI marks a profound shift in thinking. First, it puts biolo- Adams, J. W., J. R. Karr & T. C. Dewberry, 1999. 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