Article 3:

(Essay) Measuring Biological Condition, Protecting Biological Integrity

By James R. Karr, University of Washington, Seattle

Environmental change has always been a reality, and it is continuous. Change on our planet is driven by wind and water, geological activity, astronomical events, and the work of microorganisms, plants, and animals. Usually the forces with the greatest potential for cataclysmic change are rare (such as volcanic eruptions), local (such as tornadoes or lightning fires), or slow to play out (such as the advance and retreat of glaciers).

Over the past two centuries, however, this pattern has changed. The activity of one species, Homo sapiens, has become the principle driver of change on Earth’s surface. For the first time in Earth’s history, a biological agent—a single species at that—rivals or surpasses geophysical forces in shaping Earth. Human activity changes environments, sometimes in big, obvious ways, sometimes in small, subtle ways. Converting shrub-steppe to agriculture or clear-cutting a forest inevitably and visibly alters the mix of plants, insects, birds, and mammals at a site. Damming, channeling, or adding pollutants to a river inevitably, but perhaps less visibly, alters the river’s biota. Such biotic changes are most often documented as counts of extinct, threatened, and endangered species, or as declining populations or production of species with commercial or recreational value. Unfortunately, the preoccupation with imperiled and commodity species obscures wider consequences of human activity for living systems. Without a report card for those wider consequences, society is ill equipped to identify and protect ecologically intact places, restore degraded places, or make informed decisions about permits for development.

To evaluate the condition of a site, one must be able to define the attributes of “normal,” undegraded, or “healthy” environments as a model. Otherwise, how can we objectively assess if a site is degraded, or whether mitigation or restoration techniques are succeeding or even necessary? One way of setting a baseline and measuring restoration success is to define the normal “biological integrity” of a system, and then measure deviations from it. For example, a “normal,” or benchmark, body temperature of 37°C (98.6°F) provides a similar standard for individual humans. Just as the normal temperature varies with species of mammal, the “normal” species richness or relative abundance of a trophic group varies among ecosystems (e.g., between large versus small streams, grassland versus forest, and among forest types).

The phrase biological integrity was first used in 1972 to establish the goal of the Clean Water Act, “to restore and maintain the chemical, physical, and biological integrity of the Nation’s waters.” More recently, the 1997 National Wildlife Refuge System Improvement Act clarifies its conservation goal with a clear directive: “Ensure that the biological integrity, diversity, and environmental health of the System are maintained.” These mandates establish a legal foundation for protecting the nation’s biological heritage (Karr 1991; Adler 2003; Natural Resources Journal 2004).

Integrity implies an unimpaired condition, or the quality or state of being complete or undivided. Biological integrity is defined as “the ability to support and maintain a balanced, integrated, adaptive biological system having the full range of parts (genes, species, and assemblages) and processes (mutation, demography, biotic interactions, nutrient and energy dynamics, and metapopulation processes) expected in the natural habitat of a region” (Karr 1996). Inherent in this definition is that: (1) living systems act over a variety of scales from individuals to landscapes; (2) a fully functioning living system includes items one can count (the parts) plus the processes that generate and maintain them; and (3) living systems are embedded in dynamic evolutionary and biogeographic contexts that influence and are influenced by their physical, chemical, and biological environments.

Agencies and institutions responsible for implementing the Clean Water Act neglected the biological mandate for years. Under section 305(b) of the Clean Water Act, states are required to report the status of water resources within their boundaries, yet the historical dominance of numerical chemical criteria in water quality standards resulted in chronic underreporting of degradation. Conventional chemical evaluations, for example, failed to detect 50% of the damage to surface waters when compared with application of more comprehensive, sensitive, and objective biological criteria—numerical values or narrative expressions that describe the characteristics of a living aquatic assemblage. Another advantage of biological assessment is that it can detect degradation caused by the full array of human influences on living systems, not just the direct effects of chemical pollutants. Because of this strength, many state and federal agencies and citizen groups are developing programs that directly monitor and assess the condition of living systems (Davis et al. 1996; U.S. EPA 2005).

To implement biological criteria, managers need formal methods for sampling the biota, evaluating the resulting data, and clearly describing the condition of sampled areas. I developed a measurement system, called the index of biological integrity (IBI), to fill this need (Karr 1981, 1991). The complexity of biological systems and the varied impacts humans have on them require a broadly based, multi-metric index that integrates information from individual, population, assemblage, and landscape levels.

The IBI, like conventional economic indices such as the index of leading economic indicators, provides a convenient measure of the status of a complex system. Both require a baseline state against which future conditions are assessed. For IBI, that baseline—biological integrity—is the condition at a site with a biota that is the product of evolutionary and biogeographic processes in the relative absence of the effects of modern human activity.

Multi-metric indices like IBI integrate multiple biological indicators to measure and communicate biological condition. Much as a physician relies on a battery of medical tests, not just one, to diagnose illness, anyone can use an IBI to diagnose the condition of a place. This robust measure of the biological dimensions of site condition has by now been applied to challenges in basic science, resource management, engineering, public policy, law, and community participation on every continent except Antarctica, and in developing as well as developed nations. One advantage of IBI is that it is founded on empirical data so its use does not require resolution of all higher-order theoretical debates in contemporary ecology.

Initial work to develop this approach to use of biological indicators concentrated on streams with fish as focal organisms but the conceptual underpinnings of IBI have now been applied to diverse environments (streams, large rivers, wetlands, lakes, coastal areas, riparian corridors, sagebrush steppe, and others) and taxonomic groups (fishes, aquatic and terrestrial invertebrates, algae and diatoms, birds, vascular plants). Several states have incorporated biological criteria into state water quality standards (Ohio, Florida, Maine, Vermont) and biological monitoring is now a key component of EPA water management guidelines to states (USEPA 2005). IBI or conceptually similar multimetric indices are now used on six continents and in freshwater, marine, and terrestrial systems.

IBI metrics are chosen because they reflect specific and predictable responses of the biota to human activities across the landscapes. These responses are similar to dose–response curves measured by toxicologists, where an organism’s response varies with the dose of a toxic compound. Because they provide an integrative measure of the cumulative impacts of all human activities in a region or watershed, IBI and its component metrics can be viewed as ecological dose–response curves. The IBI is based in empirically defined metrics because they: (1) are biologically and ecologically meaningful; (2) increase or decrease as human influence increases; (3) are sensitive to a range of stresses; (4) distinguish stress-induced variation from natural and sampling variation; (5) are relevant to societal concerns; and (6) are easy to measure and interpret.

Several properties of the IBI and conceptually similar indices make them particularly useful for evaluating ecosystem condition (Karr and Chu 2000):
  1. A focus on biological endpoints to define condition
  2. The use of a concept of reference condition (undisturbed or minimally disturbed) as a benchmark
  3. Organization of sites into classes with a select set of environmental characteristics
  4. Assessment of change and degradation caused by human activities
  5. Standardized sampling, laboratory, and analytical methods
  6. Numerically scoring of sites to reflect site condition
  7. Definition of “bands,” or condition classes, representing degrees of degradation
The IBI has many applications, including analyses framed for selecting high-quality areas as acquisition and conservation priorities, and as a means for diagnosing the likely cause of damage at degraded at sites.

IBI metrics evaluate species richness, indicator taxa (stress intolerant and tolerant), relative abundances of trophic guilds and other species groups, presence of nonindigenous species, and the incidence of hybridization, disease, and anomalies such as lesions, tumors, or fin erosion (in fish) and head capsule abnormality (in stream insects). To determine an IBI for a location, samples are collected of invertebrates, fishes or other taxa. These samples are sorted and organisms are identified and counted. Metrics of species richness, relative abundance, or dominance of particular taxa are calculated. Metric values from the site are compared with values expected for a relatively undisturbed or natural site of the same type in the same geographic region (Figure A). Each metric is assigned a value of 5, 3, or 1 depending on whether its condition is comparable to, deviates somewhat from, or deviates strongly from the “undisturbed” reference condition. Metric scores are then summed to yield an IBI for which low values indicate more highly disturbed sites in poorer ecological condition and the highest scores indicate relatively undisturbed areas of robust ecological condition. For example, IBI for Midwestern U.S. rivers based on 12 metrics could range from a low of 12 in areas with no fish to 60 in areas with diverse fish faunas typical of pristine areas.

Figure A An example of the range of values found in a hypothetical four-metric IBI for a study of Japanese streams. The four biological metrics displayed are benthic invertebrate taxa richness (top left), richness of clinger taxa (top right), percent of individuals in sample that are legless, such as snails and worms (bottom left), and dominance measured using three most abundant taxa (bottom right). Black triangles represent values from reference steams considered to be minimally influenced by humans. Gray triangles represent values from highly disturbed streams. The large black circles represent a sampling site that has an IBI value of 16 in this four-metric IBI. (Click image to enlarge.)

All U.S. states are required to incorporate biological assessment, such as using the IBI, to establish and maintain use designations for water bodies and to support section 319 Clean Water Act nonpoint-source programs, section 305(b) Clean Water Act water quality inventory reports, and national pollution discharge elimination system (NPDES) discharge permits. Use in monitoring programs of TMDLs (total maximum daily loads of pollutants) is also expanding (Karr and Yoder 2004).

A few studies have applied the IBI approach to assessment of the condition of terrestrial systems. In the shrub-steppe environments of eastern Washington and Idaho, an IBI was able to detect the biological effects of human actions on the resident biota (Kimberling et al. 2001; Karr and Kimberling 2003). Both terrestrial invertebrates and plants were studied. Sites with minimal history of human disturbance had higher IBIs than all other categories of disturbance (physical, dump, and agriculture, Figure B). Agriculture disturbances yielded the lowest levels of biological condition. A companion study in Idaho showed that IBI was also influenced by grazing of livestock and that carefully planned restoration programs increased IBI when compared to values at similar unrestored sites.

Figure B The effect of disturbance type (UD, minimally disturbed; Physical, physical/chemical disturbance; Dump, sites where chemicals or debris were buried; and Ag, agricultural disturbance) on the average biological condition of shrub-steppe communities in eastern Washington. Terrestrial invertebrates were used in this study, which resulted in development of a 9-metric IBI for further studies of ecological health in these communities. (Data from Kimberling et al. 2001.)

A key to successful restoration, mitigation, and conservation efforts is having an objective way to measure the biological condition of sites and to compare those sites to an objectively defined benchmark condition. IBI provides a tool for doing so and, at the same time, allows managers to set specific biological goals for restoration programs.

Literature Cited

Adler, R. W. 2003. The two lost books in the water quality trilogy: The elusive objectives of physical and biological integrity. Environ. Law 33:29–77.

Davis, W. S., B. D. Snyder, J. B. Stribling, and C. Stoughton. 1996. Summary of State Biological Assessment Programs for Streams and Rivers. EPA 230-R-96-007. Office of Policy, Planning, and Evaluation, US Environmental Protection Agency, Washington, DC.

Karr, J. R. 1981. Assessment of biotic integrity using fish communities. Fisheries 6:21–27.

Karr, J. R. 1991. Biological integrity: A long-neglected aspect of water resource management. Ecol. Appl. 1:66–84.

Karr, J. R. 1996. Ecological integrity and ecological health are not the same. In P.C. Schulze (ed.), Engineering Within Ecological Constraints, pp. 97–109. National Academy Press, Washington, D.C.

Karr, J. R. and E. W. Chu. 2000. Sustaining living rivers. Hydrobiologia 422/423:1–14.

Karr, J. R. and D. N. Kimberling. 2003. A terrestrial arthropod index of biological integrity for shrub-steppe landscapes. Northwest Sci. 77:202–213.

Karr, J. R. and C. O. Yoder. 2004. Biological assessment and criteria improve total maximum daily load decision making. J. Environ. Eng. 130:594–604.

Kimberling, D. N., J. R. Karr, and L. S. Fore. 2001. Measuring human disturbance using terrestrial invertebrates in the shrub-steppe of eastern Washington (USA). Ecol. Indicators 1:63–81.

Natural Resources Journal. 2004. Special issue: Managing biological integrity, diversity, and environmental health in the national wildlife refuges. Natural Resour. J. 44(4): 931–1238.

USEPA (U. S. Environmental Protection Agency). 2005. Use of Biological Information to Better Define Designated Aquatic Life Uses in State and Tribal Water Quality Standards. EPA 822-R-05-001. Office of Water, U. S. Environmental Protection Agency, Washington, D.C.