CRAMP Rapid Assessment. Index of Biological Integrity (IBI)
An Index of Biotic Integrity (IBI) has been widely used in freshwater systems to assess the condition of ecosystems, to assist in management decisions and policymaking (Smith et al. 1995, Karr and Chu 1999).
The IBI was developed for use in warm water streams in the U.S. Midwest in 1981 (Karr and Chu 1999). It uses a multimetric design that integrates attributes that respond to anthropogenic influence. Comparison of fish community characteristics to reference conditions result in a score of 1 to 5, with a score of one having the lowest biotic integrity. All organic attributes are included for each site. Scores for these attributes are then summed, culminating in a single, unitless, index value. Use of IBI as a measurement value grew rapidly, expanding to other regions and stream types. As its application grew, the basic design was retained, although the scoring and attributes varied in response to differing environmental conditions. The central premise of IBI involves environmental classification, attribute selection, methodological development, and statistical design.
Attempts are currently underway to extend these models to nearshore marine environments (Coral Reef Functional Assessment Workshop 2004). In an extensive literature review of coral reef assessments, Jameson et al. (1998) concluded that there is insufficient information to develop biocriteria guidelines for coral reefs. The complexity and diversity of Hawaiian coral reefs makes attribute selection and establishment of reference conditions difficult.
IBI compares biological criteria in undisturbed streams to those in degraded streams to determine the deviation from original conditions (Karr and Chu 1999). To quantify this departure, establishment of reference conditions within each stream classification is necessary.
Biological criteria describe the conditions that should be present in a specific habitat, thereby providing standards to compare against assessment data. It encompasses a sequence of ambient conditions relative to the biological integrity within a particular geographic classification. Biological integrity is synonymous with natural, pristine conditions. This state is homologous with minimally or undisturbed environments, which serve as, reference sites. Assessment and monitoring data can be converted to biological indices and compared to biocriteria at these reference sites.
Impairment of the habitat can be evaluated based on its departure from the biocriteria. To develop biocriteria that describe the biological condition of a community, its structure and function is characterized by numeric or narrative values based on the assessment of the organisms present.
It has been suggested that selection of biocriteria be based on the following attributes.
The biological integrity of a region reflects the ability of the community to maintain a balance of organisms and interactions under natural, unperturbed conditions. This integrity is compromised when components of the functional organization depart from original, pristine conditions. An accurate description of the community will include aspects of the system that respond to anthropogenic perturbations. Subsequent contrasts can then be made between comparable habitats.
The development and testing of a multivariate statistical model using IBI to predict conditions at sites not previously surveyed will be valuable in establishing management priorities, regional policy and evaluation of existing programs in the Hawaiian Islands. Application of a model would allow management to implement a preventative approach to environmental degradation.
Karr J.R.and Chu E.W. 1999. Restoring Life in Running Waters: Better Biological Monitoring. Island Press, Washington, DC. 206 pp.
Smith, D. R., Ammann, A., Bartoldus, C., and Brinson, M. M. 1995. An approach for assessing wetland functions using hydrogeomorphic classification, reference wetlands, and functional indices. Technical Report WRP-DE-9, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS. NTIS No. AD A307 121.
Coral Reef Functional Assessment Workshop. Co-sponsored by the Army Corps of Engineers and University of Hawaii Sea Grant. August 23-25, 2004.
Last Update: 04/21/2008
By: Lea Hollingsworth
Hawai‘i Coral Reef Assessment & Monitoring Program
Hawai‘i Institute of Marine Biology
P.O. Box 1346
Kāne‘ohe, HI 96744