Assessing the causal relationships of ecological integrity: a re‐evaluation of Karr's iconic Index of Biotic Integrity

Abstract

The Index of Biotic Integrity (IBI) has been widely used since the 1980s to estimate ecological integrity—the capacity of an ecosystem to support and maintain its full range of components and processes. Despite this, IBI approaches have been criticized for their lack of objectivity, of justification for the selection of metrics, and of statistical rigor. In this paper, we assessed the potential of canonical correspondence analysis (CCA) and Structural equation modeling (SEM) as complementary methods for assessing ecological integrity. We use an iconic freshwater ecosystem dataset from Northeastern Illinois to assess ecological integrity using both classical IBI approach, and compare this with alternative methods. When we attempt to replicate the IBI methodology, we find issues with the approach including the possibility of the same IBI value for many possible levels of ecological integrity. We showed with the use of other methods (CCA) that the use of tolerant species, total abundance, and total richness—all defining components in IBI—can result in misleading interpretations of ecological integrity and that IBI scores might not comprehensively depict integrity scenarios. Structural equation modeling allowed us to test a conceptual causal model of ecological integrity. We found that water quality had an effect on the diversity and abundance of fish, and these in turn had an effect on trophic function, revealing important relationships between variables that contribute to ecological integrity. We conclude that CCA and SEM can complement multimetric indices, like IBI, and help with the development of more reliable, objective, and science‐based estimations of ecosystem integrity, as well as generate testable hypotheses about ecological integrity.

Assessment of Aquatic Ecosystem Health with Indices of Biotic Integrity (IBIs) in the Ganjiang River System, China

“…Fish sampling: In streams where humans can wade, an electrofisher was used for sampling, and a block was placed 10-15 m downstream for collection [38,[45][46][47]. For river segments with depths greater than 1.5 m, gill nets were used for fishing [33].…”

Monitoring of Rivers and Streams Conditions Using Biological Indices with Emphasis on Algae: A Comprehensive Descriptive Review toward River Management

“…Multi-metric techniques (biotic integrity indices) [182] are employed as an approach where an integrated balance is maintained in adaptive biological systems between elements and processes such as species, genus, assemblage and biotic interaction, nutrient and energy dynamic, meta-population process respectively in natural habitats [183,184]. The initial concept of biotic integrity, the Index of Biotic Integrity (IBI) has been developed for fish in shallow rivers [185] in the USA measuring trophic composition, species composition, and abundance and health of fish [183,186], and Karr's work is reevaluated in Capmourteres et al [187]. According to Gordon et al [7], in the case of the biotic integrity index small disturbance to the system has negligible effect on the biological integrity of the system, which was one of the presuppositions of its design [185].…”

Ecological River Health Assessment Using Multi-Metric Models in an Asian Temperate Region with Land Use/Land Cover as the Primary Factor Regulating Nutrients, Organic Matter, and Fish Composition

“…To identify such factors when assessing aquatic habitats, there is a need to develop more robust techniques and indicators of ecosystem health monitoring [ 13 ]. Consequently, many indicators and methods have been developed to assess the ecological health of river ecosystems worldwide, such as in the United States [ 4 , 14 ], United Kingdom [ 15 , 16 ], Canada [ 17 , 18 ], France [ 16 ], Germany [ 15 , 19 ], Sweden [ 20 ], Australia [ 21 ], New Zealand [ 22 ], Africa [ 23 ], Namibia [ 7 ], Sri Lanka [ 24 ], China [ 3 ], and South Korea [ 10 ]. Traditionally, river health monitoring has been based on water chemistry assessments [ 25 ]; however, recent investigations have revealed that this approach does not yield critical information about a river’s ecological health status [ 26 ].…”