Ecological integrity assessment as a metric of biodiversity: are we measuring what we say we are?

Abstract

As the recognition of the importance of biological diversity in biological conservation grows, an ongoing challenge is to develop metrics that can be used for effective conservation and management. The ecological integrity assessment has been proposed as such a metric. It is held by some to measure species composition, diversity, and habitat quality, as well as ecosystem structure, composition, and function. The methodology relies on proxy variables that include data on landscape characteristics such as patch size, abiotic factors such as hydrology, and some features of vegetation structure and composition. We suggest that the measure is flawed on four levels. First, its putative representation of general ecological form and function, and its lack of specific detail about how it actually represents those attributes, leaves the metric without the focus needed to be useful for measuring ecological features on the ground and testing associated hypotheses and predictions. Second, the proxy variables used to represent biological diversity, such as habitat (vegetation) metrics and vascular plant species diversity, are not empirically correlated with diversity of a range of taxa or of other components of the biota. Third, like other ecological indices that integrate many distinct features, the ecological integrity index is subject to the loss of information in its condensation of multi-dimensional variability into a one-dimensional index, and it may be subject to systematic bias from the conversion of raw data into categorical scores. Fourth, the sampling protocols are at risk of sampling bias, observer bias, and measurement error, any of which can confound the estimation of conservation value. In terms of biological diversity, the methodology produces an unreliable estimate of the number of vascular plant species and their relative percentages of occurrence, and an absence of any protocols for taxa other than plants. For these reasons 123Biodivers Conserv (2016) 25:1011-1035 DOI 10.1007/s10531-016-1111 we believe that ecological integrity assessment is currently of limited value as a measure of site-specific biological diversity and its change over time. A considerable amount of investigation is needed in order to have confidence in the results of an ecological integrity assessment, especially if it is to be used for regulatory purposes. We suggest further refinements and discuss alternative measures of biological diversity that provide reliable metrics for assessing change. A thoughtful choice among measures can help to identify the most appropriate assessment for conservation decisions.

The use of response measures in meta-analyses of land-use impacts on ecological communities: a review and the way forward

“…We can envisage at least three possible causes for that trade-off: (1) a strive for simplicity in the design and presentation of the studies (total species richness is straight forward measure that does not require much explanation compared to more complex measures of biodiversity); (2) space restrictions in scientific articles putting limits to the number of analyses that can be presented in a paper; and (3) the greater amounts of ecological knowledge and labour required for applying high-informative measures or approaches to several taxonomic groups. There is a general agreement in the scientific community that multiple taxonomic groups should be studied to obtain reliable estimates of the effects of a given human intervention on biodiversity (Barlow et al 2007;Brown and Williams 2016). In our evaluation, a few of the studies consistently used high-informative measures while encompassing several taxonomic groups and covering a large geographical scale (e.g., Gibson et al 2011;Fedrowitz et al 2014;Curran et al 2014;Newbold et al 2014), showing that with some effort, high-informative measures can be used even in wide-scope studies.…”

A landscape index of ecological integrity to inform landscape conservation

“…Note, if distinct ecosystems are not 480 deemed meaningful or reliably mapped, we have an alternative gradient-based approach that can be used. Second, our approach embraces the concept of ecological integrity, but defined in a manner that makes it less subject to the criticisms often leveled against the use of ecological integrity (Brown and Williams 2016). In particular, our approach does not require the establishment of a 485 reference condition or natural range of variation for each of the metrics as is customary for definitions of ecological integrity (Parrish et al 2003), which we purport is exceedingly difficult or even impossible to do in most applications.…”

“…if not impossible to validate (but see McGarigal et al 2013, which provides a partial validation of IEI based on extensive field data on a number of taxa) given the long-term nature of the predictions, which has been a major source of criticism (Brown and Williams 2016). We sought to reduce the need for formal validation of IEI by eliminating the need for a reference condition or natural range of variability and instead using quantile scaling to rate sites relative to each 565 other.…”

“…An alternative approach, but not without its critics (e.g., Brown and Williams 2016), has been to focus on ecosystems, with attention to both the biotic as well as geophysical environment, and 80 use the concept of ecological integrity to identify and prioritize places of conservation value (e.g., Tierney et al 2009, Theobald 2013, Wurtzebach and Schultz 2016, Belote et al 2017. Here the goal is to conserve the "ecological stage" by focusing on places with high ecological integrity that can sustain the biota and critical ecological processes.…”

Multiscale guidance and tools for implementing a landscape approach to resource management in the Bureau of Land Management

“…To quantify development levels, we did not use weightings for different types of development (Comer and others, 2013;Theobald, 2010Theobald, , 2013Venter and others, 2016) or fuzzy logic models (Bryce and others, 2012) that generally require assumptions about the magnitude of the response of a particular species to the change agent and rely on expert opinion, which can introduce bias (Brown and Williams, 2016). Such assumptions limit the generality, flexibility, and transparency of the index.…”