Quantification of rehabilitation success on mine site waste dumps
Faculty of Business and Law
School of Marketing, Tourism and Leisure
The Rehabilitation and Degradation Index (RDI) was developed to assesses the extent to which a rehabilitated or disturbed area has progressed toward the creation of a near-natural, self-sustaining, functional ecosystem similar to that in an adjacent undisturbed area or alternatively how a disturbance factor such as agriculture, mining or cane toads have impacted on the functional ecosystems that existed prior to the disturbance. We argue that the rehabilitation objective for most mine sites and other large-scale disturbance projects should be to restore biotic integrity to a disturbed area. However, biotic integrity is a difficult concept to measure, and so efforts to restore the integrity of a site have often focussed on non-biological measures such as chemical and geophysical parameters (Environmental Protection Authority, 2006; Jasper, 2001; Riley, 1995; Van Horne, 1983). Biotic integrity is defined here as the ability of an ecosystem to support and maintain “a balanced, integrated, adaptive community of organisms having a species composition, diversity and functional organization comparable to that of the natural habitat of the region” (Karr, 1981). A variety of bio-indicators have been used to assess the impact of a disturbance on the biotic integrity of an area or the effectiveness of a rehabilitation program in restoring the biotic integrity of an area. The rationale that underpins most of these bio-indicators is that environmental disturbance leads to a reduction in the number of species and the dominance of a few species (Patrick, 1949), and a totally degraded or polluted environment supports few or none of the species endemic to the locality. The RDI is based broadly on the concepts of the Index of Biotic Integrity that was developed by Karr et al. (1986) to measure the health of riverine ecosystems, most of which were degraded by pollution and land management practices. In a rehabilitation context, the Index measures the reverse; i.e. the progress towards the establishment of a near-natural, self-sustaining, functional ecosystem. Others have also used Karr’s method and developed similar indices; see Stribbling et al. (1998) for benthic macro-invertebrates, Majer and Beeston (1996) for ants, Bradford et al. (1998) for birds and O’Connell et al. (1998; 2000) for songbirds. Other researchers have used invertebrates (Andersen et al., 2003; Bisevac and Majer, 1998; 1999; Majer, 2001; Nakamura et al., 2003; Read, 1999), birds (Armstrong and Nichols, 2000; Chase et al., 2000; Read and Andersen, 2000), mammals (Fox, 1997; Wilson and Friend, 1999) or reptiles (Nichols and Gardner, 1997; Read, 1999) to measure the integrity of rehabilitated areas. However, many of these studies have only considered the presence of species and not their relative abundance. Thompson and Thompson (2005) provide an argument and rationale for using reptiles as the bio-indicator taxa. Below we describe the components necessary to calculate a RDI score for a particular site and describe how the RDI can be used to measure the success of a rehabilitation program. We used rehabilitated mine site waste dumps in the Ora Banda region of Western Australia (WA) to develop the index. Three broad quantifiable parameters are used in the RDI; diversity, taxonomic groups and ecological groups.