Adapting global biodiversity indicators to the national scale in Australia

Posted on Jun 9, 2014 | 0 comments

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This study by Szabo et al. (2012) illustrates how a Red List Index (RLI) can be disaggregated to understand underlying patterns and identify subsets of species for which extinction risk has changed most rapidly – and also how trends can be examined not just at the species and subspecies level but also on geographical, political and taxonomic subsets of the data.

RLIs were calculated for birds in Australia both including and excluding status changes that resulted from threats acting outside the Australian part of a visiting taxon’s distribution; this was in order to quantify the extent to which Australia national biodiversity trends are driven by external or internal threats.

The evaluation of trends in the extinction risk for birds in Australia was based on national-scale assessments undertaken in 1990, 2000 and 2010. RLIs were calculated based on the number of taxa in each Red List category and the number that changed categories between assessments in 1990, 2000 and 2010 as a result of genuine improvement or deterioration in status.

Categorisations for 1990 and 2000 were retrospectively adjusted using current (2010) knowledge. The authors assumed that the current category applied to the earlier assessments, except where there was proof that the species had experienced a genuine improvement or deterioration in status of sufficient degree to cross the Red List category thresholds. In order to assess extinction risk nationally, the IUCN Guidelines for Application of IUCN Criteria at Regional Levels were followed to account for potential source and sink effects as a consequence of interchange with populations past the national borders.

Two versions of the RLI were calculated following the methods of Butchart et al. (2007). The RLI was first calculated including only the changes in status that resulted from processes happening within Australia, even if they transpire elsewhere, in order to assess geographical variation, and to show trends in extinction risk for taxa relevant to particular policy mechanisms within Australia (on basis of jurisdiction of the six states and two territories).

The RLI was then recalculated including all status changes irrespective of the location of threat – in order to understand the extent to which national trends in taxon status are driven by external threats. This dataset was also used to show trends in extinction risk for particular taxonomic groups, calculating trends for the five most species-rich orders individually and for the remainder of species as a group.

For Australia, the majority of status changes were shown to be driven by factors outside Australia, possibly indicating that enhanced international advocacy and assistance would be necessary if local losses are to be prevented. This study also showed that jurisdictional disaggregation for example can be used to highlight performance of individual national subunits.

According to the authors, a RLI calculated from national scale assessments of extinction risk, should provide a more sensitive metric of biodiversity loss than a national disaggregation of a global index. This is because a higher proportion of species tend to qualify as threatened or Near Threatened when their extinction risk is assessed at a finer spatial scale; hence more species tend to move between categories when assessments are repeated, leading to RLI trends that are more representative of the changing status of the species concerned.

Overall, calculation of the RLI at the country level is a valuable addition to national biodiversity benchmarking.