Getting biodiversity intactness indices right: ensuring that 'biodiversity' reflects 'diversity'

The 2010 biodiversity target of a ‘significant reduction in the current rate of biodiversity loss’ presents challenges for effective measurement of changes in global/regional biodiversity. A simple ‘biodiversity intactness index’ (BII) is attractive in using available data and expert opinion, but is seen to be only weakly linked to ‘biodiversity’ in its usual sense of ‘variation’. An example illustrates how an improved BII score could result even when there are large species losses. A family of alternative biodiversity ‘representativeness indices’ better reflect variation. They use the same readily available information, plus simple species–area relationships (SAR) and genetic diversity curves. A new genetic‐diversity abundance‐fraction curve, like SAR, is linear in log–log space. The new representativeness indices incorporate, through range‐abundance curves, the abundance fraction estimates normally used for BII. Land use or climate change impacts therefore can reflect partial rather than total biodiversity losses at localities. Estimates of biodiversity gains/losses using these indices enable a novel regional planning‐based approach for addressing the 2010 target.