Abstract
As threats to species continue to increase, precise and unbiased measures of the impact these pressures are having on global biodiversity are urgently needed. Some existing indicators of the status and trends of biodiversity largely rely on publicly available data from the scientific and grey literature, and are therefore prone to biases introduced through over-representation of well-studied groups and regions in monitoring schemes. This can give misleading estimates of biodiversity trends. Here, we report on an approach to tackle taxonomic and geographic bias in one such indicator (Living Planet Index) by accounting for the estimated number of species within biogeographical realms, and the relative diversity of species within them. Based on a proportionally weighted index, we estimate a global population decline in vertebrate species between 1970 and 2012 of 58% rather than 20% from an index with no proportional weighting. From this data set, comprising 14,152 populations of 3,706 species from 3,095 data sources, we also find that freshwater populations have declined by 81%, marine populations by 36%, and terrestrial populations by 38% when using proportional weighting (compared to trends of -46%, +12% and +15% respectively). These results not only show starker declines than previously estimated, but suggests that those species for which there is poorer data coverage may be declining more rapidly.
Highlights
Quantifying trends in global biodiversity is crucial in order to understand the impacts of threats on the species and ecosystems on which humans rely [1]
The need for such metrics is pressing as threats and pressures upon the natural world continue largely unabated [2,3] and recent estimates of species extinction rates suggest they are significantly higher than background rates, having risen dramatically over the last 200 years [4,5]
To facilitate easy replication of the results presented here, an r package, rlpi, for calculating the Living Planet Index using either approach outlined below is provided with tutorial documentation, example data sets and the publically available records from the Living Planet Database [27] at https://github.com/Zoological-Society-of-London/rlpi
Summary
Quantifying trends in global biodiversity is crucial in order to understand the impacts of threats on the species and ecosystems on which humans rely [1]. The need for such metrics is pressing as threats and pressures upon the natural world continue largely unabated [2,3] and recent estimates of species extinction rates suggest they are significantly higher than background rates, having risen dramatically over the last 200 years [4,5]. Aichi Target 12 focusses on preventing the extinction of threatened species and improving and sustaining their conservation status. The mechanism required to assess progress towards this target relies on the development of PLOS ONE | DOI:10.1371/journal.pone.0169156 January 3, 2017
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