The London Zoological Society has just released its new Living Planet Report, which aims to evaluate the "health" of planet using a range of metrics and indices, as well as case studies.
It is an interesting read, although the challenges of statistically analysing and drawing conclusions from such tricky BAD (Best Available Data) cannot be overestimated! A few headline results have been picked out by the media, including the analysis of animal populations.
According to the report, global animal populations have declined by 50% during the last four decades. This isn't just the number of species (i.e. extinctions), but also the population sizes of each species - for example the number of tigers living i the wild is estimated to have declined from 100,000 to 3,000 over the last century.
There is some other nice analysis though that hasn't been as widely reported. For example, perhaps unsurprisingly the report shows a positive correlation between individual nations "Ecological Footprint" (incorporating the effects of carbon emissions, land-use change and overfishing) and the Human Development Index (HDI) (see page 18 of the booklet summary of the report). The most developed countries have the greatest impact, and countries that have increased their HDI over the past 40 years have done so at thee expense of their footprint (Page 19).
There is some interesting discussion to be had about how useful these types of analyses are though, particularly when one considers the quality of the datasets that have to be relied on.
Stephen Buckland, co-director of the National Centre for Statistical Ecology in the UK, told BBC News: "It is clear that declines are occurring, and at a more rapid rate in tropical areas with high diversity than in temperate areas where much of our diversity was lost long ago. "But there is the question in the Living PIanet Index of why some populations are monitored when others are not. Those in decline are perhaps of greater interest, and hence more likely to be monitored, than those that are stable or increasing. For practical reasons, populations that are more impacted by man are more easily monitored. "Further, the quality of the data is highly variable from one population to another, and some population trends are likely to be biased. So is there a decline? Certainly. Are animal numbers around 52% lower than 40 years ago? Probably not."