Are WWF doing things by halves? (1)

The recently released WWF “Living Planet Report 2014” has filled me with a mix of feelings. On one hand its central claim that since 1970 we have lost 52% of “population sizes of the vertebrate species” sounds scary. This is more than half of the World’s animals gone in the last 40 years. On the other hand WWF is a multi-million dollar eco-propaganda outfit living off making scary claims which does not exactly inspire confidence in their latest report.

To make sense of the WWF claims I decided to do my own research. I got off to a good start because the WWF website has download links to both the summary and full report. The summary is just a glorified media statement so I studied the full report in hope of finding out how exactly the vertebrates were counted. Having read through the WWF methodology I am still far from clear about their maths but a few perplexing details have drawn my attention.

The graph on page 18 of the report indicates the number of populations which are increasing, stable and declining:

Untitled

You may be surprised to notice that there is more green (increasing) than purple (declining) in the graph. This is not an error – more populations are increasing than declining but, as explained in the report:

Even though slightly more populations are increasing than declining, the magnitude of the population decline is much greater than that of the increase, resulting in an overall reduction since 1970.

Because WWF are not comparing the number of populations on the increase versus those in decline but rather working out the average loss ratio across all populations the above explanation sounds reasonable. The problem is WWF have already done the same exact exercise before – with different results. Their 2012 “Living Planet Report” claimed a 28% decline for the period 1970-2008 (I deliberately left the date of the report in the footnote):

2012

But the loss of animal life for almost the same assessment period of 1970-2010 now stands at 52% (again – check out the footnote):

2014

How could the ratio of loss in the animal populations have changed from 28% to 52% in two years? Was one quarter of the World’s animals slaughtered in 2009 without anyone noticing? No, as it turns out the reason for this surprising dip is a lot less dramatic – WWF used a different assessment method in the current report. On page 138 we read:

The unweighted LPI (LPI-U) methodology presented in previous editions of the Living Planet Report makes calculations based on the average rate of change across all species from year to year. (…) The LPI-D is an adapted version of this method. It has not been used in previous editions of the Living Planet Report. 

So WWF have changed their maths and the Global Living Planet Index took a massive dive. What a coincidence! So, was the previous calculation flawed? Again, let us refer to the Q & A section of the 2014 report for explanation:

The previous results were calculated using a valid peer-reviewed method. Now that the dataset is larger, it is possible to use a revision to this method producing different results that are considered to provide a better representation of trends in vertebrate species than previously. These new results do not discredit previous LPIs; rather, they are the latest outputs from what is a continually evolving process.

So, there was nothing wrong with the previous method but LPI-D provides a “better representation of trends” than before. A cynic in me is getting a bit uneasy when I hear about a revision of a perfectly adequate method, which happens – just happens – to produce much more dramatic results.

Are WWF doing things by halves? (2)

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