Scrutinised: “Earth has lost 50% of its wildlife in the past 40 years”

After all the optimism on this blog in the past few weeks, I’m now in the mood for a little debunking of pessimism. “Earth has lost 50% of its wildlife in the past 40 years” claimed the WWF’s Living Planet Report recently, and the headline was eagerly cranked out by credulous journalists. BBC Radio 4 is still making the claim, for a forthcoming programme. But five minutes of research on the Living Planet Index (on which the claim rests) would have at least shown journalists that…

“The 2014 Living Planet Index reveals a global decline in vertebrate population abundance of 52% between 1970 and 2010″

Ah, so the decline was in vertebrate animals only (invertebrates, as readers will remember, are snails, spiders, flies, beetles and suchlike). And up to 2010 rather than 2014. And 52% rather than 50%. Nice to get it a little more precise. (Some especially dim journalists even soberly mis-reported that: ““Earth has lost 50% of its species in the past 40 years”).

So I assumed that Living Planet measured every known vertebrate species, all 62,839 of them? Er, no…

“The Living Planet Database (LPD) holds time-series data for over 14,000 populations of more than 3,000 vertebrate species from around the world.”

So the Living Planet measures only “3,000 vertebrate species”. And the coverage of those 3,000 species is sampled from a total of…

“14,000 populations”.

Then Living Planet threw out around 4,000 of those populations, in the process of getting toward the headline 52% figure…

“The global LPI is calculated using [a little] over 10,000 of these population time-series”

Were those approx. 4,000 discarded populations inconvenient in some way? It’s not stated. But OK, let’s assume that there were legitimate reasons for not using them, such as being from corrupt governments known to seek international conservation grants to tackle non-existent ‘declines’. But where did these time-series come from, exactly? They were…

“gathered from a variety of sources such as journals, online databases and government reports”

And are these sources bona fide, all good trustworthy data? One has to assume so. And based on actual head-counts of wildlife? Er, not always…

“The data used in constructing the index are time series of either population size, density, abundance or a proxy of abundance. For example, the number of nests or breeding pairs recorded may be used instead of a direct count of population.”

So some source data can be made up from a “proxy of abundance … instead of a direct count”. Hmmm. Well, I’m sure the fieldworkers and their local guides, collectors and spotters were all doing their best, shinning up trees rather than dozing underneath them. But the resulting data series are all for consecutive years, surely? Er, no again…

“If the data available are from only a few, non-consecutive years, a constant annual rate of change in the population is assumed between each data year.”

As if all this wasn’t shaky enough — the headline 52% turns out to actually come from computer modelling. The modelling was used to very heavily aggregate and re-shape the above data…

“The global index is calculated as a weighted average of temperate and in tropical regions. … A generalised additive modelling framework is used to determine the underlying trend in each population time-series. Average rates of change are calculated and aggregated to the species level. Each species trend is aggregated into indices according to taxonomic group and the biogeographic realm it occurs in. These indices are weighted proportionally using the estimated number of species in each group and realm and placing the most weight on those which are the most species rich. … These indices are aggregated into three system indices – terrestrial, freshwater and marine – which are weighted equally to produce the global LPI”

So it turns out that the headline 52% ultimately turns on…

“the estimated number of species in each group”

Estimated. But it doesn’t end with estimates based on estimates and assumptions and gaps. The complex mathematical gymnastics described above have actually been subject to radical tweaking, in a complex re-jigging processes, since the last report in 2012. These changes have conveniently sent the headline figure soaring up to 52%. For instance, in the WWF’s previous Living Planet Report for 2012, their headline figure was a 28% total loss from 1970 to 2008. So what happened between 2008 and 2010 to get that figure up to the current headline of 52%? The change is due to the computer modelling being changed to a new “diversity-weighted” methodology, making the new results different from…

“The previous results [in the 2012 Report, that] 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”

So was the 2014 Report also subject to a “valid peer-reviewed method”? It’s not stated in the Report, but one very much hopes so. Though I see just two external peer reviewers are listed, one of them, interestingly, being the government Minister for Sustainable Development for Mexico.

But wait, even the underlying dataset has changed since the 2012 Report…

“the dataset is always changing as new data continue to be added … A different composition of species and populations means that new trends are continuously being added” … “13 per cent more species” have been added since 2012, with a boost of reptiles by 46%, and fish by 33% since 2012.”

So those new added trends might even tend to be mostly from… species being studied precisely because of their apparent decline? One has to wonder if that’s often the case. Threatened wildlife populations nearer to man, and therefore more likely to be impacted by man, are also more likely to be studied. Such as frogs and fish in the heavily degraded and logged jungles of South America for instance? Or in the forests of a rapidly developing Mexico?

“The global LPI [which gives the headline 52%] shows a greater decline than in 2012 because of larger declines in the terrestrial, freshwater and marine indices … [the new] method means that reptiles, amphibians and fish species, which are largely declining, are given appropriate weight in the index calculation. This results in a larger overall decline.”

So that statement identifies a big part of decline, albeit one resting on estimates-on-estimates. It’s in the amphibians (frogs and toads) and fish, mostly, and judging by the maps in the Report the losses seem to be the heaviest in South and Central America and its coastal waters. I presume pollution, logging and overfishing in the region’s many basket-case nations has some part to play in this, as well as the general development happening in relatively robust nations such as Brazil and Mexico. Frogs and amphibians are also known to have suffered a calamitous global decline — mainly due to a fungus killing them — and they have have been especially hard hit in Mexico and Central America. We also know from the recent excellent expeditions of the Census of Marine Life that the world’s oceans are indeed being heavily overfished, mostly in the global south. These are declines that are worrying and worthy of action — we certainly need a 10 year moratorium on industrial-scale mega-trawlers in the world’s oceans, better eco-governance in Central and South America, and to robustly protect frogs and bees — but the WWF does not appear to have presented evidence of an ongoing evenly-spread pan-global collapse in the biosphere.

In fact, the WWF seems to have presented evidence for optimism. The Report shows that all types of species grew in numbers in the world’s temperate regions, and wildlife is also currently doing rather well overall in Africa. In the developed world, which is likely to have the most reliable and lengthy data, wildlife numbers are up by 10% overall.

humpnycPicture: Humpback Whales are returning to the waters off New York City, 2014.

Advertisements