The World’s Wildlife May Not Have Halved, But The Decline Is Still Dangerous

According to the WWF (World Wildlife Fund for Nature) and London Zoological Society (LZS) 2014 Living Planet Index, which details the newest global trends in biodiversity, the world’s wildlife population has halved in just 40 years.

Using new and purportedly more accurate methodology than that of their previous indexes to analyze data, the report’s headline-grabbing findings were these:

  • The population of the world’s mammals, birds, reptiles, amphibians, and fish has declined by an average 52 percent in 40 yearsGlobal_LPI-95
  • Populations of freshwater species fell even further by a steep 78 percent.
  • The biggest threat to biodiversity globally comes from the combined impacts of habitat loss and degradation, driven by unsustainable human consumption. The impacts of climate change are also of increasing concern.

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The report measured over 10,000 populations of over 3,000 species. The index’ new methodology assigns more weight to species based on their regional prominence — before, it simply calculated the average decline of all species measured. This new level of data sophistication indicates that the state of biodiversity may be worse than previously thought.


Biodiversity loss, or defaunation, is a notoriously difficult thing to quantify due to the amount of data collected, the amount not collected, and how it’s processed and compiled. It’s important, therefore, to look at any research critically and in context of other findings.

Moreover, both the LZS and WWF are conservation organizations, meaning their primary goals are protection and awareness rather than scientific accuracy, and their research subject to imperfect peer-review.

So, how does the Living Planet Report stack up with scientific research, and the opinions of other experts? Here’s some other studies to add some context:

  • In April of 2014, a study on biodiversity published in the journal Science found that when looking at 35,000 plant and animal species over time, there was not a consistent loss in species numbers, but a consistent change in where these species were located. The study suggests that conservationists should prioritize these shifts in order to monitor species compositions accurately. Changes in migration, therefore, may not be taken into account during observations of regional population declines.
  • A July 2014 study’s findings (pdf) are closer to the WWF’s: according to their research, defaunation is indeed a global trend — and a dangerous one at that. The study observes that in the last 500 extinction has been at a rate comparable to past mass extinctions. Of a conservatively estimated 6 to 9 million documented species, we are likely losing 11,000 to 58,000 annually.  
  • Another study published in July of 2014 delves into the impact that defaunation has on humans. It found that decline in wildlife equates with loss of food and employment, which cause an increase in human trafficking and organized crime.
  • And it gets worse from there — research published in PNAS concludes that declining wildlife heightens the risk of disease being transmitted from animals to humans.

The takeaway

Stephen Buckland, co-director of the National Centre for Statistical Ecology, tells the BBC that though it is clear that declines are occurring, the Living Planet Index’ selective monitoring may have the right gist, but be slightly off in terms of accuracy.

“Is there a decline? Certainly,” Buckland says. “Are animal numbers around 52% lower than 40 years ago? Probably not.”

But given the findings of recent peer-reviewed studies and scientific research, even if the WWF figure isn’t exactly right, an accelerating trend of decline appears to be occurring. The potential impacts — which could hurt both the planet and human wellbeing — may indeed be a justifiable reason for concern.

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Jennifer Markert