Populations of Vertebrate Species Down 52 Percent Since 1970, Says Living Planet Index Report

Yesterday, the World Wildlife Fund activist group
published its Living Planet Index 2014 report that
calculates that the Earth is home to about half the number of
vertebrates (mammals, birds, reptiles, amphibians, fish) that it
hosted in 1970. Let’s be clear: The report is NOT saying that half
of vertebrate species have gone extinct, but that the overall
number of wild vertebrates have declined by half. The trend is
calculated using a complicated system for weighting the declines in
various vertebrate species populations. Interestingly, this report
comes just two months after a study,”Defaunation in the
Anthropocene” published in Science reported:

Among terrestrial vertebrates, 322 species have become extinct
since 1500, and populations of the remaining species show 25
percent average decline in abundance.

The comparable LPI terrestrial vertebrate figure is 39 percent
since just 1970. 

In any case, the LPI parses data from 10,380 populations of
3,038 species out of an estimated 62,839 vertebrate species that
have been described globally. From the report: 

The Living Planet Index (LPI), which measures trends in
thousands of vertebrate species populations, shows a decline of 52
per cent between 1970 and 2010 (Figure 2). In other words, the
number of mammals, birds, reptiles, amphibians and fish across the
globe is, on average, about half the size it was 40 years ago. This
is a much bigger decrease than has been reported previously, as a
result of a new methodology which aims to be more representative of
global biodiversity.

Biodiversity is declining in both temperate and tropical
regions, but the decline is greater in the tropics. The 6,569
populations of 1,606 species in the temperate LPI declined by 36
per cent from 1970 to 2010. The tropical LPI shows a 56 per cent
reduction in 3,811 populations of 1,638 species over the same
period. Latin America shows the most dramatic decline – a fall of
83 per cent. Habitat loss and degradation, and exploitation through
hunting and fishing, are the primary causes of decline. Climate
change is the next most common primary threat, and is likely to put
more pressure on populations in the future.

The report also notes some countervailing population trends:

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. 

The LPI finds that 37 percent of the population declines result
from direct exploitation, e.g. overfishing; and 31.4 and 13.4
percent is from habitat degradation and destruction, e.g., cutting
down tropical forests. 

Steep declines in animal populations have happened before. A
2008
article in the Proceedings of the National Academy of
Sciences calculated that at the end of the last Ice Age human
hunters so decimated the populations of large tasty critters that
the total biomass of the world’s terrestrial animals did not
recover to its previous level until the Industrial Revolution. But
then most of the recovered biomass consisted of human beings and
our domesticated animals. By one
estimate the world’s farms and ranches harbor today about 1.4
billion cattle, 1.9 billion sheep and goats, 980 million pigs, and
19.6 billion chickens. 

Just two months ago in my article, “Predictions
of a Man-Made Sixth Mass Extinction May Be Exaggerated,” I
argued that trends in population growth, reforestation,
agricultural productivity,and urbanization all point in a more
hopeful direction over the balance of this century with regard to
protecting wild species.