The global loss of species is even worse than previously thought, the London Zoological Society (ZSL) says in its new Living Planet Index.
30 September 2014
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| Green Photo Archive - Credit F. Iaconianni |
The report suggests populations have
halved in 40 years, as new methodology gives more alarming results
than in a report two years ago.
The report says populations of mammals,
birds, reptiles, amphibians and fish have declined by an average of
52%.
Populations of freshwater species have
suffered an even worse fall of 76%.
Severe impact
Compiling a global average of species
decline involves tricky statistics, often comparing disparate data
sets - and some critics say the exercise is not statistically valid.
The team at the zoological society say
they've improved their methodology since their last report two years
ago - but the results are even more alarming.
Then they estimated that wildlife was
down "only" around 30%. Whatever the numbers, it seems
clear that wildlife is continuing to be driven out by human activity.
The society's report, in conjunction
with the pressure group WWF, says humans are cutting down trees more
quickly than they can re-grow, harvesting more fish than the oceans
can re-stock, pumping water from rivers and aquifers faster than
rainfall can replenish them, and emitting more carbon than oceans and
forests can absorb.
It catalogues areas of severe impact -
in Ghana, the lion population in one reserve is down 90% in 40 years.
In West Africa, forest felling has
restricted forest elephants to 6-7% of their historic range.
Globally, habitat loss and hunting have
reduced tigers from 100,000 a century ago to just 3,000.
In the UK, the government promised to
halt wildlife decline - but bird numbers continue to fall.
The index tracks more than 10,000
vertebrate species populations from 1970 to 2010. It reveals a
continued decline in these populations. The global trend is not
slowing down.
'New method'
The report shows that the biggest
recorded threat to biodiversity comes from the combined impacts of
habitat loss and degradation, driven by what WWF calls unsustainable
human consumption.
The
report notes that the impacts of climate change are becoming of
increasing concern - although the effect of climate change on species
until now is disputed.
WWF is keen to avoid despair. It points
to conservation efforts to save species like:
- A Gorilla Conservation Programme in Rwanda, promoting gorilla tourism
- A scheme to incentivise small-scale farmers to move away from slash and burn agriculture in Acre, Brazil
- A project to cut the amount of water withdrawn from the wildlife-rich River Itchen in the UK.
Previously, the Living Planet Index was
calculated using the average decline in all of the species
populations measured. The new weighted methodology analyses the data
to provide what ZSL says is a much more accurate calculation of the
collective status of populations in all species and regions.
A ZSL spokesman explained to BBC News:
"For example, if most measurements in a particular region are of
bird populations, but the greatest actual number of vertebrates in
the region are fish,
then it is necessary to give a greater weighting
to measurements of fish populations if we are to have an accurate
picture of the rate of population decline for species in that region.
"Different weightings are applied
between regions, and between marine, terrestrial and freshwater
environments. We are simply being more sophisticated with the way we
use the data."
"Applying the new method to the
2008 dataset we find that things were considerably worse than what we
thought at the time. It is clear that we are seeing a significant
long-term trend in declining species populations."
(source: BBC)
