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The start of Earth's
sixth mass extinction has already been triggered, scientists say
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Humans have already triggered the start of Earth's sixth mass
extinction, thereby threatening their own future as a species, a hard-hitting
new study has claimed.
The window of opportunity
to prevent the worst diversity disaster since dinosaurs were swept from the
planet 65 million years ago is "rapidly closing", warn the authors.
In the last century
vertebrates have been disappearing at a rate 114 times higher than would
normally be expected without the destructive influence of humans, according to
the scientists, who insist their analysis is "extremely
conservative".
Press Association reports:
If the current pace of
extinction is allowed to continue, species loss will have a significant effect
on human populations in as little as three generations, it is claimed.
Once the damage is done,
it could take millions of years for nature to recover, said the researchers.
They pointed out that
since 1900, over 400 more vertebrates than expected had vanished. The lost
animals included 69 mammal, 80 bird, 24 reptile, 146 amphibian and 158 fish
species.
Today, the spectre of
extinction hung over 26% of all mammalian species and 41% of all amphibians.
Professor Paul Ehrlich,
from Stanford University in California, a leading member of the team, said:
"Without any significant doubt ... we are now entering the sixth great
mass extinction event.
"There are examples
of species all over the world that are essentially the walking dead. We are
sawing off the limb that we are sitting on."
Loss of species disrupts
ecosystems, leading to serious knock-effects felt by humans, the scientists
stressed. Crop pollination by bees and the water purification of wetlands were
two examples of biodiversity benefits which could be lost in three human
lifetimes.
Mexican lead researcher
Dr Gerardo Ceballos, from the Universidad Autonoma de Mexico, warned that
humans could one day follow in the footsteps of the dinosaurs.
"If it is allowed to
continue, life would take many millions of years to recover, and our species
itself would likely disappear early on," he said.
Mass extinctions have
occurred on five occasions throughout the history of life on Earth. The last
event happened 65 million years ago when a giant meteor smashed into the
planet, altered the climate, and wiped out the dinosaurs.
The scientists used a
conservative approach to calculate a natural "background rate" of two
mammal extinctions per 10,000 species per century.
This was the rate of
diversity loss that should be expected between mass extinctions.
Given the number of
species that had vanished over the last 100 years, it would have taken between
800 and 10,000 years for so many creatures to disappear if the background rate
had applied.
Writing in the journal
Science Advances, the researchers concluded: "Our analysis emphasizes that
our global society has started to destroy species of other organisms at an
accelerating rate, initiating a mass extinction episode unparalleled for 65
million years."
The authors said it was
still - just - possible to avert a "dramatic decay of biodiversity"
through intensive conservation, but time was running out.
They wrote: " Avoiding
a true sixth mass extinction will require rapid, greatly intensified efforts to
conserve already threatened species, and to alleviate pressures on their
populations - notably habitat loss, over-exploitation for economic gain and
climate change.
"All of these are
related to human population size and growth, which increases consumption
(especially among the rich), and economic inequity."
Sixth Great Extinction
Of Animal Species Driven By Humans, Say Scientists
Study reveals rate of extinction for species in the 20th
century has been up to 100 times higher than would have been without human impact
Guardian
News & Media reports:
The modern world is
experiencing a “sixth great extinction” of animal species even when the lowest
estimates of extinction rates are considered, scientists have warned.
The rate of extinction
for species in the 20th century was up to 100 times higher than it would have
been without man’s impact, they said.
Many conservationists
have been warning for years that a mass extinction event akin to the one that
wiped out the dinosaurs is occurring as humans degrade and destroy habitats.
But the authors of a
study published on Friday said that even when they analysed the most
conservative extinction rates, the rate at which vertebrates were being lost
forever was far higher than in the last five mass extinctions.
“We were very surprised
to see how bad it is,” said Dr Gerardo Ceballos of the National Autonomous
University of Mexico. “This is very depressing because we used the most
conservative rates, and even then they are much higher than the normal extinction
rate, really indicating we are having a massive loss of the species.” Previous
studies have warned that the impact of humans taking land for buildings,
farming and timber has been to make species extinct at speeds unprecedented in
Earth’s 4.5 billion-year history.
Ceballos said that his
study, co-authored by Paul R Ehrlich who famously warned of the impact of
humanity’s “population bomb”, employed better knowledge of natural or so-called
background extinction rates. He said it was conservative because it looked only
at species that had been declared extinct, which due to stringent rules can
sometimes take many years after a species has actually gone extinct.
Under a “natural” rate of
extinction, the study said that two species go extinct per 10,000 species per
100 years, rather than the one species that previous work has assumed.
Modern rates of
extinction were eight to 100 times higher, the authors found. For example, 477
vertebrates have gone extinct since 1900, rather than the nine that would be
expected at natural rates. “It’s really signalling we’ve entered a sixth
extinction and it’s driven by man,” said Ceballos. However, Prof Henrique
Miguel Pereira, the chair of the Group on Earth Observations Biodiversity
Observation Network, said that the new paper did not add anything
revolutionarily new.
“They argue that recent
extinction rates are up to 100 times higher than in the past. I think it
improves our documentation of the process but it does not yet confirm a sixth
mass extinction. I tend to think we have a major biodiversity crisis, but it
would take either a fast acceleration of current extinction rates or a couple
of centuries at current extinction rates, for the current process to become a
sixth mass extinction.”
The team behind the new
analysis said “rapid, greatly intensified efforts” would be needed to stop or
slow the extinctions currently underway. Ceballos pointed to the Pope Francis’s
encyclical on the environment, which was published on Thursday and lamented the
loss of the world’s biodiversity, and interventions by Barack Obama, as signs
of hope. “These important figures are starting to really grasp the problem,” he
said.
On why people should be
worried about the rate of extinctions, he said: “People say that’s really sad,
but why does it affect me? There are many reasons we should care. We are the
species that are causing the loss of all these other species.” But the most
important reason, he said, was that by losing species humanity was losing what
enabled us to have a “good standard of living”.
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