Can the 6th Mass Extinction be stopped?
Cataclysmic events drove the first five mass extinctions in Earth’s history. An asteroid ended
the age of the dinosaurs. Volcanic eruptions may have caused the Great Dying, which wiped out
much of the earth's marine life.
Altogether, the five mass extinctions caused 75 percent of the planet’s life to die out. The sixth
mass extinction may now be beginning — and we're the cause of this one.
Over the last several centuries we have constantly burned fossil fuels, like oil, coal and natural
gas. In the process, we've changed the climate for other species. Humans use more than half of
the planet’s unfrozen land for cities and logging or food. Our takeover has destroyed the natural
habitats of animals and plants.
Humans have existed for 200,000 years on Earth. Biologists (study life) and paleoecologists
(who study ancient ecosystems) estimate that humans have driven roughly 1,000 species extinct.
Early man helped hunt the biggest animals — woolly mammoths, giant kangaroos and giant
sloths — to extinction. Since 1500, we have killed off at least 322 types of animals. The
passenger pigeon, the Tasmanian tiger and, most recently, the baiji, a freshwater dolphin in
China are all gone forever.
Thousands Of Species Threatened
Another 20,000 or more species are now threatened with extinction, according to the
International Union for the Conservation of Nature. The group keeps a list of all the known
endangered plants and animals on the planet. There are 5 million or so species on the planet.
Thanks to humans, they are all 28 percent smaller on average. And as many as one third of all
animals are either threatened or endangered, a new study in Science finds.
Scientists call this sixth mass extinction the "Anthropocene defaunation." The Anthropocene is a
name some geologists call the period of time that humans have ruled the Earth — and changed it.
They can't be sure how quickly it's happening. Perhaps that's because much of it is happening to
beetles and other insects that go overlooked. But according to the study in Science, their numbers
fell by half over the past 35 years. At the same time, the human population doubled. Other recent
studies suggest that the current extinction rate is roughly 1,000 times faster than the average pace
in Earth's history. That makes this the fastest extinction event on record, even if it is not yet a
mass die-off.
The biggest animals still left on the planet — elephants, tigers, whales, among others — are most
at risk. And we humans have shown no desire to stop the activities that drive extinction.
Trying To Change Course
And yet it's not too late. In just a few recent examples, humans brought the black-footed ferret
back from just seven left. Condors have been nursed back through vaccinations and raising by
hand. Salamanders have been restored. According to another new study in Science, people have
physically moved 424 species of plants and animals to protect them from extinction.
For such efforts to succeed, careful attention must be paid both to genetics and habitat. There is
no point in bringing back the baiji dolphin, for example, if the Yangtze River in China remains
polluted and overfished. But conservation efforts can work. Fishes can bounce back when we
stop overfishing. Both the Maine haddock and Washington state coho salmon have. The
reforesting of the East Coast of the U.S. shows that when farms go away, woodlands return.
Then coyotes, deer, turkey and other wildlife move back in. The animals and plants of the
Amazon rain forest have benefited from Brazil's efforts to stop deforestation.
And amazingly, paleoecologists have shown that 20 out of 21 large mammals in India — from
leopards to muntjac deer — have survived there for the past 100,000 years. All that time, they've
lived alongside one of the largest human populations on the planet.
Not Doomed Yet
To avoid the sixth mass extinction we will probably have to push harder for conservation.
Endangered species may need to be moved to help them deal with a changing climate. Think rewilding: reintroducing species like wolves or beavers that were once in a certain ecosystem but
have since disappeared. Aggressive conservation might also mean killing off newcomer species
to preserve or make room for local plants and animals; in New Zealand, killing off local rats
have helped kakapo parrots survive.
In the most extreme case new animals could be brought in. They could fill the role of animals
that have gone extinct. For example, European sailors ate their way through the Indian Ocean
islands of Mauritius, killing off the dodo bird and the local tortoise species. But tortoises from
the neighboring Seychelles archipelago have been imported recently. They have helped restore
the island ecosystem, including bringing back endangered local trees.
There is even some hope of bringing back entirely extinct species in the future using advances in
genetics and synthetic biology. Bringing back extinct species, or replacing extinct animals with
similar ones to restore ecosystems, could pose problems. Right now, new invasive species are
hurting ecosystems, like the Asian carp invading lakes in the U.S. We'll have to be careful.
But we are not doomed to cause a sixth mass extinction, at least not yet. Based on an estimate
published in Nature in 2011, we have a century or two before our actions assure a mass
extinction. Unlike an asteroid, we could choose to change course.
Instructions:
Read article, define bold-faced words, answer questions, and write SUMMARY!
1.
2.
3.
4.
What are the 3 fossil fuels?
About how many animals have humans driven extinct?
What animals (in general) are most at risk?
What are 3 things we are doing to reduce a sixth mass extinction?
Can the 6th Mass extinction be stopped?
The most famous mass extinction came from space, but the biggest might have been because of
carbon dioxide. Cataclysms, whether the asteroid that ended the dinosaurs’ reign or the
volcanism that may have caused the Great Dying, drove the first five mass extinctions in Earth’s
history, in which 75 percent or more of the planet’s life died out. The sixth mass extinction may
now be beginning — and the apocalypse this time is us.
During the last several centuries we have burned through eons worth of fossilized sunshine,
changing the climate for our fellow species. We use more than half of the planet’s unfrozen land
for cities, logging or food, eliminating the habitats of our fellow animals and plants. Before we
even achieved civilization, we had already helped hunt the biggest, fiercest animals — woolly
mammoths, giant kangaroos and giant sloths — to extinction.
Biologists and paleoecologists estimate that humans have driven roughly 1,000 species extinct in
our 200,000 years on the planet. Since 1500, we have killed off at least 322 types of animals,
including the passenger pigeon, the Tasmanian tiger and, most recently, the baiji, a freshwater
dolphin in China. Another 20,000 or more species are now threatened with extinction, according
to the International Union for the Conservation of Nature, which keeps a list of all the known
endangered plants and animals on the planet. The population of any given animal among the five
million or so species on the planet is, on average, 28 percent smaller, thanks to humans. And as
many as one third of all animals are either threatened or endangered, a new study in Science
finds.
In the jargon it's an "Anthropocene defaunation," or sixth mass extinction, and one caused by
humans. Scientists can't be sure of the current die-off rate, perhaps because much of it is
happening to beetles and other insects that are notoriously overlooked. But according to that new
study in Science, the total number of such invertebrates fell by half over the past 35 years while
the human population doubled. Other recent studies suggest that the current extinction rate is
roughly 1,000 times faster than the average pace in Earth's history. That makes this the fastest
extinction event on record, even if it is not yet a mass die-off.
The biggest, fiercest animals still left on the planet — elephants, tigers, whales, among others —
are most at risk. And we humans have shown no inclination to stop the activities —
overexploitation for food, habitat destruction and others — that drive extinction.
And yet it's not too late. In the past few decades humans brought the black-footed ferret back
from just seven individuals; vaccinated and hand-reared condors to relative abundance; and
battled to preserve and restore populations of hellbender salamanders, to name just a few in just
North America alone. According to another new analysis in Science, people have physically
moved 424 species of plants and animals to protect them from extinction.
For such assisted migration efforts to succeed, careful attention must be paid both to genetics and
habitat. There is no point in bringing back the baiji, for example, if the Yangtze River remains
polluted and overfished. But conservation efforts can work. Fishes can rebound when fishing
pressure is removed, just as Maine haddock and Washington state coho salmon both have. The
reforesting of the U.S. eastern seaboard shows that when farms go away, woodlands return, and
coyotes, deer, turkey and other wildlife move back in. The animals and plants of the Amazon
rain forest have benefited from Brazil's efforts to curb deforestation. And in what might prove an
enduring lesson in conservation, paleoecologists have shown that 20 out of 21 large mammals in
India — from leopards to muntjac deer — have survived there for the past 100,000 years
alongside one of the largest human populations on the planet.
To avoid the sixth mass extinction we will probably have to employ more aggressive
conservation, such as moving species to help them cope with a changing climate. Think rewilding: reintroducing species like wolves or beavers that were once present in a given
ecosystem but have since disappeared. Aggressive conservation might also mean killing off
newcomer species to preserve or make room for local flora and fauna; in New Zealand, rat
extirpations have helped kakapos survive.
In the most extreme case aggressive conservation could involve bringing in new animals to fill
the role of animals that have gone extinct. For example, European sailors ate their way through
the Indian Ocean islands of Mauritius, killing off the dodo and the local tortoise species. But
closely related tortoises from the neighboring Seychelles archipelago have been imported
recently, and they have helped restore the island ecosystem, including bringing back the
endangered local ebony trees. As a result of that success, similar projects are being considered
from Caribbean islands to Madagascar. There is even some hope of bringing back entirely
extinct species in the future using the new tools of synthetic biology. (De-extinction or even
ecological replacement could cause some of the same problems as invasive species, so careful
management is required.)
But we are not doomed to cause a sixth mass extinction, at least not yet, despite consuming our
way through the world's remaining big wild animals. Based on an estimate published in Nature
in 2011, we have a century or two at present rates before our depredations assure a mass
extinction. Unlike an asteroid, we could choose to change course.