No, not doo-doo. “Dodo,” as in the dodo bird, which was driven to extinction by humans in 1681. Though by the end of this post, you will probably conclude we are in deeper doo-doo than we’ve ever been before.
Over the past half-billion years, there have been at least twenty mass extinctions, when the diversity of life on Earth has suddenly and dramatically contracted. Today 99.9% of all species that have ever existed on Earth—estimates run as high as fifty billion species—are ancient history.
Five of these extinctions—the so-called Big Five—were so devastating that they are usually put in their own category:
The Ordovician-Silurian extinction (about 439 million years ago) due to a drop in sea levels as glaciers formed, and a subsequent rise in sea levels as glaciers melted. During this extinction 25% of marine families and 60% of marine genera (the classification above species) were lost.
The Late Devonian extinction (about 364 million years ago), cause unknown. Because it appears that warm water marine species were the most severely affected, many paleontologists believe it was caused by global cooling. Glacial deposits in northern Brazil suggest another glaciation event on Gondwana, the land mass of that time. It appears that 22% of marine families and 57% of marine genera were lost.
The Permian-Triassic extinction (about 251 million years ago) was Earth’s worst extinction event, and was probably caused by volcanism in present-day Siberia. Evidence suggests that 95% of all species, 53% of marine families, 84% of marine genera, and an estimated 70% of land species of plants, insects, and vertebrate animals were killed in this catastrophe.
The End Triassic extinction (about 199-214 million years ago) was most likely caused by massive flows of lava erupting from the central Atlantic magmatic province, triggering the breakup of Pangaea, the opening of the Atlantic Ocean, and deadly global warming. Rocks from the eruptions now are found in the eastern United States, eastern Brazil, North Africa, and Spain. It appears 22% of marine families, 52% of marine genera, and an unknown percentage of vertebrate deaths resulted.
The Cretaceous-Tertiary extinction (about 65 million years ago) was famously caused by the impact of an asteroid which created the 4-mile-wide Chicxulub crater now hidden on the Yucatan Peninsula and beneath the Gulf of Mexico. During this extinction, 16% of marine families, 47% of marine genera, and 18% of land vertebrate families, including the dinosaurs, were killed.
A majority of scientists believe that a sixth mass extinction is underway. They’ve even given it a name: The Holocene extinction event.
This isn’t Bible-thumping prophesy. There’s empirical evidence that the present extinction is happening right now and is going faster than that which wiped out the dinosaurs. Animals are going extinct 100 to 1,000 (maybe even 1,000 to 10,000) times faster than at the normal background extinction rate, which is about 10 to 25 species per year. Since 1900 alone, 69 mammal species are believed to have gone extinct, along with about 400 other types of vertebrates. Evidence for species lost among nonvertebrate animals and other kinds of living things is much more difficult to come by, researchers say, but there’s little reason to believe that the rest of life on Earth is faring any better.
Though it’s difficult to put a precise figure on the projected losses, it is estimated that if current trends continue, by the end of this century as many as half of Earth’s species will be gone. And unlike a meteorite or large volcanic eruption, the cause of this extinction event is us.
Specifically, five major human activities are to blame:
Habitat destruction including human-induced climate change;
Pollution with carbon emissions that drive climate change and ocean acidification and toxins that alter and poison ecosystems;
Introduction of invasive species;
Human overpopulation including land clearing for farming, logging and settlement; and
Over-harvesting (hunting, fishing, and gathering).
Of the five activities above, human-induced climate change and pollution have gotten the most attention.
We are all familiar with the argument that high amounts of greenhouse gas emissions (primarily carbon dioxide, methane, and nitrous oxide) trap heat from the sun. Other human activities such as habitat destruction and fragmentation are making the earth inhospitable to life. Through global trade and international travel, humans have transported countless species into ecosystems that are not prepared for them. Invasive/aliens species displace native species through predation, competition, and disease organisms.
Chemical plants fix more atmospheric nitrogen than all natural terrestrial processes combined, and fisheries remove more than a third of the primary production of the temperate coastal waters of the oceans. We have pumped enough carbon dioxide into the air to alter the climate and to change the chemistry of the oceans.
Farming, logging, and building have transformed between a third and a half of the world’s land surface, and even these figures probably understate the effect, since habitat not being actively exploited may still be fragmented. Most of the world’s major waterways have been diverted or dammed or otherwise manipulated—in the United States, only 2% of rivers run unimpeded—and people now use half the world’s readily accessible freshwater runoff.
Such dramatic ecological change and biodiversity loss will also put humans in danger within just three generations, particularly if we also lose crucial pollinators such as the honeybee.
Though these facts have been known at least from the early ’90s, researchers released another report in June of this year in an attempt to provoke action. “If it is allowed to continue, life would take many millions of years to recover, and our species itself would likely disappear early on,” said one of the lead researchers, Gerardo Ceballos from the Universidad Autónoma de México.
“We are sawing off the limb that we are sitting on,” said Paul Ehrlich, another researcher.
Their results are published in the journal Science Advances.
But it’s not all bad news—the researchers remarked that we could still avoid such steep biodiversity loss through intense conservation action. “But that window of opportunity is rapidly closing,” they conclude.
Another of the researchers, Anthony Barnosky, says there are a few key steps people can take:
Reduce your carbon footprint—this is to hold back climate change from falling below critical levels and to prevent altered conditions which can ravage fragile ecosystems.
Never buy products made from a threatened or endangered species—this includes items like ivory, animal furs and rhino horns.
Eat less meat—40% of the Earth is currently under cultivation, and if the lands used to feed livestock were used to grow crops for people, there would be 50% to 70% more calories available for humans to eat, which is enough to feed an additional billion people. It would eliminate the need to clear natural ecosystems like rainforests for farmland.
Are we going to do enough to fix the situation? Probably not.
As long as corporations and other players who profit from the exploitation of the earth continue to promulgate disinformation, skeptics and deniers will continue to accuse most of us of wearing foil hats. There will continue to be asshole dentists who have to bag just one more trophy before they’re all gone (in the last couple days, a Minnesota woman who vandalized the dentist’s sign was arrested by the long arm of the law). Poachers will continue to kill rhinos for their horns so Asian men can get hard-ons (as it turns out, a myth). Escape to another planet is probably a pipe dream; anyway, who would have us? As long as there are people like me who are relieved we’ll be dead before the bill comes due, humanity’s extinction is assured.
At least we know what’s going to kill us. It will be death by a thousand cuts.
But maybe some kid will come along and change the whole thing. You can always hope.
96° and Clear