Their reign lasted roughly 170 million years, and the latest news is that what finally did them in wasn’t simply the notorious asteroid that slammed into the Yucatan 65 million years ago. According to a new study, if the asteroid had hit just a little earlier or later (a few million years either way), the dinosaurs might well still be around today.
Instead, it hit at a time of major climate change on Earth. Volcanoes had been blotting out sunlight and lowering temperatures. Several of the oceans were freezing over. Plants were suffering, so the herbivorous dinos had less to eat, which, in turn, meant less prey for the large predators.
And then “Smack!”
All in all, it was just too much for the whole dinosaur species – except for those who were already developing into birds.
According to Dr. Steve Brusatte, who led a new study in Biological Reviews,
“The dinosaurs were victims of colossal bad luck. Not only did a giant asteroid strike, but it happened at the worst possible time, when their ecosystems were vulnerable.”
Still, they had a good run – nearly a thousand times as long as Homo sapiens, who arrived 200,000 years ago and only developed language and other recognizably human skills about 50,000 years ago.
The number of invertebrate animals, such as beetles, butterflies, spiders and worms, has decreased by 45 percent.While all previous five mass extinctions unfolded over many thousands of years, the Sixth Extinction is happening at an accelerating pace – up to a thousand times the typical rate of about one extinction per every 10 million species each year. A special section of Science magazine describes how, while human population has doubled in the past 35 years, most nonhuman species are collapsing. In particular, the number of invertebrate animals, such as beetles, butterflies, spiders and worms, has decreased by 45 percent.
Among larger animals, up to one in three vertebrates (animals with a backbone) are threatened or endangered. This is not only calamitous for them; it sets up a feedback loop that turns human into a threatened species, too. Dr. Rodolfo Dirzo, who led the study “Defaunation in the Anthropocene”, explains that when, for example, you remove large animals like elephants, zebras, giraffes, etc., the whole region is quickly overtaken by rodents, leading to an abundance of the disease-carrying parasites whom they harbor. This, in turn, leads to plagues among humans.
“Where human density is high, you get high rates of defaunation, high incidence of rodents, and thus high levels of pathogens, which increases the risks of disease transmission. Who would have thought that just defaunation would have all these dramatic consequences? But it can be a vicious circle.”
Are we humans likely to take the kind of drastic action – like shutting down all industrial civilization immediately and permanently (no power, no gas, nothing) – that might pull things back from the brink? According to the U.K.’s popular Daily Express:
Experts today sounded the death knell for life on Earth warning we are devastatingly close to reaching an evolutionary tipping point.
(As regards what to do about it, the newspaper offers a few “Related Articles” that helpfully include: “How to survive anything from a zombie apocalypse to a natural disaster” and “From cloning to robot war, Doomsday is just round the corner.”)
Also in the news this week:
Scientists have added 367 bird species to the International Union for Conservation of Nature’s Red List of threatened species. 87 of these are threatened with extinction.
The IUCN also warned that pangolins are being eaten to extinction. These scaly anteaters, who look a bit like artichokes, are the new delicacy in China and Vietnam, and they are rapidly disappearing from the face of the planet. (Last year, a Chinese fishing boat ran aground on endangered coral reefs off the coast of the Philippines. It was carrying more than 2,000 pangolins to market.)
And in the House of Representatives, the House Committee on Natural Resources voted to weaken the Endangered Species Act.