Heed the Warnings: Why We’re on the Brink of Mass Extinction
Evolutionary biologist Sean B. Carroll, executive producer of the doc Mass Extinction: Life At the Brink, on why mankind’s days are numbered.
“How strange it is that the past is so little understood and so quickly forgotten… I have tried to drag history up a little nearer to our own times in case it should be helpful as a guide in present difficulties.”
Winston Churchill, 1929
About 9:30 p.m. on Palm Sunday in 1965, a tornado struck Toledo, Ohio. I was just four years old and asleep when my Dad felt the pressure drop and called the family to the basement.
I didn’t know what a tornado was, I just knew that it was terrifying. All I could hear as we huddled in the dark basement were fire trucks and ambulances racing nearby. The F4 twister cut a long swath of destruction that crossed just four blocks from my house. Fifteen people were killed, more than 200 were injured, and more than 300 families lost their homes.
We had no warning. At the time, sirens were not yet standard in tornado country.
After what remains the largest disaster in Toledo history, the city installed sirens. But so many years later, I still get a tense feeling in my stomach when I see a strong storm approaching.
Fifty years ago, we were just beginning to learn some important lessons from natural disasters, epidemics, and manmade tragedies. As we gather this holiday season to take stock of all that we have to be grateful for, at the top of our list should be those who have had the foresight and resolve to make our world safer.
From 1962-1965, there was a worldwide epidemic of rubella, the so-called “German measles.” During that time, an estimated 12.5 million cases occurred in the U.S., resulting in 2,100 neonatal deaths, more than 11,000 fetal deaths, 2000 cases of encephalitis, and more than 20,000 infants born with congenital blindness, deafness, and heart defects.
Thanks to the development of a vaccine in 1969, fewer than 25 cases now occur per year.
And in 1965, after more than 7,000 studies from 1920-1960 that linked smoking and health problems, Congress adopted the Federal Cigarette Labeling and Advertising Act which required the placement of health warnings on cigarette packs. Thanks to these and other anti-smoking measures, the fraction of adult Americans who smoke has dropped steadily from 42 percent in 1965 to about 18 percent today, saving an estimated 8 million lives from smoking-related deaths.
And thanks to countless experts on car accidents, plane crashes, train wrecks, earthquakes, and hurricanes, a lot more people have enjoyed a lot more Thanksgivings. Seat belt use alone is credited with saving 300,000 lives over the past forty years.
But now, to that list of calamities to learn from, we need to add “mass extinctions.”
Yes, because nature’s warning lights are flashing. In the past forty years, Earth has lost half of its wild animal populations. Africa’s lions are one telling example. Thought the King of the Beasts was protected?
Think again. Fifty years ago, about 400,000 lions roamed Africa. Today, there are only about 30,000 remaining, as they have disappeared from twenty-six countries.
The fraction of species now at risk of extinction in the near future includes over one quarter of all species being monitored including mammals, reptiles, birds, and fish.
The potential losses of species are on a scale that is rivaled by only a few events in the last 500 million years of Earth’s history. Five times during that span, the majority of species on the planet vanished in a short interval of time. Scientists have now identified the triggers of two of those events: an asteroid that struck Earth 66 million years ago and wiped out dinosaurs and much more, and massive eruptions of volcanoes underneath Siberia that decimated the world 252 million years ago.
While the triggers for these two calamities were different, detailed study of what unfolded in the past reveals a common mode of destruction that is relevant to understanding our predicament today: in each case, mass extinction resulted from large and rapid environmental change on a global scale. Indeed, the main weapons of mass destruction unleashed by the Siberian eruptions included enormous quantities of the very familiar climate-changing gas carbon dioxide. The great concern of scientists today is that the potential global temperature changes projected over the next century approach those that took place 252 million years ago.
But these concerns about climate-changing gases are hardly new. In February 1965, President Lyndon B. Johnson told Congress: “This generation has altered the composition of the atmosphere on a global scale through . . . a steady increase in carbon dioxide from the burning of fossil fuels.”
There are now a lot of scientists with tense stomachs.
Let’s hope that fifty years from now, future generations might be thanking us for heeding the warnings.
About the author: Sean B. Carroll, Ph.D., is an evolutionary biologist at the University of Wisconsin, Madison, and vice president for science education at the Howard Hughes Medical Institute. He is an executive producer of a new film, Mass Extinction: Life at the Brink, which will premiere on Smithsonian Channel Nov. 30 at 8 PM ET/PT.