Most scientists are in agreement that the Earth has entered it’s sixth mass extinction event. Occasionally, approximately every 100 million year or so, a large percentage of existing species die off in a short period of time. The causes of these mass extinctions are varied, collisions with extraterrestrial debris and super volcanos are just a couple of possibilities. For primitive bacteria, it was their own waste product, oxygen, that was almost the end of life on this planet. What makes the current extinction event so unusual is that humans are entirely to blame. And not only are we the cause of this extinction event, we are apparently setting a speed record. Up until now, mass extinctions occurred over thousands of years. In an effort to show we are the equal of any natural process, we are on pace to eliminate 50% of the world’s species within a few hundred years, the blink of an eye in the geologic time scale.
I use the words “natural process” as if our actions were unnatural, and that is not accurate. Our actions are as natural as those of any other creature that crawls, swims or flies, and it is quite possible that humans are merely the next vector for an event whose time has come again. People automatically assume that mass extinctions are terrible occurrences, and they definitely are for species existing at the time of the extinction event. However, for the species that arise after the event, they are a blessing. If not for Chixulub, the comet or asteroid whose collision hastened the end of the dinosaurs, humans would still be nocturnal insectivores, gnawing roaches in the dark. Mammals had their chance to compete directly with dinosaurs, and it did not go well. Between the Cambrian and Mesozoic Periods 95% of the world’s species died off. It was the largest extinction event this planet has known, and it cleared the slate for an evolutionary free-for-all. The ancestors of mammals and dinosaurs competed for dominance on a relatively even playing field, and dinosaurs became the undisputed rulers of the world while mammals never amounted to more than a hairy prey item…until the dinosaurs were removed.
One of the interesting things about mass extinction events is that dominant animal groups are removed or severely diminished, and something totally new arises from the rubble to take their place. Fish, amphibians, reptiles, dinosaurs and mammals have all had their day. Birds missed out somehow, but maybe their day is still coming. Since there have only been five events so far, we can’t say with certainty that the dominant animal group is always eliminated, but that’s the way it has always happened in the past. If the trend continues, it will be interesting to see which group inherits the mantle of superiority when humans are no more.
The thing that has me preoccupied with endings and beginnings are recent findings involving a couple of very photogenic species, polar bears and monarch butterflies. It’s no secret that our planet is warming and the polar ice caps are receding drastically. Polar bears are dependent upon ice for their survival. The less ice there is, the fewer polar bears we’ll have. It’s quite possible that refuges will remain in the very far north where polar bears can bide their time till the next Ice Age (the ice will come again), but even places as far north as Svalbard are now reporting ice-free summers. Humans are more directly responsible for the decline in the monarch butterfly population. We have logged the groves where they winter, and we’ve gone to great lengths to elminate the milkweed they depend on. Most recently, the adoption of genetically modified corn, corn that can tolerate huge amounts of pesticide and/or have poisonous pollen, may be the final nail in their coffin. In a matter of decades, the Eastern population has declined by more than 80%. The Pacific population appeared to be slowly recovering or at least remaining stable, but between the winter of 2018 and 2019 80% of the butterflies disppeared. There are non-migratory populations of monarchs that are not affected, but the days of huge, hanging clusters comprised of thousands of monarchs may nearly be gone.
I know that life will carry on, that someday, perhaps after humans are long gone, new species will arise to take the place of the ones the planet has lost. However, regardless of how or why the extinction takes place, a world without polar bears and masses of monarchs covering branches and entire trees will seem diminished, a less magical place than the one we now live in.