Are we witnessing the Sixth Mass Extinction?
The title sounds alarming and catastrophic. Many people will dismiss it right away and would say that I am exaggerating by insinuating that something like that is actually going on. I cannot say for sure that it is happening, that is why the title of the post has a question mark, however, I am going to present some facts in an objective way.
The world has undergone 5 mass extinctions of species. The first is called the Ordovician-Silurian extinction and occurred around 439 million years ago. 25% of marine families and 60% of marine genera were lost. The second one is called the Late devonian extinction and happened 364 million years ago. 22% of marine families and 57% of marine genera disappeared. The third, and the worst of all, called the Permian-Triassic extinction, occured about 251 million years ago. 95% percent of all specias died out, 53% of marine families, 84% of marine genera and 70% of land species also were gone. The fourth one is called the End Triassic extinction and happened 200 million years ago. 22% of marine families and 52 percent of marine genera disappeared. The fifth one is called the Cretacous-Tertiary extinction and occured 65 million years ago.. It is famous because it included the death of the dinosaurs. 16% of marine families, 47% of marine genera and 18% of lnd vertebrate families became extinct.
Extinction occurs all the time. Species disappear at a rate that oscillates between 1-10 species per year. This is called background extinction rate. Mass extinction occurs when this rate markedly increases causing great number of species to disappear in a short period of time. We have to remember that short period, in a geological scale can mean a couple thousand years.
Mass extinctions occur due to a major disruption in the Earth's ecosystems, either by internal causes, e.g, melting glaciers or volcanic activity; or external causes like asteroid impacts.
Currently, and for some years now, species are disappearing at a rate of 30000 per year. It this rate continues, 50% of all species will have disappeared in 100 years, enough to call it a mass extinction. There is a major disruption of Earth's ecosystems going on, due to global warming and due to the space that humankind is occupying as its population keeps to grow.
The solutions are not easy and will have to include a limitation in the increase of the population and the stopping of global warming. Both processes would take tens to hundreds of years, so in my opinion, there is little that can be done, except to try to minimize the effects of our own activity. There is another pathway. In the event of the collapse of civilization due to lack of fossil fuels or lack of food to feed the billions of people that will be born, war, famine and disease will take care of the human population and would be the means of nature to restore the equilibrium that has been broken.