The scientific world is still torn about the actual impact of humans on the decline in biodiversity and the extinction of animal and plant species. Or rather: there is total agreement on the fact that, through our fault, current extinction rates are very rapid, and are accelerating year after year. It is not yet clear, however, whether we have already passed the fateful threshold of “mass extinction”: there are those who maintain that we are in the middle, those who believe that, however serious, the situation is not yet catastrophic.
Other than asteroid. And then there are, so to speak, the middle ground: a new study from the Leverhulme Center for Anthropocene Biodiversity at the University of York, published in Global Change Biologyargues on the one hand that we have not yet reached mass extinction, on the other that the rates we are reaching have not been seen for 66 million years – that is, since the Chicxulub asteroid wiped out the dinosaurs.
A look at past extinctions. The study is the result of a review of decades of studies on environmental changes and ongoing extinction, to which the team has combined the results of a series of workshops held by ecology and biology experts, and aimed at comparing current extinction rates with those we can derive from the fossil record. There review begins 130,000 years ago, when humans began to wipe out the first giants of the past, from mammoths to Megatheriumthe giant sloth: analysis shows that, as humans expanded from Africa to the rest of the globe, many insular species were the next victims.
Comparison with past extinction rates, in particular those following the fall of the Chicxulub asteroid, demonstrates that the current rate is comparable to the Eocene-Oligocene extinction, which occurred 34 million years ago due to a global cooling. However, dinosaur extinction rates have not yet been reached.
Infernal pace. This doesn’t mean that it won’t happen: the Eocene-Oligocene extinction, for example, lasted millions of years, while the one caused by us humans is going at a decidedly higher rate, given that for now it “covers” about 100,000 years. In other words, the last mass extinction was climate-driven and occurred at natural rates; what we are experiencing, however, is being constantly accelerated by our activity, which in turn speeds up (and by a lot) what is happening to the global climate.
We can avoid catastrophe. In short: compared to 34 million years ago, we are in the midst of an extinction artificially accelerated by our actions, and if the speed continues to grow at this rate we could soon find ourselves in a situation comparable to the post-catastrophe one of 66 million years ago.
At that point, denying that we are experiencing a mass extinction caused by human activity, the fastest ever, will be impossible, but the study says that we still have time to reverse the trend.
