Al Gore wrote in An Inconvenient Truth that global warming “is causing the loss of living species at a level comparable to the extinction event that wiped out the dinosaurs 6.5 million years ago.” As is often the case when the former vice president addresses climate change, he could not be more wrong.
It is estimated there are currently more than 10 million species on Earth—more than at any other time in history. New species are constantly replacing old. Although humans have been responsible for the extinction of some species in recent centuries, extinctions have always been an integral part of life. And, despite recent claims that the Australian brown rat is the first mammal to have been killed off by human-induced climate change, not a single species has been shown to even be threatened or endangered by so-called man-made global warming.
A range of interrelated phenomena contribute to extinctions. They include temperature changes, habitat destruction, competition, invasive diseases, and reproductive failure. Species are more vulnerable when there are major temperature changes over a short period, which is what most experts believe caused the end of the dinosaurs following an asteroid impact. Some scientists are now predicting major extinctions in Southeast Asia from deforestation. The introduction of the brown snake in Guam during World War II is thought to have eliminated a dozen bird species there. The human population was decimated in Europe when the bubonic plague migrated from China. The wooly mammoth and sabre tooth tiger became extinct in North America because their reproductive rate could not keep up with population losses. And there is no question that human activities have contributed to extinctions as our population expanded into animal habitats.