All over this planet, millions of species representing the end point of 4 billion years of evolution, living in ecosystems representing the end point of millions of years of ecological interaction, are being made extinct at a rate probably unprecedented in the history of Earth, and towards an end point seen only a few times in that history.
An incredible 100,000 or so species are estimated to be going extinct each year towards a total loss in just a few decades of at least half those existing just 100 years ago (when the extinction rate first gathered pace). My feeling is that estimates like “a half” represent scientists being cautious. That really the planet is faced with the extinction of 90% or more, and the last time that happened was a quarter of a billion years ago. The last time anything like the extent of the events of these two centuries happened was 65 million years ago as a large meteor exploded against the planet. The last significant set of extinctions was around 25,000 years ago as the climatic events of the end of the ice ages drove many large species, especially mammals, to extinction.