It’s estimated there are 8.7 million species alive on planet Earth today. But scientists have only named and cataloged about fifteen percent of that number and there’s increasing concern about the rate at which species are going extinct.
A 2009 study by researchers at Stockholm Resilience Center identified nine planetary boundarieswhich, if crossed, could put us on a course for irreversible global environmental change. Biodiversity - the variety of life on Earth - was one of the nine, and the researchers concluded we've already far exceeded the safe rate of species extinction.
Indeed, we are currently experiencing an unprecedented rate of extinctions, putting us in the midst of the sixth mass extinction event in the history of the planet - the only one caused by humans. Top threats to biodiversity include habitat destruction, climate change, and the movement of species around the planet by human activities.
But pinning down the number of species and the rate of extinction is tricky. The total number of species on Earth is a mathematical estimate; we've only cataloged about 1.3 million species. And scientists don't even agree on the definition of what constitutes a species. Clearly, the challenges facing efforts to keep track of the diversity of life on Earth extend far beyond technology.