The Numbers Add Up
Extinction is a normal part of life on Earth. And by analyzing the fossil record, scientists have come up with a number known as the background rate of extinction. It's the rate at which species go extinct under normal circumstances, without the influence of asteroid collisions, climate changes, massive volcanic eruptions or other extraordinary factors. According to Peter Douglas Ward, the background rate of extinction is one to five animals per year.
Most researchers agree that today's extinction rate is far beyond the background rate of extinction. According to the U.N. Convention on Biological Diversity, three species are becoming extinct each hour — which is faster than new species are discovered. According to the American Museum of Natural History, this extinction rate is the fastest in the Earth's history.