Question

How did we end up with 8.7 million species?​

Answer 1

About 8.7 million (give or take 1.3 million) is the new, estimated total number of species on Earth -- the most precise calculation ever offered -- with 6.5 million species on land and 2.2 million in oceans. Announced by the Census of Marine Life, the figure is based on a new analytical technique. The number of species on Earth had been estimated previously at 3 million to 100 million.