How many species live on Earth?

The figures of 8.7 million total and 2.2 million marine come from a 2011 estimate, not a complete census of life. Mora and colleagues statistically estimated about 8.7 ± 1.3 million eukaryotic species worldwide, including about 2.2 ± 0.18 million marine species. This is a model-based estimate with substantial uncertainty; “the rest on land” is an oversimplification because freshwater and other habitats are not simply terrestrial.