According to Australian ecologist Robert May, estimates of the number of species on our planet vary wildly — from a few million to about one trillion. Part of the problem is that many lifeforms occupy very specific habitats, many of them difficult for humans to access. Additionally, microorganisms are much harder to catalog by species, and it’s not clear that they biodiversity patterns used to estimate the number of species of other organisms even apply to microbes.

Key Takeaways:

  • As it is hard to account for all life due to size and location, scientists usually estimate the number of species.
  • This estimation is likely too small as it fails to account for many microorganisms that inhabit the earth.
  • Due to the challenges cataloging all species and the high rates of extinction, we are often failing to even learn some of these before they are no longer here.

“We know more accurately the number of books in the US Library of Congress than we know even the order or magnitude – millions and billions and so on – of species living on our planet, wrote the Australian-born ecologist Robert May.”

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