How many species live on the planet today? No one knows.
How many species live in Europe today? No one knows that either. You would think that in one of the most densely-populated regions of the world (and the home of Linnaeus, father of our current taxonomic system) we would have an answer to this question. Unfortunately, we still have a long way to go toward cataloging life on Earth according to a recent study published in PLoS.
The authors of the study compiled a list of multicellular species that have been named over the past 250 years. This graph shows the cumulative number of species named in Europe since 1758:
The number of new bird species that are discovered each year leveled off in the late 1800s. That’s not surprising since a lot of people like to look for birds. They are also easy to find, catch, and compare with each other.
However, new species are continuously being found in most other groups of organisms. Overall, the total number of species that are named each year in Europe (panel A) continues to increase, with no indication that it is leveling off. On average, 770 new species have been described and named each year since the 1950s, which is about 2 new species each day. And this is just in Europe! Our knowledge of tropical biodiversity is incredibly poor.
What’s going on? For one, there is no overall plan for cataloging biodiversity. No one organization is in charge, so the process is inefficient.
Another reason for the slow progress is that there aren’t enough people with the skills to find and name new species. In fact, one of the most surprising findings of this study is that over half of all the new species documented each year are not professional taxonomists — in other words, these folks don’t have a paid position for doing this work. They are experts in identifying and naming new species, but they are either amateurs or retired taxonomists. The rate of finding new species would be much slower without their contribution, so encouraging more people to get out there to search would help speed things along.
So, what is needed is a plan and more people to do the work. Currently, the number of named species on the planet is around 1.9 million. But the estimated number is much, much larger. If the same rate of discovery continues, we’ll be in the dark for a long time:
“The frontiers of biodiversity exploration and discovery are generally considered to be in the tropics and if the actual number of species on the planet is 5–30 million, at the current rate several centuries will be necessary to describe and name them all.”
We’ve got our work cut out for us. And if we don’t know the number of species on the planet, there are a lot of species facing extinction that we don’t even know exist.
Fontaine B, van Achterberg K, Alonso-Zarazaga MA, Araujo R, Asche M, et al. (2012) New Species in the Old World: Europe as a Frontier in Biodiversity Exploration, a Test Bed for 21st Century Taxonomy. PLoS ONE 7(5): e36881. doi:10.1371/journal.pone.0036881