Yet another estimate of the number of species on earth

This week in PLoS Biology, paper was published that estimates the number of species on earth being around the 8 million mark (give or take 2 million). This study takes a rarefaction-type approach, seeing how the rate of discovery of higher taxa is decreasing, and extrapolating from that to the species level, resulting in the figure of 8.7 million with an error range of 1.3 million.

This study is nothing new—there's been a number of estimates published over the past two decades that attempt to give a number to the total diversity of life on earth. While this one does appear to be a bit more robust, all these studies are based on various assumptions, and have given some very different figures. There seems to be some sort of convergence on the 10 million mark, but at the end of the day, we just don't know.

I guess the value of these papers are that they make public how far we have to go before we know the most basic thing about the other organisms that share the world with us. I still surprise people when I tell them my tales of discovering new species, the general belief being that we know essentially all there is to know about biology. However, unless there are some useful outcomes (e.g. increased funding or employment) from them, I view these papers with a certain cynicism. We know the task ahead of us is huge. It'd be great to be able to dive into it whole-heartedly and without needing to worry about the finances.

The paper did alert me to the World Taxonomist Database, a register of taxonomists from around the world and encompassing all taxa. The register gives contact details for each of the researchers in the database, as well as their taxonomic and geographic interests. It's a very handy resource.