How many species are there? We need to know.

30 August 2011 | News story

If we are to meet the challenges facing tomorrow's world, we need a clearer understanding of how many species underpin the structure and functioning of ecosystems, says researcher Robert May. Links to three stories are shared by Keith Wheeler, CEC Chair.

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8.7 million species exist on Earth, study estimates
By Juliet Eilperin, August 23, The Washington Post

For centuries scientists have pondered a central question: How many species exist on Earth? Now, a group of researchers has offered an answer: 8.7 million.

Although the number is still an estimate, it represents the most rigorous mathematical analysis yet of what we know — and don’t know — about life on land and in the sea. The authors of the paper, published Tuesday evening by the scientific journal PLoS Biology, suggest that 86 percent of all terrestrial species and 91 percent of all marine species have yet to be discovered, described and catalogued.

The new analysis is significant not only because it gives more detail on a fundamental scientific mystery but because it helps capture the complexity of a natural system that is in danger of losing species at an unprecedented rate. Full story >> 

Why Worry about How Many Species and Their Loss?

Abstract
We are astonishingly ignorant about how many species are alive on earth today, and even more ignorant about how many we can lose yet still maintain ecosystem services that humanity ultimately depends upon. Mora et al.'s paper is important in offering an imaginative new approach to assessing total species numbers, both on land and in the sea. Full story >>

Citation: May RM (2011) Why Worry about How Many Species and Their Loss? PLoS Biol 9(8): e1001130. doi:10.1371/journal.pbio.1001130

How Many Species Are There on Earth and in the Ocean?

Abstract
The diversity of life is one of the most striking aspects of our planet; hence knowing how many species inhabit Earth is among the most fundamental questions in science. Yet the answer to this question remains enigmatic, as efforts to sample the world's biodiversity to date have been limited and thus have precluded direct quantification of global species richness, and because indirect estimates rely on assumptions that have proven highly controversial. Here we show that the higher taxonomic classification of species (i.e., the assignment of species to phylum, class, order, family, and genus) follows a consistent and predictable pattern from which the total number of species in a taxonomic group can be estimated. This approach was validated against well-known taxa, and when applied to all domains of life, it predicts ~8.7 million (±1.3 million SE) eukaryotic species globally, of which ~2.2 million (±0.18 million SE) are marine. In spite of 250 years of taxonomic classification and over 1.2 million species already catalogued in a central database, our results suggest that some 86% of existing species on Earth and 91% of species in the ocean still await description. Renewed interest in further exploration and taxonomy is required if this significant gap in our knowledge of life on Earth is to be closed. Full story >>

Citation: Mora C, Tittensor DP, Adl S, Simpson AGB, Worm B (2011) How Many Species Are There on Earth and in the Ocean? PLoS Biol 9(8): e1001127. doi:10.1371/journal.pbio.1001127