Recently, a student in my environmental legislation class approached me and asked a really good question: “Doesn’t teaching about environmental issues year after year all the time get you down? There are so many depressing things happening in the world.” This caught me off guard. My first response was: “Actually, yes. Sometimes it does get me down. How could it not?” But then we started talking about some of the positive trends and successes over the past few decades. Our discussion moved toward the fact that scientists continue to make progress discovering new species and answering one of the biggest questions in biology: How many species are there on our Earth? That seemed to turn the conversation around.
So, I thought I’d put together a few stories that have recently caught my attention.
In 2012, approximately 18,000 new species were cataloged by scientists around the world, according to the International Institute for Species Exploration (IISE) at Arizona State University. In 2009, nearly 20,000 were documented. Each year, the IISE puts together a top ten list of newly described species … their list from 2012 includes some pretty amazing creatures, including a primate, the Lesula Monkey (Cercopithecus lomamiensis). A primate? We haven’t even identified all the primates?
Even in Europe, birthplace of modern taxonomy, one study estimates that more than 700 new species are cataloged each year. That’s more than two species each day! And a good chunk of them are described by amateur taxonomists.
And a recent study gives hope that extinct species may not actually be gone but lurking somewhere. The Hula painted frog, previous thought to have been extinct, has been seen a handful of times recently in Israel, apparently still hanging in there. New research suggests that this frog is the only species in its taxonomic group.
And one of my favorites … fifteen new species of birds have been described in Amazonia. One of them is the muppet-Bowie bird:
Over the past decade, we also seem to be getting closer to a good estimate of how many species actually exist on the planet. You would think that we would have some scientific consensus on this number, but take a look at any biology or environmental science textbook and you’ll find the same broad range quotes … between 5 and 100 million species. There’s a huge difference between 5 and 100 million! And since our current list of named species is just 1.5 million it has seemed that we have a long way to go.
However, recent scientific studies appear to be narrowing in on the lower end of that huge range … somewhere around 10 million, perhaps less (though there is still a considerable difference of opinion).
For example, Costello et al. (2013) write in a recent article in Science (Can we name Earth’s species before they go extinct) that the number of species on our planet is 5 million — plus or minus 3 million. Still a wide range, but smaller. They also argue that it is within our abilities – with increased funding and research efforts, of course — to describe most of them within the next 50 years.
Another example of a lower and narrower estimate comes from Mora et al. (2011), who make a good case that there are around 8.7 million species — plus or minus 1.3 million. Carl Zimmer’s summary of their work raises some of the scientific issues that make the whole enterprise of naming species as challenging as it is. For example, there is much greater uncertainty around groups of species that have been traditionally understudied, like fungi, which many push the total estimate higher. Additionally, these estimates are for eukaryotic organisms (bacteria are not included).
I’ll admit, it is a little disappointing that there might not be 100 million species living somewhere on Earth. But since this post was supposed to focus on positive trends, I’ll be happy with the idea that we might actually be able — in the not-so-distant future — to list the species that share the planet with us (before many of them go extinct, that is).
Citations for Peer-Reviewed Sources:
Costello MJ, May RM, and Stork NE. 2013. Can We Name Earth’s Species Before They Go Extinct? Science 25 January 2013: 339 (6118), 413-416. DOI:10.1126/science.1230318
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
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