Thursday, April 14, 2016

The Hawaiian extinction bomb: global numbers don't come close



The global extinction crisis is pretty bad, unless you actually include all the extinctions.

Not to do so is a little like arguing that tsunami damage wasn’t bad—as long as you don’t count the coastal areas.
 
In which case it’s worse than bad. It can be catastrophic. And the Hawaiian Islands are an example of just how bad the global extinction crisis is.

(Image: Laminella sanguinea, one of a handful of remaining amastrid land snail species, this one a tree-dweller in Wai`anae Mountains. Credit:: Kenneth A. Hayes.)

One of the standards of species condition is the International Union for Conservation of Nature Red List, which attempts to document the conservation status of all species of life—animals, plants, even fungi. But it’s way behind, and hasn’t even yet considered a lot of species.

IUCN lists as extinct just a few hundred of the tens of thousands of listed species. A tiny fraction of an understated total.You can visit the IUCN site here.

In some large Hawaiian genera, more than half the species are gone, and sometimes far more than half.

A paper in the journal Conservation Biology last year looked at a genus of Hawaiian land snails, Amastridae.

The paper, “Extinction in a hyperdiverse endemic Hawaiian land snail family and implications for the underestimation of invertebrate extinction,” was written by Claire Regnier, Philippe Bouchet, Kenneth A. Hayes, Norine W. Yeung, Carl C. Christensen, Daniel J.D.Chung, Beno─▒t Fontaine, and Robert H. Cowie. They are researchers from France, the Mainland, and the Bishop Museum and University of Hawai`i.

There are 325 known species of Amastridae, many known only from ancient chalky shells found in soil and sediment, only 15 are absolutely known to still survive.Of the total of 325, at the time the paper was written, IUCN listed just 33 as extinct. But the paper’s authors say that’s not nearly the whole story.

In fact, the authors say, 43 are from fossil evidence and almost surely extinct, 88 more are also certainly extinct. Another 179 lack evidence of extinction, but most are probably gone.

Yes, that leaves 15 of 325 that are certainly still surviving. There are probably a few more, but not many more. Rats may be a big cause of extinctions. Indeed, almost all of the extinct Amastridae are ground-dwelling, where they would have been easy prey.

And things don’t look good for the future: “All amastrid populations remain precarious, and all 15 extant species should be considered critically endangered. For example, the only two known populations of A. spirizona, in the Waianae Mountains, have been monitored for some years and are declining continually,” the authors write

The authors argue that the IUCN’s failure to accurately assess the loss, and its understatement of the actual numbers “has been used to downplay the biodiversity crisis.”

They admit that islands are special cases, and don’t necessarily represent the global picture, but the opposite is also true.

“In general, oceanic island biotas are especially susceptible to extinction and global rate generalizations do not reflect this,” the collaborators wrote.

And it’s not just snails that are disappearing from the islands, of course. We have lost most of our forest birds. Two-thirds of the 113 species of birds known to have existed in the Hawaiian Islands are now certainly extinct. Several others haven’t been seen in decades and are probably gone as well.


Researchers talk about our being in the world’s sixth massive wave of extinctions. But the world’s biodiversity loss is nothing compared to that in the Hawaiian Islands.  

The loss globally is not in the hundreds, as IUCN suggests, but in the tens of thousands, said Robert Cowie,  a Hawai`i researcher and one of the authors of the snail study.

“We showed, based on extrapolation from a random sample of land snail species from all over the world, and via two independent approaches, that we may already have lost 7 percent (130,000 extinctions) of all the animal species on Earth,” Cowie said.

© Jan TenBruggencate 2016

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