Over at Wired Science they are talking about extinction. It seems a couple of University of Queensland scientists have more-or-less reposted what I wrote a few years back. No doubt a case of parallel evolution! As Wired Science notes:
There may be many more “extinct” mammals waiting to be rediscovered than conservation biologists previously thought.
Categorizing a mammal species as extinct has rested upon two criteria: It has not been seen for more than 50 years, or an exhaustive search has come up empty. But “extinct” species occasionally turn up again, and some species have disappeared more than once. Australia’s desert rat kangaroo, for example, was rediscovered in 1931 after having gone missing for almost a century, only to disappear again in 1935 when invasive red foxes moved into the area of the remaining survivors.
In order to determine how often extinct species had been rediscovered, University of Queensland scientists Diana Fisher and Simon Blomberg created a dataset of 187 mammal species that have been reported extinct, extinct in the wild, or probably extinct since 1500, as well as those which have been rediscovered. They also looked at historical data on the threats that caused species to become extinct — or brought them close to it — including habitat loss, introduced species and overkill by humans.
It turns out that rumors of the extinction of over a third of these species have turned out to be premature, the scientists report in the Proceedings of the Royal Society B September 29. At least 67 species — a little over a third of those presumed to be extinct — were later found again. And in most cases, these were animals that had been hardest hit by habitat loss. Humans and invasive species have been significantly more efficient killers; it’s rare that a species reported extinct due to one of these causes has been seen again.
“If you think that a missing species is extinct and the main cause of decline was introduced predators such as feral foxes, cats or rats, then you are very likely to be right,” Fisher said. But, she added, “If the main cause of decline was habitat loss, you are quite likely to be wrong if you say that it’s extinct, unless it was restricted to a very small area.”
In fact I wrote exactly the same thing back when I was director of the Population and Habitat program at the National Audubon Society.
An email memo I wrote in 2003 made it up as post on this blog in 2005 as "Thinking About Species Lost" and again in 2006 as "Condors and Species Lost". As I noted at the time:
Here's the scoop: Over the course of the last 400 years, only about 820 species of vascular plants and vertebrate animals are listed as having gone extinct by the IUCN Red List. In addition, the IUCN reports several species being "rediscovered" every year after having previously listed them as "lost...
The death of any species is important, but I also want to know the circumstances of the decline or extinction. I consider the loss of the Passenger Pigeon and the Eskimo Curlew (there were once millions of these birds flying over vast areas of this continent) a much more significant tale than the loss of a species of flightless rail on a small island in the Pacific. One extinction signals the total loss of a once very common species that was successful over a very large area. The other signals the total loss of a very rare species that was NOT successful over a very large area. There are very different lessons to be learned from these very different stories.
Most people are surprised to learn that most extinctions are of the latter type (fairly unsuccessful species in very isolated locations) and not the former (fairly successful species in fairly common locations). They are further amazed to discover that habitat loss is a much rarer cause of species extinction than the introduction of rats, cats, goats and pigs -- or of indiscriminate hunting. If you go through the IUCN Redlist of extinct species, for example, you find zeros for most countries (no known endemic species pushed into extinction), but incredible numbers of extinctions for such tiny islands as Mauritius (41 extinct species), Réunion (16 extinct species), Saint Helena (29 extinct species), French Polynesia (67 extinct species), and the Cook Islands (15 extinct species). In fact, these little spots of land, along with Hawaii, account for about 200 of the 812 species pushed into extinction over the course of the last 400 years.
In a 2007 post entitled "Are There More Species Now than Ever Before?," I wrote:
Every year about as many previously "extinct" species are "found" and crossed off the list as are added to the list.
Recent examples include the pale-headed brush-finch, the coontail plant, the Uinta Mountain snail, the Golden-crowned manakin, the Ventura Marsh Milkvetch, the San Fernando Valley Spineflower, the Los Angeles Sunflower, the Bavarian Pine Vole, and Gilbert's Potoroo.
The IUCN notes that "In the last 500 years, human activity has forced 816 species to extinction," yet the IUCN also make regular announcements about formerly "extinct" species being refound.
The question of what to do with animal and plant species that are "created" or "recreated" also muddies the water somewhat. Selective breeding is bringing back the extinct Burchell's zebra and Quagga, for example, while hybridization is occurring so often between plant and animal species that species creation of some kind is clearly occurring at a very rapid rate.
If we are willing to declare the Asian lion a separate species teetering on the edge of extinction even though "the [genetic and visual] difference is less than that found between different human racial groups," why not count the fertile progeny of lion and tiger crosses as a new species as well (ligers and tigons)?
Bird and plant crosses are so frequent that they are almost impossible to list and document.
So are we losing species or gaining? Can it be said -- straight-faced -- that there are now more species than ever before?
Of course, talking about the true nature of species loss is not designed to make you popular in the world of direct-mail nonprofits!
After my email memo on species loss went out, the Legislative Director at Audubon called me in and said another Big Green nonprofit group was in the process of putting out a massive direct mail piece claiming Pronghorn Antelope were almost extinct!
The instructions were clear: Shut up about the science! Never mind the fact that this was a subspecies whose "pure genetic stock" had been compromised by imports more than 50 years earlier. Never mind the fact that more than a million Pronghorn were still gamboling around in Wyoming alone. Shut up! If we have to salute bad science and myth in order to keep the direct mail returns up at another Green Group, then by God, that is what we we will do.
|Gilbert's Potoroo today.|