More Endangered Species Idiocy

2 05 2007

There’s been plenty news about the potential de-listing of various endangered species over the past few months (i.e. grizzly bears, wolves, manatees, and american crocodile, to name a few), and the plan to further strip the Endangered Species Act of any power whatsoever has not gone unnoticed. According to this LiveScience article, more than 36 scientists have signed a letter protesting the removal of important species from protection, as well as pointing out that further restrictions on the ESA would further harm endangered populations.

While the some species (like those listed above) seem to have come back from the brink of extinction, now is hardly the time to open up hunting on such animals (as is the case with wolves and bears, some states wanting to reduce wolf populations by as much as 2/3) or to allow irresponsible behavior in critical habitat (like making speeding laws more lax in Florida’s waterways where manatees live). If anything, these animals should get continued protection to ensure that their populations are in fact stable and healthy, not merely open up hunting again when some arbitrary number is reached. Have we learned nothing about extinction from the heath hen?

For those not familiar with the story, the heath hen was a rather distinctive subspecies of the Greater Prairie Chicken, having a range from Virginia to New Hampshire. Being rather plentiful and easily available, the birds were hunted until they existed nowhere except the island of Martha’s Vineyard, Massachusetts (the locale where the film Jaws was shot), and eventually the population got as low as 70. Thankfully, there was a ban on hunting on the area in which the heath hens resided became protected, eventually allowing the populations to rise to approximately 2,000 individuals. Such numbers alone, however, would not save the heath hen from extinction. Because the birds were restricted to such a small area a harsh brush fire was absolutely devastating to them, combined with harsh winters, increased predation by raptors (the birds, not the dinosaurs), disease, a higher ratio of males:females, and low genetic diversity as a result of inbreeding all did their part in making these birds extinct by 1932 (protection started around 1908).

What can we learn from our folly in trying to save the heath hen? Perhaps the most important idea (which is almost never discussed) is that when you parcel out land and restrict species to a small patch they become more vulnerable to extinction. If the heath hens had the chance to spread out they may have survived, but being restricted to a small area meant that one severe fire or breakout of disease would be utterly catastrophic. Keeping species enclosed in a certain area also decreases gene flow as members are not leaving to new areas and creating differing gene flows; all the breeding has to take place within one population that is already inbred. These facts also make us realize that just because the number of individuals goes up does not mean that all is well; without the genetic diversity to back those numbers up a species can still be quite vulnerable, especially to disease. You would think that the extinction of the heath hen would have been paid attention to more closely and impact the way we attempt to manage species today, but it appears that this isn’t the case.

While I’m glad many species are doing well I worry that they’ll soon be in dire straits if the government lifts protection, the efforts made under the ESA merely putting off extinction rather than removing it as a threat altogether. If we’re going to save species we need to create corridors and pathways along which they can move and proliferate; creating little conservation islands isn’t going to work and will only make the species we tried so hard to save more vulnerable. These are fairly obvious facts, things that I would expect the Fish and Wildlife Service to know, but yet they seem to pay attention only to the numbers and don’t really seem to care about the long-term health or stability of species.



2 responses

16 05 2007

[…] agree that merely trying to create pockets of wilderness will not work; as I discussed during a discussion of current endangered species, we would do well to remember that although the heath hen seemed to rally its numbers in […]

13 07 2007
Extinction is apparently all the rage… « Laelaps

[…] Extinction is not something that has only occurred in the past, however; it is still occurring today. In a new PLoS Biology paper “Projected Impacts of Climate and Land-Use Change on the Global Diversity of Birds,” Jetz, Wilcove, and Dobson determine that global climate change in high latitudes and destruction (and restriction) of habitat in tropical regions will probably significantly reduce a number of bird species. Part of the modern extinction problem, as outline in David Raup’s book Extinction: Bad Genes or Bad Luck?, narrowing the range of a species can set them up for extinction, even when they seem to be doing well or even recovering. The classic case study is of heath hens in New England, where despite the fact that the population was recovering, the species died out in the blink of an eye because enough adverse factors accumulated to wipe all the birds out almost overnight (see an earlier post here). […]

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