A Tangent On: Extinction
A northern long-eared bat suffering from white nose syndrome (1).
A few weeks ago, the House of Representatives voted to block the uplisting of the northern long eared bat from threated to endangered status and to prevent the lesser prairie chicken being from listed under the Endangered Species Act at all. With the Senate having already passed similar measures earlier this year, the two bills will now be sent to President Biden, who it seems likely will veto them. Still, these acts of Congress suggest a precarious future for federal protection of both species and also add to concerns over the future of the Endangered Species Act more generally at a time when we should be stepping up our conservation efforts.There are a lot of things that we could be talking about in the aftermath of this vote, but right now, I want to focus on a press release put out by House Republicans on the Natural Resources Committee. The release contains a few statements from different lawmakers explaining their support for the two bills and include a particular talking point that I think is demonstrative of an important and all-to-common misunderstanding about how extinction works. Washington Representative Dan Newhouse puts the pro-delisting position most clearly in his statement:
“As Chairman of the Western Caucus, I know firsthand how radical environmental groups will weaponize the Endangered Species Act in an attempt to end resource development and prevent responsible forest management— and these listings of the Northern Long-Eared Bat and the Lesser Prairie Chicken are their latest attempt. The Biden Administration continues to ignore our nation’s farmers, ranchers, and landowners who have worked tirelessly to help recover the Lesser Prairie Chicken’s population through habitat restoration, and uplisted the Northern Long-Eared Bat despite admitting the population decline is due to an incurable disease—not a loss of habitat. These resolutions are critical to preventing burdensome government overreach, and I will continue highlighting the importance of reforming the Endangered Species Act through the Western Caucus-Natural Resources Committee ESA Working Group to prevent future overreaching listings.”
Newhouse's description of the bat's plight is perfectly accurate. The northern long eared bat (Myotis septentrionalis), along with many North American bat species, has declined rapidly and severely due to white nose syndrome, a cold-loving fungal disease which infects bats while they are hibernating in large, multispecies colonies during the winter. In the case of the northern long eared bat, white nose has led to a population decline of at least 97%. There is no known cure.
And yet, the fact that the northern long eared bat's decline is due to disease and not habitat loss should not disqualify it from being listed as Endangered and receiving associated protections, as Newhouse claims. First, despite what Minnesota Representative Pete Stauber writes in his own statement, the bats have not become endangered "through no of fault of humans." White nose is present in Europe, where it has no effect on bat populations, suggesting that it is native there and was brought here, like many other ravenous, population crashing diseases, by human trade (Leopardi et al. 2015). We are likely responsible, if somewhat indirectly, for the decline of this species and we have an ethical responsibility to try and save it.
More to the point though, the idea that we do not have to protect an endangered species' habitat because its decline was mainly the result of other causes is not even remotely supported by what we know about how extinctions happen. To understand why, we need to look at the story of a close relative of the lesser prairie chicken, the other species delisted by these bills. The heath hen (Tympanuchus cupido cupido) was a subspecies of greater prairie chicken which, back in the day, was a common inhabitant of the coastal heath barrens of the Atlantic coast. After European colonization, however, overhunting and suppression of the natural fire regimes that maintained their habitat caused the birds to decline. By the 1870s, they were exterminated entirely from the mainland, surviving only on Martha's Vineyard.
The heath hen was one of the first species in North America for which a concerted effort at conservation was made. The local government on Martha's Vineyard banned hunting and created a preserve for the birds and over time, their population slowly began to grow.
Then, in 1916, disaster struck when a large wildfire swept through the heath hen's breeding grounds. When heath hens were abundant, this wouldn't have been a big deal. Heath hens depended on fire, after all, to maintain the open habitats in which they lived and, back then, populations were large enough and spread out enough that localized disturbances like a large wildfire would not threaten the whole species. In 1916, however, there were only 2,000 birds left and most of them were concentrated in the path of the fire. The next year, a census found only 150 birds remaining, most of which were males. This was obviously a problem for building the population back up again and the species continued to decline over the next decade. By 1929, there was only one bird left - a male nicknamed "Booming Ben" by locals. He was last seen in 1932.
The heath hen was the first species (or, rather, subspecies) that scientists were able to study as it went extinct in real time, and its story still contains some important lessons for today. For our purposes here, it's important to note the multiple variables that played a part in the heath hen's extinction, including overhunting, habitat loss, natural disaster, and inbreeding after the fire left behind mostly males. These first two factors were the main causes of the decline of the heath hen, but they weren't the direct cause of the bird's final drop into oblivion. Once a species gets down to a critically small population size, and especially if that population is concentrated in only a few, isolated habitats, it becomes vulnerable to all sorts of other threats that would not have had much of an impact when its population was higher or even during its decline. Fire did not push the heath hen to the edge of extinction (indeed, it probably would have helped move it back if reintroduced earlier), but that one particular wildfire certainly contributed to pushing it over.
Likewise, habitat loss may not have been a major contributor to the decline of the northern long-eared bat, but now that its numbers are so low, the loss of just a few key habitat patches could be enough to push it over the edge. These key, limited habitat patches consist mostly of the caves in which the bats hibernate; they seem to be pretty flexible in choosing the forest habitats that they spend the rest of the year in and conducting selective logging operations or clearcuts that leave most of a larger forest patch intact doesn't seem to bother them, as noted by the Fish and Wildlife Service themselves (Alston et al. 2019; Bergeson et al. 2021). The critical habitat provision of the Endangered Species Act allows regulators to take these kinds of nuances into account when they define what critical habitat looks like and what kinds of activates do or do not count as "destruction or adverse modification" (ESA Section 7(a)(2)). In fact, this is exactly what we see in the rules that governed northern long eared bat protection when the species was still classified as threatened.
All this is probably why analysis of public records does not actually support the narrative pushed by Newhouse and others that the Endangered Species Act is a major regulatory burden and threat to resource development (Barry et al. 1992; Malcom and Li 2015). What it means to protect critical habitat varies depending on the species and its needs. For the northern long eared bat, interim guidelines for best management practices seem to focus much more on measures that would reduce the likelihood of killing individual bats or disrupting their breeding (both potentially series issues in a very small population) rather than just banning logging all together where the bats are or may be present.
Anyways, my larger point here is that extinction is a complicated process. Ideally, you want to get out ahead of it before a species declines by too much so that you can focus on the main cause of its decline and shore up its population with limited social or economic impact. Once a species reaches the point that the northern long eared bat has reached, however, you need to start taking into account factors that you wouldn't have been as worried about back when populations were larger, factors which may require more disruption of everyday life to combat. At this point, the situation is code red - the species is hanging on by a thread and if you want to save it, you need to be willing to do everything physically, financially, and morally possible to keep it from being cut.
Author's Note: This post was edited on 8/20/2023 to provide a more nuanced look at the threats faced by northern long eared bats and the current state of the regulatory landscape with respect to their listing, as well as how these relate to the larger point being made about the conservation of critically endangered species.
Sources:
Alston, J. M., Abernethy, I. M., Keinath, D. A., & Goheen, J. R. (2019). Roost selection by male northern long-eared bats (Myotis septentrionalis) in a managed fire-adapted forest. Forest Ecology and Management, 446, 251-256.
Barry, D., Harroun, L., & Halvorson, C. (1992). For conserving listed species, talk is cheaper than we think: The consultation process under the Endangered Species Act. World Wildlife Fund.
Bergeson, S. M., Confortin, K. A., Carter, T. C., Karsk, J. R., Haulton, S., & Burnett, H. (2021). Northern long-eared bats roosting in a managed forest in south-central Indiana. Forest Ecology and Management, 483, 118928.
Leopardi, S., Blake, D., & Puechmaille, S. J. (2015). White-nose syndrome fungus introduced from Europe to North America. Current Biology, 25(6), R217-R219.
Malcom, J. W., & Li, Y. W. (2015). Data contradict common perceptions about a controversial provision of the US Endangered Species Act. Proceedings of the National Academy of Sciences, 112(52), 15844-15849.
Photo Credits:
(1) "Northern long-eared bat with visible symptoms of WNS" - by U.S. Fish and Wildlife Service (CC BY 2.0)
(2) This photo is in the public domain.
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