What do cave-dwelling bats, the extinct passenger pigeon, and the American Chestnut blight have to do with each other . . .
When the infamous fungal blight hit the American Chestnut in 1904, the forest management officials reacted as anyone would to an intruder in the home: they came out with guns blazing. They employed organic fungicides, chemicals, quarantine, and finally clearcut huge “firebreaks” into the forest in the hopes that the blight would at least be contained. They cared deeply, they worked hard — and ultimately, they failed. By 1940, the 4-billion strong population of American Chestnuts had been decimated, leaving the tree all but extinct in its mature form.
Why did these well-meaning, dedicated, intelligent conservationists fall short? Perhaps because there was nothing anyone could do. But perhaps also because they looked at the blight as essentially a simple (if formidable) problem: fungus killing trees. A certain and straightforward equation, but with ecology, you only ever notice the tip of the iceberg. Under the surface there lies such a complex system that any action you take (or don’t take) will have an infinite cascade of unpredictable consequences.
Now that another devastating fungus is sweeping down out of northeastern Appalachia — this time one that threatens nearly the entire multi-species population of insectivorous cave-dwelling bats in this country — modern ecologists would do well to remember the story of the American Chestnut — and the people who tried to save it.
White-Nose Syndrome (WNS), the “bat blight”, was first observed in New York in 2006, and has since radiated south and west along the cavernous Appalachians in classic epidemiological fashion, leaving climbing mortality in its wake. While the epidemic quickly seized the attention of both the caving and the conservation communities, and has been researched by both government and non-governmental organization (NGO) scientists, the precise cause of the mass mortality has not yet been conclusively determined. There are, however, very strong correlations implicating a soil-dwelling fungus, Geomyces destructans, in the syndrome. Bats with WNS can be observed during hibernation with G. destructans — a whitish, spotty fungal bloom — visible on their faces, ears, and wings. These bats behave unusually during hibernation: displaying agitation, changing roosts, taking flight into the winter landscape — and dying, by the thousands. Autopsies commonly yield the cause of death as a combination of starvation and exposure, and the mortalities associated with WNS accordingly occur primarily during the hibernation season.
Little Brown Bat With WNS Facial Fungus Credit: U.S. Fish and Wildlife
While controversy about the epidemic remains, the current best possible theory is that the fungusG. destructans — suspected to be an overseas import like the Chestnut blight — eats away at bats’ skin, causing them to wake frequently during hibernation in order to control the irritation. Failing to truly hibernate, the bats burn their fat reserves early, and must resort to the high-risk, low-gain endeavor of hunting in the middle of winter. With this as the strongest theory and time running out, management of the syndrome has focused upon containing and eradicating G. destructans. Fungicides have been explored (tools which would wipe out over half the biota in the average fungus-rich cave habitat), as well as quarantine — even the approach of eradicating whole bat populations (cutting bat “firebreaks”, if you will) has been both entertained and attempted. And yet, like the chestnut blight, WNS advances implacably. Turning back the tape: when the chestnuts were threatened at the beginning of the previous century, scientists and conservation managers failed to pay attention to the rest of the chestnut forest’s ecology in their haste to combat the trees’ new, exotic enemy. They payed little heed, for example, to the impact of the recent extinction of the passenger pigeon upon the trees’ nutrition.
The pigeons, which before the late 1800s had boasted populations so high that they “darkened the sky for days”, had been a keystone species that cycled nutrients from the fields where they hunted back to the forests where they roosted. All of the fresh fertilizer that the chestnut forest needed to thrive was amply provided by those hordes of excrement-producing birds. But the passenger pigeon’s ecological niche depended on its vast numbers, and in the face of the habitat destruction and mass extermination that resulted from the pigeon’s clash with humanity, their population plummeted rapidly, rendering the bird ecologically extinct by 1890, and completely extinct by 1914. Having effectively existed without the pigeons for ten plus years, by the time the blight struck, the chestnuts were essentially a malnourished species. As anyone working in health care knows, the ravages of a disease upon a malnourished population is dramatically amplified over that of a population with good nutrition, yet the trees’ overall health was never the focus of any attempts to protect them.
Conservationists also failed to credit the trees with any genetic resilience, automatically taking the heroic approach and assuming that the trees would not adapt to or resist the fungus on their own, and would therefore never make it without humanity playing the role of rescuer. The chestnuts’ situation was certainly dire, but no species exists unless it has adapted, again and again over the course of its evolution, to changing circumstances. In taking it upon ourselves to battle the fungus with heavy chemicals, and in cutting down vast numbers of trees in attempted quarantine, we neutralized any hope the chestnut had to recover naturally — especially considering that the trees were starving. Would the chestnut have recovered without our intervention? Quite possibly not. Would it have had a better shot were it not lacking nutrition? Definitely. Has the chestnut recovered with our intervention? Not really. There are ongoing attempts to create blight-resistant hybrids, and a few mature trees can be found outside of the trees’ historic range, but the vast chestnut-dominated forests of the previous century are not to be found anywhere.
Blight Scars on Chestnut Bark
So a century later, approaching the dying bats, can we offer anything other than chemicals, futile quarantine and population culling? Some of us are trying: the scientific and managerial approaches so far have ranged across the full spectrum of possible options; and many of them demonstrate decided advances in ecological sophistication. Yet many of the WNS management programs remain tangled up in politics, which tends to promote whichever approach just gets something done,darn it, regardless of how futile — or even potentially harmful — those efforts might be. Seeing such devastating epidemics sweep through our natural systems as we see these days on a regular basis is wrenching and terrifying for those of us who value our ecology; even more difficult is to accept the fact that sometimes there is nothing we can do, or at least that what we should do isn’t immediately obvious. But it might be that the skills of zooming the lens back and trying to grasp the big picture, of looking beyond the obvious, and of acquiring the discipline and wisdom to know when to hold back in addition to when to act, are the skills we need to hone if the bats — and the rest of the ecosystem — are to have any hope.
Ecology and epidemic management are both complex, fascinating, and highly charged topics. I try to be thorough in my research and careful in all of the statements that I make, but I can’t tell you I know for sure what is happening any more than the next guy. I also won’t take credit for the research or the brilliant ecological connections described in this blog; that work is being done by hundreds of curious, dedicated people working in those fields, and I simply want to share it. For a more complete exploration of the connection between the extinction of the passenger pigeon and the American chestnut epidemic, please visit The Permaculture Activist site and read Peter Bane’s article Keystones and Cops: An Eco-Mystery Thriller, originally printed in May 2003. Bane’s article is a fascinating read, and is the initial source for the picture I paint here about the progression of that historic ecologic tragedy. For more information about the bats, and about WNS research, WNS management, and WNS controversy, the two sites below are good places to start. I can’t speak for where you’ll end up . . .
White-Nose Syndrome Timeline and Reference List
Current Research and Management Strategies