Monday, August 22, 2011

Creating Resilience: Trophic Cascades and Climate Change by Moderator Cristina Eisenberg


Ecologist
Robert Paine summed up the effects of keystone predator removal by saying, “You can change the nature of the world pretty simply. All you need to do is remove one species.”

In The Wolf’s Tooth, I compare ecosystems from which carnivores have been removed to a game of Jenga. This game involves removing wooden blocks one at a time from a tower without causing it to collapse. As you remove them, the tower starts to teeter, loosening some of the blocks, making them easier to remove. Eventually the whole system collapses.

In an ecological game of Jenga in an aspen forest, you might begin by removing species that may seem redundant. If you remove the black-capped chickadees first, not much happens, the system continues functioning more or less as usual. The number of chestnut-backed chickadees increases to fill the gap left by the black-caps. If you remove short-tailed weasels next, the mouse population initially increases, but then the coyotes start eating the surplus mice, as do the northern harriers, and mouse numbers go back down to the level they were at before you removed the weasels. A casual observer might not notice much missing. If you continue by removing white-tailed deer, the other ungulate species carry on, filling in the gap by producing more elk and moose.

Aspen with barren understory
in a wolfless area in the
Northern Rocky Mountains/ Photo credit: Cristina Eisenberg
However, when you remove predators in your ecological game of Jenga, the whole system starts to teeter. Ungulate numbers explode, because cougars and bears can’t put much of a dent in them. The ungulates start running out of food. Birds that nest and feed in the aspen canopy’s mid-story leave. With sustained intense browsing, shrubs and wildflowers disappear. And in less than a decade you are left with an impoverished aspen stand that contains maybe one third of the species it once did.


Resilient, healthy understory in an area
with abundant wolves in the
Northern Rocky Mountains/
Photo credit: Cristina Eisenberg
Can you think of other keystone species removals that could cause ecosystems to tip into “alternative” states?

When you put the impacts of wolf removal in the context of climate change, things become even more serious. Scientists Evelyn Hutchinson and E. O. Wilson have stated that there is no such thing as a redundant species. All species have a role, and multiple species of the same type of animal or plant exist to ensure ecological stability and resilience. Keystone predators increase biodiversity. Accordingly, landscapes from which keystone predators have been removed will experience a loss of stability. As global changes in climate occur, which involve sudden weather events or catastrophic fires, such systems may lack the resilience to adapt to change and continue to function in a healthy manner.
How do normally occurring disturbances (e.g., fires, floods) different from the disturbance patterns associated with climate change?

Metaphors work well to explain the concept of ecosystem resilience. In their seminal book Panarchy, ecologists Gunderson and Holling use the metaphor of a raft to describe an ecosystem. The resilience of the raft depends of course on its biophysical context. But it depends equally on its occupants—which may be human—their objectives, and their social institutions.

How does the concept of ecological resilience relate to resilience in human societies?

Biodiversity loss has become a crucial issue in the past two decades, as human-caused ecosystem modifications continue to precipitate extinction. Human actions that create islands of habitat in a sea of development exacerbate the effects of keystone predator removal. Saving all the pieces, as Aldo Leopold put it so long ago, can do much to help ecosystems stay resilient in the face of climate change. But doing so, as we will discuss next week, involves our social and political institutions, public policy, and humans opening their minds and hearts.

How can we incorporate the concept of resilience into natural resources policy?

14 comments:

Mark LaRoux said...

This vaguely reminds me of playing Spore in the 'Intergalactic Stage' where you add/substitute plants, then animals in ascending trophic levels on a newly terraformed planet. "Hey, I've got this stuff covered...I've done this in a game."
Not really, it's actually hard to play and depressing when you think of Wilson/McArthur's island biogeography and apply it to our 'islands' of biodiversity that slowly wink out one by one like voices treading water in an overturned raft built by Gunderson and Holling. (Glad they didn't use an ark and really mess with our metaphors, or call them chakras and make a chart) Aspirin anyone?
I guess my best example of human resilience (or lack of) is our new immigration law here in Alabama. Did we think out the fact that 'illegal' working people would leave our state in fear of being caught, and that farm employers would be stuck with crops in the field and no one to pick them because the people on unemployment aren't willing to get out in the field and pick crops for the same amount they make sitting at home? )I don't really blame them, though.) Where's my human society trophic backup? We punish agribusiness for politics again.
I'd like to propose introducing Mexican wolves into north Alabama to eliminate the 'coyote problem'....you know, since they are both 'invasives' but the Mexicans are from a different country (like they would know this) rather than just from the western US.
sorry, the best I can do this week is shrill humor about my state...this stuff is tough to think about and I'm trying to reread Dennis McCarthy's "Here Be Dragons" and apply it to your book. Good stuff between the 2 of you.

Cristina Eisenberg said...

Dear Mark,

Thanks for your comments. Trophic cascades, and creating landscapes where we coexist with keystone predators, are as much about human nature as they are about science and resource management. In a few days we will be discussing the policy implications of trophic cascades. Whether one examines social systems or ecological systems (Aren't they really the same thing?), everything is connected. The tolerance we have as humans for diversity and natural forces will take us far in terms of creating a more resilient, diverse world--one that sustains the human spirit as well as whole ecosystems.

Bob said...

How can we incorporate the concept of resilience into natural resources policy?

Well, as long as we staff management levels of Fish & Wildlife Departments with anti-predator hunters, there is small likelihood. As long as we fund F&W departments with hunting permits, there is small likelihood. We have to break the iron triangles that have persisted in this country regarding wildlife management, land management, fisheries, and extraction industries.

I want to learn the science, but I am slow on these ‘assignments’ as I’m spending a large amount of my time trying to stop this year’s assault on Washington state’s anti-hounding law. In spite of the science, WDFW continues to push hounding of cougars and a kill-rate higher than during the bounty years. WDFW also wants to limit wolves to 15 breeding pairs throughout the entire state. Until we get rid of the anti-science bias in this country, natural resources policy will continue the trophic degradation policies now in place.

Scientists such as Dr Eisenberg need to encourage more articles in the mainstream media. Articles such as Smithsonian’s “It All Falls Down,” based on Ripple and Beschta, or the Washington Post piece about the Science article “Trophic Downgrading of Planet Earth,” (Estes et al.) are good examples of explaining the current science. Scientists need to take a more outspoken position on policy issues. But then, it comes down to funding, and our current tax policies make scientists tread carefully to avoid drying up funds from sponsors.

I’m sure this question has to do with predator-prey relationships, and trying to maintain natural balance, habitat and connectivity at a landscape level. We won’t succeed there unless we convince the average voter that the impacts on their lives are real, and expensive to them. Our problem is that “a lie will be halfway around the world before truth can pull its shoes on.”

Bob said...

I hope that we might pursue further the idea that Puma concolor seems to cause less fear in ungulates than wolves. Certainly Ripple & Beschta 2006 Zion study indicates that cougar maintain diversity. Dr. Eisenberg mentions in her book p. 184 that cougars are not functioning as keystone predators (in a particular area)--could it be that cougars are below their biologically effective population density? The assertion that cougars are abundant in the area might be perception rather than fact. In Washington, everyone knows cats are overrunning the state-everyone except the scientists that actually take a cougar census and a few of us that follow the science. In any case, this is an interesting topic that I'd like to see pursued. I would expect difference in herd behavior because of coursing vs ambush/pouncing, but wouldl still suspect that ungulates would avoid margins that provide cover for lions.

Cristina Eisenberg said...

Dear Bob,

With regard to cougars and their ability to function as keystone predators: that is the topic of the research I am doing in Glacier National Park and Waterton Lakes National Parks, and also on the High Lonesome Ranch in Colorado. The High Lonesome Ranch has an enormous cougar population, and the elk are wiping out the aspen. This is complex, as there are cattle involved as well in that system. In Glacier and Waterton, the cougar is definitely not acting as a keystone. Nobody knows why this is, and I am doing long-term studies, one in an area that has a high population of wolves, another in an area that has a recolonizing wolf population (Colorado) to measure these effects. One thought is that in systems dominated by elk, which these are, the cougar is unable to act as a keystone. Cougars do not typically prey on adult elk. They prey on elk calves. This may be why in elk-dominated systems they do not act as keystone predators.

Cristina Eisenberg said...

Dear Bob,

With regard to your comment about making science more widely accessible to a broader audience--that was precisely the topic of one of papers I presented at the recent Society for Ecological Restoration conference in Merida, Yucatan. Along that vein, I am currently working on my second book for Island Press, it is about all the large carnivores and how we manage them from Alaska to Mexico, and will include the stories about our human relationships with and the conservation status and environmental laws that regulate management of cougars, wolves, grizzly bears, jaguars, wolverines, and lynx. This book, titled "The Carnivore Way," should be out in 2013.

Cristina Eisenberg said...

Dear Bob,

With regard to your comment about hunting, I want to say that I am a hunter. I hunt elk. I hunt cow elk for conservation purposes in areas where there are too many elk and not enough predators such as wolves. I use the meat to feed my family and my field crew. I am in the field right now studying wolf effects in Alberta, and I am feeding my crew with the meat of the elk I harvested last December in an area with too many elk. This November I hope to harvest another cow elk. I believe agencies and humans should use hunting as a means for creating healthier ecosystems. This means taking our cues from American conservationist Aldo Leopold, who 70 years ago advocated using hunting as a powerful conservation tool. Not quite the same as having keystone predators in an ecosystem, but it helps.

As far as agencies are concerned, the directors of several agencies are joining me in the field to learn more about how to apply trophic cascades principles to agency management of wildlife and wildlife habitat and whole ecosystems. This gives me much hope that those who lead our wildlife and natural resources management agencies are considering the big picture, the web of life, and "all our relations" as I refer to this in "The Wolf's Tooth" in making decisions about wildlife managment.

Bob said...

Thank you, Dr, Eisenberg. I'll look forward to seeing your research and book. I believe that blogs such as this one are helpful, but am happy to see that scientists are discussing broader outreach. I understand the nuances of science and "what we know," but a forceful statement such as Dr Paine's (opening, above) does more good than the nuanced discussions of whether it's provable or leads to a tautological definition of 'keystone.' (BTW In a phone conversation Dr Paine pointed me toward Terborgh & Estes’ Trophic Cascades which also led me to The Wolf’s Tooth. I called his office as everything I was reading referred to Robert Paine.)

Bob said...

Regarding hunting, the context of my comments was my earlier post http://wildread.blogspot.com/2011/08/yellowstone-and-beyond-fear-as.html#comments which you might not have seen as it was ‘late.’ Your comments here partially answered some of my questions. By “anti-predator hunters” I was specifically referring to the small group of hunters that believes massive reduction, or even extirpation, of predators leads to better hunting, and that see any wild animal attack on a human as failure of the system to remove carnivores. A better choice of my words in the referenced post would have been “people that are anti-predator.”

My objection to wildlife funding through hunting tags is that it makes agencies prone to bad decisions to maintain revenues—in spite of the agencies’ expenditures for science. Washington DFW finances some great cougar research, but as results move up through the agency, biased filters seem to filter the conclusions of the biologists so as to offer more recreation (revenue). Top level managers and Commissioners receive biased information, and resultant decisions come out biased. As scientists more directly involve themselves in popular publishing, I would hope that current scientific thought would permeate our collective psyche making bias noticeable. (But then, having read about climate change since the early ‘70s, maybe not.) It is heartening to hear that some agency directors are joining you.

Bob said...

I wonder whether there is some minimum-sized territory (maximum population density) that cougars (and wolves) tolerate, and in areas where elk have established overwhelming presence, there is just too much meat to manage, but social pressure (or development/lack of connectivity) keeps more cats out? In other words, are these areas in which heavy hunting of predators allowed elk takeover, and elk have gone past a tipping point, or are these relatively pristine systems? (Obviously not HL Ranch.) Alternative prey sources will also be interesting, as a single cat risks more attacking an elk than a deer. Perhaps a large elk herd will attack a cat that has taken down a member, before the cat can drag its kill to a safe area? Could there be a back-channel of fear once the consumer level reaches a critical mass?

If I understand what I have read, you are describing High Lonesome Ranch as an area with (effectively) an even number of trophic levels. Perhaps Homo sapiens needs to assume the apex role while waiting for the wolves to return. I have to believe that the system is perturbated, and in the long run will seek a new stasis level. I believe that the most important part of any system is the broken or missing part. With proper science and outreach, maybe we can stop breaking or losing so many parts.

Dr. Eisenberg, I hope to see your papers, and progress reports. I would be interested to read your paper for the Society for Ecological Restoration conference in Merida, Yucatan. A goal I have set for myself is to bring research into the public’s view by trying to interest the media in interviews and round-table discussions of biologists and trophic scientists. Your perspective could help immensely. Since reading A Sand County Almanac some forty years ago, I have through continued reading come to the conclusion that we shouldn’t sports hunt the top predators and that we must learn to co-exist and to tolerate predators that are going about their business. Legislators need to hear the science, and must start thinking in landscape terms as must F&W managers.

While I see your scheduled stint as moderator has nearly ended, I hope this discussion can continue. I greatly enjoyed The Wolf’s Tooth and look forward to reading your new book, and your research papers. I hope you will post them on the OSU website.

Thank you for your generous allocation of time.
hank you for your work.

Cristina Eisenberg said...

Dear Bob,

In my study areas in Montana and Alberta I am finding a very high density of wolves--and a very high density of elk (>10 per square kilometer). My findings do not support the assertion that the wolves are wiping out the elk. The elk are in superb health. However, they are also extremely wary, likely due to wolf presence. This makes them much harder to spot and hunt than when wolves were not in this system. We all have much to learn about what it means to create healthier ecosystems and living with carnvores. We have come a long way when one considers that 30 years ago there were essentially no wolves in the lower 48 United States, and now this species is present in several states. But we still have a long way to go as we learn about managing them and the other carnivores using more progressive models.

Mark LaRoux said...

An interesting article on beavers is on the Wall Street Journal front page (bottom) today (Aug. 30), its about beavers in western states. I'm curious if most western ranchers/farmers are supportive of beavers after decades of shooting them on sight. Here, they do wonders during droughts (like right now) as they retain water in slow draining pools rather than allowing it to runoff right after a rain, which would increase silt, hence decreasing fish numbers. Mosquitoes are a problem with this beaver abundance, but mostly due to introduced species...the Asian tiger mosquitos are hell on us right now. Hmm...keep adding levels? Mosquito fish?
Last year, I corresponded with a lady in Oklahoma that had a female mountain lion on her property, and she was wondering why it settled on her place. When she described the beaver ponds, I was chuckling and thinking "Hey, if I was a mountain lion, this is where I'd go too....a 'mountain lion Walmart' with a huge meat selection next to the water (always follow the water). I'll echo Bob's pessimism with top level managers/Washington but add that the system can/may be worked through the states...if 1 brings in more tourist dollars by being 'predator friendly', then the others will watch money slowly siphon away...just like the trophic system that they depend on does...energy isn't wasted, just moved (money as water...follow the water). We see the same thing with gambling/casino money here, surrounded by gambling on all sides. Imagine how much people would pay to hunt elk here in Alabama, rather than having to travel to the west. Just for fun, imagine Alabama pro-predator and still anti-gambling, holding it's own in revenue and talking ecotourism with the big boys. We tried that in the 30's in the Tuscaloosa area...and hunted them out before they could even breed. Some of us are slow learners, but we get there.
(Bob's iron triangles) The whole point behind the ESA was that it was supposed to be immune from money influencing it's mandate (follow the money....uh, water), but even this has been perverted through endless arguements, lawsuits, and 'experts' that never agree on what a 'species' even is. Witness the red wolf fiasco...does it deserve protection? Of course, but we can argue ad nauseum whether it's a species or not...even to the point of using mtDNA SNP's from dogs.....European dogs?...and boxers and poodles at that!...to extrapolate canid variation. Heaven forbid our coyotes breed with red wolves as they'd become 'killing machines' that would rival our inner city gangs in being 'fearsome'. Why does Eurocentrism keep seeping into our science in odd ways? Why the fear?
Slowly, I'd say that some of the 'cowboy ethic' that we were taught as kids (mostly through TV here in the east/south) has actually become a European ethic itself...shoot first if scared, snakes are scary so kill them, smush them spiders, wolves are bad and eat livestock (which are invasives themselves), cougars pick livestock over wild prey, bears and people can't coexist, etc. The fear extends to lots of points in our lives....TSA, military funding, FEMA (my favorite) yet what's our number 1 killer of Americans? number 1 killer of babies? Not according to the media.
I'm not sure if educating the populace isn't less effective as finding 'keystone politicians' and 'keystone comedians' that can point out what our society does to discourage predators. Maybe we need more 'keystone hunters' and 'keystone reporters' also.

Mark LaRoux said...

Well, looky there, somebody had the same idea I had about Mexican Gray wolves, just a little further south:
http://azstarnet.com/news/local/border/article_4f0197be-f9cd-11e0-9665-001cc4c002e0.html
(5 Mexican Gray wolves released in Sierra San Luis mountains). If you can't win on a unfavorable battlefield, outflank them! Viva Naturalia!

Anonymous said...

Hi Cristina,

I enjoyed reading your book The wolf's Tooth. I have linked this blog to our website on rewilding:
http://www.anatolianleopardfoundation.org/

Would be great to link-in with one another.

Regards,

Erwin van Maanen
Anatolian Leopard Foundation