Loss of Predators in Northern Hemisphere Affecting Ecosystem Health

The entire report, Large Predators Limit Herbivore Densities in Northern Forest Ecosystems, is available here.

ScienceDaily (Apr. 9, 2012) — A survey on the loss in the Northern Hemisphere of large predators, particularly wolves, concludes that current populations of moose, deer, and other large herbivores far exceed their historic levels and are contributing to disrupted ecosystems. The research, published recently by scientists from Oregon State University, examined 42 studies done over the past 50 years.

It found that the loss of major predators in forest ecosystems has allowed game animal populations to greatly increase, crippling the growth of young trees and reducing biodiversity. This also contributes to deforestation and results in less carbon sequestration, a potential concern with climate change.

“These issues do not just affect the United States and a few national parks,” said William Ripple, an OSU professor of forestry and lead author of the study. “The data from Canada, Alaska, the Yukon, Northern Europe and Asia are all showing similar results. There’s consistent evidence that large predators help keep populations of large herbivores in check, with positive effects on ecosystem health.”

Densities of large mammalian herbivores were six times greater in areas without wolves, compared to those in which wolves were present, the researchers concluded. They also found that combinations of predators, such as wolves and bears, can create an important synergy for moderating the size of large herbivore populations.

“Wolves can provide food that bears scavenge, helping to maintain a healthy bear population,” said Robert Beschta, a professor emeritus at OSU and co-author of the study. “The bears then often prey on young moose, deer or elk — in Yellowstone more young elk calves are killed by bears than by wolves, coyotes and cougars combined.” In Europe, the coexistence of wolves with lynx also resulted in lower deer densities than when wolves existed alone.”

In recent years, OSU researchers have helped lead efforts to understand how major predators help to reduce herbivore population levels, improve ecosystem function and even change how herbivores behave when they feel threatened by predation — an important aspect they call the “ecology of fear.”

“In systems where large predators remain, they appear to have a major role in sustaining the diversity and productivity of native plant communities, thus maintaining healthy ecosystems,” said Beschta. “When the role of major predators is more fully appreciated, it may allow managers to reconsider some of their assumptions about the management of wildlife.”

In Idaho and Montana, hundreds of wolves are now being killed in an attempt to reduce ranching conflicts and increase game herd levels. The new analysis makes clear that the potential beneficial ecosystem effects of large predators is far more pervasive, over much larger areas, than has often been appreciated.

It points out how large predators can help maintain native plant communities by keeping large herbivore densities in check, allow small trees to survive and grow, reduce stream bank erosion, and contribute to the health of forests, streams, fisheries and other wildlife.

It also concludes that human hunting, due to its limited duration and impact, is not effective in preventing hyper-abundant densities of large herbivores. This is partly “because hunting by humans is often not functionally equivalent to predation by large, wide-ranging carnivores such as wolves,” the researchers wrote in their report.

“More studies are necessary to understand how many wolves are needed in managed ecosystems,” Ripple said. “It is likely that wolves need to be maintained at sufficient densities before we see their resulting effects on ecosystems.”

“The preservation or recovery of large predators may represent an important conservation need for helping to maintain the resiliency of northern forest ecosystems,” the researchers concluded, “especially in the face of a rapidly changing climate.”

12 thoughts on “Loss of Predators in Northern Hemisphere Affecting Ecosystem Health”

  1. Matt, That’s quite a tempting and juicy hook…I’ll bite..

    To be honest and in all sincerity I’m struggling thru the logic on this one….help me out.

    Lets use our Northern Rockies for example.

    Fire gone for over 100 years in most areas….

    Wolves gone 50 years or so….

    Predator-prey “balance” (for the most part) continues (for 50+ years – ~~5 generations of predator/prey) until wolves are “extirpated” (at least in sufficient numbers to have the impacts that this research suggests)….

    In theory, even after fire supression here in the Northern Rockies, wolves eat the herbivores that eat young trees/seral stage – essentially keeping the native plant communites “in check”…

    Wolves are extirpated. Not enough wolves, too many herbivores – not enough young trees/seral stage (cause the herbivores keep eating it up).

    This is where I lose the logic….(and we’re not talking Yellowstone, where I’d agree, the willows have come back and the trophic pyramid has been re-established). If I’m all wet on this I’ll be the first to admit it..I’m just not getting the arguement.

    Elk (as a surrogate for “herbivores”) numbers peaked in the 80’s/90’s, some 40 years or so after wolves were gone, at least in Idaho/Montana.

    The resultant “overpopulation” of herbivores (suggested by this research) would indicate that plant succession coulda/woulda/shoulda been retarded…not enough young trees and early seral plant communities surviving….that herbivores in the absence of predators (wolves)would perpetually overbrowse/graze native plant communities.

    The fire suppression arguement (until the recent advent of Baker’s stuff – future post???) would indicate the opposite… that there is too much mid seral and older plant communities. Not enough early seral….not enough diversity or resilience.

    Elk numbers have since crashed, at least on NFS (forest) lands, and have increased elsewhere, mostly agricultural and private lands. Not enough QUALITY or DISTRIBUTION of early successional habitats say the experts (on NFS lands).

    So again, here’s where I struggle….which arguement trumps the other??? Or are they so intertwined that they are not obvious to the average practioner? I hate to see such a galvanizing arguement presented in a way that concludes “more studies are necessary”.

    Logging (responsible forest management(call it restoration if you must)) can create more acres of young trees/early successional habitat. Generally funds itself, if planned correctly. Prescribed fire fits this bill as well, where mechanical treatments are not ecologically/socially feasible.

    Hunting (responsible carnivore and herbivore (“game”) management), funded through license and tag sales can maintain populations of animals that eat/feed each other and eat young trees….self funded. “Responsible” (and ethical) being the operable part of that sentence…the actions of one do not reflect on the whole (yuou know what Im talking about).

    I’m asking what the ultimate (for you Matt) conclusion or implications of this study would be??? Less carnivore management? (hunting), less forest management? (logging), less fire supression? less people? More what??? Solutions are welcome.

  2. Self evident really, but one wouldn’t think so from the amount of different opinions that exist on the subject. And let us not forget that the same applies to the ocean’s eco system, sea mammals (who are accused of eating too much fish) are vital to its health…

  3. Thanks, JZ. I was busy with other stuff yesterday, but had many of the same thoughts.

    This is one of those studies that basically says. Things used to be different. (fact)They were better then for “ecosystems.” (value)
    So we need to do something different to make things more like they used to be (value).

    Based on a claim of legitimacy of “science”, based on “science” being objective (empirical, not normative).

    Accident or intentional- study came up at the same time that wolves are a hot issue?

    “More studies are necessary to understand how many wolves are needed in managed ecosystems,” Ripple said. “It is likely that wolves need to be maintained at sufficient densities before we see their resulting effects on ecosystems.”

    “The preservation or recovery of large predators may represent an important conservation need for helping to maintain the resiliency of northern forest ecosystems,” the researchers concluded, “especially in the face of a rapidly changing climate.”

    Wouldn’t this be an equally valid argument for reintroducing grizzly bears to central California? Why or why not?

    • Thanks Matthew for posting this and thanks Sharon and JZ for providing this dialogue.

      “Accident or intentional- study came up at the same time that wolves are a hot issue?” (asks Sharon)

      When have “management” (reality: MISmanagement) and wolves NOT been a hot issue Sharon?

      “Extinction of Woolly Mammoth, Saber-Toothed Cat May Have Been Caused by Human Predators
      (July 1, 2010) — A new analysis of the extinction of woolly mammoths and other large mammals more than 10,000 years ago suggests that they may have fallen victim to the same type of “trophic cascade” of ecosystem … > read more

      there’s plenty more studies to draw from, conveniently accessed on the Science Daily site:

      “Prey Not Hard-Wired To Fear Predators
      (June 20, 2007) — Are Asian elk hard-wired to fear the Siberian tigers who stalk them? When wolves disappear from the forest, are moose still afraid of them? No, according to a study by a Wildlife Conservation Society …” > read more

      “Loss of Large Predators Disrupting Multiple Plant, Animal and Human Ecosystems
      (July 14, 2011) — The enormous decline of large, apex predators and “consumers” ranging from wolves to lions, sharks and sea otters may represent the most powerful impacts humans have ever had on Earth’s ecosystems, a … ” > read more

      “Global Warming Threatens Moose, Wolves
      (Aug. 17, 2007) — Global warming is impacting more than the water levels in the Great Lakes. It could be the beginning of the end for the moose and wolves of Isle Royale. And if it is, a Michigan Technological … ” > read more

      “Marine Predators in Trouble
      (Dec. 5, 2011) — Iconic marine predators such as sharks, tunas, swordfish, and marlins are becoming increasingly rare under current fishing trends, say … ” > read more

      My point being, for all the hubris-filled claims of this “management” culture and assumed prowess being expressed on NCFP by representatives of agencies with a well-demonstrated history of management failures — I’m struck this has not produced an iota of self-reflection.

      For all the recent agency hype of “restoration and stewardship” to be managed for the goal of “resiliency”, (the coyly phrased), Adaptive Management Strategy, etc. in the Planning Rule, all it takes is an article like this to watch the agency culture of resistance emerge to demonstrate the aforementioned terms are little more than sloganeering to cover-up what managers will continue to do:

      Mismanage, as if there weren’t important lessons of well-demonstrated ignorance which should have been learned from long ago.

      Please — Do less until you know more.
      Please — Spread the word our evolution as a species requires humility and the capacity to learn from past mistakes, adaptation of behavior…

      • Yep, let’s blame dead foresters for today’s problems. Sadly, doing nothing has been shown to be the wrong thing to do. AND, let’s blame “dumb cancerous humans” for their fiery impacts on the perfectly-protected flammable fuels, so valiantly fought for.

        • Thanks again Larry, for illustrating so vividly, my points raised.

          Not sure who you’re quoting there, but I agree completely we seem to have no shortage of dumb humans who are suffering an epidemic of cancer. While they are being eliminated from the gene pool, unfortunately, and many may be considered as dumb (such as those disregarding warnings on cigarettes and dying of cancer, etc.) others are cancerous though, not by their personal choices, but due to larger policies beyond their control. The same could be said for predators suffering “management”.

          I see a pattern here.

          I reiterate my plea:
          Spread the word our evolution as a species requires humility and the capacity to learn from past mistakes, adaptation of behavior…,etc., etc.

      • About moose, I ran into a researcher who was studying moose somewhere in Wyoming and watching them adapt to climate change. My impression of his presentation was that they followed the season up to the high country, and the timing did not so much matter as the sequence of greening up was the same with the moose moving to higher elevations was the same. Sorry I forgot his name but he was actually observing empirical moose behavior. Just sayin’

        • I recently visited Utah for the first time, and spent a day with Dr. Charles Kay, driving through the mountains. At one point we spotted two moose down by a creek. I was pretty shocked as I have seen very few moose in my life (mostly Canada), and had no idea they were in Utah. Apparently they are smart enough to follow food around, but not so smart as to be concerned about climate change.

          Charles says the moose were brought in several decades ago, and seem to be doing ok. Much of Charles’ work has been with elk and browse in Yellowstone, and he bases his findings on empirical evidence — first hand observation and historical photographs. As you might imagine, his conclusions regarding this study would be significantly different than Ripple and Beschta’s. Again. And for the same reasons.

  4. I think this study also leaves out the fact that until 30 or 40 years ago human hunting was generally a lot less limited (most western states have switched from over-the-counter permits toi a lottery system in the 60’s through 80’s only after noticing major declines in large game populations) and was likely a huge part of the equation before that. Human hunting only has such a limited impact now because many areas are off-limits to hunting (e.g. national parks) and because most states now purposefully limit this through a lottery system.

    Prior to the establishment of national parks and other areas where hunting is not allowed humans likely were the main predator affecting large herbivore numbers, not wolves. This study seems to completely ignore the effect of human and paints a picture as if large non-human carnivores are the only control on herbivores. I guess this is point ties back to the the discussion from a week or so ago about the importance of ‘framing’ with humans being part of nature or a-part from it.

  5. To further confound the issue – what about the impact noxious and invasive plants have had on ecosystems in the Northern Hemisphere (or anywher for that matter)?

    A simple search would yield dozens if not hundreds of peer reviewed pieces of scientific research that quanify the impacts of noxious and invasive plants. The research is pretty mature and few studies conclude with “more research is necessary”….

    A simple search got this as the first hit: http://www.weedawareness.org/impacts.html
    Utilitarian, but succinct.

    Another search on ScienceDaily yielded only 29 results, most of which was negative to weed management citing the risk of herbicide resistance…

    Despite the (undisputed) fact that noxious an invasve plants have a significant and long lasting impact to the ecology of an ecosystem, this is seldom brought up as a topic of conversation…..why? not “sexy” enough???

    Do I need to take a picture of myself adorned with backack sprayer, spray wand in hand kneeling next to a field of blue stained weeds with a “sadistic” smile on my face to get weeds newsworthy enough to rate attention?

    Really, if we are going to expose and deliberate on all things that affect ecosystem health we should not stop where the money stops….in fact weed management is a gold mine…….

    Just another viewpoint.

  6. It is a fact that elk had been almost completely extirpated from Oregon by 1900. The story is they were sent in by railroad from Jackson Hole before WW I (and still before highway trucking). People were not allowed to hunt these animals until the 1930s, so that the populations could build. During the past 20 or 30 years we have reached record high elk numbers of well over 100,000 — despite tens of thousands being killed by hunters every year.

    In 1900 in Oregon there were no roads for motorized vehicles because there were no motorized vehicles. When automobiles came into use, rich people started building roads to such places as Multnomah Falls and Crater Lake, and governments started building them to connect towns and postal routes. As highway miles were constructed by the thousands, elk populations also continued to increase by thousands.

    In 1900 there were lots of wolves in Oregon. By 1950 they had all been killed. Now a few have moved in again, from reintroduced Canadian packs.

    So . . . we need road closures to improve elk habitat, and we need wolves to keep elk numbers down so they won’t destroy their habitat. When does this “science” stop? When does common sense rear its ugly head and say “what the hell are these people even thinking, much less talking about?” At some point we need to put an end to this nonsense.


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