Yesterdays Post regarding David Mech's CAUTIONARY COMMENTS ABOUT NEITHER MAKING WOLVES OUT TO BE SAINTS OR SINNERS elicited a number of important and illuminating comments from blog reader and citizen conservationist Stan Moore..........Stan has worked with many of the nation's top biologists and has a reputationa as a serious thinker in the field of prey, habitat and predators.........................We thank Stan for providing the information below on trophic cascades pro and con

From: stan moore hawkman11@hotmail.com
To: Meril, Rick
Subject: RE: new paper by Mech FYI -- another cautionary paper


Rick

Debates among wildlifers can be delicious!   Stan   PS:  I tend to believe that the theory of trophic cascades is defensible, but variable in time and space.  Nature is not static, and tends to reach an equilibrium following ecological changes, such as after recolonization of apex predators.

  For instance, Great Horned Owls dominated former Peregrine Falcon nesting habitat following the DDT era, and impeded the reintroduction program for peregrines in the Upper Midwest.  Eventually peregrines altered the balance and were able to hold their own and defend their recolonized territories.

 I think mesopredators should be able to adapt, too.  The science should decifer the mechanisms and cause and effect relationships instead of simply counting critters and trying to guess why the numbers change, in my opinion.  But it is easier said than done, and funding is always an issue.

Take care,

Stan
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Trophic cascades in Yellowstone: The first 15 years after wolf reintroduction

• William J. Ripple 
• Robert L. Beschta

• Department of Forest Ecosystems and Society, Oregon State University, Corvallis, OR 97331, United States

Abstract

The 1995/1996 reintroduction of gray wolves (Canis lupus) into Yellowstone National Park after a 70 year absence has allowed for studies of tri-trophic cascades involving wolves, elk (Cervus elaphus), and plant species such as aspen (Populus tremuloides), cottonwoods (Populus spp.), and willows (Salix spp.).

To investigate the status of this cascade, in September of 2010 we repeated an earlier survey of aspen and measured browsing and heights of young aspen in 97 stands along four streams in the Lamar River catchment of the park's northern winter range. We found that browsing on the five tallest young aspen in each stand decreased from 100% of all measured leaders in 1998 to means of <25% in the uplands and <20% in riparian areas by 2010.

Correspondingly, aspen recruitment (i.e., growth of seedlings/sprouts above the browse level of ungulates) increased as browsing decreased over time in these same stands. We repeated earlier inventories of cottonwoods and found that recruitment had also increased in recent years. We also synthesized studies on trophic cascades published during the first 15 years after wolf reintroduction. Synthesis results generally indicate that the reintroduction of wolves restored a trophic cascade with woody browse species growing taller and canopy cover increasing in some, but not all places.

After wolf reintroduction, elk populations decreased, but both beaver (Caster canadensis) and bison (Bison bison) numbers increased, possibly due to the increase in available woody plants and herbaceous forage resulting from less competition with elk. Trophic cascades research during the first 15 years after wolf reintroduction indicated substantial initial effects on both plants and animals, but northern Yellowstone still appears to be in the early stages of ecosystem recovery.

 In ecosystems where wolves have been displaced or locally extirpated, their reintroduction may represent a particularly effective approach for passive restoration.
 

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Wolves chasing Elk-----part of the web of life for millenia in North America

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The role of large predators in maintaining riparian plant communities and river morphology Robert L. Beschta, , William J. Ripple Department of Forest Ecosystems and Society, Oregon State University, Corvallis, OR 97331, United States Abstract Studies assessing the potential for large predators to affect, via trophic cascades, the dynamics of riparian plant communities and the morphology of river channels have been largely absent in the scientific literature. Herein, we consider the results of recent studies involving three national parks in the western United States: Yellowstone, Olympic, and Zion. Within each park, key large predators were extirpated or displaced in the early 1900s and subsequent browsing pressure by native ungulates initiated long-term declines in recruitment (i.e., growth of seedlings/sprouts into tall saplings and trees) of palatable woody species and impairment of other resources. Channel responses to browsing-suppressed riparian vegetation included increased widths of active channels via accelerated bank erosion, erosion of floodplains and erraces, increased area of unvegetated alluvium, channel incision, and increased braiding. A reduced frequency of overbank flows indicated these rivers have become increasingly disconnected from historical floodplains because of channel widening/incision. Results from Zion National Park also identified major biodiversity affects (e.g., reduced abundance of plant and animal species). Although these studies were conducted in national parks, results may have implications concerning riparian plant communities, biodiversity, and channel morphology for streams and rivers draining other public lands in the western US. It is on these lands that native and introduced ungulates have often heavily utilized riparian areas, largely in the absence of key predators, with significant consequences to plant communities and channels. Graphical abstract Figure options Research highlights ► We assessed trophic cascades associated with large mammalian predators. ► Loss of large predators allowed ungulates to degrade riparian plant communities. ► Browsing-suppressed riparian vegetation ultimately led to altered channels. Keywords Channel morphology; Bank erosion; Riparian vegetation; Ungulates; Predators; Trophic cascades Figures and tables from this article: Fig. 1. Top-down perspective of how extirpation of wolves can cascade through lower trophic levels (ungulate prey and plants) to eventually affect the character of river systems. Adapted from: Ripple and Beschta, 2004a. Figure options Fig. 2. Location of Yellowstone, Olympic, and Zion National Parks and associated biomes in the western United States. Adapted from Olson et al. (2001). Figure options Fig. 3. Photo chronosequence of the Gallatin River and its floodplain showing the status of riparian willow communities in (a) summer of 1924, (b) summer of 1949, (c) late spring of 1961, and (d) summer of 2003. Riparian vegetation associated with the floodplain shows progressive degradation from 1924 through 1961 because of high levels of elk browsing following wolf extirpation in the mid-1920s. Also, conifer "high-lining" (i.e., removal of lower branches by elk browsing), not evident in the right center of the 1924 photo, is visible in the 1949 and 1961 photos. In 2003, 7 years after wolf recolonization, willow communities along the Gallatin River floodplain are beginning to recover. Adapted from: Ripple and Beschta, 2004b. Figure options Fig. 4. Discharge–frequency relationships (dashed lines) for Reaches A, B and C of the upper Gallatin River, based on regional equations from Parrett and Johnson (2004). The shaded area encompasses the range of return periods for Reach A (control) and plotted points represent bankfull discharges and associated return periods for four cross-sections within each reach. Adapted from: Beschta and Ripple, 2006a. Figure options Fig. 5. Age structure of (a) black cottonwood (n = 547 trees) along the Hoh, Queets, and East Fork Quinault River and (b) bigleaf maple (n = 282 trees) along the Hoh and East Fork Quinault Rivers, western Olympic National Park, showing decline in tree recruitment following the extirpation of wolves. The exponential function (dashed line) was fitted to measured tree frequencies for the period1800–1910; its extension into the period 1910–2000 represents a general expectation of tree frequencies had wolves not been extirpated. Tree frequencies outside the lower 95% confidence limit are represented by "*". Adapted from: Beschta and Ripple, 2008. Figure options Fig. 6. (a) A 1994 orthophoto showing the Hoh River and its active channel along a portion of the Hoh River study reach (Olympic National Park visitor center is located on the north side of the river near photo center). (b) A 1.8-m high (above water surface) transitional fluvial terrace along the north side of the Hoh River south of the visitor center. The terrace is comprised of coarse gravel/cobble in the lower 1.2 m and grades into sand in the upper 0.6 m. Erosion of these vertical banks during periods of high flow continues to increase the width of the channel as well as increase the input of coarse sediment and organic debris (trees) into the river. Adapted from: Beschta and Ripple, 2008. Figure options Fig. 7. Age structure of riparian cottonwood along (a) North Creek (cougars common; n = 777 trees) and (b) the North Fork of the Virgin River in Zion Canyon (cougars rare; n = 262 trees) in Zion National Park. The exponential function (dashed line) was fitted to measured tree frequencies for North Creek study reaches; this same relationship has been plotted along with tree frequencies for the Zion Canyon study reaches illustrating a general cessation of cottonwood recruitment (i.e., missing age classes) after cougars were displaced and deer became abundant. Adapted from: Ripple and Beschta, 2006a. Figure options Fig. 8. (a) Trophic cascade indicated by inverse patterns of abundance across trophic levels to stream channel variables, and (b) observed species abundance of biodiversity indicators associated with "cougars common" and "cougars rare" areas of Zion National Park. Adapted from: Ripple and Beschta, 2006a. Figure options Fig. 9. (a) Up-valley view of the Lamar River from near its confluence with Soda Butte Creek (August 2003). Vertical river banks continue to erode during periods of high flow, wide active channels, expansive areas of unvegetated alluvium, and the generally braided character of channel following the loss of riparian vegetation in previous decades from intensive elk herbivory after the extirpation of wolves. (b) Trampling and high level herbivory in recent years by bison along the Lamar River limit recovery of riparian plant communities and prevent streambanks from stabilizing (September 2009). Figure options Figure options Table 1. General characteristics of the parks and study areas. Table options Table 2. Catchment area and other channel characteristics associated with 8-km long river reaches inside and outside of Olympic National Park in the western Olympic Peninsula (adapted from Beschta and Ripple, 2008). Reach elevation and channel slope measurements from 1:24,000 USGS topographic maps; wetted and active channel width measurements (± standard errors) from 1994 orthophotos (1-m resolution). Table options  2011 Elsevier B.V. ---------------------------------------------------------------------------------------------------------------------- Commentary Missing lynx and trophic cascades in food webs: A reply to Ripple et al.† John R. Squires1,*, Nicholas J. DeCesare2, Mark Hebblewhite2, Joel Berger3 Article first published online: 28 AUG 2012 The Wildlife Society, 2012 Abstract Ripple et al. (2011) proposed a hypothesis that the recovery of gray wolves (Canis lupus) may positively affect the viability of threatened Canada lynx (Lynx canadensis) populations in the contiguous United States through indirect species interactions. Ripple et al. (2011) proposed 2 key trophic linkages connecting wolf restoration with lynx recovery. First, recovering wolf populations may benefit lynx through reduced interference and exploitative competition with coyotes (C. latrans). Second, recovering wolf populations may benefit lynx through reduced exploitative competition among ungulates and snowshoe hares (Lepus americanus), the primary prey of lynx. Both proposed linkages have weak or contradictory empirical support in the available literature on lynx–hare ecology, casting doubt on the utility of Ripple et al.'s (2011) hypothesis. Debate over Ripple et al.'s (2011) hypothesis demonstrates the importance of experimental or comparative documentation when proposing trophic cascades in complex food webs. In this case, publishing unsupported opinions as hypotheses that concern complex trophic interactions is a potential disservice to lynx conservation through misallocated research, conservation funding, and misplaced public perception. © 2012 The Wildlife Society.