Recolonizing wolves trigger a trophic cascade in Wisconsin (<scp>USA</scp>)

Callan, Ramana; Nibbelink, Nathan P.; Rooney, Thomas P.; Wiedenhoeft, Jane E.; Wydeven, Adrian P.

doi:10.1111/1365-2745.12095

Cited by 63 publications

(42 citation statements)

References 70 publications

(105 reference statements)

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“…The wolves restored a tritrophic cascade, where direct predation and behavioral impacts on American elk (Cervus elaphus) have increased regeneration of Populus and Salix spp., with indirect effects on other wildlife and geomorphology (60). Controversy exists over the exact role of wolves in these dynamics (59), but similar effects are reported elsewhere in North America (61,62) and Europe (63). Other experiments have focused on large herbivores.…”

Section: Current Scientific Basis For Trophic Rewildingmentioning

confidence: 90%

Science for a wilder Anthropocene: Synthesis and future directions for trophic rewilding research

Svenning

Pedersen

Donlan

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

457

506

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Trophic rewilding is an ecological restoration strategy that uses species introductions to restore top-down trophic interactions and associated trophic cascades to promote self-regulating biodiverse ecosystems. Given the importance of large animals in trophic cascades and their widespread losses and resulting trophic downgrading, it often focuses on restoring functional megafaunas. Trophic rewilding is increasingly being implemented for conservation, but remains controversial. Here, we provide a synthesis of its current scientific basis, highlighting trophic cascades as the key conceptual framework, discussing the main lessons learned from ongoing rewilding projects, systematically reviewing the current literature, and highlighting unintentional rewilding and spontaneous wildlife comebacks as underused sources of information. Together, these lines of evidence show that trophic cascades may be restored via species reintroductions and ecological replacements. It is clear, however, that megafauna effects may be affected by poorly understood trophic complexity effects and interactions with landscape settings, human activities, and other factors. Unfortunately, empirical research on trophic rewilding is still rare, fragmented, and geographically biased, with the literature dominated by essays and opinion pieces. We highlight the need for applied programs to include hypothesis testing and science-based monitoring, and outline priorities for future research, notably assessing the role of trophic complexity, interplay with landscape settings, land use, and climate change, as well as developing the global scope for rewilding and tools to optimize benefits and reduce human-wildlife conflicts. Finally, we recommend developing a decision framework for species selection, building on functional and phylogenetic information and with attention to the potential contribution from synthetic biology.conservation | megafauna | reintroduction | restoration | trophic cascades

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Section: Current Scientific Basis For Trophic Rewildingmentioning

confidence: 90%

Science for a wilder Anthropocene: Synthesis and future directions for trophic rewilding research

Svenning

Pedersen

Donlan

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

457

506

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“…For example, Mexican gray wolves in southwestern North America have not yet been restored to an ecologically effective density in relation to that of their main prey, elk, because of ongoing conflicts with livestock grazing and repeated management translocations (62). Likewise, recent wide-scale hunting of recovering gray wolf populations in parts of the Great Lakes region and the western United States may reduce wolf populations below sizes at which they are able to exert their effects on communities and ecosystems (63)(64)(65). Furthermore, wolves and other carnivores may have little influence on other species in areas where human hunters have disproportionate effects on prey densities (66).…”

Section: Reviewmentioning

confidence: 99%

Status and Ecological Effects of the World’s Largest Carnivores

Ripple

Estes

Beschta

et al. 2014

Science

2,702

2,641

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Background:The largest terrestrial species in the order Carnivora are wide-ranging and rare because of their positions at the top of food webs. They are some of the world's most admired mammals and, ironically, some of the most imperiled. Most have experienced substantial population declines and range contractions throughout the world during the past two centuries. Because of the high metabolic demands that come with endothermy and large body size, these carnivores often require large prey and expansive habitats. These food requirements and wide-ranging behavior often bring them into confl ict with humans and livestock. This, in addition to human intolerance, renders them vulnerable to extinction. Large carnivores face enormous threats that have caused massive declines in their populations and geographic ranges, including habitat loss and degradation, persecution, utilization, and depletion of prey. We highlight how these threats can affect the conservation status and ecological roles of this planet's 31 largest carnivores.

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“…As a response to perceived predation risk, often heterogeneously distributed across the landscape (52), herbivores may select less risky areas, creating spatial variability in herbivore pressure and thus varying impacts on vegetation (34,53). Therefore, the presence of predators can allow local increases in the abundance of woody species, such as observed after the introduction of wolves in temperate woodlands followed by reduced browsing pressure from deer and locally enhanced recruitment of palatable shrubs and trees (45,(54)(55)(56), resembling that observed in exclosures (Fig. 1E).…”

Section: Spatially Structured Landscapesmentioning

confidence: 99%

Combining paleo-data and modern exclosure experiments to assess the impact of megafauna extinctions on woody vegetation

Bakker

Gill

Johnson

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

311

299

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Until recently in Earth history, very large herbivores (mammoths, ground sloths, diprotodons, and many others) occurred in most of the World's terrestrial ecosystems, but the majority have gone extinct as part of the late-Quaternary extinctions. How has this large-scale removal of large herbivores affected landscape structure and ecosystem functioning? In this review, we combine paleo-data with information from modern exclosure experiments to assess the impact of large herbivores (and their disappearance) on woody species, landscape structure, and ecosystem functions. In modern landscapes characterized by intense herbivory, woody plants can persist by defending themselves or by association with defended species, can persist by growing in places that are physically inaccessible to herbivores, or can persist where high predator activity limits foraging by herbivores. At the landscape scale, different herbivore densities and assemblages may result in dynamic gradients in woody cover. The late-Quaternary extinctions were natural experiments in large-herbivore removal; the paleoecological record shows evidence of widespread changes in community composition and ecosystem structure and function, consistent with modern exclosure experiments. We propose a conceptual framework that describes the impact of large herbivores on woody plant abundance mediated by herbivore diversity and density, predicting that herbivore suppression of woody plants is strongest where herbivore diversity is high. We conclude that the decline of large herbivores induces major alterations in landscape structure and ecosystem functions.browsers | ecosystem functions | herbivore diversity | landscape structure | megaherbivore During the late Quaternary, megafaunas were drastically reduced in most regions (1, 2), representing the start of an ongoing trophic downgrading that has resulted in the loss of entire functional guilds and relaxation of top-down control in today's ecosystems (3). A high proportion of the large herbivores that have survived into the Anthropocene (4) are now drastically reduced in range and abundance, rendering them functionally extinct, or have been replaced by livestock in much of their historic ranges (5-8). How has this loss of wild-living large herbivores affected landscape structure and ecosystem functioning?Contemporary large herbivores have strong effects on the abundance of woody species, plant diversity, nutrient cycling, and other biota (9). Most likely, the ecological effects of preextinction herbivores were as large, possibly much more so given the great size and diversity of the lost large herbivore assemblages (10, 11). We hypothesize that Pleistocene herbivore assemblages, including large and megaherbivore browsers, would have greatly reduced woody plant abundance and altered species composition and landscape structure, if present at sufficient densities. We review the impact of large herbivores (≥45 kg in body weight) on woody vegetation, with a focus on megaherbivores (≥1,000 kg), and combine information from ...

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Recolonizing wolves trigger a trophic cascade in Wisconsin (USA)

Cited by 63 publications

References 70 publications

Science for a wilder Anthropocene: Synthesis and future directions for trophic rewilding research

Science for a wilder Anthropocene: Synthesis and future directions for trophic rewilding research

Status and Ecological Effects of the World’s Largest Carnivores

Combining paleo-data and modern exclosure experiments to assess the impact of megafauna extinctions on woody vegetation

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