Grazer behavior can regulate large-scale patterning of community states

Karatayev, Vadim A.; Baskett, Marissa L.; Kushner, David J.; Shears, Nick T.; Caselle, Jennifer E.; Boettiger, Carl

doi:10.1101/722215

Cited by 6 publications

(12 citation statements)

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“…Because it generates multiple stable equilibria, the Hollingtype III predation function plays a critical role in the model. While findings of alternative stable states with different shift thresholds (hysteresis) support type III (Ling et al, 2019), direct empirical estimates of functional form do not always do so (Dunn and Hovel, 2019;Karatayev et al, 2019). Another crucial assumption is the treatment of pulse perturbations and hysteresis.…”

Section: Discussionmentioning

confidence: 99%

“…Specifically, urchin grazing on kelp is modeled as a Holling type-III functional response for which the proportion of kelp consumed per urchin (grazing efficiency or proportion of available kelp consumed per urchin or the average product of kelp density) depends on kelp density, starting off very low at very low kelp densities, increasing at a decreasing rate at low kelp densities, reaching a maximum, and decreasing, at first at an increasing and then at a decreasing absolute rate, approaching zero at very high kelp densities (Holling, 1959a,b;Ludwig et al, 1997;Scheffer et al, 2001). While a Holling type IV function, which at high kelp densities, exhibits declining total (not just the proportion of) kelp consumption per urchin, has been used (Karatayev et al, 2019), a type III is preferred here because it allows both grazer switching and satiation. Support for the type III functional response is provided by the same factors that dampen the numerical response.…”

Section: Modeling Assumptionsmentioning

confidence: 99%

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Kelp Forests: Catastrophes, Resilience, and Management

Wilman

2021

Front. Ecol. Evol.

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Resilient kelp forests provide foundation habitat for marine ecosystems and are indicators of the ecosystems’ sustainable natural capital. Loss of resilience and imperfectly reversible catastrophic shifts from kelp forests to urchin barrens, due to pollution or loss of a top predator, are part of an ecological tipping point phenomenon, and involve a loss in sustainable natural capital. Management controls to prevent or reverse these shifts and losses are classified in a number of ways. Systemic controls eliminate the cause of the problem. Symptomatic controls use leverage points for more direct control of the populations affected, urchin harvesting or culling, or kelp enhancement. There is a distinction between ongoing structural (press) controls versus temporary or intermittent perturbation (pulse) controls, and one between shift preventing versus shift reversing or restorative controls. Adaptive management and the options it creates both focus on reductions in uncertainty and control policies with the flexibility to take advantage of those reductions. The various management distinctions are most easily understood by modeling the predator-urchin-kelp marine ecosystem. This paper develops a mathematical model of the ecosystem that has the potential for two different catastrophic shifts between equilibria. Pulse disturbances, originating from exogenous abiotic factors or population dynamics elsewhere in the metacommunity, can activate shifts. A measure of probabilistic resilience is developed and used as part of an assessment of the ecosystem’s sustainable stock of natural capital. With perturbation outcomes clustered around the originating equilibrium, hysteresis is activated, resulting imperfect reversibility of catastrophic shifts, and a loss in natural capital. The difficulty of reversing a shift from kelp forest to urchin barren, with an associated loss in sustainable natural capital, is an example. Management controls are modeled. I find that systemic and symptomatic, and press and pulse, controls can be complementary. Restorative controls tend to be more difficult or costly than preventative ones. Adaptive management, favoring flexible, often preventative, controls, creates option value, lowering control costs and/or losses in sustainable natural capital. Two cases are used to illustrate, Tasmania, Australia and Haida Gwaii, Canada.

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Section: Discussionmentioning

confidence: 99%

Section: Modeling Assumptionsmentioning

confidence: 99%

Kelp Forests: Catastrophes, Resilience, and Management

Wilman

2021

Front. Ecol. Evol.

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“…Establishing the presence and conditions leading to alternative stable states based on field data alone is rarely feasible due to the need for long-term data of each state at large spatial scales under identical environmental conditions (Petraitis and Dudgeon 2004; Petraitis 2013). Simple data-driven mechanistic models therefore represent a common approach to quantifying the potential for alternative stable states to explain observed patterns in diverse ecosystems (Ives et al 2008; Mumby et al 2007, 2013; Karatayev et al 2021). Our results show that the results of such simple models might be robust to food web complexity with aggregate feedbacks.…”

Section: Discussionmentioning

confidence: 99%

Quantifying the relevance of alternative stable states in many-species food webs

Karatayev

Baskett

Nes

2020

Preprint

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Overexploitation can lead to a rapid collapse of consumers that is difficult to reverse if ecosystems exhibit alternative stable states. However, support for this phenomenon remains predominantly limited to simple models, whereas food webs might dissipate the feedback loops that create alternative stable states through species-specific demography and interactions. Here we develop a general model of consumer-resource interactions with two types of processes: either specialized feedbacks where individual resources become unpalatable at high abundance or aggregate feedbacks where overall resource abundance reduces consumer recruitment. We then quantify how the degree of interconnectedness and species differences in demography affect the potential for either feedback to produce consumer- or resource-dominated food web states. Our results highlight that such alternative stable states could be more likely to happen when aggregate feedbacks or lower species differences increase redundancy in species contributions to persistence of the consumer guild. Conversely, specialized palatability feedbacks with distinctive species roles in guild persistence reduce the potential for alternative states but increase the likelihood that losing vulnerable consumers cascades into a food web collapse at low stress levels, a fragility absent in few-species models. Altogether, we suggest that species heterogeneity has a greater impact on whether feedbacks prevent consumer recovery than on the presence of many-species collapses.

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“…Our model combines the ecological dynamics of Karatayev et al (2021) with the spatial dynamics of Kanary et al (2014). We consider populations of kelp and urchins cohabit in a one-dimensional coastline Ω.…”

Section: Modelmentioning

confidence: 99%

How far to build it before they come? Analyzing the use of the Field of Dreams hypothesis to bull kelp restoration

Arroyo-Esquivel

Baskett

McPherson

et al. 2021

Preprint

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In restoration ecology, the Field of Dreams Hypothesis posits that restoration efforts that create a suitable environment could lead to eventual recovery of the remaining aspects of the ecosystem through natural processes. Natural processes following partial restoration has lead to ecosystem recovery in both terrestrial and aquatic systems. However, understanding the efficacy of a “field of dreams” approach requires comparison of different approaches to partial restoration in terms of spatial, temporal, and ecological scale to what would happen with more comprehensive restoration efforts. We explore the relative effect of partial restoration and ongoing recovery on restoration efficacy with a dynamical model based on temperate rocky reefs in Northern California. We analyze our model for both the ability and rate of bull kelp forest recovery under different restoration strategies. We compare the efficacy of a partial restoration approach with a more comprehensive restoration effort by exploring how kelp recovery likelihood and rate change with varying intensities of urchin removal and kelp outplanting over different time periods and spatial scales. We find that, for the case of bull kelp forests, setting more favorable initial conditions for kelp recovery through implementing both urchin harvesting and kelp outplanting at the start of the restoration project has a bigger impact on the kelp recovery rate than applying restoration efforts through a longer period of time. Therefore partial restoration efforts, in terms of spatial and temporal scale, can be significantly more effective when applied across multiple ecological scales in terms of both the capacity and rate of achieving the target outcomes.Open Research StatementThe data used in this work is presented in McPherson et al. (2021). The code used to run the simulations can be found in https://github.com/jarroyoe/kelp-restoration-modeling

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Grazer behavior can regulate large-scale patterning of community states

Cited by 6 publications

References 73 publications

Kelp Forests: Catastrophes, Resilience, and Management

Kelp Forests: Catastrophes, Resilience, and Management

Quantifying the relevance of alternative stable states in many-species food webs

How far to build it before they come? Analyzing the use of the Field of Dreams hypothesis to bull kelp restoration

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