Ecological thresholds and large carnivores conservation: Implications for the Amur tiger and leopard in China

The ecological threshold concept describes how changes in one or more factors at thresholds can result in a large shift in the state of an ecosystem. This concept focuses attention on limiting factors that affect the tolerance of systems or organisms and changes in them. Accumulating empirical evidence for the existence of ecological thresholds has created favorable conditions for practical application to wildlife conservation. Applying the concept has the potential to enhance conservation of two large carnivores, Amur tiger and leopard, and the knowledge gained could guide the construction of a proposed national park. In this review, ecological thresholds that result from considering a paradigm of bottom-up control were evaluated for their potential to contribute to the conservation of Amur tiger and leopard. Our review highlights that large carnivores, as top predators, are potentially affected by ecological thresholds arising from changes in climate (or weather), habitat, vegetation, prey, competitors, and anthropogenic disturbances. What's more, interactions between factors and context dependence need to be considered in threshold research and conservation practice, because they may amplify the response of ecosystems or organisms to changes in specific drivers. Application of the threshold concept leads to a more thorough evaluation of conservation needs, and could be used to guide future Amur tiger and leopard research and conservation in China. Such application may inform the conservation of other large carnivores worldwide

Technological vs ecological switch and the environmental Kuznets curve

We consider an optimal technology adoption AK model in line with Boucekkine Krawczyk and Vallée (2011): an economy, caring about consumption and pollution as well, starts with a given technological regime and may decide to switch at any moment to a cleaner technology at a given permanent or transitory output cost. At the same time, we posit that there exists a pollution threshold above which the assimilation capacity of Nature goes down, featuring a kind of irreversible ecological regime. We study how ecological irreversibility interacts with the ingredients of the latter optimal technological switch problem, with a special attention to induced capital-pollution relationship. We find that if a single technological switch is optimal, one recovers the Environmental Kuznets Curve provided initial pollution is high enough. If exceeding the ecological threshold is optimal, then the latter configuration is far from being the rule.Technology adoption; ecological irreversibility; Environmental Kuznets Curve; Multi-stage optimal control

Competition Among Companies: Coexistence and Extinction

We study a spatially homogeneous model of a market where several agents or companies compete for a wealth resource. In analogy with ecological systems the simplest case of such models shows a kind of "competitive exclusion" principle. However, the inclusion of terms corresponding for instance to "company efficiency" or to (ecological) "intracompetition" shows that, if the associated parameter overcome certain threshold values, the meaning of "strong" and "weak" companies should be redefined. Also, by adequately adjusting such a parameter, a company can induce the "extinction" of one or more of its competitors.Comment: 5 pages, 3 figures include

Naming More of What We Know: Critical Memoirs & the Ecological Metaphor as a Threshold Concept in Writing

Naming More of What We Know: Critical Memoirs & the Ecological Metaphor as a Threshold Concept in Writing contributes to the work begun by Adler-Kassner and Wardle to gather and name Writing Studies\u27 body of disciplinary knowledge as threshold concepts. This thesis answers their call to engage in the ongoing development of threshold concepts by offering an additional critical construct: Writing as ecological. To explicitly acknowledge that writing is ecological is an essential addition to the content of our knowledge because it (1) meets the threshold-concept criteria adapted from Meyer and Land (2003), (2) establishes a codified, embodied, 3-dimensional system of knowledge management which corrects many flattened metaphors Writing Studies currently employs, and is (3) already ubiquitous in our scholarship. The exigence for this argument is established in two ways: (a) Through an analysis of that ubiquity and the ecological metaphor\u27s origins from 1980 to present; and (b) through an autoethnographic illustration of ecological embodiment through memoir. Though framed through the disciplinary frameworks with which I am best versed, Composition, Rhetoric, and Literacy Studies, this project\u27s implications address all Writing Studies factions. Written in two major parts, this work first establishes a theoretical foundation for threshold concepts, for the ecological metaphor, and for personal narrative as an embodied means of expression worthy of analysis. The latter half is delivered as a series of memoir vignettes, each exemplifying through storytelling some of the many ways in which writing is ecological. Ultimately, this project hopes to establish a symbiotic relationship between threshold concepts and the ecological metaphor. Through this symbiosis, naming and teaching writing ecologies as a threshold concept negotiates an explicit corrective to linear habits of thought and our often problematic boundary-creating tendencies through a deeper understanding of the ways in which writing is fluid, complex, and networked

Resilience in Ecology and Belief

Replaced with revised version of paper 06/18/08. Former title: Non-Linearity in Belief and Environmental Risk DynamicsBelief dynamics, ecological hysteresis, water scarcity, groundwater dependent ecosystems, threshold effects, Environmental Economics and Policy, Resource /Energy Economics and Policy, Risk and Uncertainty,

Community-driven dispersal in an individual-based predator-prey model

We present a spatial, individual-based predator-prey model in which dispersal is dependent on the local community. We determine species suitability to the biotic conditions of their local environment through a time and space varying fitness measure. Dispersal of individuals to nearby communities occurs whenever their fitness falls below a predefined tolerance threshold. The spatiotemporal dynamics of the model is described in terms of this threshold. We compare this dynamics with the one obtained through density-independent dispersal and find marked differences. In the community-driven scenario, the spatial correlations in the population density do not vary in a linear fashion as we increase the tolerance threshold. Instead we find the system to cross different dynamical regimes as the threshold is raised. Spatial patterns evolve from disordered, to scale-free complex patterns, to finally becoming well-organized domains. This model therefore predicts that natural populations, the dispersal strategies of which are likely to be influenced by their local environment, might be subject to complex spatiotemporal dynamics.Comment: 43 pages, 7 figures, vocabulary modifications, discussion expanded, references added, Ecological Complexity accepte

Water quality related macroinvertebrate community responses to environmental gradients in the Portoviejo River (Ecuador)

The Portoviejo River, located in the central western part of Ecuador, has been heavily impacted by damming, intensive agriculture and untreated wastewater discharge. Unfortunately, detailed information on the water quality and the ecological status of the Portoviejo River is not available, inhibiting decision-making and the development of water management plans. Therefore, the aims of this study were (1) to assess the ecological water quality, (2) to investigate the point along the environmental gradient where the most significant change in macroinvertebrate community occurs and (3) to find potential macroinvertebrate taxa that significantly change in abundance and frequency of occurrence along the Portoviejo River. To this end, macroinvertebrate and physico-chemical data were collected and hydro-morphological conditions were recorded at 31 locations during the dry season of 2015. The results showed that the ecological water quality of the sampling sites ranged from good to bad. In addition, the Threshold Indicator Taxa ANalysis was used to examine changes in macroinvertebrate communities and revealed significant community change points for sensitive taxa declining at a conductivity value of 930 (mu S.cm(-1)) and nitrate-nitrogen concentrations of 0.6 mg.L-1. In addition, the thresholds estimated for tolerant taxa were set at a conductivity value of 1430 mu S.cm(-1) and nitrate-nitrogen concentration of 2.3 mg. L. Atyidae, Corbiculidae, Thiaridae, Acari, Baetidae and Leptohyphidae can be considered indicator taxa, showing shifts in the community. This study suggests that values of conductivity and nitrate-nitrogen concentrations should not exceed the threshold levels in order to protect macroinvertebrate biodiversity in the Portoviejo River