88 research outputs found
A General Modeling Framework for Describing Spatially Structured Population Dynamics
Variation in movement across time and space fundamentally shapes the abundance and distribution of populations. Although a variety of approaches model structured population dynamics, they are limited to specific types of spatially structured populations and lack a unifying framework. Here, we propose a unified networkâbased framework sufficiently novel in its flexibility to capture a wide variety of spatiotemporal processes including metapopulations and a range of migratory patterns. It can accommodate different kinds of age structures, forms of population growth, dispersal, nomadism and migration, and alternative lifeâhistory strategies. Our objective was to link three general elements common to all spatially structured populations (space, time and movement) under a single mathematical framework. To do this, we adopt a network modeling approach. The spatial structure of a population is represented by a weighted and directed network. Each node and each edge has a set of attributes which vary through time. The dynamics of our networkâbased population is modeled with discrete time steps. Using both theoretical and realâworld examples, we show how common elements recur across species with disparate movement strategies and how they can be combined under a unified mathematical framework. We illustrate how metapopulations, various migratory patterns, and nomadism can be represented with this modeling approach. We also apply our networkâbased framework to four organisms spanning a wide range of life histories, movement patterns, and carrying capacities. General computer code to implement our framework is provided, which can be applied to almost any spatially structured population. This framework contributes to our theoretical understanding of population dynamics and has practical management applications, including understanding the impact of perturbations on population size, distribution, and movement patterns. By working within a common framework, there is less chance that comparative analyses are colored by model details rather than general principles
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Valuing Supporting Soil Ecosystem Services in Agriculture: A Natural Capital Approach
Soil biodiversity through its delivery of ecosystem functions and attendant supporting ecosystem servicesâbenefits soil organisms generate for farmersâunderpins agricultural production. Yet lack of practical methods to value the long-term effects of current farming practices results, inevitably, in short-sighted management decisions. We present a method for valuing changes in supporting soil ecosystem services and associated soil natural capitalâthe value of the stock of soil organismsâin agriculture, based on resultant changes in future farm income streams. We assume that a relative change in soil organic C (SOC) concentration is correlated with changes in soil biodiversity and the generation of supporting ecosystem services. To quantify the effects of changes in supporting services on agricultural productivity, we fitted production functions to data from long-term field experiments in Europe and the United States. The different agricultural treatments at each site resulted in significant changes in SOC concentrations with time. Declines in associated services are shown to reduce both maximum yield and fertilizer-use efficiency in the future. The average depreciation of soil natural capital, for a 1% relative reduction in SOC concentration, was 144 ⏠haâ»Âč (SD 47 ⏠haâ»Âč) when discounting future values to their current value at 3%; the variation was explained by site-specific factors and the current SOC concentration. Moreover, the results show that soil ecosystem services cannot be fully replaced by purchased inputs; they are imperfect substitutes. We anticipate that our results will both encourage and make it possible to include the value of soil natural capital in decisions.Keywords: soil organic carbon, economic valuation, ecological intensification, sustainable agriculture, land us
Drivers of future alien species impacts: an expertâbased assessment
Understanding the likely future impacts of biological invasions is crucial yet highly challenging given the multiple relevant environmental, socioâeconomic and societal contexts and drivers. In the absence of quantitative models, methods based on expert knowledge are the best option for assessing future invasion trajectories. Here, we present an expert assessment of the drivers of potential alien species impacts under contrasting scenarios and socioecological contexts through the midâ21st century. Based on responses from 36 experts in biological invasions, moderate (20%â30%) increases in invasions, compared to the current conditions, are expected to cause major impacts on biodiversity in most socioecological contexts. Three main drivers of biological invasionsâtransport, climate change and socioâeconomic changeâwere predicted to significantly affect future impacts of alien species on biodiversity even under a bestâcase scenario. Other drivers (e.g. human demography and migration in tropical and subtropical regions) were also of high importance in specific global contexts (e.g. for individual taxonomic groups or biomes). We show that some bestâcase scenarios can substantially reduce potential future impacts of biological invasions. However, rapid and comprehensive actions are necessary to use this potential and achieve the goals of the Postâ2020 Framework of the Convention on Biological Diversity
Ventral and dorsal striatal dopamine efflux and behavior in rats with simple vs. co-morbid histories of cocaine sensitization and neonatal ventral hippocampal lesions
xposing animal models of mental illness to addictive drugs provides an approach to understanding the neural etiology of dual diagnosis disorders. Previous studies have shown that neonatal ventral hippocampal lesions (NVHL) in rats produce features of both schizophrenia and addiction vulnerability.
Objective
This study investigated ventral and dorsal striatal dopamine (DA) efflux in NVHL rats combined with behavioral sensitization to cocaine.
Methods
Adult NVHL vs. SHAM-operated rats underwent a 5-day injection series of cocaine (15 mg/kg/day) vs. saline. One week later, rats were cannulated in nucleus accumbens SHELL, CORE, or caudateâputamen. Another week later, in vivo microdialysis sampled DA during locomotor testing in which a single cocaine injection (15 mg/kg) was delivered.
Results
NVHLs and cocaine history significantly increased behavioral activation approximately 2-fold over SHAM-saline history rats. DA efflux curves corresponded time dependently with the cocaine injection and locomotor curves and varied significantly by striatal region: Baseline DA levels increased 5-fold while cocaine-stimulated DA efflux decreased by half across a ventral to dorsal striatal gradient. However, NVHLs, prior cocaine history, and individual differences in behavior were not underpinned by differential DA efflux overall or within any striatal region.Conclusion
Differences in ventral/dorsal striatal DA efflux are not present in and are not required for producing differential levels of acute cocaine-induced behavioral activation in NVHLs with and without a behaviorally sensitizing cocaine history. These findings suggest other neurotransmitter systems, and alterations in striatal network function post-synaptic to DA transmission are more important to understanding the interactive effects of addictive drugs and mental illness
Sensemaking, sensegiving and absorptive capacity in complex procurements
This study explores and describes i) the nature of knowledge exchange processes at the frontline employee (FLE) level and ii) how FLE sensemaking processes affect buyer firm knowledge management practices in complex procurement contexts. The study utilizes an in-depth case analysis in the mining industry to identify a taxonomy of four buyer sensemaking investment/supplier collaboration profiles, to describe three sensegiving supplier roles (âconfidence buildersâ, âcompetent collaboratorsâ, and âproblem-solversâ) and to explore how these evolve during complex procurement implementation. The study concludes with a conceptual model of the apparent linkages between sensemaking, sensegiving and buyer firm absorptive capacity in complex procurements. This study shows how micro-level (FLE) interactions influence macro-level knowledge integration (absorptive capacity) in the buyer firm. For managers, the study shows how the allocation of time and resources affects FLE-level knowledge exchange, with ultimate effect on buyer firm absorptive capacity
Enhancing monitoring and transboundary collaboration for conserving migratory species under global change: The priority case of the red kite
Calls for urgent action to conserve biodiversity under global change are increasing, and conservation of migratory species in this context poses special challenges. In the last two decades the Convention on the Conservation of Migratory Species of Wild Animals (CMS) has provided a framework for several subsidiary instruments including action plans for migratory bird species, but the effectiveness and transferability of these plans remain unclear. Such laws and policies have been credited with positive outcomes for the conservation of migratory species, but the lack of international coordination and on-ground implementation pose major challenges. While research on migratory populations has received growing attention, considerably less emphasis has been given to integrating ecological information throughout the annual cycle for examining strategies to conserve migratory species at multiple scales in the face of global change. We fill this gap through a case study examining the ecological status and conservation of a migratory raptor and facultative scavenger, the red kite (Milvus milvus), whose current breeding range is limited to Europe and is associated with agricultural landscapes and restricted to the temperate zone. Based on our review, conservation actions have been successful at recovering red kite populations within certain regions. Populations however remain depleted along the southern-most edge of the geographic range where many migratory red kites from northern strongholds overwinter. This led us to a forward-looking and integrated strategy that emphasizes international coordination involving researchers and conservation practitioners to enhance the science-policy-action interface. We identify and explore key issues for conserving the red kite under global change, including enhancing conservation actions within and outside protected areas, recovering depleted populations, accounting for climate change, and transboundary coordination in adaptive conservation and management actions. The integrated conservation strategy is sufficiently general such that it can be adapted to inform conservation of other highly mobile species subject to global change.Financial and logistic support were provided by GREFA, IREC, UCLM (Universidad de Castilla-La Mancha), CSIC and MITECO.Peer reviewe
ForAdapt: Supporting collaborative decision making for managing wildlife and ecosystem services in transboundary protected areas of Europe
Integrating conservation and natural resource management (CNRM) across international borders has been recognized as necessary to maintain biodiversity and ecosystem services in the face of broad-scale pressures including growing resource demands, invasive species, natural hazards, and climate change. Implementing transboundary CNRM strategies raises three prominent challenges: (1) engaging decision makers and stakeholders from local to regional scales and across borders; (2) linking local-scale management decisions to measureable objectives at landscape to regional scales; and (3) learning and adapting to the complexity of decision making under multiple objectives and scales. To address these challenges, we used a collaborative decision-analytic approach to support cross-border CNRM in multiple European transboundary protected areas (PAs) through the EU-funded ForAdapt project. The approach includes elements of structured decision making and has been applied in non-transboundary contexts and comprised iterative steps of identifying ultimate objectives, external factors (at least partly beyond control of the PA managers), resource allocation options, predictive model linking actions to the objectives, and the optimal allocation option. We applied and evaluated the approach for the first time in two transboundary conservation contexts. For the Triglav National Park (SL) and Prealpi Giulie Nature Park (IT) we identified a recommended 10-year transboundary resource allocation strategy for satisfying stakeholders concerned about brown bear and associated ecosystem services in the Julian Alps Ecoregion. We used participatory methods to develop a Bayesian decision network that accounted for competing stakeholder objectives and future uncertainties regarding perceived competence of the park managers and agreement among Alpine countries regarding bear management. The ultimate objectives were to maintain bear population carrying capacity and sustainable agriculture while minimizing stakeholder conflicts. The recommended allocation led to a concrete transboundary strategy for park managers to collaboratively engage stakeholders, data gatherers, and regional decision-makers in this transboundary pilot region for enhancing ecological connectivity under the Alpine Convention. The second case study focuses on Bavarian Forest National Park (DE) and Ć umava National Park (CZ), which provides a recommended strategy for communication between and beyond parks regarding many of their CNRM activities. Together, these case studies demonstrate the efficiency of a collaborative decision-analytic approach for overcoming challenges of transboundary management and conservation for wildlife, biodiversity, and ecosystem services. Based on our own experience and independent feedback from stakeholders, we believe the approach will be useful in other transboundary CNRM contexts where there are already established working relationships between PA managers. peerReviewe
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