The Experts below are selected from a list of 191304 Experts worldwide ranked by ideXlab platform
Clark Gray - One of the best experts on this subject based on the ideXlab platform.
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Country-Specific Effects of Climate Variability on Human Migration.
Climatic change, 2016Co-Authors: Clark Gray, Erika K. WiseAbstract:Involuntary Human Migration is among the social outcomes of greatest concern in the current era of global climate change. Responding to this concern, a growing number of studies have investigated the consequences of short to medium-term climate variability for Human Migration using demographic and econometric approaches. These studies have provided important insights, but at the same time have been significantly limited by lack of expertise in the use of climate data, access to cross-national data on Migration, and attention to model specification. To address these limitations, we link data on internal and international Migration over a 6-year period from 9812 origin households in Kenya, Uganda, Nigeria, Burkina Faso and Senegal to high-resolution gridded climate data from both station and satellite sources. Analyses of these data using several plausible specifications reveal that climate variability has country-specific effects on Migration: Migration tends to increase with temperature anomalies in Uganda, tends to decrease with temperature anomalies in Kenya and Burkina Faso, and shows no consistent relationship with temperature in Nigeria and Senegal. Consistent with previous studies, precipitation shows weak and inconsistent relationships with Migration across countries. These results challenge generalizing narratives that foresee a consistent migratory response to climate change across the globe.
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Measuring the environmental dimensions of Human Migration: The demographer's toolkit
Global environmental change : human and policy dimensions, 2014Co-Authors: Elizabeth Fussell, Lori M. Hunter, Clark GrayAbstract:In recent years, the empirical literature linking environmental factors and Human Migration has grown rapidly and gained increasing visibility among scholars and the policy community. Still, this body of research uses a wide range of methodological approaches for assessing environment–Migration relationships. Without comparable data and measures across a range of contexts, it is impossible to make generalizations that would facilitate the development of future Migration scenarios. Demographic researchers have a large methodological toolkit for measuring Migration as well as modeling its drivers. This toolkit includes population censuses, household surveys, survival analysis and multi-level modeling. This paper's purpose is to introduce climate change researchers to demographic data and methods and to review exemplary studies of the environmental dimensions of Human Migration. Our intention is to foster interdisciplinary understanding and scholarship, and to promote high quality research on environment and Migration that will lead toward broader knowledge of this association.
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Heat stress increases long-term Human Migration in rural Pakistan
Nature climate change, 2014Co-Authors: Valerie Mueller, Clark Gray, Katrina KosecAbstract:Evidence on the relationship between Human Migration and climatic events is limited. Now research links information from a longitudinal survey in rural Pakistan to satellite-derived measures of climate variability. Results show that heat stress consistently increases the long-term Migration of men owing to impacts on income.
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Environmental Influences on Human Migration in Rural Ecuador
Demography, 2013Co-Authors: Clark Gray, Richard E. BilsborrowAbstract:The question of whether environmental conditions influence Human Migration has recently gained considerable attention, driven by claims that global environmental change will displace large populations. Despite this high level of interest, few quantitative studies have investigated the potential effects of environmental factors on Migration, particularly in the developing world and for gradual but pervasive forms of environmental change. To address this, a retrospective Migration survey was conducted in rural Ecuador and linked to data on topography, climate, and weather shocks. These data were used to estimate multivariate event history models of alternative forms of mobility (local mobility, internal Migration, and international Migration), controlling for a large number of covariates. This approach is generalizable to other study areas and responds to calls for the development of more rigorous methods in this field. The results indicate that adverse environmental conditions do not consistently increase rural out-Migration and, in some cases, reduce Migration. Instead, households respond to environmental factors in diverse ways, resulting in complex migratory responses. Overall, the results support an alternative narrative of environmentally induced Migration that recognizes the adaptability of rural households in responding to environmental change.
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Soil Quality and Human Migration in Kenya and Uganda.
Global environmental change : human and policy dimensions, 2011Co-Authors: Clark GrayAbstract:Soil degradation is widely considered to be a key factor undermining agricultural livelihoods in the developing world and contributing to rural out-Migration. To date, however, few quantitative studies have examined the effects of soil characteristics on Human Migration or other social outcomes for potentially vulnerable households. This study takes advantage of a unique longitudinal survey dataset from Kenya and Uganda containing information on household-level soil properties to investigate the effects of soil quality on population mobility. Random effects multinomial logit models are used to test for effects of soil quality on both temporary and permanent Migration while accounting for a variety of potential confounders. The analysis reveals that soil quality significantly reduces Migration in Kenya, particularly for temporary labor Migration, but marginally increases Migration in Uganda. These findings are consistent with several previous studies in showing that adverse environmental conditions tend to increase Migration but not universally, contrary to common assumptions about environmentally-induced Migration.
Anna Nagurney - One of the best experts on this subject based on the ideXlab platform.
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Evolution variational inequalities and projected dynamical systems with application to Human Migration
Mathematical and Computer Modelling, 2006Co-Authors: Anna Nagurney, Jie PanAbstract:In this paper, we explore the relationship between projected dynamical systems and evolution variational inequalities (also sometimes referred to as parabolic variational inequalities). The methodology of evolution variational inequalities is then utilized for the first time to model the dynamic adjustment of a socio-economic process in the context of Human Migration. The questions of dynamics and convergence of algorithms in this framework are addressed and answered. In particular, we provide existence and uniqueness results for the solution path without assuming Lipschitz continuity and propose a finite-difference scheme for the solution of the Human Migration problem. The algorithm, an ordinary implicit scheme, is a discrete-time version of the model. Its convergence estimate is also established.
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Using Markov chains to model Human Migration in a network equilibrium framework
Mathematical and Computer Modelling, 1994Co-Authors: Jie Pan, Anna NagurneyAbstract:In this paper, we develop a multistage network equilibrium model of Human Migration. The model provides a general framework for describing the dynamics of populations, and takes advantage of the special network structure of the problem. Unlike earlier network equilibrium models of Migration, the model allows for chain Migration in that Humans can move from location to location in a ''chaining'' fashion, which is more realistic from an application perspective, than simply allowing for Migration from a given origin to a direct destination in a single step. For the purpose of modeling and analysis, we utilize finite state nonhomogeneous Markov chains to handle the Migration. A stable population distribution is then shown to exist under certain assumptions.
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Human Migration networks
European Journal of Operational Research, 1992Co-Authors: Anna Nagurney, Jie Pan, Lan ZhaoAbstract:Abstract In this paper we develop a new multiclass Human Migration network equilibrium model which explicitly incorporates the cost of movement between locations. The equilibrium conditions reflect that no individual in the system in any given class has any incentive to alter his location. The equilibrium conditions are then formulated as a variational inequality problem and qualitative properties discussed. A decomposition algorithm which takes advantage of the special network structure of the problem is then proposed and numerical results presented. This research brings and yet another application in operations research into the realm of network equilibrium problems.
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International Human Migration networks under regulations
European Journal of Operational Research, 1Co-Authors: Anna Nagurney, Patrizia DanieleAbstract:Abstract International Human Migration has transformed economies and societies. The new millennium, with climate change and its impacts, and increasing conflicts and displacements, has experienced a great increase in international migrants, with associated challenges faced by governments. In this paper, we advance the modeling, analysis, and solution of international Human Migration problems by developing a network model with regulations. The formalism uses the theory of variational inequalities, coupled with Lagrange analysis, in order to gain insights as to the impacts of the regulations on utilities of multiple classes of migrants, and on the equilibrium flows. Our results add to the literature on operations research for societal impact, inspired by the real world.
Michael W. Deem - One of the best experts on this subject based on the ideXlab platform.
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Modular knowledge systems accelerate Human Migration in asymmetric random environments
arXiv: Populations and Evolution, 2016Co-Authors: Dong Wang, Michael W. DeemAbstract:Migration is a key mechanism for expansion of communities. In spatially heterogeneous environments, rapidly gaining knowledge about the local environment is key to the evolutionary success of a migrating population. For historical Human Migration, environmental heterogeneity was naturally asymmetric in the north-south (NS) and east-west (EW) directions. We here consider the Human Migration process in the Americas, modeled as random, asymmetric, modularly correlated environments. Knowledge about the environments determines the fitness of each individual. We present a phase diagram for asymmetry of Migration as a function of carrying capacity and fitness threshold. We find that the speed of Migration is proportional to the inverse complement of the spatial environmental gradient, and in particular we find that north-south Migration rates are lower than east-west Migration rates when the environmental gradient is higher in the north-south direction. Communication of knowledge between individuals can help to spread beneficial knowledge within the population. The speed of Migration increases when communication transmits pieces of knowledge that contribute in a modular way to the fitness of individuals. The results for the dependence of Migration rate on asymmetry and modularity are consistent with existing archaeological observations. The results for asymmetry of genetic divergence are consistent with patterns of Human gene flow.
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Modular knowledge systems accelerate Human Migration in asymmetric random environments.
Journal of the Royal Society Interface, 2016Co-Authors: Dong Wang, Michael W. DeemAbstract:Migration is a key mechanism for expansion of communities. In spatially heterogeneous environments, rapidly gaining knowledge about the local environment is key to the evolutionary success of a migrating population. For historical Human Migration, environmental heterogeneity was naturally asymmetric in the north–south (NS) and east–west (EW) directions. We here consider the Human Migration process in the Americas, modelled as random, asymmetric, modularly correlated environments. Knowledge about the environments determines the fitness of each individual. We present a phase diagram for asymmetry of Migration as a function of carrying capacity and fitness threshold. We find that the speed of Migration is proportional to the inverse complement of the spatial environmental gradient, and in particular, we find that NS Migration rates are lower than EW Migration rates when the environmental gradient is higher in the NS direction. Communication of knowledge between individuals can help to spread beneficial knowledge within the population. The speed of Migration increases when communication transmits pieces of knowledge that contribute in a modular way to the fitness of individuals. The results for the dependence of Migration rate on asymmetry and modularity are consistent with existing archaeological observations. The results for asymmetry of genetic divergence are consistent with patterns of Human gene flow.
Deepak Mathur - One of the best experts on this subject based on the ideXlab platform.
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Population Dynamics of Early Human Migration in Britain.
PloS one, 2016Co-Authors: Mayank N. Vahia, Uma Ladiwala, Pavan Mahathe, Deepak MathurAbstract:Background Early Human Migration is largely determined by geography and Human needs. These are both deterministic parameters when small populations move into unoccupied areas where conflicts and large group dynamics are not important. The early period of Human Migration into the British Isles provides such a laboratory which, because of its relative geographical isolation, may allow some insights into the complex dynamics of early Human Migration and interaction. Method and Results We developed a simulation code based on Human affinity to habitable land, as defined by availability of water sources, altitude, and flatness of land, in choosing the path of Migration. Movement of people on the British island over the prehistoric period from their initial entry points was simulated on the basis of data from the megalithic period. Topographical and hydro-shed data from satellite databases was used to define habitability, based on distance from water bodies, flatness of the terrain, and altitude above sea level. We simulated population movement based on assumptions of affinity for more habitable places, with the rate of movement tempered by existing populations. We compared results of our computer simulations with genetic data and show that our simulation can predict fairly accurately the points of contacts between different migratory paths. Such comparison also provides more detailed information about the path of peoples’ movement over ~2000 years before the present era. Conclusions We demonstrate an accurate method to simulate prehistoric movements of people based upon current topographical satellite data. Our findings are validated by recently-available genetic data. Our method may prove useful in determining early Human population dynamics even when no genetic information is available.
Shiguang Miao - One of the best experts on this subject based on the ideXlab platform.
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Mass Human Migration and Beijing’s urban heat island during the Chinese New Year holiday
Science Bulletin, 2015Co-Authors: Jingyong Zhang, Fang Yuan, Jingjing Dou, Shiguang MiaoAbstract:Population movements around the Chinese New Year (CNY), which are much larger in recent years than before, are the largest annual Human Migration in the world. However, it is still largely unknown how or to what extent such mass Human Migration affects urban climate. Here, we investigate the role of mass Human Migration in influencing Beijing’s urban heat island (UHI) during the CNY holiday for the period of 2004–2013. We find that the UHI effects expressed as daily mean (ΔT mean), maximum (ΔT max), and minimum (ΔT min) temperature differences between urban and rural areas show a weakening trend during the CNY week relative to the background period (4 weeks including 2–3 weeks before and 2–3 weeks after the CNY week). In particular, large reductions occurred during the CNY week for the period of 2009–2013, when nearly half of population left the city before the CNY holiday. ΔT mean, ΔT max, and ΔT min averaged over the period of 2009–2013 during the CNY week were 0.64, 0.45, and 0.83 °C lower than during the background period, representing relative reductions of 35 %, 66 %, and 27 %, respectively. Our findings highlight the important role of modern mass Human Migration for urban climate based on a case study in Beijing.