Urbanization

Abstract: Studying the economy of cities is relevant for a number of reasons. First of all, because most of the planet's population is grouped in them. Secondly, because they concentrate the main social problems that humanity has and, finally, because they are also the greatest source of creativity, innovation and development opportunities to solve those problems. Cities group companies and people who interact with each other both within their scope and with their peers in other cities. The general framework in which the current economy operates is, in general, the city and if the latter does not create the conditions for the economic activity to be sustainable, not only the city, but the country itself will suffer the consequences.

Abstract: Urban areas are hot spots that drive environmental change at multiple scales. Material demands of production and human consumption alter land use and cover, biodiversity, and hydrosystems locally to regionally, and urban waste discharge affects local to global biogeochemical cycles and climate. For urbanites, however, global environmental changes are swamped by dramatic changes in the local environment. Urban ecology integrates natural and social sciences to study these radically altered local environments and their regional and global effects. Cities themselves present both the problems and solutions to sustainability challenges of an increasingly urbanized world.

Abstract: The world’s population is concentrated in urban areas. This change in demography has brought landscape transformations that have a number of documented effects on stream ecosystems. The most consistent and pervasive effect is an increase in impervious surface cover within urban catchments, which alters the hydrology and geomorphology of streams. This results in predictable changes in stream habitat. In addition to imperviousness, runoff from urbanized surfaces as well as municipal and industrial discharges result in increased loading of nutrients, metals, pesticides, and other contaminants to streams. These changes result in consistent declines in the richness of algal, invertebrate, and fish communities in urban streams. Although understudied in urban streams, ecosystem processes are also affected by urbanization. Urban streams represent opportunities for ecologists interested in studying disturbance and contributing to more effective landscape management.

Abstract: An economic behavioral model of rural urban migration is formulated which represents a realistic modification and extension of the simple wage differential approach commonly found in the literature and this probablistic approach is incorporated into a rigorous model of the determinants of urban labor demand and supply which when given values for the crucial parameters can be used among other things to estimate the equilibrium proportion of the urban labor force that is not absorbed by the modern industrial economy. Additionally the model will provide a convenient framework for analyzing the implications of alternative policies designed to alleviate unemployment by varying 1 or more of the principal parameters. A more realistic picture of labor migration in less developed nations would be one that views migration as a 2 stage phenomenon: in the 1st stage the unskilled rural worker migrates to an urban area and spends a certain period of time in the "urban traditional" sector; and the 2nd stage is reached with the eventual attainment of a more permanent modern sector job. This 2 stage process allows one to ask some basic questions concerning the decision to migrate the proportionate size of the urban traditional sector and the implications of accelerated industrial growth and/or alternative rural urban real income differentials on labor participation in the modern economy. In the model the decision to migrate from rural to urban areas is functionally related to 2 principal variables: the urban rural real income differential and the probability of obtaining an urban job. To understand better the nature of the supply function to be used in the overall model of the determinants of urban unemployment it is helpful to state the underlying behavioral assumptions of the model of rural urban migration: it is assumed that the percentage change in the urban labor force as a result of migration during any period is governed by the differential between the discounted streams of expected urban and rural real income expressed as percentage of the discounted stream of expected rural real income; the planning horizon for each worker is identical; the fixed costs of migration are identical for all workers; and the discount factor is constant over the planning horizon and identical for all potential migrants. The model demonstrates the overall net impact of allowing these parameters to vary over time and/or choosing alternative values. It underlines in a simple and plausible way the interdependent effects of industrial expansion productivity growth and the differential expected real earnings capacity of urban versus rural activities on the size and rate of increase in labor migration and therefore ultimately on the occupational distribution of the urban labor force. Possibly the most significant policy implication that emerged from the model is the great difficulty of substantially reducing the size of the urban traditional sector without a concentrated effort at making rural life more attractive.

Abstract: When measured by extent and intensity, urbanization is one of the most homogenizing of all major human activities. Cities homogenize the physical environment because they are built to meet the relatively narrow needs of just one species, our own. Also, cities are maintained for centuries in a disequilibrium state from the local natural environment by the importation of vast resources of energy and materials. Consequently, as cities expand across the planet, biological homogenization increases because the same “urban-adaptable” species become increasingly widespread and locally abundant in cities across the planet. As urbanization often produces a local gradient of disturbance, one can also observe a gradient of homogenization. Synanthropic species adapted to intensely modified built habitats at the urban core are “global homogenizers”, found in cities worldwide. However, many suburban and urban fringe habitats are occupied by native species that become regionally widespread. These suburban adapters typically consist of early successional plants and “edge” animal species such as mesopredator mammals, and ground-foraging, omnivorous and frugivorous birds that can utilize gardens, forest fragments and many other habitats available in the suburbs. A basic conservation challenge is that urban biota is often quite diverse and very abundant. The intentional and unintentional importation of species adapted to urban habitats, combined with many food resources imported for human use, often produces local species diversity and abundance that is often equal to or greater than the surrounding landscape. With the important exception of low-income areas, urban human populations often inhabit richly cultivated suburban habitats with a relatively high local floral and faunal diversity and/or abundance without awareness of the global impoverishment caused by urbanization. Equally challenging is that, because so many urban species are immigrants adapting to city habitats, urbanites of all income levels become increasingly disconnected from local indigenous species and their natural ecosystems. Urban conservation should therefore focus on promoting preservation and restoration of local indigenous species.