231 research outputs found
Creating incentives for increased public engagement in ecosystem management through urban commons
No full textOver half the world's population currently lives in urban areas; by 2030, nearly five billion people are expected to live in cities (Ash et al. 2008). Between 2010 and 2030, the amount of the built mass on the earth is predicted to double, creating ever-greater demands on the services that nearby and distant ecosystems provide (Grimm et al. 2008). With a greater proportion of humans living in metropolitan areas, urban ecosystems will experience increased land-use and land-cover change. Currently, urbanisation endangers more species and is more geographically ubiquitous than any other human activity; urban sprawl is rapidly transforming critical habitats of global value, such as the Atlantic Forest Region of Brazil, the Cape of South Africa and coastal Central America (Elmqvist et al. 2008). Urbanisation leads not only to increased homogenisation of fauna and flora (McKinney 2002) but also to an impoverished biology in metropolitan areas, which arguably serves as a constant reminder of the presumed unimportance of biodiversity and so may contribute to ‘environmental generational amnesia’ among the greater public (Miller 2005). To gain the much-needed broad-based public support for a sustainable use of ecosystems, both within and outside cities, the places where people live and work need to offer opportunities for meaningful interactions with functioning ecosystems (Rosenzweig 2003, Miller 2005, Andersson et al. 2007, Colding 2007). In this respect, and to help mitigate the growing disconnection of urban residents from nature (Pyle 1978, 1993), the dynamics of property rights determining human relationships to land can have powerful ramifications and be worthy of scholarly analysis to provide propositions about both the manner in which land ownership in cities evolves (Webster 2003) and its potential outcomes, such as the provision of the ecosystem services critical to human well-being (Daily 1997, Millennium Ecosystem Assessment 2005). It is increasingly recognised that today's institutions match current changes in ecosystems and their dynamics poorly (Millennium Ecosystem Assessment 2005, Folke et al. 2007).</p
Colding, Ørsted, and the Meanings of Force
No full textTHE DANISH PHYSICIST and engineer Ludvig August Colding (1815-1888) is known to historians of nineteenth-century physics as the author of one of several formulations, during the 1840s, of the concept that eventually gained currency as the principle of the conservation of energy. Thanks largely to the work of Per Dahl, the substance of Colding's work and a rough idea of the route he followed has been known for several decades.1 In brief, Colding sought experimental corroboration, in terms of the frictional heat produced via the expenditure of a measured amount of mechanical work, of a rough notion of the general imperishability of the forces of nature that he derived from an originally metaphysical conviction concerning the imperishability of the human spirit regarded as a species of force. Nor has the importance gone unnoticed of (Holding's relationship to Hans Christian Ørsted (1777-1851), to whom Colding was attached for many years as student and protégé Ørsted had disclosed the interactive relationship between electricity and magnetism in 1820 and was a highly visible proponent of the notion of the unity of nature, as showcased in particular in the collection of essays he entitled The spirit in nature? Yet some of the important details in this overall picture remain unclear. The quality of Colding's metaphysical beliefs has not been explored in appropriate depth, nor has the significance been established of his brief reference to the role played in the development of his ideas by the antimateri alistic pronouncements of zoologist and physiologist Daniel Frederik Eschricht (1798-1863).3 Nor have we been adequately enlightened as to the significance of what he referred to as d'Alembert's principle of lost forces, or to the status of such a principle in the mechanics of the period.4 And his relationship to Ørsted is problematic. Although there would appear to be some important con nection between Colding's and Ørsted's general views on nature and its forces, and Ørsted occasionally asserted some kind of unity among the forces of nature, he failed signally to appreciate the significance of Colding's work when it was given him to evaluate.5 The solution to this apparent paradox will be sought through an understanding of Ørsted's changing conception of force and its relationship to the "activities" of heat, light, electricity, magnetism, and chemical activity.6 Without paying proper attention to language, historians have tended to read back into Ørsted's usages meanings of "force" that came to it in large part as a result of the work of Colding and his generation.
Notes on the Cheeger and Colding version of the Reifenberg theorem for metric spaces
No full textThe classical Reifenberg\u27s theorem says that a set which is sufficiently well approximated by planes uniformly at all scales is a topological Hölder manifold. Remarkably, this generalizes to metric spaces, where the approximation by planes is replaced by the Gromov-Hausdorff distance. This fact was shown by Cheeger and Colding in an appendix of one of their celebrated works on Ricci limit spaces [8]. Given the recent interest around this statement in the growing field of analysis in metric spaces, in this note we provide a self contained and detailed proof of the Cheeger and Colding result. Our presentation substantially expands the arguments in [8] and makes explicit all the relevant estimates and constructions. As a byproduct we also shows a biLipschitz version of this result which, even if folklore among experts, was not present in the literature. This work is an extract from the doctoral dissertation of the second author
Generic mean curvature flow I; generic singularities
No full textAuthor Manuscript August 26, 2009It has long been conjectured that starting at a generic smooth closed embedded surface in R[superscript 3], the mean curvature flow remains smooth until it arrives at a singularity in a neighborhood of which the flow looks like concentric spheres or cylinders. That is, the only singularities of a generic flow are spherical or cylindrical. We will address this conjecture here and in a sequel. The higher dimensional case will be addressed elsewhere. The key to showing this conjecture is to show that shrinking spheres, cylinders, and planes are the only stable self-shrinkers under the mean curvature flow. We prove this here in all dimensions. An easy consequence of this is that every singularity other than spheres and cylinders can be perturbed away.National Science Foundation (U.S.) (Grant DMS-0606629)National Science Foundation (U.S.) (Grant DMS-0405695)National Science Foundation (U.S.). Focused Research Group (Grant DMS-0854774)National Science Foundation (U.S.). Focused Research Group (Grant DMS-0853501
Social-ecological analysis of climate induced changes in biodiversity – outline of a research concept
No full textThe interactions of changes in climate and biodiversity with societal actions, structures and processes are a priority topic within the international scientific debate – and thus, a relevant subject matter for BiKF’s work. This paper outlines a concept for transdisciplinary research within BiKF. It focuses on the analysis of social-ecological systems supporting society with biodiversity driven ecosystem services. Such research is considering different issues: defining sustainable societal adaptations to climate induced biodiversity changes; permitting adequate understanding of the social-ecological reproduction of ecosystem functions, including their conservation and restoration; analysing the societal values and socio-economic utilisation of ecosystem services. Gaining knowledge in these areas provides an improved basis for decision-making in biodiversity and resource management
Local Assessment of Stockholm: Revisiting the Stockholm Urban Assessment
No full textIn the year 2003, the Stockholm Urban Assessment (SUA) was selected as a sub-global assessment within the global Millennium Ecosystem Assessment (MA, Ecosystems and human well-being: synthesis. Island Press, Washington, DC, 2005). This chapter revisits SUA and fills in important knowledge gaps in the assessment as well as provides insights on urban resilience building. The chapter applies a critical perspective on the present urban development trajectory of the Stockholm metropolitan area. It emphasizes the need to understand ways in which informally managed green spaces contribute to ecological functions in urban settings. The chapter provides a background of the Stockholm region and the current challenges it faces, followed by a synthesis of the major insights conveyed in SUA related to informal ecosystem management. The chapter concludes by proposing policy recommendations of general implications for urban resilience building.</p
The Role of Ecosystem Services in Contemporary Urban Planning
No full textUrban sprawl is often characterised as a serious land use problem. It refers to the spread of urban congestion into adjoining suburbs and rural areas, often resulting in the loss of ecosystems and their services. This chapter reviews two of the most prevalent planning strategies proposed to combat urban sprawl, i.e. smart growth (or new urbanism) and green infrastructure planning. The former is predominantly derived from a frustration over the failure of American planning projects, and is increasingly adopted among planners in North American and European metropolitan regions. The latter is predominantly proposed by ecologists and biodiversity conservationists, and has shaped conservation planning in many countries. Both planning strategies propose compact urban development as a way to combat adverse effects of urban sprawl. However, and as pointed out in this chapter, many types of ecosystem services are generated in the developed landscape, also in sprawling suburban settings. It is also important to account for ecosystem services in smart growth projects and to engage a wider set of urban residents in management of these services in order to mitigate ecological illiteracy. The chapter elucidates some of the key characteristics and propositions of both approaches and provides examples of urban designs that hold potential to work as frameworks in contributing to sustainable governance of ecosystem services.</p
Analysis of hunting options by the use of general food taboos
No full textA hypothetical model was built, using the STELLA II software program, to test several hunting options for a human hunting group. Different outcomes of possible hunting modes are analysed, such as a change in hunting rate, prey hunted, or species avoided or not avoided by taboos. The model consists of five sectors that reflect a short food chain in an upper Amazonian ecosystem. There is a vegetation sector, a predator sector, and two sectors consisting of browsers and grazers. The last sector represents a human group, known as the Ecuador Achuar. The critical factor analysed is how differences in hunting rate affect a target resource, and how this resource may be affected by general food taboos. The major results of the model are that general food taboos may not be an adaptive short term strategy for hunters, but that a 'moderate' hunting mode may be the most effective option for the human group. Since the model is a simplification of the real world, no general conclusions for management should be drawn from the results.</p
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