512 research outputs found
Chapin F., Stuart Jr. — Human activity patterns in the city. Things people do in time and in space
No full textC D. Chapin F., Stuart Jr. — Human activity patterns in the city. Things people do in time and in space. In: Population, 31ᵉ année, n°2, 1976. p. 507
An introduction to the study of social evolution; the prehistoric period, by F. Stuart Chapin.
No full textInteractions between changing climate and biodiversity: Shaping humanity's future
No full textScientists have known for more than a century aboutpotential human impacts on climate (1). In the last 30 y,estimates of these impacts have been confirmed andrefined through increasingly precise climate assess-ments (2). Other global-scale human impacts, includingland use change, overharvesting, air and water pollu-tion, and increased disease risk from antibiotic resis-tance, have risen to critical levels, seriously jeopardizingthe prospects that future generations can thrive (3–5).Earth has entered a stage characterized by humandomination of critical Earth system processes (6–8).Although the basic trajectories of these changes arewell known, many of the likely consequences areshrouded in uncertainty because of poorly understoodinteractions among these drivers of change and there-fore their effects on ecosystems and societies.Fil: Stuart Chapin III, F.. University of Alaska; Estados UnidosFil: Díaz, Sandra Myrna. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentin
Functional diversity revealed by removal experiments
No full textThe dominant protocol to study the effects of plant diversity on ecosystem functioning has involved synthetically assembled communities, in which the experimental design determines species composition. By contrast, the composition of naturally assembled communities is determined by environmental filters, species recruitment and dispersal, and other assembly processes. Consequently, natural communities and ecosystems can differ from synthetic systems in their reaction to changes in diversity. Removal experiments, in which the diversity of naturally assembled communities is manipulated by removing various components, complement synthetic-assemblage experiments in exploring the relationship between diversity and ecosystem functioning. Results of recent removal experiments suggest that they are more useful for understanding the ecosystem effects of local, nonrandom extinctions, changes in the natural abundance of species, and complex interspecific interactions. This makes removal experiments a promising avenue for progress in ecological theory and an important source of information for those involved in making land-use and conservation decisions.Fil: Díaz, Sandra Myrna. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Symstad, Amy J.. United States Geological Survey; Estados UnidosFil: Chapin III, F. Stuart. University Of Alaska; Estados UnidosFil: Wardle, David A.. Landcare Research; Nueva Zelanda. Swedish University of Agricultural Sciences; SueciaFil: Huenneke, Laura F.. New Mexico State University; Méxic
Social-Ecological Sustainability in Alaskan Boreal Forests: The Challenges of Global Change: Occasional Paper No. 1
No full text"Human activities are altering many factors that determine the fundamental properties of ecological and social systems. Is sustainability a feasible goal in a world in which these controls are changing with a directional trend over time? This is global problem, but Alaska is particularly appropriate place to address this question because of rapid climate warming. This has profoundly affected factors that influence landscape processes (climate regulation and disturbance spread) and natural hazards; the goods that people harvest from ecosystems such as food, water, and wood; and many of the cultural benefits that people derive from ecosystems. Four broad policy strategies emerge for sustaining social-ecological systems at times of rapid change: (a) reducing vulnerability by sustaining basic ecological processes and reducing those hazards and stress that cause changes; (b) increasing adaptability by maintaining a diversity of options and experimenting with potentially innovative solutions; (c) fostering resilience by learning to cope with surprises and strengthening feedbacks that stabilize the current state of the system; and (d) facilitating transformation to new, potentially more beneficial states by taking advantage of opportunities created by crisis. Each strategy provides societal benefits, and all of them can be pursued simultaneously."Not peer reviewe
Approaches to defining a planetary boundary for biodiversity
No full textThe idea that there is an identifiable set of boundaries, beyond which anthropogenic change will put the Earth system outside a safe operating space for humanity, is attracting interest in the scientific community and gaining support in the environmental policy world. Rockstrom et al. (2009) identify nine such boundaries and highlight biodiversity loss as being the single boundary where current rates of extinction put the Earth system furthest outside the safe operating space. Here we review the evidence to support a boundary based on extinction rates and identify weaknesses with this metric and its bearing on humanity's needs. While changes to biodiversity are of undisputed importance, we show that both extinction rate and species richness are weak metrics for this purpose, and they do not scale well from local to regional or global levels. We develop alternative approaches to determine biodiversity loss boundaries and extend our analysis to consider large-scale responses in the Earth system that could affect its suitability for complex human societies which in turn are mediated by the biosphere. We suggest three facets of biodiversity on which a boundary could be based: the genetic library of life; functional type diversity; and biome condition and extent. For each of these we explore the science needed to indicate how it might be measured and how changes would affect human societies. In addition to these three facets, we show how biodiversity's role in supporting a safe operating space for humanity may lie primarily in its interactions with other boundaries, suggesting an immediate area of focus for scientists and policymakers
Methane Emissions From Lakes In Northeast Siberia And Alaska
No full textDissertation (Ph.D.) University of Alaska Fairbanks, 2006Large uncertainties in the budget of atmospheric methane (CH4), an important greenhouse gas whose relative greenhouse effect is 23 times stronger than that of carbon dioxide (CO2), limit the accuracy of climate-change projections. Concentrations of atmospheric CH 4 have been rising during recent decades, particularly at high northern latitudes. The causes of this increase are not well understood. Here I describe and quantify an important source of methane---bubbling from northern lakes---that has not been incorporated in previous regional or global methane budgets. I introduce a new method to accurately measure ebullition (bubbling), which accounted for 95% of CH4 emissions from North Siberian thaw lakes. Documenting the patchiness of ebullition increased previous estimates of CH4 flux from lakes 5-fold in Siberia and 2.5- to 14-fold in Alaska. Extrapolating estimates of measured fluxes, I show that North Siberian yedoma (Pleistocene-aged organic-rich loess) thaw lakes emit 3.8 Tg CH 4 yr-1. An independent mass-balance approach based on carbon lost from permafrost that thawed beneath lakes revealed that lakes emit 4-5 Tg CH4 yr-1. Adding these emissions significantly increases present estimates of northern wetland contributions (<6-40 Tg yr-1) to the atmospheric CH4 budget. Thermokarst (thaw) erosion was the primary driver of CH4 emissions in lakes. A 14.7% expansion of thaw lakes from 1974 to 2000 increased lake CH 4 emissions by 58% in Siberia, demonstrating a positive feedback to climate warming. The Pleistocene age of CH4 (14C age 35,570-42,800 years in Siberia and 14,760-26,020 years in Alaska) emitted from hotspots along active thermokarst margins of lakes demonstrated that recruitment of a previously sequestered carbon source contributes to this feedback. Finally, reconstruction of yedoma's distribution at the Last Glacial Maximum together with compilation of thaw lake basal ages that developed at the onset of Holocene warming, suggested that thaw lake development contributed up to 70% of the rapid increase in atmospheric CH4 during deglaciation. About 425 Gt C remain preserved in the yedoma ice complex in North Siberia. If this Siberian permafrost warms more rapidly in the future as projected, the positive feedback of ebullition from expanding thaw lakes could increase the rate of high-latitude warming
Biodiversity loss threatens human well-being.
No full textThe diversity of life on Earth is dramatically affected by Human alterations of ecosystems. Compelling evidence now shows that the reverse is also true: biodiversity in the broad snsse affects the properties of ecosystem and, therefore, the benefits that humans obtain from them. In this article, we provide a synthesis of the most crucial messages emerging from the latest scientific literature and international assessments of the role of biodiversity in ecosystem services and human well- being. Human societies have beeb built on biodiversity. Many activities indispensable for human subsistence lead to biodiversity loss, and this trend is ikely to continue in the future. We clearly benefit from the diversity of organisms that we have learned to use for medicines, food, fibers, and other renwable resources. In addition, biodiversity has always been an integral part of the human experience and there are many moral reasons to preserve it for its own sake. What has been less recognized is that biodiversity also influences human well- being, including the access to water and basic materials for a satifactory life, and security in the face of environmental change, through its effects on the ecosystem processes that lie at the core of the Earth´s most vital life support system.Fil: Díaz, Sandra Myrna. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Fargione, Joseph. Universidad Nacional de Córdoba; Argentina. University Of New Mexico; Estados UnidosFil: Chapin III, Francis Stuart. University Of Alaska; Estados UnidosFil: Tilman, David. University of Minnesota; Estados Unido
Establishment of native plants on disturbed sites in arctic Alaska
No full textDissertation (Ph.D.) University of Alaska Fairbanks, 1988Roads, camps and other structures associated with the Trans-Alaska Pipeline were placed on gravel pads to protect underlying permafrost. Gravel was mined from floodplains, resulting in loss of riparian wildlife habitat. Revegetation of abandoned pads using non-native grasses has been unsuccessful. Native plants might be more persistent and contribute to replacing lost habitat. The naturally-occurring pioneer community on gravel pads consists mainly of willows Salix alaxensis and S. glauca, fireweed Epilobium latifolium, horsetails Equisetum arvense and legumes in the genera Astragalus, Oxytropis and Hedysarum, all species of riparian gravel bars. Ten years after abandonment mean total cover of native species on 16 gravel pads was only 2.7% and mean number of species per site was 4.4. Distance from riparian seed sources explained 25% and 40% of variation in cover and diversity respectively. Legumes were more restricted to sites near the river than were fireweed and willows. In the laboratory, no germination of S. alaxensis occurred at water potentials MPa, which probably occur often on gravel pads. In the field, germination was increased by watering or by a rough surface which provided moister microsites. Growth of seedlings was limited by the supply of mineral nutrients. Survival was high and not limited by availability of water or nutrients. In the laboratory, few legume seeds germinated at water potentials MPa. In the field, germination was higher on a rough surface which provided moister microsites. Greenhouse experiments indicated that symbiotically-fixed nitrogen contributed significantly to the growth of legume seedlings, especially when availability of mineral N was low. Rhizobia-free legume seedlings transplanted to a gravel pad developed nodules whether or not they were inoculated with rhizobia, but total weight and nodule weight tended to be higher in inoculated seedlings. Some native plants, primarily riparian species, are capable of establishing and growing on abandoned gravel pads. The low cover and diversity of naturally-colonized sites are attributed to (1) limited dispersal from riparian seed sources, (2) lack of water for germination, and (3) lack of nutrients to support growth. Both willows and legumes have promise for use in restoration
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