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121.
This paper addresses two questions: (1) Given a commitment at the national level to reduce greenhouse gas (GHG) emissions, what tools are available to national-level governments to induce complimentary actions required at subnational levels? (2) In the absence of a serious commitment at national and regional levels to reduce GHG emissions, what is the scope for, and jurisdictional rights of, cities to undertake actions? In this context, federal, regional and municipal legislation relevant for GHG emissions is examined in Canada, the USA and Germany. Regarding the first question, different national governments find themselves in considerably different positions to implement climate initiatives at subnational levels, with the German government in the strongest position and the Canadian government in the weakest. The implications of this for a nation's willingness to adopt emission reduction targets could be serious. Regarding the second question, there are few significant differences among Canadian, US and German municipalities' jurisdictional capabilities (and limitations) to reduce GHG emissions. Though limited in their legal capacity, these municipalities demonstrate that through their own, often informal, initiatives they can reinforce and compliment the more formal, regulatory actions by senior-level governments, thereby paving the way for senior-level governments to deliver meaningful domestic emission reductions.  相似文献   
122.
ABSTRACT: Vertical attenuation of photosynthetically active radiation (PAR) in clear waters of central Florida theoretically can vary almost 50 percent during a sunny summer day as a result of changing solar elevation. We used a simple formula to partially adjust the attenuation coefficient in Tampa Bay and Charlotte Harbor for changing solar elevation of the direct beam and then used multiple regression analysis to estimate the relative contribution of different water properties or constituents to the adjusted attenuation coefficient, kadj. Color, on an average, was responsible for 18 percent of kadj, chlorophyll a for 21 percent, nonchiorophyll suspended matter for 55 percent, and seawater for the remaining 6 percent. In both estuaries, kadj increased with decreasing salinity as a result of freshwater runoff adding color, suspended matter, and nutrients. Nutrients affected attenuation by stimulating phytoplankton growth and increasing concentrations of chlorophyll a. Reduced nutrient loading to upper Tampa Bay (Hilisborough Bay) in the early to mid-1980's appears to have decreased concentrations of chlorophyll a, increased water clarity, and increased seagrass recolonization. Assuming other attenuating substances remained unchanged, the decrease in the average concentration of chlorophyll a from 30 to 15 μg L?1 would correspond to an increase in the depth of light penetration necessary for seagrass survival (>10 percent incident light) from 1.0 to 1.5 m, which, on a relatively flat sea bed (slope of 2 m/km), would increase the area potentially available for seagram recolonization by 0.25 km2/km of shoreline.  相似文献   
123.
ABSTRACT: Recent years have seen an accelerating trend toward devolution and privatization of water supply and distribution infrastructure. This paper discusses and analyzes the experience to date of the federal Bureau of Reclamation's efforts to title transfer to non federal entities. The paper also discusses the concepts of federalism and devolution in the context of Reclamation's title transfer activities.  相似文献   
124.
Ecological surprises, substantial and unanticipated changes in the abundance of one or more species that result from previously unsuspected processes, are a common outcome of both experiments and observations in community and population ecology. Here, we give examples of such surprises along with the results of a survey of well-established field ecologists, most of whom have encountered one or more surprises over the course of their careers. Truly surprising results are common enough to require their consideration in any reasonable effort to characterize nature and manage natural resources. We classify surprises as dynamic-, pattern-, or intervention-based, and we speculate on the common processes that cause ecological systems to so often surprise us. A long-standing and still growing concern in the ecological literature is how best to make predictions of future population and community dynamics. Although most work on this subject involves statistical aspects of data analysis and modeling, the frequency and nature of ecological surprises imply that uncertainty cannot be easily tamed through improved analytical procedures, and that prudent management of both exploited and conserved communities will require precautionary and adaptive management approaches.  相似文献   
125.
Larval and post-larval crab distribution was surveyed in three different habitats in Kachemak Bay, Alaska to determine temporal and spatial variability. Distribution varied temporally and spatially from June 2005 to September 2006. Nine sites of varying habitat complexity were surveyed monthly using scuba surveys and light traps to measure habitat variables and quantify crab zoeae and megalopae. A total of 10,016 crabs belonging to seven families were identified. Four species comprised the majority (97%) of the total crab assemblages and included Cancer oregonensis, Fabia subquadrata, Telmessus cheiragonus, and Pugettia gracilis. Peak abundances occurred in summer but varied on small temporal scales with species. No single bay-wide variable determined the appearance of all species. Depending on species, appearance may be influenced by seasonality of environmental variables. Spatially, highest abundances occurred in habitats with less structural complexity. Spatial differences in crab abundance may have resulted from variability on large scale physical transport mechanisms and not kelp-mediated flow alterations.  相似文献   
126.
Effective ecosystem‐based management requires understanding ecosystem responses to multiple human threats, rather than focusing on single threats. To understand ecosystem responses to anthropogenic threats holistically, it is necessary to know how threats affect different components within ecosystems and ultimately alter ecosystem functioning. We used a case study of a Mediterranean seagrass (Posidonia oceanica) food web and expert knowledge elicitation in an application of the initial steps of a framework for assessment of cumulative human impacts on food webs. We produced a conceptual seagrass food web model, determined the main trophic relationships, identified the main threats to the food web components, and assessed the components’ vulnerability to those threats. Some threats had high (e.g., coastal infrastructure) or low impacts (e.g., agricultural runoff) on all food web components, whereas others (e.g., introduced carnivores) had very different impacts on each component. Partitioning the ecosystem into its components enabled us to identify threats previously overlooked and to reevaluate the importance of threats commonly perceived as major. By incorporating this understanding of system vulnerability with data on changes in the state of each threat (e.g., decreasing domestic pollution and increasing fishing) into a food web model, managers may be better able to estimate and predict cumulative human impacts on ecosystems and to prioritize conservation actions.  相似文献   
127.
128.
This article explores the potential for microhydro installations in Nepal to improve adaptive capacity in addition to their ability to mitigate greenhouse gas emissions. After explaining its methods of data collection—namely field research and research interviews—the article explores the climate change adaptation benefits of microhydro plants being promoted under the Renewable Energy Development Project (REDP). Besides displacing fossil fuels, in particular kerosene for lighting, microhydro electrification offers an effective way of improving community assets and bolstering social resilience (thereby enhancing the adaptive capacity of communities there). Our own survey of REDP project sites reveals how microhydro units have improved community income levels, equalized gender roles, enhanced access to education and information, and reduced migration patterns. The article concludes by highlighting three key lessons—the role of extensive community mobilization, proactive capacity building for efficient electricity use, and the need for comprehensiveness—for those wishing to adapt to climate change in other rural and developing economies.  相似文献   
129.
Open space areas protected by local communities may augment larger scale preservation efforts and may offer overlooked benefits to biodiversity conservation provided they are in suitable ecological condition. We examine protected areas established by local communities through ballot initiatives, a form of direct democracy, in California, USA. We compare ecological conditions of wooded habitats on local ballot protected sites and on sites protected by a state-level conservation agency. Collectively, we found few differences in ecological conditions on each protected area type. Ballot sites had greater invasive understory cover and larger trees. Community dissimilarity patterns suggested ballot sites protect a complementary set of tree species to those on state lands. Overall, geographic characteristics influenced onsite conditions more than details of how sites were protected. Thus, community-driven conservation efforts contribute to protected area networks by augmenting protection of some species while providing at least some protection to others that might otherwise be missed.Electronic supplementary materialThe online version of this article (10.1007/s13280-020-01469-8) contains supplementary material, which is available to authorized users.  相似文献   
130.
Environmental contamination resulting from the production or release of harmful chemicals can lead to negative consequences for wildlife and human health. Perfluorinated alkyl acids (PFAAs) were historically produced as protective coatings for many household items and currently persist in the environment, wildlife, and humans. PFAAs have been linked to immune suppression, endocrine disruption, and developmental toxicity in wildlife and laboratory studies. This study examines the American alligator, Alligator mississippiensis, as an important indicator of ecosystem contamination and a potential pathway for PFAA exposure in humans. Alligator meat harvested in the 2015 South Carolina (SC) public hunt season and prepared for human consumption was collected and analyzed for PFAAs to determine meat concentrations and relationships with animal body size (total length), sex, and location of harvest. Of the 15 PFAAs analyzed, perfluorooctane sulfonate (PFOS) was found in all alligator meat samples and at the highest concentrations (median 6.73 ng/g). No relationship was found between PFAA concentrations and total length or sex. Concentrations of one or all compounds varied significantly across sampling locations, with alligators harvested in the Middle Coastal hunt unit having the highest PFOS concentrations (median 16.0 ng/g; p = 0.0001). Alligators harvested specifically from Berkley County, SC (located in the Middle Coastal hunt unit) had the highest PFOS concentrations and the greatest number of PFAAs detected (p < 0.0001). The site-specific nature of PFAA concentrations in alligator meat observed in this study suggests a source of PFAA contamination in Berkley County, SC.  相似文献   
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