Rangeland management and climate hazards in drylands: dust storms,desertification and the overgrazing debate     

Nick Middleton 《Natural Hazards》2018,92(1):57-70

This paper examines the theory and supporting evidence for links between desertification, drought and dust storms with a particular focus on studies undertaken in and around the Gobi Desert. Overgrazing of rangeland by pastoralists has been the most commonly cited cause of desertification in global drylands for more than 30 years, but the evidence supporting this link is not always convincing. Nonetheless, overgrazing, desertification and dust storms are frequently connected, regardless. Drought is another well-known and important driver of vegetation cover change. Distinguishing between vegetation cover adversely affected by drought and that reduced by grazing is imperative for policy makers because identifying the incorrect driver of vegetation change risks the development of inappropriate policy.  相似文献   

A qualitative risk assessment for the impacts of climate change on nationally and internationally important geoheritage sites in Scotland     

Rachel M.L. Wignall  John E. Gordon  Vanessa Brazier  Colin C.J. MacFadyen  Nick S. Everett 《Proceedings of the Geologists' Association. Geologists' Association》2018,129(2):120-134

Climate change is a significant concern for nature conservation in the 21?st century. One of the goals of the 2014 Scottish Climate Change Adaptation Programme is to identify the consequences of climate change for protected areas and to put in place adaptation or mitigation measures. As a contribution to the process, this paper develops a methodology to identify the relative level of risk to nationally and internationally important geological and geomorphological sites in Scotland from the impacts of climate change. The methodology is based on existing understanding of the likely responses of different types of geosite to specific aspects of climate change, such as changes in rainfall, rising sea levels or increased storminess, and is applied to assess the likelihood of damaging impacts on groups of similar geoheritage features in sites with similar characteristics. The results indicate that 80 (8.8%) of the ～900 nationally and internationally important geoheritage sites in Scotland are at ‘high’ risk from climate change. These include active soft-sediment coastal and fluvial features, finite Quaternary sediment exposures and landforms in coastal and river locations, active periglacial features, sites with palaeoenvironmental records, finite or restricted rock exposures and fossils. Using this risk-based assessment, development of indicative geoheritage climate-change actions have been prioritised for these sites. Depending on the characteristics of the sites, management options may range from ‘do nothing’ to rescue excavations and posterity recording. Monitoring is an essential part of the management process to trigger evidence-based interventions.  相似文献   

Lid tectonics-Preface     

Craig O'Neill  Nick M.W.Roberts 《地学前缘(英文版)》2018,9(1):1-2

正The idea that plate tectonics may not have operated deep in Earth's Precambrian past has a long legacy.What predated plate tectonics is unknown,and advances in data-from geochemical,geological and tectonic,to paleomagnetic,as well as modelling ap-  相似文献   

Discussion of “Evapotranspiration modelling using support vector machines”*     

Robert J. Abrahart  Christian W. Dawson  Linda M. See  Nick J. Mount  Asaad Y. Shamseldin 《水文科学杂志》2013,58(8):1442-1450

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Ottawa: the knowledge city and a labyrinth of obstacles     

Nick Novakowski 《GeoJournal》2010,75(6):553-565

This research provides a comparative examination of Ottawa as an archetype of a knowledge city. Among Canada’s four largest cities, Ottawa is unique in terms of the characteristics of its labor force, the nature of its employment mix, and its infrastructure. Since the high-tech downturn of 2001, some of Ottawa’s options as a knowledge city seem to be contracting, despite some simultaneously encouraging signs (like recovering employment levels in the high-tech sector). This raises a question about Ottawa’s potential longevity as a knowledge center. The challenge is to understand the inventory of obstacles faced by the city, and address the sort of alchemy required to maintain and improve its competitiveness as a knowledge city.  相似文献   

Iron oxides in comet 81P/Wild 2     

John C. BRIDGES  Mark J. BURCHELL  Hitesh C. CHANGELA  Nick J. FOSTER  J. Alan CREIGHTON  James D. CARPENTER  Steve J. GURMAN  Ian A. FRANCHI  Henner BUSEMANN 《Meteoritics & planetary science》2010,45(1):55-72

Abstract– We have used synchrotron Fe‐XANES, XRS, microRaman, and SEM‐TEM analyses of Stardust track 41 slice and track 121 terminal area slices to identify Fe oxide (magnetite‐hematite and amorphous oxide), Fe‐Ti oxide, and V‐rich chromite (Fe‐Cr‐V‐Ti‐Mn oxide) grains ranging in size from 200 nm to ～10 μm. They co‐exist with relict FeNi metal. Both Fe‐XANES and microRaman analyses suggest that the FeNi metal and magnetite (Fe₂O₃FeO) also contain some hematite (Fe₂O₃). The FeNi has been partially oxidized (probably during capture), but on the basis of our experimental work with a light‐gas gun and microRaman analyses, we believe that some of the magnetite‐hematite mixtures may have originated on Wild 2. The terminal samples from track 121 also contain traces of sulfide and Mg‐rich silicate minerals. Our results show an unequilibrated mixture of reduced and oxidized Fe‐bearing minerals in the Wild 2 samples in an analogous way to mineral assemblages seen in carbonaceous chondrites and interplanetary dust particles. The samples contain some evidence for terrestrial contamination, for example, occasional Zn‐bearing grains and amorphous Fe oxide in track 121 for which evidence of a cometary origin is lacking.  相似文献