The complex interactions between human activity and natural processes determine non-linear dynamics in ecosystems that can difficult their management. Human settlements in arid lands contribute to the modification of disturbance regimes, including the introduction of new disturbances and the elimination of others. In consequence, they can alter the functional mechanisms that allow systems to overcome limiting factors, leading to desertification. In this revision, we evaluated the effects of the changes on disturbance regimes produced by the different forms of land transformation on the structure and function of ecosystems of the Monte Biogeographical Province, in Argentinean arid west. Two approaches were used: the analysis of land use history and the analysis of the effects of the main disturbances on the dynamics of different communities. We concluded that throughout the history of the Monte Desert, the joint action of natural and anthropic agents has resulted in complex dynamics that lead most area of the Monte to a moderate to severe status of desertification. The modification of the disturbance regime had strong consequences for several aspects of the dynamics of communities, such as species composition and diversity, water dynamics, soil conditions, trophic structure and productivity of Monte Desert ecosystems. However, disturbance regimes could be managed to promote favorable transitions in ecosystems and, therefore, could be a tool for optimizing productivity of agro-ecosystems, and recovering and conserving natural ecosystems. 相似文献
After describing briefly some of the outstanding features of the uncommonly cold and wet year 1695, one of the coldest years
of the Little Ice Age, an annotated translation is presented of a contemporary review of the unusual weather events of the
year in Europe. The original was published in 1702 in Frankfurt am Main, Germany, in vol. XIV of the seriesTheatrum Europaeum. The annotation relates to the historical events of the year that were substantially affected by the weather, events to which
rather abstruse references are made in the aforementioned contemporary account. In addition to the fact that the contemporary
review describes the uncommon weather conditions of 1695, it appears to be the first extended weather review in history. 相似文献
Mine planning is influenced by many sources of uncertainty. Significant sources of geological uncertainty in mine planning include uncertainty in layout of geological domains and uncertainty in metal grades. These two sources of uncertainty cannot be modeled separately because the distribution of the grade is controlled usually by geological domains. Two approaches exist for combining these two sources of uncertainty: the joint simulation approach and the cascade approach. In this paper, these two approaches were compared using a real case study. To this end, uncertainty in iron grade (quantitative variable) and ore zones (qualitative variable) was modeled using both approaches. There were some considerable differences in the results obtained by each approach, which confirm the importance of choosing the most appropriate approach with consideration of the dominate features of a deposit.
There is a growing concern that countries should reduce their dependence on fossil fuels for electricity generation and look to other cleaner technologies. Hydroelectricity is one such option. However, given that hydropower is dependent on rainfall and associated runoff for power generation, it is susceptible to both the positive and negative impacts of climate change, such as increases in temperature and changes in precipitation and runoff. In this paper, impacts on hydropower generation have been organised as either changes in long-term trends or short-term variability and shocks. These impacts could either manifest themselves as direct impacts on hydropower generation potential or as indirect impacts (or ancillary impacts) such as increased competition for water. Citing examples from around the world, this paper investigates the scale of these projected impacts, and the potential cost implication of inaction. It concludes by making recommendations for possible adaptive options to build resilience in response to local impacts. 相似文献
Institutional barriers and bridges to local climate change impacts adaptation affecting small rural municipalities and Conservation Authorities (CAs are watershed agencies) in Eastern Ontario (Canada) are examined, and elements of a community-based adaptation strategy related to water infrastructures are proposed as a case-study in community adaptation to climate change. No general water scarcity is expected for the region even under unusually dry weather scenarios. Localized quantity and quality problems are likely to occur especially in groundwater recharge areas. Some existing institutions can be relied on by municipalities to build an effective adaptation strategy based on a watershed/region perspective, on their credibility, and on their expertise. Windows of opportunity or framing issues are offered at the provincial level, the most relevant one in a federal state, by municipal emergency plan requirements and pending watershed source water protection legislation. Voluntary and soon to be mandated climate change mitigation programs at the federal level are other ones. 相似文献
Posterior probabilities of occurrence for Zn-Pb Mississippi Valley Type (MVT) mineralization were calculated based on evidence
maps derived from regional geology, Landsat-TM, RADARSAT-1, a digital elevation model and aeromagnetic data sets in the Borden
Basin of northern Baffin Island, Canada. The vector representation of geological contacts and fault traces were refined according
to their characteristics identified in Landsat-TM, RADARSAT-1, DEM, slope, aspect, and shaded relief data layers. Within the
study area, there is an association between the occurrence of MVT mineralization and proximity to the contact of platformal
carbonates and shale units of the adjacent geological formation. A spatial association also tends to exist between mineralization
and proximity to E-W and NW-SE trending faults. The relationships of known MVT occurrences with the geological features were
investigated by spatial statistical techniques to generate evidence maps. Supervised classification and filtering were applied
to Landsat-TM data to divide the Society Cliffs Formation into major stratigraphic subunits. Because iron oxides have been
observed at some of the MVT occurrences within the Borden Basin, Landsat-TM data band ratio (3/1) was calculated to highlight
the potential presence of iron-oxides as another evidence map. Processed Landsat-TM data and other derived geological evidence
maps provided useful indicators for identifying areas of potential MVT mineralization.
Weights of evidence and logistic regression were used independently to integrate and generate posterior probability maps showing
areas of potential mineralization based on all derived evidence maps. Results indicate that in spite of the lack of important
data sets such as stream or lake sediment geochemistry, Landsat-TM data and regional geological data can be useful for MVT
mineral-potential mapping. 相似文献
Tools that support public engagement with sustainability are essential for local sustainability planning. This research investigates the ability of two geographic information system (GIS)-based tools to promote discussion of sustainability in a suburban context. A local ecological footprint tool and a community environmental atlas (an environmentally themed online mapping system) were created for seven suburban boroughs of Montreal. Variations of both tools have been used to support sustainability efforts, but their use has not been widely evaluated. Working from a public participation GIS (PPGIS) framework that recognizes the powerful influence of data representation, this research uses focus groups to evaluate how well these tools address three criteria that have emerged from the literature on public engagement in sustainability: interdependency across systems, reflexivity about personal and social decision making, and interactions across spatial scales. Whereas the atlas remains advantageous for discussing local spatial specifics, it was found that the ecological footprint helped people see the interconnections among systems, integrate local and global aspects of sustainability, and reflect on the values and assumptions underlying current social and economic structures. 相似文献
In this article, we use parcel-based land-use data to analyze 50 years of residential development in the Toronto region. We test two hypotheses: (1) Toronto’s form does not conform to conventional definitions of suburban sprawl and (2) Toronto’s suburban development shows high levels of continuity over time with relatively high densities and mixed housing types. Contrary to recent research suggesting a convergence of urban forms among North American metropolitan regions, Ontario’s robust planning system has created a distinctive, highly consistent pattern of residential development that has, for half a century, achieved many of the core goals of smart growth including relatively compact, contiguous, and concurrent development. This form continues to be automobile dependent, however, and is not producing many of the benefits ascribed to smart growth. Rather than continuing to adopt United States-inspired smart growth policies, a more ambitious set of initiatives will be required to address current regional challenges. 相似文献