首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   36篇
  免费   0篇
环保管理   4篇
基础理论   32篇
  2014年   4篇
  2013年   1篇
  2012年   3篇
  2011年   1篇
  2009年   4篇
  2008年   7篇
  2007年   2篇
  2005年   5篇
  2004年   1篇
  2003年   1篇
  2002年   1篇
  1990年   1篇
  1989年   1篇
  1987年   3篇
  1986年   1篇
排序方式: 共有36条查询结果,搜索用时 31 毫秒
31.
Abstract:  Climate change poses a challenge to the conventional approach to biodiversity conservation, which relies on fixed protected areas, because the changing climate is expected to shift the distribution of suitable areas for many species. Some species will persist only if they can colonize new areas, although in some cases their dispersal abilities may be very limited. To address this problem we devised a quantitative method for identifying multiple corridors of connectivity through shifting habitat suitabilities that seeks to minimize dispersal demands first and then the area of land required. We applied the method to Proteaceae mapped on a 1-minute grid for the western part of the Cape Floristic Region of South Africa, to supplement the existing protected areas, using Worldmap software. Our goal was to represent each species in at least 35 grid cells (approximately 100 km2) at all times between 2000 and 2050 despite climate change. Although it was possible to achieve the goal at reasonable cost, caution will be needed in applying our method to reserves or other conservation investments until there is further information to support or refine the climate-change models and the species' habitat-suitability and dispersal models.  相似文献   
32.
33.
Bird Conservation in Brazil   总被引:2,自引:0,他引:2  
Abstract:  Brazil has one of the richest avifaunas in the world, with recent estimates varying from 1696 to 1731 species. About 10% (193 taxa) of these are threatened. The Amazon has the highest number of species, followed by the Atlantic Forest and the Cerrado; most of Brazil's endemic birds, however, are in the Atlantic Forest. Brazil's threatened species occur mostly in the Atlantic Forest, especially in the southeast lowlands and the northeast. The Cerrado has the second highest number of threatened species. The two major threats to Brazilian birds are habitat loss, degradation, and fragmentation and hunting, most especially for illegal commerce. A number of conservation and research initiatives over the last 20 years have significantly improved our capacity to address and resolve major issues for bird conservation. Brazil requires a National Bird Conservation Plan to draw up priorities for research and conservation over the next decade.  相似文献   
34.
Abstract: Climate‐change scenarios project significant temperature changes for most of South America. We studied the potential impacts of predicted climate‐driven change on the distribution and conservation of 26 broad‐range birds from South America Cerrado biome (a savanna that also encompass tracts of grasslands and forests). We used 12 temperature or precipitation‐related bioclimatic variables, nine niche modeling techniques, three general circulation models, and two climate scenarios (for 2030, 2065, 2099) for each species to model distribution ranges. To reach a consensus scenario, we used an ensemble‐forecasting approach to obtain an average distribution for each species at each time interval. We estimated the range extent and shift of each species. Changes in range size varied across species and according to habitat dependency; future predicted range extent was negatively correlated with current predicted range extent in all scenarios. Evolution of range size under full or null dispersal scenarios varied among species from a 5% increase to an 80% decrease. The mean expected range shifts under null and full‐dispersal scenarios were 175 and 200 km, respectively (range 15–399 km), and the shift was usually toward southeastern Brazil. We predicted larger range contractions and longer range shifts for forest‐ and grassland‐dependent species than for savanna‐dependent birds. A negative correlation between current range extent and predicted range loss revealed that geographically restricted species may face stronger threat and become even rarer. The predicted southeasterly direction of range changes is cause for concern because ranges are predicted to shift to the most developed and populated region of Brazil. Also, southeastern Brazil is the least likely region to contain significant dispersal corridors, to allow expansion of Cerrado vegetation types, or to accommodate creation of new reserves.  相似文献   
35.
There are serious problems related to the use and conservation of international rivers. Riparian nations tend to use their waters and to transfer negative impacts, such as pollution, to other countries. This paper examines the work of the International Law Commission as it seeks to elaborate a framework convention for the use and conservation of shared watercourses. Although this task is still in progress, basic substantive principles such as 'equitable apportionment' and 'prohibition against appreciable harm' seem to be widely agreed upon. The immediate need is the development of and the agreement on, procedural systems for conflict resolution.  相似文献   
36.
Abstract:  Conservation biologists mostly agree on the need to identify and protect biodiversity below the species level but have not yet resolved the best approach. We addressed 2 issues relevant to this debate. First, we distinguished between the abstract goal of preserving the maximum amount of unique biodiversity and the pragmatic goal of minimizing the loss of ecological goods and services given that further loss of biodiversity seems inevitable. Second, we distinguished between the scientific task of assessing extinction risk and the normative task of choosing targets for protection. We propose that scientific advice on extinction risk be given at the smallest meaningful scale: the elemental conservation unit (ECU). An ECU is a demographically isolated population whose probability of extinction over the time scale of interest (say 100 years) is not substantially affected by natural immigration from other populations. Within this time frame, the loss of an ECU would be irreversible without human intervention. Society's decision to protect an ECU ought to reflect human values that have social, economic, and political dimensions. Scientists can best inform this decision by providing advice about the probability that an ECU will be lost and the ecological and evolutionary consequences of that loss in a form that can be integrated into landscape planning. The ECU approach provides maximum flexibility to decision makers and ensures that the scientific task of assessing extinction risk informs, but remains distinct from, the normative social challenge of setting conservation targets.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号