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排序方式: 共有618条查询结果,搜索用时 181 毫秒
371.
Siegfried Franck Werner von BlohChristoph Müller Alberte BondeauB. Sakschewski 《Ecological modelling》2011,222(12):2019-2026
The maximum population, also called Earth's carrying capacity, is the maximum number of people that can live on the food and other resources available on planet Earth. Previous investigations estimated the maximum carrying capacity as large as about 1 trillion people under the assumption that photosynthesis is the limiting process. Here we use a present state-of-the-art dynamic global vegetation model with managed planetary land surface, Lund-Potsdam-Jena managed Land (LPJmL), to calculate the yields of the most productive crops on a global 0.5° × 0.5° grid. Using the 2005 crop distribution the model predicts total harvested calories that are sufficient for the nutrition of 11.4 billion people. We define scenarios where humankind uses the whole land area for agriculture, saves the rain forests and the boreal evergreen forests or cultivates only pasture to feed animals. Every scenario is run in an extreme version with no allowance for urban and recreational needs and in two soft versions with a certain area per person for non-agricultural use. We find that there are natural limits of the maximum carrying capacity which are independent of any increase in agricultural productivity, if non-agricultural land use is accounted for. Using all land planet Earth can sustain 282 billion people. The save-forests-scenario yields 150 billion people. The scenario that cultivates only pasture to feed animals yields 96 billion people. Nevertheless, we should always have in mind that all our calculated numbers for the carrying capacity refer to extreme scenarios where humankind may only vegetate on this planet. Our numbers are considerably higher than the general median estimate of upper bounds of human population found in the literature in the order of 10 billion. 相似文献
372.
Erik Olsen Alf Ring Kleiven Hein Rune Skjoldal Cecilie H. von Quillfeldt 《Journal of Coastal Conservation》2011,15(2):257-269
Place-based management is any management action having implications for a specified area. Place-based management is seen as
a key component to practical implementation of ecosystem approach to management, with marine spatial planning (MSP) being
the currently most promoted approach. In the present paper we address the challenges of place-based management at local, regional
and global (oceanic) spatial scales using case studies from the Northeast Atlantic with examples from Norway. Both ecological,
governance and management complexity increases with increasing geographic scale, with associated increases in uncertainty
and thus increasing need for managing under the precautionary approach. A process where (ecologically) valuable and vulnerable
areas are defined early on is essential to successful place-based management under the ecosystem approach. Integrating across
sectors and achieving necessary cooperation between involved institutions and stakeholders is also necessary. 相似文献
373.
374.
Occurrences and potential risks of 16 fragrances in five German sewage treatment plants and their receiving waters 总被引:1,自引:1,他引:0
Ursula Klaschka Peter Carsten von der Ohe Anne Bschorer Sonja Krezmer Manfred Sengl Marion Letzel 《Environmental science and pollution research international》2013,20(4):2456-2471
Fragrances are used in a wide array of everyday products and enter the aquatic environment via wastewater. While several musk compounds have been studied in detail, little is known about the occurrence and fate of other fragrances. We selected 16 fragrance compounds and scrutinized their presence in Bavarian sewage treatment plants (STP) influents and effluents and discussed their ecological risks for the receiving surface waters. Moreover, we followed their concentrations along the path in one STP by corresponding time-related water sampling and derived the respective elimination rates in the purification process. Six fragrance substances (OTNE, HHCB, lilial, acetyl cedrene, menthol, and, in some grab samples, also methyl-dihydrojasmonate) could be detected in the effluents of the investigated sewage treatment plants. The other fragrances under scrutiny were only found in the inflow and were eliminated in the purification process. Only OTNE and HHCB were found in the receiving surface waters of the STP in congruent concentrations, which exceeded the preliminary derived environmental thresholds by a factor of 1.15 and 1.12, respectively, indicating potential risks. OTNE was also detected in similar concentration ranges as HHCB in muscles and livers of fish from surface waters and from ponds that are supplied with purified wastewater. The findings show that some fragrance compounds undergo high elimination rates, whereas others—not only musks—are present in receiving surface water and biota and may present a risk to local aquatic biota. Hence, our results suggest that the fate and potential effects of fragrance compounds in the aquatic environment deserve more attention. 相似文献
375.
Tim Ruploh Hans-Joachim Bischof Nikolaus von Engelhardt 《Behavioral ecology and sociobiology》2013,67(2):175-184
Adolescence is the pivotal transitional phase during which animals become sexually and socially mature and acquire the skills to cope with a variety of environmental challenges on their own. We investigated in a bird species, the zebra finch, how the social environment experienced during this period influences their behaviour in a sexual context. Zebra finches were kept in pairs (male–female or male–male) or larger mixed-sex groups (three males and three females) during adolescence and the long-term consequences were studied on courtship behaviour, aggressiveness and attractiveness in 42 males. To investigate the stability of the observed effects over time, all behavioural tests were repeated approximately 4 months after the initial recordings. Males that grew up with a single female showed the most intense courtship and highest aggressiveness and were most attractive to females, while group-reared males had the lowest courtship and aggressiveness and were the least attractive. The observed differences in courtship and aggressiveness were stable, while the differences in attractiveness disappeared over time. These findings are very similar to earlier studies on guinea pigs, indicating that the observed effects represent a general phenomenon, not restricted to mammals with a similar function and presumably also similar underlying mechanisms. 相似文献
376.
377.
Abstract: In the Neotropics ongoing deforestation is producing open and heavily fragmented landscapes dominated by agriculture, mostly plantations and cattle pastures. After some time agriculture often becomes uneconomical and land is abandoned. Subsequent habitat regeneration may be slow because seed inputs are restricted by a lack of incentives—such as suitable roost sites—for seed dispersers to enter deforested areas. Increasing environmental awareness has fostered growing efforts to promote reforestation. Practical and cost-efficient methods for kick-starting forest regeneration are, however, lacking. We investigated whether artificial bat roosts for frugivorous bat species can attract these key seed dispersers to deforested areas, thereby increasing seed rain. We installed artificial bat roosts in a forest-pasture mosaic in the Costa Rican Atlantic lowlands and monitored bat colonization and seed dispersal. Colonization occurred within a few weeks of installation, and 10 species of bats occupied the artificial roosts. Five species of frugivorous or nectarivorous bats colonized artificial roosts permanently in both primary habitat and in deforested areas, in numbers similar to those found in natural roosts. Seed input around artificial roosts increased significantly. Sixty-nine different seed types, mostly of early-successional plant species, were transported by bats to artificial roosts in disturbed habitats. The installation of artificial bat roosts thus successfully attracted frugivorous bats and increased seed inputs into degraded sites. This method is likely to speed up early-vegetation succession, which in turn will attract additional seed dispersers, such as birds, and provide a microhabitat for seeds of mid- and late-successional plants. As well as supporting natural forest regeneration and bat conservation, this cost-efficient method can also increase environmental awareness among landowners. 相似文献
378.
Storm surges: perspectives and options 总被引:4,自引:1,他引:3
This review paper attempts to summarize the scattered and fragmented knowledge about past and possible future changing storm-surge
statistics using the particularly well-studied case of the North Sea as an example. For this region, a complete and robust
analysis methodology has been developed in recent years. This methodology is based on dynamical and statistical models. Using
the concept of dynamical downscaling, development during recent decades, when sufficiently good and homogeneous weather data
exist, has been “reconstructed,” and scenarios of possible future change are described. “Localization” allows estimation of
changes at specific sites, e.g., harbors. As local water-level statistics depend not only on climate variations but also on
local modifications of the local bathymetry, new options for adaptation emerge. For the case of Hamburg, an option for such
future adaptations is discussed. 相似文献
379.