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221.
Vulnerability to climate variability and change in East Timor 总被引:2,自引:0,他引:2
This paper presents the results of a preliminary study of climate vulnerability in East Timor. It shows the results of projections of climate change in East Timor. The country's climate may become hotter, drier, and increasingly variable. Sea levels are likely to rise. The paper then considers the implications of these changes on three natural resources--water, soils, and the coastal zone--and finds all to be sensitive to changes in climate and sea level. Changes in the abundance and distribution of these resources is likely to cause a reduction in agricultural production and food security, and sea-level rise is likely to damage coastal areas, including Dili, the capital city. 相似文献
222.
Hatim O. Sharif Almoutaz A. Hassan Sazzad Bin-Shafique Hongjie Xie Jon Zeitler 《Journal of the American Water Resources Association》2010,46(5):881-891
Sharif, Hatim O., Almoutaz A. Hassan, Sazzad Bin-Shafique, Hongjie Xie, and Jon Zeitler, 2010. Hydrologic Modeling of an Extreme Flood in the Guadalupe River in Texas. Journal of the American Water Resources Association (JAWRA) 1-11. DOI: 10.1111/j.1752-1688.2010.00459.x Abstract: Many of the storms creating the greatest rainfall depths in Texas, measured over durations ranging from one minute to 48 hours, have occurred in the Texas Hill Country area. The upstream portion of the Guadalupe River Basin, located in the Texas Hill Country, is susceptible to flooding and rapid runoff due to thin soils, exposed bedrock, and sparse vegetation, in addition to the Balcones Escarpment uplift contributing to precipitation enhancement. In November 2004, a moist air mass from the Gulf of Mexico combined with moist air from the Pacific Ocean resulted in the wettest November in Texas since 1895. Although the peak discharges were not the highest on record, the U.S. Geological Survey (USGS) stream gauge on the Guadalupe River at Gonzales, Texas reported a daily mean discharge of 2,304 m3/s on November 23, 2004 (average discharge is 53 m3/s). In this paper, we examine the meteorological conditions that led to this event and apply a two-dimensional, physically based, distributed-parameter hydrologic model to simulate the response of a portion of the basin during this event. The study results clearly demonstrate the ability of physically based, distributed-parameter simulations, driven by operational radar rainfall products, to adequately model the cumulative effect of two rainfall events and route inflows from three upstream watersheds without the need for significant calibration. 相似文献
223.
This paper examines potential effects of predicted climate changes on the forage conditions during both summer and winter for semidomesticated reindeer in Sweden. Positive effects in summer ranges include higher plant productivity and a longer growing season, while negative effects include increased insect harassment. Forage quality may change in both positive and negative ways. An increase in shrubs and trees in alpine heaths is also likely. A warmer climate means shorter winters, which will have positive effects for the survival of reindeer. However, warmer and wetter weather may also result in increased probabilities of ice-crust formations, which strongly decrease forage availability. A warmer climate with higher forest productivity will also likely reduce lichen availability through competitive interactions. Adaptations to these changes will include maintaining a choice of grazing sites in both summer and winter. However, this capacity may already be severely limited because of other forms of land use. 相似文献
224.
Simone L. Stevenson Skipton N. C. Woolley Jon Barnett Piers Dunstan 《Conservation biology》2020,34(3):622-631
Marine protected areas (MPAs) are the preferred tool for preventing marine biodiversity loss, as reflected in international protected area targets. Although the area covered by MPAs is expanding, there is a concern that opposition from resource users is driving them into already low-use locations, whereas high-pressure areas remain unprotected, which has serious implications for biodiversity conservation. We tested the spatial relationships between different human-induced pressures on marine biodiversity and global MPAs. We used global, modeled pressure data and the World Database on Protected Areas to calculate the levels of 15 different human-induced pressures inside and outside the world's MPAs. We fitted binomial generalized linear models to the data to determine whether each pressure had a positive or negative effect on the likelihood of an area being protected and whether this effect changed with different categories of protection. Pelagic and artisanal fishing, shipping, and introductions of invasive species by ships had a negative relationship with protection, and this relationship persisted under even the least restrictive categories of protection (e.g., protected areas classified as category VI under the International Union for Conservation of Nature, a category that permits sustainable use). In contrast, pressures from dispersed, diffusive sources (e.g., pollution and ocean acidification) had positive relationships with protection. Our results showed that MPAs are systematically established in areas where there is low political opposition, limiting the capacity of existing MPAs to manage key drivers of biodiversity loss. We suggest that conservation efforts focus on biodiversity outcomes and effective reduction of pressures rather than prescribing area-based targets, and that alternative approaches to conservation are needed in areas where protection is not feasible. 相似文献
225.
Design principles and common pool resource management: an institutional approach to evaluating community management in semi-arid Tanzania 总被引:1,自引:0,他引:1
This paper analyses the role of institutions in the management of common pool resources (CPRs) in semi-arid Tanzania. Common property regimes have often been considered inadequate for the management of CPRs because of the problems of excludability, but they are becoming more widely supported as the way forward to overcome the problems of resource use and degradation in developing countries. A series of design principles for long enduring common property institutions have been proposed by Ostrom, but there is concern that they are not applicable to a wide range of real life situations or that they may be specific to certain types of CPR. Here, we compare these principles to the situation prevailing in 12 villages in six districts in semi-arid Tanzania. Data on management institutions were collected through semi-structured interviews and meetings at district and village level. The combined information was used to make a qualitative assessment of the strength with which each design principle appeared to operate in the management of forest, pasture and water resources. Boundaries, conflict and negotiation in CPR management are of key importance in semi-arid regions. However, the need for flexibility in order to deal with ecological uncertainty means that many management institutions would be considered weak or absent according to the design principle approach. This supports the view that the design principles should not be used as a 'blueprint to be imposed on resource management regimes' rather that they provide a framework for investigating common property regimes with the proviso that, certainly for semi-arid regions, they may highlight where management cannot be explained by institutional theory alone. 相似文献
226.
Rastall AC Getting D Goddard J Roberts DR Erdinger L 《Environmental science and pollution research international》2006,13(4):256-267
Goal, Scope and Background
Some anthropogenic pollutants posses the capacity to disrupt endogenous control of developmental and reproductive processes
in aquatic biota by activating estrogen receptors. Many anthropogenic estrogen receptor agonists (ERAs) are hydrophobic and
will therefore readily partition into the abiotic organic carbon phases present in natural waters. This partitioning process
effectively reduces the proportion of ERAs readily available for bioconcentration by aquatic biota. Results from some studies
have suggested that for many aquatic species, bioconcentration of the freely-dissolved fraction may be the principal route
of uptake for hydrophobic pollutants with logarithm n-octanol/water partition coefficient (log Kow) values less than approximately
6.0, which includes the majority of known anthropogenic ERAs. The detection and identification of freely-dissolved readily
bioconcentratable ERAs is therefore an important aspect of exposure and risk assessment. However, most studies use conventional
techniques to sample total ERA concentrations and in doing so frequently fail to account for bioconcentration of the freely-dissolved
fraction. The aim of the current study was to couple the biomimetic sampling properties of semipermeable membrane devices
(SPMDs) to a bioassay-directed chemical analysis (BDCA) scheme for the detection and identification of readily bioconcentratable
ERAs in surface waters.
Methods
SPMDs were constructed and deployed at a number of sites in Germany and the UK. Following the dialytic recovery of target
compounds and size exclusion chromatographic clean-up, SPMD samples were fractionated using a reverse-phase HPLC method calibrated
to provide an estimation of target analyte log Kow. A portion of each HPLC fraction was then subjected to the yeast estrogen
screen (YES) to determine estrogenic potential. Results were plotted in the form of 'estrograms' which displayed profiles
of estrogenic potential as a function of HPLC retention time (i.e. hydrophobicity) for each of the samples. Where significant
activity was elicited in the YES, the remaining portion of the respective active fraction was subjected to GC-MS analysis
in an attempt to identify the ERAs present.
Results and Discussion
Estrograms from each of the field samples showed that readily bioconcentratable ERAs were present at each of the sampling
sites. Estimated log Kow values for the various active fractions ranged from 1.92 to 8.63. For some samples, estrogenic potential
was associated with a relatively narrow range of log Kow values whilst in others estrogenic potential was more widely distributed
across the respective estrograms. ERAs identified in active fractions included some benzophenones, various nonylphenol isomers,
benzyl butyl phthalate, dehydroabietic acid, sitosterol, 3-(4-methylbenzylidine)camphor (4-MBC) and 6-acetyl-1,1,2,4,4,7-hexamethyltetralin
(AHTN). Other tentatively identified compounds which may have contributed to the observed YES activity included various polycyclic
aromatic hydrocarbons (PAHs) and their alkylated derivatives, methylated benzylphenols, various alkylphenols and dialkylphenols.
However, potential ERAs present in some active fractions remain unidentified.
Conclusions and Outlook
Our results show that SPMD-YES-based BDCA can be used to detect and identify readily bioconcentratable ERAs in surface waters.
As such, this biomimetic approach can be employed as an alternative to conventional methodologies to provide investigators
with a more environmentally relevant insight into the distribution and identity of ERAs in surface waters. The use of alternative
bioassays also has the potential to expand SPMD-based BDCA to include a wide range of toxicological endpoints. Improvements
to the analytical methodology used to identify ERAs or other target compounds in active fractions in the current study could
greatly enhance the applicability of the methodology to risk assessment and monitoring programmes. 相似文献
227.
Polybrominated diphenyl ethers (PBDEs) have become widely distributed as environmental contaminants due to their wide-spread use as flame retardants. Their structural similarity to other halogenated organic pollutants, for example polychlorinated biphenyls (PCBs), has led to speculation that they may have similar toxicological properties and effects. Recent focus on PBDEs as possible priority pollutants has also led to an increasing need for reference standards of PBDEs for toxicological studies and for environmental analysis. In this work we synthesized a series of fluorinated PBDEs (F-PBDEs) which can be used as possible internal standards, as an alternative to high-cost alternatives, such as the (13)C-labelled analogues. F-PBDEs have been synthesized by using different coupling reactions and by bromination of fluorinated starting materials. 相似文献
228.
229.
Brian S. Helms Jon E. Schoonover Jack W. Feminella 《Journal of the American Water Resources Association》2009,45(1):157-169
Abstract: We evaluated the impact of land cover on fish assemblages by examining relationships between stream hydrology, physicochemistry, and instream habitat and their association with fish responses in streams draining 18 watersheds of the Lower Piedmont of western Georgia. Several important relationships between land use and physicochemical, hydrological, and habitat parameters were observed, particularly higher frequency of spate flows, water temperatures, and lower dissolved oxygen (DO) with percentage impervious surface (IS) cover, higher habitat quality with percentage forest cover, and elevated suspended solid concentrations with percentage pasture cover. Fish assemblages were largely explained by physicochemical and hydrological rather than habitat variables. Specifically, fish species diversity, richness, and biotic integrity were lower in streams that received high frequency of spate flows. Also, overall fish assemblage structure as determined by nonmetric multidimensional scaling was best described by total dissolved solids (TDS) and DO, with high TDS and low DO streams containing sunfish‐based assemblages and low TDS and high DO streams containing minnow‐based assemblages. Our results suggest that altered hydrological and physicochemical conditions, induced largely by IS, may be a strong determinant of fish assemblage structure in these lowland streams and allow for a more mechanistic understanding of how land use ultimately affects these systems. 相似文献
230.
Protandry in western cicada killer wasps, (Sphecius grandis,Hymenoptera: Sphecidae): an empirical study of emergence time and mating opportunity 总被引:2,自引:0,他引:2
Summary
Sphecius grandis is a univoltine, colonial wasp. Females mate once and are sexually receptive when they emerge in July and early August. Males generally emerge earlier in the summer than females. The opportunity for each male to acquire mates is a function of the number of females emerging during his lifetime and the number of competitiors that are active when the females emerge. I determined a mating opportunity index (MOI) for each male in an aggregation of wasps for three separate summers, and correlated the MOI of individual males with their emergence date. The MOI of a male estimates the potential contribution that timing of emergence makes to his reproductive success. In 1984 males emerging near the mean of the male emergence distribution had the highest MOI. These males emerged between one and two weeks prior to the mean female emergence date. However, in 1981 late emerging males had the highest MOI. In 1983 there was no significant difference in MOI among males. As a result of between-year variation in female emergence schedules and in the duration of male lifetime, the selection pressures influencing male emergence time vary between years. 相似文献