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201.
Robert I. McDonald 《The Environmentalist》2006,26(4):221-225
Environmental scientists are continually discovering new and emerging environmental problems. There have been many studies
of how a particular environmental problem has occurred, its costs to society, and its (potential) resolution. However, to
date there have been few studies of the rate at which new environmental problems are generated by human technological innovations.
In this note, I present a conceptual framework that will help quantify how many now-unknown problems we may expect to occur
in a given sector. Two brief case studies illustrate the difficulty of finding appropriate dataset for fitting the full model,
however. Policy implications of the conceptual framework are discussed, with different kinds of economic sectors requiring
different approaches. 相似文献
202.
203.
204.
Assessing the carbon balance of circumpolar Arctic tundra using remote sensing and process modeling. 总被引:1,自引:0,他引:1
Stephen Sitch A David McGuire John Kimball Nicola Gedney John Gamon Ryan Engstrom Annett Wolf Qianlai Zhuang Joy Clein Kyle C McDonald 《Ecological applications》2007,17(1):213-234
This paper reviews the current status of using remote sensing and process-based modeling approaches to assess the contemporary and future circumpolar carbon balance of Arctic tundra, including the exchange of both carbon dioxide and methane with the atmosphere. Analyses based on remote sensing approaches that use a 20-year data record of satellite data indicate that tundra is greening in the Arctic, suggesting an increase in photosynthetic activity and net primary production. Modeling studies generally simulate a small net carbon sink for the distribution of Arctic tundra, a result that is within the uncertainty range of field-based estimates of net carbon exchange. Applications of process-based approaches for scenarios of future climate change generally indicate net carbon sequestration in Arctic tundra as enhanced vegetation production exceeds simulated increases in decomposition. However, methane emissions are likely to increase dramatically, in response to rising soil temperatures, over the next century. Key uncertainties in the response of Arctic ecosystems to climate change include uncertainties in future fire regimes and uncertainties relating to changes in the soil environment. These include the response of soil decomposition and respiration to warming and deepening of the soil active layer, uncertainties in precipitation and potential soil drying, and distribution of wetlands. While there are numerous uncertainties in the projections of process-based models, they generally indicate that Arctic tundra will be a small sink for carbon over the next century and that methane emissions will increase considerably, which implies that exchange of greenhouse gases between the atmosphere and Arctic tundra ecosystems is likely to contribute to climate warming. 相似文献
205.
The musselsMytilus galloprovincialis andM. trossulus on the Pacific coast of North America 总被引:2,自引:0,他引:2
Most recent authors have called the bay mussels of the Pacific coast of North AmericaMytilus edulis Linnaeus, 1758. Thirteen samples ofedulis-like mussels were collected from California, Oregon, and Alaska, USA, in 1985, 1986 and 1987. Electrophoretic evidence from wight loci indicates that these samples consist of two genetically distinct groups, neither of which is similar toM. edulis from the Atlantic Ocean. Mussels in southern California are very similar toM. galloprovincialis Lamarck, 1819 from the Mediterranean Sea; it is probable thatM. galloprovincialis was introduced accidentally to southern California. Mussels in Oregon and Alaska are similar to those from the Baltic Sea and parts of eastern Canada; the nameM. trossulus Gould, 1850 has priority for this taxon. In central and nothern California,M. galloprovincialis, M. trossulus and their hybrids co-occur. Despite the presence of hybrids betweenM. galloprovincialis andM. trossulus, the genetic integrity which they maintain across large areas of the world warrants their recognition as two distinct species. 相似文献
206.
Paul G. McDonald Anahita J. N. Kazem Jonathan Wright 《Behavioral ecology and sociobiology》2007,61(10):1623-1635
‘False feeding,’ where helpers arrive at nests with food but fail to provision the young, has been reported in several cooperative
species. This and other potentially ‘deceptive’ behavior has been interpreted as indicating that helping may operate as a
signal within such social groups. We critically examine these phenomena in the provisioning behavior of the bell miner Manorina melanophrys. Excessively close observation distances can artificially elevate the rate of false feeding in this (and other) species,
but once this had been accounted for, there was little evidence for any ‘deceptive’ behavior by helpers or breeders. Natural
and experimentally induced variation in the presence of a potential conspecific audience at the nest did not have any consistent
influence upon the rate of false feeds, which was low at 7.94% of 6,880 nest visits. Instead, encountering unexpectedly low
levels of brood demand provided a more parsimonious explanation for those visits where helpers failed to feed nestlings or
ate the food themselves. Failure to completely transfer a load to nestlings was more likely when the load contained a high
proportion of sticky lerp, indicating a simple prey-transfer problem. Finally, individuals that arrived at nests without prey
were often members of neighboring breeding pairs, suggesting that these few non-feeding visits may instead involve an information-gathering
function. We, therefore, suggest that future studies explicitly exclude the possibility of observer disturbance and all aspects of normal provisioning behavior before applying the terms ‘false feeding’ or ‘deceptive’ and inferring anything more
than straightforward helping at the nest. 相似文献
207.
Growth trajectories of morphological characters may change during ontogeny, but this change is often overlooked or, at best, is estimated visually. An objective method was developed for determining discontinuities in morphological measurements of three species of oceanic squids: Chtenopteryx sicula (Vérany, 1851), Mastigoteuthis magna Joubin, 1913, and Brachioteuthis sp. 3. The specimens were collected on the Amsterdam Mid North Atlantic Plankton Expeditions (1980-1983) along a transect from 55°N to 25°N along 30°W. Discontinuities were quantified via an iterative, model II, piecewise linear regression (PLR) analysis, whereby the regression model incorporated a fixed breakpoint that was increased in each iteration across the range of dorsal mantle lengths (DMLs). The iteration with the lowest LOSS value was selected as the best estimate of the breakpoint. In C. sicula, 7 of 10 measured characters had a single breakpoint, and 5 of these occurred at 7-9 mm DML. In M. magna, only 4 of 12 characters had breakpoints, 3 of which occurred at 4-7 mm DML. More, larger specimens would likely yield additional breakpoints. In Brachioteuthis sp. 3, 12 of 14 characters had discernable breakpoints; 3 characters had 2 breakpoints. Most breakpoints occurred at 11-12 mm DML, and all were found at larger sizes than in the other species. This clustering of breakpoints into discrete size ranges may be considered an allomorphosis, and this rapid morphological change may correlate with rapid ecological change. 相似文献
208.
Using Montane Mammals to Model Extinctions Due to Global Change 总被引:2,自引:0,他引:2
We use data on the species-area relationship and the nested subset structure of the boreal mammal faunas inhabiting isolated mountaintops in the Great Basin to develop a simple quantitative model that predicts the number and identity of species that would go extinct under an assumed scenario of changing climate and vegetation. Global warming of 3°C is predicted to cause the loss of 9–62% of the species inhabiting each mountain range and the extinction of three of fourteen species throughout the region. These results suggest (1) that it is possible to make highly plausible predictions about the susceptibility of species to extinction without detailed information about their population biology, and (2) that global and regional environmental changes seriously threaten the survival of species that are restricted in distribution to both natural "habitat islands" and biological reserves. 相似文献
209.
Satellite Remote Sensing of Terrestrial Net Primary Production for the Pan-Arctic Basin and Alaska 总被引:2,自引:0,他引:2
J. S. Kimball M. Zhao K. C. McDonald S. W. Running 《Mitigation and Adaptation Strategies for Global Change》2006,11(4):783-804
We applied a terrestrial net primary production (NPP) model driven by satellite remote sensing observations of vegetation
properties and daily surface meteorology from a regional weather forecast model to assess NPP spatial and temporal variability
for the pan-Arctic basin and Alaska from 1982 to 2000. Our results show a general decadal trend of increasing NPP for the
region of approximately 2.7%, with respective higher (3.4%) and lower (2.2%) rates for North America and Eurasia. NPP is both
spatially and temporally dynamic for the region, driven largely by differences in productivity rates among major biomes and
temporal changes in photosynthetic canopy structure and spring and summer air temperatures. Mean annual NPP for boreal forests
was approximately 3 times greater than for Arctic tundra on a unit area basis and accounted for approximately 55% of total
annual carbon sequestration for the region. The timing of growing season onset inferred from regional network measurements
of atmospheric CO2 drawdown in spring was inversely proportional to annual NPP calculations. Our findings indicate that recent regional warming
trends in spring and summer and associated advances in the growing season are stimulating net photosynthesis and annual carbon
sequestration by vegetation at high latitudes, partially mitigating anthropogenic increases in atmospheric CO2. These results also imply that regional sequestration and storage of atmospheric CO2 is being altered, with potentially greater instability and acceleration of the carbon cycle at high latitudes. 相似文献
210.
Deer hunter satisfaction is investigated from two perspectives, (1) satisfaction with the hunt/harvest and (2) satisfaction with the overall hunting trip experience. Regression analysis is used to determine what variables best predict satisfaction with the hunt and the hunting experience. Results indicate that animal population variables (number of deer seen, shot at, bagged) are the best determinants of a quality deer hunt, while environmental (outdoors) and social (crowding and hunter behavior) are the best predictors of a quality hunting trip experience. Wildlife managers and researchers need to realize that deer hunters view the hunt/harvest as different from the hunting trip experience and need to manage for both aspects of hunter satisfaction. 相似文献