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31.
Across the globe, groups are experimenting with initiatives to create alternatives to the dominant food system. What role might research play in helping to strengthen and multiply these initiatives? In this paper we discuss two research projects in Australia and the Philippines in which we have cultivated hybrid collectives of academic researchers, lay researchers and various non-human others with the intention of enacting community food economies. We feature three critical interactions in the “hybrid collective research method”: gathering, which brings together those who share concerns about community food economies; reassembling, in which material gathered is deliberatively rebundled to amplify particular insights; and translating, by which reassembled ideas are taken up by other collectives so they may continue to “do work”. We argue that in a climate-changing world, the hybrid collective research method fosters opportunities for a range of human and non-human participants to act in concert to build community food economies. 相似文献
32.
Kirk R. Vincent Jonathan M. Friedman Eleanor R. Griffin 《Environmental management》2009,44(2):218-227
Removal of nonnative riparian trees is accelerating to conserve water and improve habitat for native species. Widespread control
of dominant species, however, can lead to unintended erosion. Helicopter herbicide application in 2003 along a 12-km reach
of the Rio Puerco, New Mexico, eliminated the target invasive species saltcedar (Tamarix spp.), which dominated the floodplain, as well as the native species sandbar willow (Salix exigua Nuttall), which occurred as a fringe along the channel. Herbicide application initiated a natural experiment testing the
importance of riparian vegetation for bank stability along this data-rich river. A flood three years later eroded about 680,000 m3 of sediment, increasing mean channel width of the sprayed reach by 84%. Erosion upstream and downstream from the sprayed
reach during this flood was inconsequential. Sand eroded from channel banks was transported an average of 5 km downstream
and deposited on the floodplain and channel bed. Although vegetation was killed across the floodplain in the sprayed reach,
erosion was almost entirely confined to the channel banks. The absence of dense, flexible woody stems on the banks reduced
drag on the flow, leading to high shear stress at the toe of the banks, fluvial erosion, bank undercutting, and mass failure.
The potential for increased erosion must be included in consideration of phreatophyte control projects. 相似文献
33.
Using the reproductive capacity of fish appears to be a suitable approach for risk assessment in the aquatic environment since fish are a typical representative thereof and in addition they are of considerable societal value. Generally the early embryonic stages are considered to be one of the most sensitive parts of a fish's life cycle. A method has been developed to use the state of health of live, naturally spawned fish embryos from plankton samples for biological effects monitoring. During the years 1985–1987 in the southern North Sea and in 1991–1992 in the whole of the North Sea fish eggs were sampled from surface waters and examined for developmental abnormalities. Elevated embryo malformation rates were detected in the plume of the major rivers Elbe and Rhine as well as along the eastern coast of England. Occurring malformations are thought to be pollution-related and may be used to define areas of environmental deterioration. The method is discussed in view of its suitability for biological effects monitoring using malformations in fish embryos as biomarkers. 相似文献
34.
A fabric filter has been on-line for one year on a coal-fired boiler that is primarily a peaking unit within the power schedule. For the first six months, Eastern Kentucky coal with 2.5% sulfur was the fuel source for 30% of the time, with low-sulfur Montana coal constituting the remaining fuel during the operation period. Bag life has been excellent with no bag failures reported to date, and the pressure drops have been low. There has never been an auxilliary heat source to preheat the fabric filter for start-up, nor to reheat the fabric filter when operating at reduced load with associated low back-end temperatures. Conclusions are that the filter cake formed does protect the bags from blinding at low load conditions, and a special acid-resistant finish applied to the glass fibers protects the bags when high-sulfur coal is burned at low temperatures. Overall, this installation provides an excellent data base for cycling service and high-sulfur coal usage with a fabric filter. 相似文献
35.
Kirk Hamilton 《Environment, Development and Sustainability》2003,5(3-4):419-436
Genuine saving measures the real change in0 total wealth, factoring in the depreciation of produced assets, depletion of natural resources, pollution damages, and expenditures on education. This paper presents a theoretical framework for measuring changes in wealth in total and per capita terms, establishes the link between savings measures and prospects for social welfare, and provides summary empirical estimates of the savings measures. China excepted, the majority of countries below median income are distinguished by apparent declines in total wealth per capita. 相似文献
36.
Anderson KE Gadau J Mott BM Johnson RA Altamirano A Strehl C Fewell JH 《Ecology》2006,87(9):2171-2184
We examined the distribution and ancestral relationships of genetic caste determination (GCD) in 46 populations of the seed-harvester ants Pogonomyrmex barbatus and P. rugosus across the east-to-west range of their distributions. Using a mtDNA sequence and two nuclear markers diagnostic for GCD, we distinguished three classes of population phenotypes: those with GCD, no evidence of GCD, and mixed (both GCD and non-GCD colonies present). The GCD phenotype was geographically widespread across the range of both morphospecies, occurring in 20 of 46 sampled populations. Molecular data suggest three reproductively isolated and cryptic lineages within each morphospecies, and no present hybridization. Mapping the GCD phenotype onto a mtDNA phylogeny indicates that GCD in P. rugosus was acquired from P. barbatus, suggesting that interspecific hybridization may not be the causal agent of GCD, but may simply provide an avenue for GCD to spread from one species (or subspecies) to another. We hypothesize that the origin of GCD involved a genetic mutation with a major effect on caste determination. This mutation generates genetic conflict and results in the partitioning and maintenance of distinct allele (or gene set) combinations that confer differences in developmental caste fate. The outcome is two dependent lineages within each population; inter-lineage matings produce workers, while intra-lineage matings produce reproductives. Both lineages are needed to produce a caste-functional colony, resulting in two reproductively isolated yet interdependent lineages. Pogonomyrmex populations composed of dependent lineages provide a unique opportunity to investigate genetic variation underlying phenotypic plasticity and its impact on the evolution of social structure. 相似文献
37.
The distribution, solid-phase speciation, and desorption/dissolution of As in waste iron-based drinking water treatment residuals 总被引:1,自引:0,他引:1
Arsenic concentrations and solid-phase speciation were assessed as a function of depth through Fe-media beds for two commercially available products (Granular Ferric Hydroxide-GFH and Bayoxide E33-E33) from pilot-scale water treatment field tests. These results were compared with data from solution (de-ionized water-DI-H2O) concentrations of As equilibrated with Fe-media in an anoxic environment at 4 degrees C. The materials had a high capacity for As (GFH media 9620 mg kg(-1) As, E33 Media 5246 mg kg(-1)). Arsenic concentrations decreased with bed depth. For E33, X-ray absorption near-edge spectroscopy results showed that As(V) was the dominant solid-phase species. For GFH, As(III) was detected and the proportion (relative to As(V)) of As(III) increased with bed depth. Arsenic concentrations in DI-H2O equilibrated with the media were low (35 microg l(-1)) over a period of 50 d. Arsenic concentrations in the equilibrated solutions also decreased with depth. Results from tests on soluble As speciation show that As in solution is in the form of As(V). Kinetic desorption experiments carried out at different pH values (3, 5, 7, 8, and 9) show that the media exhibit some acid/base neutralization capacity and tend to bind As sufficiently. Concentrations of As in the pH desorption experiments were in the same order of magnitude as the toxicity characteristic leaching procedure extractions (tens of microgl(-1)) except at low pH values. For the GFH media tested at a pH of three, As increases in solution and is mainly associated with colloidal (operationally defined as between 0.1 and 1.0 microm) iron. 相似文献
38.
Environmental Management - Monitoring long-term changes in aquatic biodiversity requires the effective use of historical data that were collected with different methods and varying levels of... 相似文献
39.
A simple energy-balance model, relating energetic requirements of fish schools to food production, was used to predict shoal sizes. Lower limits to school size are unlikely to be set by food but rather by predation. Upper limits depend on both food and school behavior, being greater for schools that break up to feed than for schools that remain continuously cohesive. Faced with a decreasing food supply, a school could either break into smaller schools or change behavior, increasing the area available for foraging. The models suggest that environmental productivity needs to be considered when examining fishery statistics such as
(catch per unit effort), where maximum catch may be limited by maximum school size. 相似文献
40.
A swarm of honeybees provides a striking example of an animal group performing a synchronized departure for a new location;
in this case, thousands of bees taking off at once to fly to a new home. However, the means by which this is achieved remain
unclear. Shortly before takeoff, one hears a crescendo of a high-pitched mechanical signal—worker piping—so we explored the
role of this signal in coordinating a swarm’s mass takeoff. Specifically, we examined whether exclusively nest site scouts
produce the worker piping signal or whether it is produced in a relay or chain reaction fashion. We found no evidence that
bees other than the scouts that have visited the swarm’s chosen nest site produce piping signals. This absence of relay communication
in piping suggests that it is a signal that only primes swarms for takeoff and that the release of takeoff is triggered by
some other signal or cue; perhaps the takeoff of bees on the swarm periphery as they reach flight temperature in response
to piping. 相似文献