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1.
Coarse-resolution thematic maps derived from remotely sensed data and implemented in GIS play an important role in coastal and marine conservation, research and management. Here, we describe an approach for fine-resolution mapping of land-cover types using aerial photography and ancillary GIS and ground data in a large (100 × 35 km) subtropical estuarine system (Moreton Bay, Queensland, Australia). We have developed and implemented a classification scheme representing 24 coastal (subtidal, intertidal, mangrove, supratidal and terrestrial) cover types relevant to the ecology of estuarine animals, nekton and shorebirds. The accuracy of classifications of the intertidal and subtidal cover types, as indicated by the agreement between the mapped (predicted) and reference (ground) data, was 77-88%, depending on the zone and level of generalization required. The variability and spatial distribution of habitat mosaics (landscape types) across the mapped environment were assessed using K-means clustering and validated with Classification and Regression Tree models. Seven broad landscape types could be distinguished and ways of incorporating the information on landscape composition into site-specific conservation and field research are discussed. This research illustrates the importance and potential applications of fine-resolution mapping for conservation and management of estuarine habitats and their terrestrial and aquatic wildlife.  相似文献   

2.
The numbers and pattern of distribution of dark-bellied brent geese Branta b. bernicla feeding inland around Chichester and Pagham Harbours, West Sussex in winter 1979/80 are described.A maximum of 11,000 birds fed inland. Taking the winter as a whole, 70% fed within 200 m of the coast. 68% of inland-feeding birds occurred on grass. This was partly influenced by deliberate scaring of the geese from cereals. 14% of the available area of grass around Chichester was used by geese but only 6% was heavily grazed. Of the area of cereals, 13% was used with 4% heavily grazed.Unless disturbed, the brent geese usually remained inland for most of the day, regardless of the state of the tide, returning to roost overnight on intertidal areas. The more uniformly distributed food supply in fields enabled the geese to feed in larger, more compact flocks than they could do on the estuary.The provision of grassland refuges is suggested as a means of alleviating conflict with agriculture. For Chichester Harbour up to five refuge areas may be required where the geese can feed undisturbed. Each refuge should not only provide the food requirements of the geese but be large enough to provide a buffer against human disturbance on surrounding land. The total refuge area should probably be not less than about 400 ha, on which many of the normal farming practices can continue. Refuges should be situated adjacent to the coast and the grass sward needs to be closely grazed by livestock or mown in the summer to provide a suitable short sward for the wintering geese.  相似文献   

3.
Expanding populations of geese feeding on farmland during winter and spring conflict with agricultural interests along their migratory flyway in north-western Europe. In Mid-Norway, farmers scare spring-staging pink-footed geese Anser brachyrhynchus off their land to protect crops, and this has had clear effects on goose distribution. To protect the geese, Norwegian authorities have implemented economic compensation to farmers to discourage scaring, but this has not been prioritised to accommodate the biological requirements and dispersal patterns of the geese, though such an approach is clearly needed. To address this need, we assessed the negative effects of scaring geese during 2004-2007, and built a species distribution model to identify sites suitable for goose foraging. We subsequently combined known foraging sites with sites identified by our model and prioritised these sites according to their connectivity, perimeter area ratio, years of historic use and proximity to roost. By combining historic data on foraging sites, a species distribution model, and a simple, accountable site selection process we demonstrate how the current compensation scheme can be made 10 times more efficient through strategic prioritisation. Our approach has direct implications for alleviating similar goose-agriculture conflicts throughout Europe.  相似文献   

4.
I investigated the effect of CO2-enrichment on productivity of two aquatic plant species [Zostera marina L., Nereocystis luetkeana (Mert.) P. & R.] that form significant components of coastal ecosystems in the Pacific Northwest. Short-term (i.e., 2-hr) experiments showed that doubling CO2 resulted in up to a 2.5-fold increase in Zostera net apparent productivity (NAP). Nereocystis NAP was increased 2.2 – 2.8 fold. In experiments involving seven enrichment treatments, NAP increased with increasing CO2 between ambient (1.0×) and 2.5× CO2 in both Zostera and Nereocystis. Nereocystis and Zostera NAP was lowest at highest (i.e., 5×) CO2 concentrations. In growth experiments, mean growth rate of Zostera increased with increasing CO2 during one of the two trials. I conclude that increasing CO2 in the surface waters of the coastal ocean would predictably result in increased NAP of these two species. These results supplement limited published data showing that shallow estuarine and marine systems are vulnerable to increased carbon dioxide.  相似文献   

5.
We analysed population trends of 24 wildfowl species in Mexico. Wildfowl numbers peaked during the early 1980s; lowest counts were recorded in 1997. Total wildfowl numbers (all species combined) and duck numbers (duck species combined) showed significant short-term (1981-2000) declines, while geese (goose species combined) showed a significant long-term (1961-2000) increase. Six wildfowl species suffered significant long-term declines, while four showed increases. During 1981-2000, 11 species declined, but none had significant increases. Redhead (Aythya americana), Mexican duck (Anas diazi), northern pintail (A. acuta) and black brant (Branta bernicla nigricans) should be given high conservation priority because of the high proportions of their North American populations in Mexico. Declining numbers of the later two species should trigger further investigation into the possibility of assigning them legal protection status. Other species with apparent declines in numbers should also be more closely monitored. For setting hunting limits in the country, the population status of each species should be accounted for, as well as the condition of breeding populations the previous spring. Other species with poor data or combined counts should be targeted for basic population studies. We suggest that the mid-winter counts be expanded to cover non-surveyed areas and conducted every year to more precisely detect wildfowl population change. Integrated to a site-selection analysis, the information presented here can provide the basis for a wildfowl conservation strategy in Mexico.  相似文献   

6.
This paper applies the cost-benefit analysis framework to the issue of wild geese conservation in Scotland. Wild goose numbers have risen rapidly over the past 30 years, bringing nature conservationists into conflict with farmers whose crops are damaged. We estimate the costs of damage due to goose grazing to farmers in two goose areas, Strathbeg and Islay. Conservation benefits are estimated using a contingent valuation survey of the Scottish population, and we find that benefits outweigh costs by a very considerable margin. This can be seen as providing support for recent UK government moves to compensate farmers in goose areas in order to further conservation.  相似文献   

7.
The former and present distribution of white clawed crayfish (Austropotamobius pallipes) in the province of Granada (southern Spain) is studied. Before 1980 it was widely distributed but at present only 16 populations exist. The decline is related to the presence of the freshwater red-swamp crayfish (Procambarus clarkii), an American species, vector of the aphanomycosis disease, introduced to the Iberian Peninsula in 1974 and now widely distributed in the watercourses and marshes of southern Spain. To establish an appropriate conservation policy for A. pallipes at its southernmost distribution limit, we studied watercourses from two river basins, Genil and Guadiana Menor, (tributaries of the Guadalquivir River). P. clarkii inhabits the medium to lower reaches of these two river basins (with its upper limit at 820 m a.s.l.). The distribution of this species was best explained by the effect of three of the 12 analyzed variables: altitude, water-current and minimum winter temperatures. From our results, the repopulation of the native crayfish is almost impossible in those reaches inhabited by P. clarkii. However, based on the habitat selection study, it is clear that upper reaches are unsuitable for the red-swamp crayfish, where the native white-clawed crayfish may have greater survival possibilities, and these sites can be used for future restocking projects.  相似文献   

8.
This paper is the sequel to an earlier publication (see Biological Conservation, Vol. 5, No. 4 pp. 243–250, October 1973) on the conservation status of deer and describes an IUCN programme for the conservation of world-threatened deer. Research requirements for conservation of deer that are currently threatened with extinction are discussed. The immediate conservation objective is to ensure the species' or subspecies' survival, and the long-term objective is to restore their productive status in the wild. A framework for research to provide data to guide conservation practices is outlined. It comprises a set of research questions, to aid the planning of studies, and statements of the conservation action potential of the results of these investigations. The proposed organization of the IUCN programme and its current status is described. University and other research institutions that would be interested in participating or co-operating in the programme are invited to write to IUCN.  相似文献   

9.
The Peary caribou Rangifer tarandus pearyi is an unique subspecies confined almost entirely to the Canadian Arctic Archipelago. The decline of the population by 89% on the western Queen Elizabeth Islands between 1961 and 1974 has continued until at least 1977. The decline was principally caused by climatic changes but Peary caribou are potentially under additional pressure from hunting and disturbances associated with increasing industrial activities. We believe there are only 10–15,000 Peary caribou in Canada, and the subspieces was classified as ‘Threatened’ in 1979. The population dynamics of Peary caribou are unique among North American ungulates because weather, especially winter weather, dominates not only the reproductive rate but also recruitment and adult survival. The inter-island movements are a significant adaptation not only to sparse ranges and snow conditions, but also to recolonisation of islands that periodically, through a series of severe winters, lose their caribou.  相似文献   

10.
Volume-weighted pH values in central New Mexico have averaged 3.8 to 5.1 during the period 1979–1985. Samples collected at a high altitude site (3200m) have lower pH values than found for low altitude samples (1400m). Both dry deposition and event-averaged pH values have been higher than the volume-weighted averages due to neutralization by terrestrial material. During the period 1980–1984, changes in pH values and wet sulfate loading have correlated to S02 emissions from regional non-ferrous smelters. Sulfur isotope analyses of sulfate extracted from regional rain samples yielded a δ34SCD(%) of + 3.91 ± 1.1, indicating very little regional differentiation which, in turn, suggests that the regional atmospheric sulfate scavenged by precipitation is well-mixed and relatively homogeneous.  相似文献   

11.
 Migratory geese affect agricultural production by removing biomass and by depositing fecal nutrients. This study used 15N as a tracer to examine the quantitative effects of goose fecal N contributions on agricultural production. Barley (Hordeum vulgare cv. Datal) was grown for the production of 15N-labeled grain and straw. Two Canada geese (Branta canadensis Taverners) were fed the grain after harvest to obtain 15N-labeled and unlabeled feces. Net N mineralization and micro-plot studies both indicated that in comparison to barley grain and straw, goose feces provided the greatest amount of available N to the soil and to the subsequent crop, and consequently higher barley yields (59% and 62% increase, respectively). However, C mineralization was greater from grain, with 56% evolved compared to 49% and 26% for feces and straw, respectively. Goose feces also provided the greatest addition of N for the barley plants, with fertilizer N recovery efficiency (FNRE) of 16%, compared to FNRE of 10% from the grain amendment, and 1.2% from the straw amendment. The amount of N available in fecal material from leftover grain consumed by grazing geese is small in comparison to total crop needs, but is a potential source of mineral N during the critical early growth of crops grown in cold, high-latitude soils. Received: 16 May 1999  相似文献   

12.
In the environs of the town of El Kala in northeast Algeria there are some extensive wetlands of great ornithological, and probably also other biological, importance. The most important are ‘Lake’ Tonga, a marsh of about 2700 ha with much Scirpus lacustris; Lake Oubeïra, a freshwater lake of about 2200 ha; Lake Mellah, where fresh water from brooks and sea water meet, of about 800 ha; Garaet el Mekhada, a Scirpus maritimus marsh of about 5600 ha and swamp forests, which could not be investigated.Many species of waterfowl were seen in the second half of May, 1976. From these and some other observations probable breeding may be derived in many cases. Important species in the region are: squacco heron Ardeola ralloides (about 100 seen), cattle egret Bubulcus ibis (about 2000 seen), little egret Egretta garzetta (about 65 seen), grey heron Ardea cinerea (rare), purple heron Ardea purpurea (about 60 seen, possibly far more present), little bittern Ixobrychus minutus, bittern Butaurus stellaris and night heron Nycticorax nycticorax.Beside herons, the following species were seen: ferruginous duck Aythya nyroca (about 100 seen, probably far more numerous and hidden by the vegetation), white-headed duck Oxyura leucocephala (some 50 seen, probably present in greater numbers), marbled teal Anas angustirostris, purple gallinule Porphyrio porphyrio (common in Tonga). Interesting birds of prey in the region were griffon vulture Gyps fulvus (up to 30), marsh harrier Circus aeruginosus (rather numerous in Tonga), tawny eagle Aquila rapax (probably breeding on one place) and Eleonora's falcon Falco eleonorae (up to 5).As to probable breeding birds, Tonga has the greatest density of species and individuals, but other wetlands also have important aspects.Probably the most important lake for breeding birds, Fetzara (near Annaba), was drained in 1937. Marbled teal, ferruginous duck and purple gallinule were very common there, and white-headed duck, purple heron, squacco heron, night heron, little egret, spoonbill Platalea leucorodia, glossy ibis Plegadis falcinellus, grey-lag goose Anser anser, red-crested pochard Netta rufina and gadwall Anas strepera used to breed.A brief review is given of wintering waterfowl, mainly based on counts by different observers in the period 1971–1979. Large numbers of waterfowl have been seen in Lake Oubeïra; up to 5000 pintail Anas acuta, up to 14000 wigeon Anas penelope, up to 27000 pochard Aythya ferina, up to 9000 tufted duck Aythya fuligula and up to 32000 coot Fulica atra, up to 850 black-necked grebe Podiceps nigricollis and up to 2300 little grebe Tachybaptus ruficollis.In Lake Mellah up to 9000 pochard have been seen, up to 12000 tufted duck, and up to 35000 coot.In Garaet al Mekhada up to 25000 wigeon, up to 5000 coot and up to 8000 grey-lag geese have been seen. It seems quite possible that the 95000 wigeon seen by Smart in the artificial lake of the Barrage de la Cheffia in 1974 fed in Mekhada. An insight of waterfowl averages during the different counts can be obtained from the reports, mentioned in the references.All large wetlands mentioned have a high, actual or potential, ecological value. Each of them deserves protection and, from the ecological viewpoint, Fetzara merits inundation. Protection should be aimed at the preservation of the special character of each of the wetlands and of their mutual relationship for birds.The region is the most important in Algeria for wintering duck and coot (an average of 93000 from 1974–1978) and probably also for breeding waterfowl (especially Tonga) in spite of the high quality of La Macta in West Algeria.For the preservation of this diversity, several factors are essential, e.g., water level, water quality, absence of exotic elements in the water fauna and a relatively low shooting pressure (with little disturbance). It is important to prevent drainage of the lakes and of their surroundings, afforestation of the adjacent land, deforestration and erosion in the catchment areas, introduction of exotic fish species—and it is important to introduce good rules concerning shooting.This complex of wetlands is part and parcel of an extensive area of high biological interest, of which the marine habitats and large semi-natural forests are also remarkable.It is to be hoped that this entity will be efficiently protected in the framework of the National Park of El Kala Project.  相似文献   

13.
Long-term monitoring, 1973 to 1987, of reactions to liming and reacidification of a forest lake ecosystem near the Swedish west coast is reported in this study. Treatment of Lake Lysevatten with a slag product of limestone in 1974 resulted in neutralization and a positive alkalinity. Prolonged dissolution proceeded for about 7 yr whereby 86% dissolved. During 1984–86 Lake Lysevatten approached maximum reacidification with high Al concentrations and an affected biota. Asellus aquaticus L. decreased and dominance within chironomid groups approached preliming conditions. However, the most obvious biological change was the development of the filamentous algal genus Mougeotia and increased growth of Sphagnum. Populations of both plants increased notably when pH declined to about 5. Our study suggests that extensive reacidification (pH < 6.0) of limed lakes should be avoided by successive treatments to prevent development of destabilized lake ecosystems.  相似文献   

14.
An individuals-based model, MORPH, was used to assess the quality of Poole Harbour, UK, for five overwintering shorebirds: dunlin Calidris alpina, redshank Tringa totanus, black-tailed godwit Limosa limosa, oystercatcher Haematopus ostralegus and curlew Numenius arquata. Site quality, and the effect of environmental change, was measured as predicted overwinter survival. Dunlin had the highest prey biomass densities and were the least likely to be affected by reductions in their food supply, lower temperatures or loss of terrestrial habitats. Black-tailed godwits and curlew had the lowest prey biomass densities and were the most likely to be affected by reductions in their food supply, lower temperatures and loss of terrestrial habitats. All five shorebird species were seriously affected by simulated sea-level rise. Conservation issues identified for the Poole Harbour SPA were the relatively low densities of larger size classes of polychaete worms, the importance of maintaining and managing surrounding terrestrial habitats and the effect of sea-level rise on the length of time for which intertidal food supplies are available.  相似文献   

15.
The movements of seven species of waders within and through the estuarine complex of the Firth of Forth, Scotland, were studied by dye-marking and ringing in three winters, 1978–1981. The species studied formed two groups (which may be part of a continuum). Grey plovers Pluvialis squatarola, turnstones Arenaria interpres, oystercatchers Haematopus ostralegus and redshanks Tringa totanus tended to stay within the same part of the estuary throughout the winter. Bar-tailed godwits Limosa lapponica, dunlins Calidris alpina and knots C. canutus ranged more widely. Knots dispersed rapidly throughout the whole of the Firth, and probably elsewhere. Retraps of ringed birds indicated year-to-year differences broadly similar to the within-winter ones. The results are compared with data from elsewhere, and are discussed in relation to large-scale reclamation proposals for the Forth.  相似文献   

16.
Omnivory is a common feeding strategy in terrestrial arthropods, and omnivores that partake of a mixed diet often gain developmental and reproductive advantages. We determined the palatability and preference of plant and animal foods for two omnivorous mole crickets, Scapteriscus vicinus Scudder and Scapteriscus borellii Giglio-Tos. Adults of both species fed more readily on carrots than bermudagrass blades, rhizomes, and roots. When given a choice, S. vicinus preferentially fed on carrots (plant diet) whereas S. borellii preferred mealworms (animal diet). Nymphs of both species were reared on animal, plant, or mixed (plant–animal rotation) diets. S. borellii fed mealworms developed faster, with greater body mass and survival, and a longer pronotal length compared to individuals fed only carrots. Nymphs of S. vicinus, however, performed slightly better when fed mealworms, and poorer when given a mixed diet. Omnivory among Scapteriscus mole crickets may be a beneficial adaptation for insects in low nitrogen, grassland environments. This work suggests that these two species respond differently to plant and animal diets. S. borellii has a survival and developmental advantage by ingesting animal tissue. Diet will influence the age distribution of field populations, and this may influence interactions with their grass host and natural enemies.  相似文献   

17.
Since 1994 the Barnacle Goose Management Scheme (BGMS) has integrated conservation and agricultural aims on the Scottish side of the Solway Firth. In the 4 years before the introduction of the BGMS, the density of barnacle geese (Branta leucopsis) on the Wildfowl & Wetlands Trust Reserve at Caerlaverock was four times higher than on the non-Reserve area. In the 6 years following establishment of the BGMS, the density of geese on non-Reserve fields rose so that the Reserve had twice the density of the non-Reserve area. No difference in density was found between fields in the Feeding Zone and Intermediate Zone of the BGMS. The density of barnacle geese around the study area appears to be at a maximum under current management regimes. The remaining geese from this increasing population are using other feeding areas. This may lead to further conservation-agriculture conflict in the future, but could be mitigated through expanding the range and quality of the BGMS, through increasing the dedicated reserve network, or through a combination of the two.  相似文献   

18.
基于鹅舍气流场CFD模拟的通风系统结构优化与验证   总被引：4，自引：4，他引：0  
针对鹅舍内机械通风时大量气流扩散于鹅舍上方而位于地面鹅只通风效果受阻的气流问题,提出一种基于计算流体力学(computational fluid dynamics,CFD)的结构优化方案。通过在舍内主梁下端安装相同高度且与气流方向呈一定倾角的多个可拉伸卷膜构造方法,提高种鹅舍内有效的通风效率。依据试验现场边界条件,构建并求解了鹅舍的三维稳态模型,舍内40个测点的风速模拟值与实测值均方根误差为0.152 m/s,最大绝对误差为0.29 m/s,平均相对误差为2.04%,验证了建立的鹅舍CFD模型的准确性。根据不同优化方案数值模拟了27组不同改造后鹅舍内气流场分布情况,仿真得出最优组合方案:在42 m长的舍内安装卷膜个数为10个,卷膜与主梁竖直方向倾斜角度为60o以及卷膜最大下拉高度为1.2 m时舍内通风效率最高、气流分布最均匀。通过现场实测,对比改造前后40个测点的风速值,试验结果表明:改造后鹅舍较常规鹅舍平均风速增加0.527 m/s,舍内气流不均匀系数降低32.2%。该试验结果为种鹅舍的结构设计、同类型畜禽舍结构优化以及改善通风降温效果调控提供了一定的参考依据。  相似文献   

19.
The nitrate content of three heavy clay soils (Evesham, Denchworth and Lawford series) was examined after direct drilling or ploughing, and of another clay soil (Denchworth series) with or without mole drainage and after tine cultivation. Autumn-sown crops were grown at all these sites during the years 1973–80. Except in 1974–75, the nitrate concentration of the soil solution sampled from direct-drilled plots was less than from the ploughed plots, particularly in late autumn and early winter. By January the plots which had been ploughed contained 12–65 kg N ha?1 more mineral nitrogen than direct-drilled plots, but differences between cultivation treatments disappeared rapidly and had gone by early March. After tine cultivation, the nitrate content of the soil profile was not affected by the contrasting drainage status of the plots with or without mole drainage. These results support the view that although denitrification can be greater in direct-drilled soil, the larger nitrate concentrations present in ploughed soil result from the soil disturbance exposing less accessible substrates to mineralization by microbes. By this means, considerable amounts of mineral nitrogen are made available at the beginning of the winter, during the establishment of autumn-sown crops.  相似文献   

20.
We used models integrating road maps, traffic volume, and snake movements to examine the potential for roads to contribute to mortality in two species of water snakes that differ in their vagility, use of terrestrial habitats, and conservation status. Road networks and traffic volumes typical of three regions in Indiana, USA, may account for mortality of 14-21% of the population per year in the more vagile, terrestrial, and imperiled copperbelly water snake (Nerodia erythrogaster neglecta) but only 3-5% mortality in the more sedentary, aquatic, and common northern water snake (Nerodia sipedon). The majority (>91%) of road crossings and associated mortality are predicted to occur during overland migrations to other wetlands, suggesting roads bisecting travel routes between wetlands may function as mortality sinks. Our models highlight the proportionately greater risk of mortality for the more vagile and imperiled species, N. e. neglecta, and suggest current wetland conservation strategies that focus on the wetland alone are unlikely to adequately protect wetland biodiversity from certain types of anthropogenic habitat modification. What is needed is a landscape approach to wetland conservation that considers not only the quality of wetlands and nearby terrestrial habitats, but also ensures that terrestrial corridors between wetlands remain permeable and offer safe passage for wildlife.  相似文献   

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