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1.
Recovery planning is a key component of many threatened species conservation initiatives and can be a powerful awareness raising
tool. One of the largest impediments to conservation efforts in the Pacific region however, is the lack of ecological data
and its subsequent effects on the development of feasible and useful recovery plans for threatened species. Without these
plans, the understaffed, underfunded and often technically ill-equipped conservation agencies face huge difficulties in planning,
prioritizing and conducting conservation activities to adequately protect biodiversity. The Fiji sago palm, Metroxylon vitiense, is an endemic endangered palm species whose survival is heavily dependent on a feasible species recovery plan. It is geographically
restricted and threatened by habitat destruction and overexploitation for thatch for the tourism industry and palm heart consumption
by local consumers. Despite its threatened status, M. vitiense is not currently protected by national or international legislation. Recent field surveys and extensive stakeholder consultation
have resulted in the production of a species recovery plan highlighting the importance of the species and advocating sustainable
harvesting rather than complete bans to promote conservation. This article summarizes the recovery plan and its current effects
on the status of M. vitiense in Fiji. We also discuss the role of different stakeholders in the conservation of M. vitiense, including the absence of significant behavioral changes by the largest consumer - the tourism industry, and the importance
of recovery plans for biodiversity conservation in the Pacific. 相似文献
2.
Biodiversity,ecohydrology, threat status and conservation priority of the freshwater fishes of river Gomti,a tributary of river Ganga (India) 总被引:1,自引:1,他引:0
Extensive surveys were conducted to explore the diversity of fishes, distribution patterns, abundance, threat, and habitat
status in the upper, middle, and lower stretch of river Gomti, a tributary of river Ganga. Altogether 56 fish species belonging
to 20 families and 42 genera were collected from various sampling sites. Of the 56 species, five belong to the ‘endangered’
(EN) category and 11 belong to the vulnerable (VU) category. Six major categories of habitat were identified and pattern of
fish assemblage and dominant genera in each habitat studied. Considerable differences were observed in the fish species richness
and relative abundance (RA) of the species in the different sampling sites of river Gomti. Shannon–Wiener biodiversity index
has been calculated for the fishes indicating considerable variation (p < 0.05) across the river. Apart from Indian Major Carps (Labeo rohita, Catla catla, Cirrhinus mrigala), Chitala chitala, Notopterus notopterus, Ompok pabda, O. bimaculatus, Labeo bata, L. calbasu, Cirrhinus reba, Channa marulius, Bagarius bagarius, and Clupisoma garua were the important species. All the species have been reported for the first time in this river. Indiscriminate catch, poisoning,
using of fine mesh sized nets, dumping of sewage, siltation, water abstraction, changing land use pattern, decreased water
discharge, and exotic species threaten the fish diversity. Urgent need exists for taking up research on the priority fish
species and their habitat. Restoration measures have been proposed based on ecosystem scale approach for fish biodiversity
conservation. 相似文献
3.
Human-induced global climate change presents a unique and difficult challenge to the conservation of biodiversity. Despite
increasing attention on global climate change, few studies have assessed the projected impacts of sea-level rise to threatened
and endangered species. Therefore, we estimated the impacts of rising sea levels on the endangered Lower Keys marsh rabbit
(Sylvilagus palustris hefneri) across its geographic distribution under scenarios of current conditions, low (0.3-m), medium (0.6-m), and high (0.9-m)
sea-level rise. We also investigated the impacts of allowing vegetation to migrate upslope and not allowing migration and
of two land-use planning decisions (protection and abandonment of human-dominated areas). Not surprisingly, under all simulations
we found a general trend of decreasing total potential LKMR habitat with increasing sea-level rise. Not allowing migration
and protecting human-dominated areas both tended to decrease potential LKMR habitat compared with allowing migration and abandoning
human-dominated areas. In conclusion, conservation strategies at multiple scales need to be implemented in order to reduce
the impact of global climate change on biodiversity and endangered species. At the regional level, managers must consider
land-use planning needs that take into account the needs of both humans and biodiversity. Finally, at the local scale those
agencies that are in charge of endangered species conservation and ecosystem management need to rethink static approaches
to conservation or else stand by and watch ecosystems degrade and species go extinct. This can be accomplished by bioclimatic
reserve systems where climatically underrepresented areas are included in conservation planning along with the standard concerns
of threat, opportunity, connectivity, and viability. 相似文献
4.
Luan Xiaofeng Qu Yi Li Diqiang Liu Shirong Wang Xiulei Wu Bo Zhu Chunquan 《Journal of environmental management》2011
The Amur Tiger (Panthera tigris altaica) is one of the world’s most endangered species. Recently, habitat fragmentation, food scarcity and human hunting have drastically reduced the population size and distribution areas of Amur tigers in the wild, leaving them on the verge of extinction. Presently, they are only found in the north-eastern part of China. In this study, we developed a reference framework using methods and technologies of analytic hierarchy process (AHP), remote sensing (RS), geographic information system (GIS), GAP analysis and Natural Break (Jenks) classification to evaluate the habitat and to set the conservation priorities for Amur tigers in eastern areas of Heilongjiang and Jilin Provinces of northeast China. We proposed a Habitat Suitability Index (HSI) incorporating 7 factors covering natural conditions and human disturbance. Based on the HSI values, the suitability was classified into five levels from the most to not suitable. Finally, according to results of GAP analysis, we identified six conservation priorities and designed a conservation landscape incorporating four new nature reserves, enlarging two existing ones, and creating four linkages for Amur tigers in northeast China. The case study showed that the core habitats (the most suitable and highly suitable habitats) identified for Amur tigers covered 35,547 km2, accounting for approximately 26.71% of the total study area (1,33,093 km2). However, existing nature reserves protected only (7124 km2 or) 20.04% of the identified core habitats. Thus, enlargement of current reserves is necessary and urgent for the tiger’s conservation and restoration. Moreover, the establishment of wildlife corridors linking core habitats will provide an efficient reserve network for tiger conservation to maintain the evolutionary potential of Amur tigers facing environmental changes. 相似文献
5.
Wazir Singh Lakra Uttam Kumar Sarkar Rupali Sani Kumar Ajay Pandey Vineet Kumar Dubey Om Prakash Gusain 《The Environmentalist》2010,30(4):306-319
In the present communication habitat ecology, species diversity; distribution and different indices of fish biodiversity management
were studied in a Central India river (River Betwa, a tributary of River Ganga basin approved under India’s first river linking
plan). Correlation between fish species richness with the hydrological attributes showed good relationship and water depth,
dissolved oxygen and pH were found the most important variables in shaping fish assemblage. Altogether, sixty-three fish species
belonging to 20 families and 45 genera were collected from five sampling stations spread along the upstream, mid stream and
lower streams. Cyprinids were the most dominated group represented by 26 species belonging to 15 genera, followed by Bagridae
(6 species from 3 genera), and Schilbeidae (4 species from 4 genera). The distribution of fish showed interesting pattern
and about 10% species were common to all the sites showing long migration range. Shannon-Weiner diversity index showed considerable
variation and ranged from 1.89 to 3.51. Out of 63 species status of 10 species were not known due to data deficit, 29 categorized
as lower risk, 14 as vulnerable, 8 as endangered, while the remaining two species were introduced. Our study shows that the
River supports considerable diversity of the fishes and is important for conservation and about 34% fish fauna is threatened
being either vulnerable or endangered. We assessed that the river supports considerable percentage of food fish (89.47), ornamental
fish (49.12%) and sport fish (5.26%). Among the eight major types of fish habitats identified along the entire stretch of
river, open river, shallow water and deep pools were habitats contributing maximum diversity. Fish species richness (FSR)
were significantly different (P < 0.05) in all the habitats except channel confluence and scour pool. Trophic niche model may be useful for assessing altered
as well as less altered fish habitat of the tropical rivers. Since this river will be interlinked in near future, this study
would be useful for conservation planning and management and also for future assessment after interlinking. Issues related
to various threats to aquatic environment and conservation management strategies have been discussed. 相似文献
6.
We propose a biodiversity credit system for trading endangered species habitat designed to minimize and reverse the negative
effects of habitat loss and fragmentation, the leading cause of species endangerment in the United States. Given the increasing
demand for land, approaches that explicitly balance economic goals against conservation goals are required. The Endangered
Species Act balances these conflicts based on the cost to replace habitat. Conservation banking is a means to manage this
balance, and we argue for its use to mitigate the effects of habitat fragmentation. Mitigating the effects of land development
on biodiversity requires decisions that recognize regional ecological effects resulting from local economic decisions. We
propose Landscape Equivalency Analysis (LEA), a landscape-scale approach similar to HEA, as an accounting system to calculate
conservation banking credits so that habitat trades do not exacerbate regional ecological effects of local decisions. Credits
purchased by public agencies or NGOs for purposes other than mitigating a take create a net investment in natural capital
leading to habitat defragmentation. Credits calculated by LEA use metapopulation genetic theory to estimate sustainability
criteria against which all trades are judged. The approach is rooted in well-accepted ecological, evolutionary, and economic
theory, which helps compensate for the degree of uncertainty regarding the effects of habitat loss and fragmentation on endangered
species. LEA requires application of greater scientific rigor than typically applied to endangered species management on private
lands but provides an objective, conceptually sound basis for achieving the often conflicting goals of economic efficiency
and long-term ecological sustainability. 相似文献
7.
Jason Bried Tim Tear Rebecca Shirer Chris Zimmerman Neil Gifford Steve Campbell Kathy O’Brien 《Environmental management》2014,54(6):1385-1398
Monitoring is essential to track the long-term recovery of endangered species. Greater emphasis on habitat monitoring is especially important for taxa whose populations may be difficult to quantify (e.g., insects) or when true recovery (delisting) requires continuous species-specific habitat management. In this paper, we outline and implement a standardized framework to facilitate the integration of habitat monitoring with species recovery efforts. The framework has five parts: (1) identify appropriate sample units, (2) select measurable indicators of habitat requirements, (3) determine rating categories for these indicators, (4) design and implement appropriate data collection protocols, and (5) synthesize the ratings into an overall measure of habitat potential. Following these steps, we developed a set of recovery criteria to estimate habitat potential and initially assess restoration activities in the context of recovering an endangered insect, the Karner blue butterfly (Lycaeides melissa samuelis). We recommend basing the habitat potential grading scheme on recovery plan criteria, the latest information on species biology, and working hypotheses as needed. The habitat-based assessment framework helps to identify which recovery areas and habitat patches are worth investing in and what type of site-specific restoration work is needed. We propose that the transparency and decision-making process in endangered insect recovery efforts could be improved through adaptive management that explicitly identifies and tracks progress toward habitat objectives and ultimate population recovery. 相似文献
8.
This study investigated the genetic relationships between the rare terrestrial orchid Diuris fragrantissima and three closely related purple flowered species using Amplified Fragment Length Polymorphisms. The purple-flowered species
were found to form individual phenetic clusters confirming recognition of D. fragrantissima at the rank of species. Levels of genetic variation were lower within D. fragrantissima than within its closest relatives but were higher than expected for severely bottlenecked species. Gene flow was detected
among all species (Nm = 2.34) and populations (Nm = 0.65) however low among population gene flow indicates that populations
may be at risk of divergence. This study has implications for the conservation of D. fragrantissima. 相似文献
9.
The present study aims to identify the potential habitat for swamp deer (Cervus duvauceli duvauceli Cuvier) in Jhilmil Jheel Conservation Reserve in the Uttarakhand province of India using multi-criteria analysis. The study
area represents one of the last remnant habitats of the flagship species, the swamp deer in Uttarakhand, which is considered
as vulnerable. The study showed that only 6.08% of the study area (225 km2) was highly suitable to suitable for the swamp deer. An area of 135.52 km2 (60.23%) turned out to be moderately suitable. Within the officially designated Conservation Reserve (area 37.84 km2), 10.91% (4.13 km2) area was found highly suitable to suitable, while 74.19% (28.07 km2) happens to be moderately suitable. Only 14 km2 area, which was found as suitable habitat for swamp deer falls short of the space required by a population of 134 animals.
The problem could be mitigated if the agricultural land (2.47 km2) adjacent to the Jhilmil Jheel is brought under the Reserve management. This would provide additional area to meet the fodder
requirement. The study brings out a particularly grim situation with limited options for conservation and management of the
swamp deer in the Indo-Gangetic plains. It also emphasizes the role of geospatial techniques in quick appraisal of habitat
attributes and identification of potential sites for protected areas. 相似文献
10.
The US Department of Defense (DOD) manages over 10.1 million ha of land, much of which is used for training military personnel.
However, vast sections receive little or no use, and military lands have become refuges for many species. At Fort McCoy, Wisconsin,
USA, populations of the endangered Karner blue butterfly (Lycaeides melissa samuelis) are found in oak and pine barren communities where wild lupine (Lupinus perennis), a perennial forb required by Karner blue butterfly larvae, still occurs. Oak and pine barren communities are disturbance-dependent,
and the barrens ecosystems in the Midwest have declined in extent by 98% because of fire suppression, succession, and habitat
fragmentation. We studied the effects of disturbance by military manuever training on the density of lupine and Karner blue
butterfly at Fort McCoy. We also wanted to determine whether military training activity could enhance Karner blue butterfly
habitat.
At locations where tracked vehicles had driven through lupine patches, the abundance of lupine and nectar-producing plants
was greater in the median strip between vehicle ruts than in vehicle ruts or 5 m outside the vehicle ruts. The proportion
of lupine stems with Karner blue butterfly larvae feeding sign (the ratio of stems fed upon to stems examined) was greater
in areas where military vehicles had traveled than where they had not. The proportion of lupine stems with feeding sign and
lupine stem density was also positively related to the occurrence of prior bivouacs and fires caused by military munitions.
Shrub and forest canopy abundance were lower in areas traveled by tracked vehicles. At the scale of the lupine patch, lupine
abundance and the proportion of lupine stems with feeding sign were positively correlated with military training activities,
suggesting that maintenance of lupine habitat can be achieved in concert with military training. 相似文献
11.
Alternative energy development is increasing, potentially leading to negative impacts on wildlife populations already stressed
by other factors. Resource managers require a scientifically based methodology to balance energy development and species conservation,
so we investigated modeling habitat suitability using Maximum Entropy to develop maps that could be used with other information
to help site energy developments. We selected one species of concern, the Lesser Prairie-Chicken (LPCH; Tympanuchus pallidicinctus) found on the southern Great Plains of North America, as our case study. LPCH populations have been declining and are potentially
further impacted by energy development. We used LPCH lek locations in the state of Kansas along with several environmental
and anthropogenic parameters to develop models that predict the probability of lek occurrence across the landscape. The models
all performed well as indicated by the high test area under the curve (AUC) scores (all >0.9). The inclusion of anthropogenic
parameters in models resulted in slightly better performance based on AUC values, indicating that anthropogenic features may
impact LPCH lek habitat suitability. Given the positive model results, this methodology may provide additional guidance in
designing future survey protocols, as well as siting of energy development in areas of marginal or unsuitable habitat for
species of concern. This technique could help to standardize and quantify the impacts various developments have upon at-risk
species. 相似文献
12.
Richard A. Valdez Colleen Cunningham Ali Effati Deborah L. Freeman 《Journal of the American Water Resources Association》2023,59(5):1084-1098
Warmwater fish habitat in the San Juan River of the southwestern United States has been reduced by over 30% as a result of water depletion, reservoir inundation, and cold-water dam releases combined with drought-related changes in hydrology. This reduction and a suite of other factors have contributed to declines in native fish populations including the federally endangered Colorado Pikeminnow (Ptychocheilus lucius) and Razorback Sucker (Xyrauchen texanus). Conservation efforts for these species include determining flow needs; protecting, managing, and augmenting habitats; and stocking hatchery fish. But the young of stocked fish have low survival due largely to a paucity of nursery habitat not being reformed and maintained under current conditions. Flow recommendations for Navajo Dam releases designed to mimic the river's natural hydrograph have not been met due to water shortages, and the desired outcomes of increased channel complexity and enhanced fish habitat have not been observed. Forecasted hydrology that includes ongoing drought shows that achieving the flow targets through further dam reoperations is unlikely. Mechanical construction of early life-stage habitats is a highly recommended complement to flow management for offsetting the effects of flow reduction and habitat loss. Habitats with features that are effective and resilient under a range of flows are important in counterbalancing the effects of climate change. 相似文献
13.
Integrating Nonindigenous Aquatic Plant Control with Protection of Snail Kite Nests in Florida 总被引:1,自引:0,他引:1
The endangered snail kite (Rostrhamus sociabilis) feeds primarily on the freshwater apple snail (Pomacea paludosa) in Florida. The nonindigenous, floating water hyacinth (Eichhornia crassipes) and water lettuce (Pistia stratiotes) impede kites from finding snails. Effective control of these aquatic plants in the littoral zone of central and south Florida
lakes benefits kites by maintaining open foraging habitat. However, incidental herbicide spraying of nesting substrates result
in nest collapse when kites breed in nonwoody, emergent plants [cattail (Typha spp.) and giant bulrush (Scirpus validus)] in the outer littoral zone during lower lake levels. Many endangered species recovery plans and their implementation have
experienced problems due to inaction and/or noncooperation by various governmental agencies and their personnel. Herein, we
describe the development and implementation of a buffer zone strategy to prevent secondary impacts from an aquatic plant control
program to snail kites nesting on lakes in central and south Florida. A strategy was jointly developed by personnel of five
state and federal agencies to control herbicide application near kite nesting areas during the normal breeding season. Although
requiring various modifications during its implementation, this cooperative effort successfully integrated aquatic plant control
objectives with snail kite conservation on Lake Okeechobee during 1988. The program was expanded the following year to lakes
Kissimmee and Tohopekaliga. Since the implementation of the snail kite impact preclusion program, no nest loss was attributed
to incidental herbicide applications on lakes Okeechobee, Kissimmee, and Tohopekaliga. 相似文献
14.
Kirk W. Davies Jonathan D. Bates Dustin D. Johnson Aleta M. Nafus 《Environmental management》2009,44(1):84-92
Mowing is commonly implemented to Artemisia tridentata ssp. wyomingensis (Beetle & A. Young) S.L. Welsh (Wyoming big sagebrush) plant communities to improve wildlife habitat, increase forage production
for livestock, and create fuel breaks for fire suppression. However, information detailing the influence of mowing on winter
habitat for wildlife is lacking. This information is crucial because many wildlife species depended on A. tridentata spp. wyomingensis plant communities for winter habitat and consume significant quantities of Artemisia during this time. Furthermore, information is generally limited describing the recovery of A. tridentata spp. wyomingensis to mowing and the impacts of mowing on stand structure. Stand characteristics and Artemisia leaf tissue crude protein (CP), acid detergent fiber (ADF), and neutral detergent fiber (NDF) concentrations were measured
in midwinter on 0-, 2-, 4-, and 6-year-old fall-applied mechanical (mowed at 20 cm height) treatments and compared to adjacent
untreated (control) areas. Mowing compared to the control decreased Artemisia cover, density, canopy volume, canopy elliptical area, and height (P < 0.05), but all characteristics were recovering (P < 0.05). Mowing A. tridentata spp. wyomingensis plant communities slightly increases the nutritional quality of Artemisia leaves (P < 0.05), but it simultaneously results in up to 20 years of decrease in Artemisia structural characteristics. Because of the large reduction in A. tridentata spp. wyomingensis for potentially 20 years following mowing, mowing should not be applied in Artemisia facultative and obligate wildlife winter habitat. Considering the decline in A. tridentata spp. wyomingensis-dominated landscapes, we caution against mowing these communities. 相似文献
15.
Three different systems of designating protected areas in a Mediterranean region in southeastern Spain were studied, referring
to their effectiveness and efficiency for protecting both the breeding territories and the suitable habitat of a set of ten
raptor species. Taking into consideration the varying degrees of endangerment of these species, a map of multispecies conservation
values was also drawn up and superimposed on the three protected-area systems studied. In order to compare the levels of protection
afforded by the three systems, we considered two indices that measured their relative effectiveness and efficiency. The effectiveness
estimated the proportion of territories or optimal habitat protected by the networks while efficiency implicitly considered
the area of each system (percentage of breeding territories or optimal habitat protected per 1% of land protected). Overall,
our results showed that the most efficient system was that formed by the set of regional parks and reserves (17 protected
breeding territories per 100 km2), although, given its small total area, it was by far the least effective (only protecting the 21% of the breeding territories
of all species and 17% of the area of high conservation value). The systems formed by the Special Protection Areas (designated
under the EU “Birds Directive”) and by the Special Conservation Areas (designated under the EU “Habitats Directive”) notably
increased the percentages of protected territories of all species (61%) and area of high conservation value (57%), but their
efficiency was not as high as expected in most cases. The overall level of protection was high for all species except for
the Lesser Kestrel (Falco naumanni), an endangered falcon that inhabits pseudo-steppe and traditional agricultural habitats, which are clearly underrepresented
in the protected-area network of the study region. 相似文献
16.
Dry grasslands are one of the most species rich and endangered types of vegetation in Europe. In the Czech Republic, dry grasslands
are mainly of anthropogenic origin and were formed as a result of grazing after the clear-cutting of thermophilous oak woods.
Gradual changes in the farming landscape throughout the 20th century, particularly in the 1960s, resulted in the abandonment
of the relatively infertile habitats of dry grasslands. After abandonment, dry grasslands decline and degrade due to the gradual
overgrowth of woody species and expansion of perennial tall grasses. In the year 2000, a grazing management program was introduced
in the protected areas within the territory of Prague City to maintain the species diversity of dry grasslands. The responses
of the expansive grass species, Arrhenatherum elatius L. and multiple woody species (especially, Prunus spinosa L.) to differences in grazing periods were monitored for over a decade. Grazing in spring through the end of June had the greatest impact on the reduction of A. elatius and woody species. Grazing in the height of summer through autumn did not reduce the cover of these plants, and may support
the prosperity of both A. elatius and the woody species due to higher levels of nutrients. 相似文献
17.
Under the Canadian Species at Risk Act (SARA), Garry oak (Quercus garryana) ecosystems are listed as “at-risk” and act as an umbrella for over one hundred species that are endangered to some degree.
Understanding Garry oak responses to future climate scenarios at scales relevant to protected area managers is essential to
effectively manage existing protected area networks and to guide the selection of temporally connected migration corridors,
additional protected areas, and to maintain Garry oak populations over the next century. We present Garry oak distribution
scenarios using two random forest models calibrated with down-scaled bioclimatic data for British Columbia, Washington, and
Oregon based on 1961–1990 climate normals. The suitability models are calibrated using either both precipitation and temperature
variables or using only temperature variables. We compare suitability predictions from four General Circulation Models (GCMs)
and present CGCM2 model results under two emissions scenarios. For each GCM and emissions scenario we apply the two Garry
oak suitability models and use the suitability models to determine the extent and temporal connectivity of climatically suitable
Garry oak habitat within protected areas from 2010 to 2099. The suitability models indicate that while 164 km2 of the total protected area network in the region (47,990 km2) contains recorded Garry oak presence, 1635 and 1680 km2 of climatically suitable Garry oak habitat is currently under some form of protection. Of this suitable protected area, only
between 6.6 and 7.3% will be “temporally connected” between 2010 and 2099 based on the CGCM2 model. These results highlight
the need for public and private protected area organizations to work cooperatively in the development of corridors to maintain
temporal connectivity in climatically suitable areas for the future of Garry oak ecosystems. 相似文献
18.
Edith González Afanador Michael E. Kjelland X. Ben Wu Neal Wilkins William E. Grant 《The Environmentalist》2016,36(3):310-328
The present research focused on using spatial analysis to determine relationships among land ownership property sizes and landscape structure, with a focus on conservation management implications. Indices and metrics of ownership property sizes and landscape structure were calculated for 20 km buffer areas around 31 North American Breeding Bird Survey transects, 12 located within the Edwards Plateau ecoregion and 18 in contiguous ecoregions. The number of bird species observed at each transect provided a measure of avian species richness associated with land cover classes for each respective transect (González in Urban influence on diversity of avifauna in the Edwards Plateau of Texas: effect of property sizes on rural landscape structure, Texas A&M University, 2005). Spatial correlations were calculated between each pair of the landscape indices. Spatial analysis identified a “threshold of habitat fragmentation” for the 500 acre (ac) ownership property size. Significant spatial correlations among variables showed that property sizes lower than 500 ac produced habitat fragmentation represented by a decrease in mean patch size (MN) and proximity among habitat patches (Index PROX). Spatial analysis also made possible the prioritization of ecological sub-regions of the Edwards Plateau for conservation or restoration. The Live Oak-Mesquite Savannah showed the highest average ownership property size (7305 ac) and the highest values of patch richness. Based on the results, management in the Live Oak-Mesquite Savannah sub-region should focus on the conservation of land mosaic diversity to assure native avian species turnover (Whittaker 1972). In Balcones Canyon Lands, 64 % of land was covered by farms smaller than 500 ac and the overall average ownership property size was above the threshold of fragmentation (1440 ac), implying that management policies there should focus both on habitat conservation and on restoration. In contrast, 71 % of land in the Lampasas Cut Plains was covered by farms smaller than 500 ac, and average ownership property size was very close to the fragmentation threshold (625 ac). Consequently, the results indicate that management in the Lampasas Cut Plains sub-region should focus on habitat restoration (e.g., corridors that connect isolated habitat patches). In general, the threshold of ownership property size, 500 ac, is important for conservation planning because below that threshold of property size, habitat patch size begins to decrease and the distance between equivalent patches of habitat increases. Isolated patches act as islands within a sea of less suitable habitat which produce negative effects on biodiversity. Identifying the spatial characteristics indicative of habitat fragmentation, or the likelihood thereof, is an important issue for conservation planning in places with urban sprawl influence. 相似文献
19.
Gleditsia triacanthos and the native dominant Lithraea ternifolia in montane forests of central Argentina, considering life history and demographic traits of both the alien and the native
species and different site conditions for population growth (good and bad sites). Matrix models are applied to project the
consequences of differences in vital rates for population growth. Analyzing these models helps identify which life cycle transitions
contributed most to population growth. Obtained population growth rates are considered to assess predicted rates of spread
using the reaction-diffusion (R-D) model. G. triacanthos presents many of the life history traits that confer plants high potential for invasiveness: fast growth, clonal and sexual
reproduction, short juvenile period, high seed production, and high seed germinability. These traits would ensure G. triacanthos invasive success and the displacement of the slow-growing, relatively less fecund native L. ternifolia. However, since disturbance and environmental heterogeneity complicate the invasibility pattern of G. triacanthos in these montane forests, the outcome of the invasion process is not straightforward as could be if only life history traits
were considered.
Great variation in demographic parameters was observed between populations of each species at good and bad sites. Though both
good and bad sites signified increasing or at least stable populations for G. triacanthos, for L. ternifolia bad sites represented local extinction. Analyzing the results of matrices models helps design the optimal management for
the conservation of L. ternifolia populations while preventing the invasion by G. triacanthos. The predicted asymptotic rate of spread for G. triacanthos at the good site was fourfold greater than the predicted one for L. ternifolia, although the difference was much smaller considering the bad site. The usefulness of the R-D model to study this invasion
system is discussed. 相似文献
20.
Multiple-species habitat conservation plans (MSHCPs) are designed to eliminate project-by-project review and minimize species-by-species conflicts; but these one-time, short-term processes invariably compress the divergent expectations of interest groups into an exercise driven by economic, amenity, and aesthetic values rather than scientific values. Participants may define an MSHCP as an exchange of habitat preserves for federal permits to take populations of endangered animals and plants, but the outcome is typically driven by overarching arguments over land development and suburban sprawl. Existing land uses also constrain the size, shape, and linkages among wildlife habitats, leading to a divergence of MSHCPs from the scientific preserve selection and design literature. Problems created by constraints to preserve configuration (e.g., land costs, fragmentation, pre-existing amounts of edge, lack of connectivity) must be resolved by long-term, post facto management. To date, estimates of preserve persistence have not been used in MSHCPs. Rather than focus on map-based exercises of preserve elements, it may be more productive to set goals for the persistence of species (states) and ecosystems (processes) within the preserves-accepting that preserve configurations and arrays will be defined by the landscape and politics of suburban areas and that long-term management will provide the primary means of maintaining biodiversity along the wildland/urban interface. 相似文献