bluuebunny/crossref_metadata_2025 huggingface dataset:
Threats to Imperiled Freshwater Fauna
Authors: Richter Brian D. , Braun David P. , Mendelson Michael A. , Master Lawrence L.
Published: March 2003

Threats to imperiled freshwater fauna in the U.S. were assessed through an experts survey addressing anthropogenic stressors and their sources. Specifically, causes of historic declines and current limits to recovery were identified for 135 imperiled freshwater species of fishes, crayfishes, dragonflies and damselflies, mussels, and amphibians. The survey was designed to identify threats with sufficient specificity to inform resource managers and regulators faced with translating information about predominant biological threats into specific, responsive actions. The findings point to altered sediment loads and nutrient inputs from agricultural nonpoint pollution; interference from exotic species; and altered hydrologic regimes associated with impoundment operations as the three leading threats nationwide, accompanied by many lesser but still significant threats. Variations in threats among regions and among taxa were also evident. Eastern species are most commonly affected by altered sediment loads from agricultural activities, whereas exotic species, habitat removal/damage, and altered hydrologic regimes predominate in the West. Altered sediment loading from agricultural activities and exotic species are dominant problems for both eastern mussels and fishes. However, eastern fishes also appear to be suffering from municipal nonpoint pollution (nutrients and sediments), whereas eastern mussels appear to be more severely affected by altered nutrient impacts from hydroelectric impoundments and agricultural runoff. Our findings suggest that control of nonpoint source pollution associated with agriculture activities should be a very high priority for agricultural producers and governmental support programs. Additonally, the large number of hydropower dams in the U.S. subject to federal re‐licensing in coming years suggests a significant opportunity to restore natural hydrologic regimes in the affected rivers.
Historical and Contemporary Maternal Population Structuring in the Endangered Hastings River Mouse (Pseudomys oralis)
Authors: Jerry Dean R. , Dow Tanya A. , Elphinstone Martin S. , Baverstock Peter R.
Published: March 2003

The Hastings River mouse (Pseudomys oralis) is a small, endangered Australian conilurine rodent. Only about 200 specimens of this rodent have ever been caught, and little is known about its biology. At present, populations of this species appear to be severely fragmented. We used temperature‐gradient gel electrophoresis and DNA sequencing to investigate maternal population structuring in this species and to determine if the pattern of fragmentation is the consequence of anthropogenic influences. Based on a 345 bp section of the mitochondrial control region, all sample localities were found to be genetically distinct, with only 1 haplotype out of 11 found present in more than one sample locale. Phylogenetic reconstructions from sequence data clustered haplotypes into two distinct clades, demonstrating that contemporary population structure in the Hastings River mouse has a historical component. The discovery that populations of the Hastings River mouse are not only currently genetically isolated but have been separated for long periods of evolutionary time has clear management ramifications for the conservation of this species. In particular, each population should now be treated as demographically independent and administered as a separate management unit.

 Estructura Histórica y Contemporánea de la Población Materna de el Ratón del Rio Hastings (Pseudomys oralis) en Peligro de Extinción. 

El ratón del río Hastings (Pseudomys oralis) es un roedor australiano pequeño en peligro de extinción. Unicamente 200 especímenes de este roedor han sido capturados y se conoce muy poco de su biologia. Actualmente, las poblaciones de esta especie aparentan estar severamente fragmentadas. Utilizamos gel electroforésis de gradiente de temperatura y secuenciado de ADN para investigar la estructura poblacional materna en la especie y para examinar si los patrones de fragmentación son consecuencia de influencias antropogénicas. Basados en secciones de 345 bp de la region de control mitocondrial, todas las muestras fueron encontradas genéticamente distintas, con un haplotipo de once encontrados presente en mas de una muestra. Reconstrucciones filogenéticas de datos de secuencias agrupó haplotipos en dos grupos distintivos, demostrando que poblaciones contemporáneas del raton del río Hastings tiene un componente histórico. El descubrimiento de que poblaciones del ratón del río Hastings no estan solo aisladas genéticamente en la actualidad, sino que han estado separadas por largos períodos de tiempo evolucionario tiene ramificaciones claras de manejo para la conservación de esta especie. En particular, cada población deberá ser tratada ahora como demográficamente independiente y administrada como una unidad de manejo separada.
Attitudes toward Sustainability and Extinction
Authors: Mace Georgina M. , Hudson Elodie J.
Published: March 2003

Abstract:
Conservation biologists and natural resource managers are both working to maintain species, but their approaches and priorities differ. The contrast was highlighted when the World Conservation Union (IUCN) listed some commercial fish species, such as the Atlantic cod (Gadus morhua), in the 1996 Red List of Threatened Animals. These species qualified under IUCN’s criteria because they had undergone a marked decline in abundance. Disagreements over these listings revealed fundamental differences between resource managers and conservation biologists. Resource managers aiming to maximize continuing yields using specific, explicit, and data‐rich models, generally have not considered risk assessment and sometimes face the necessity for political compromises. Conservation biologists generally consider a wide diversity of species and operate in a data‐poor and precautionary context with an overall aim of minimizing extinction risk. The IUCN Red List is an extreme case in point and uses simple criteria for evaluating the conservation status of all species. Under these circumstances, it can do little more than indicate a species’ status in order to prompt further investigation by the appropriate body. We suggest that productive collaboration between conservation biologists and resource managers will start with an understanding of these different perspectives and will benefit from common interests in precautionary approaches, ecosystem approaches, and adaptive management studies.
Predicting the Landscape‐Scale Distribution of Alien Plants and Their Threat to Plant Diversity
Authors: Higgins Steven I. , Richardson David M. , Cowling Richard M. , Trinder‐Smith Terry H.
Published: March 2003

Abstract:
Invasive alien organisms pose a major threat to global biodiversity. The Cape Peninsula, South Africa, provides a case study of the threat of alien plants to native plant diversity. We sought to identify where alien plants would invade the landscape and what their threat to plant diversity could be. This information is needed to develop a strategy for managing these invasions at the landscape scale. We used logistic regression models to predict the potential distribution of six important invasive alien plants in relation to several environmental variables. The logistic regression models showed that alien plants could cover over 89% of the Cape Peninsula. Acacia cyclops and Pinus pinaster were predicted to cover the greatest area. These predictions were overlaid on the current distribution of native plant diversity for the Cape Peninsula in order to quantify the threat of alien plants to native plant diversity. We defined the threat to native plant diversity as the number of native plant species (divided into all species, rare and threatened species, and endemic species) whose entire range is covered by the predicted distribution of alien plant species. We used a null model, which assumed a random distribution of invaded sites, to assess whether area invaded is confounded with threat to native plant diversity. The null model showed that most alien species threaten more plant species than might be suggested by the area they are predicted to invade. For instance, the logistic regression model predicted that P. pinaster threatens 350 more native species, 29 more rare and threatened species, and 21 more endemic species than the null model would predict. Comparisons between the null and logistic regression models suggest that species richness and invasibility are positively correlated and that species richness is a poor indicator of invasive resistance in the study site. Our results emphasize the importance of adopting a spatially explicit approach to quantifying threats to biodiversity, and they provide the information needed to prioritize threats from alien species and the sites that need urgent management intervention.
Economic Incentives for Management of Venezuelan Caiman
Authors: Thorbjarnarson John , Velasco Alvaro
Published: March 2003

Abstract:
In Venezuela, the harvest of spectacled caiman (Caiman crocodilus) has generated significant economic benefits for citizens and the government wildlife department. Between 1983 and 1995 more than 1 million caiman were harvested, with an export value in excess of $US 115 million. Although limited survey data restrict quantitative comparisons, most indications suggest that the harvest has been within sustainable limits. Hunting is conducted on private lands in the central Venezuelan plains where caiman populations benefit from cattle ranching management activities, particularly the construction of dry‐season water holes. For ranchers, caiman hunting produces a high return on investment, but the overall earnings are small when compared to those produced by cattle. Caiman are mostly a quick and easy source of income that complements cattle ranching, and there is little incentive to actively manage caiman populations. The only evidence that the income from caiman harvests generates economic incentives to protect caiman populations is that landowners sold the skins of caiman illegally hunted in other areas, so as not to reduce their own caiman populations and possibly diminish future hunting quotas. There is no evidence that caiman harvesting generates economic incentives to protect natural habitat, because caiman benefit from human alteration of savanna habitats associated with the much more economically important cattle ranching activities. Recent changes in how hunting quotas are assigned have reduced economic incentives for landowners to protect caiman populations, but the changes have made the quota‐setting procedure simpler. One of the greatest conservation benefits of the program has been its ability to generate operating funds for the traditionally cash‐strapped government wildlife agency through a variety of taxes and user fees. Due to a recent government restructuring, however, program proceeds will now go to the central treasury and will no longer benefit wildlife management programs.
Wild Dog Demography in Hluhluwe‐Umfolozi Park, South Africa
Authors: Maddock Ant
Published: March 2003

Abstract:
Wild dogs (  Lycaon pictus) are highly threatened carnivores, and conservation of their dwindling numbers is needed. Isolated populations contribute little to these conservation efforts, so linking populations of dogs is a necessary goal to prevent extinction. I gathered demographic information from a small population of wild dogs in Hluhluwe‐Umfolozi Park, KwaZulu‐Natal, South Africa. Photographs and archive records from 1981 to 1996 were used to compile information on this population. Demographic parameters from the released population were compared with information on wild dogs elsewhere. Most demographic parameters of the Hluhluwe‐Umfolozi Park population were similar to published information from other populations. The main difference was the effect of a single pack on population performance: pack formation was unlikely, unrelated animals were rare, and major losses (emigration and mortalities) occurred. Increasing the number of packs by introducing more dogs would be useful but would be only a short‐term solution. Increasing the local population size and artificially linking populations in southern Africa appears to be the only longer‐term solution to ensure the viability of wild dogs on the subcontinent.
Managing Protected Woodlands: Fuelwood Collection and Law Enforcement in Lake Malawi National Park
Authors: Abbot Joanne I. O. , Mace Ruth
Published: March 2003

Abstract:
We examined the decisions women make in their collection of fuelwood within a protected area in Malawi. We used law enforcement data and behavioral observations of fuelwood harvesting practices to examine the risk of detection and penalties posed by law enforcement activities. Our results indicate that, at their current levels, law enforcement patrols have little effect on wood collection practices. The low risk of detection and light penalties appear to favor illegal wood collection, which is practiced by the majority of women. Alternative strategies should be pursued to enhance the conservation of the woodland and its management as a fuelwood resource for local communities.
Bat Use of Remnant Old‐Growth Redwood Stands
Authors: Zielinski William J. , Gellman Steven T.
Published: March 2003

Most of the old‐growth redwood (Sequoia sempervirens) in California has been cut; regenerating forests will probably never resemble those that were harvested, and what old growth remains on private land occurs in small, isolated remnant patches. The landscapes in which these stands occur differ so markedly from their original condition that their value as habitat to many species of wildlife, including bats, is unknown. Previous research in unfragmented redwood forests demonstrated that bats use basal hollows in old‐growth redwoods as roosts. We sought to determine whether bats use similar old‐growth trees as roosts when they occur in small, remnant patches of isolated old growth on commercial forest land. We compared bat occurrence in remnant and contiguous stands by collecting guano in traps suspended in hollows and by monitoring flight activity with ultrasonic bat detectors. Hollows in trees within the remnant stands had significantly more guano deposited per tree than the trees within the contiguous forest. The mean numbers of bat passes per night were statistically indistinguishable between the two treatments, although mean flight activity in the remnant stands was greater than in the contiguous forest. Bats frequently used basal hollows in small (<5 ha) stands of remnant old growth, which may be due to the closer proximity of remnants to stream courses, to their greater interface with edge where foraging success may be greater, or to the fact that the lower density of hollow‐bearing trees in remnants than in contiguous forest favored greater use per tree. Significant use of small, residual old‐growth redwood provides reason to maintain these remnants in managed landscapes as potentially important habitat for forest bats.
Response of Red‐Backed Voles to Recent Patch Cutting in Subalpine Forest
Authors: Hayward Gregory D. , Henry Stephen H. , Ruggiero Leonard F.
Published: March 2003

We examined the response of southern red‐backed voles (Clethrionomys gapperi) to patch cutting in a forested landscape in which 23% of the forest cover had been removed by timber harvest. We live trapped voles in and around 18 patchcuts in one watershed of southern Wyoming. Although we found a significant difference in capture rates between patchcut interior and forest habitats in 1 of 2 years, voles did not strongly avoid the interior of patchcuts. This result contrasts with results from most studies of voles in clearcut ecosystems, which report that red‐backed voles are generally rare or absent from clearcuts. Capture rates were highest on both sides of the patchcut edge, which also contrasts with studies of voles at the edges of forest remnants. The use of patchcut interior and edge habitats could not be explained as a consequence of juvenile voles dispersing to those habitats or males moving through the habitat in search of mates. We suggest that, despite similar physiognomy in patchcut and clearcut sites, the differences in landscape structure in perforated versus fragmented landscapes lead to very different patterns of vole movement. Understanding the scales at which voles perceive landscapes as coarse‐ or fine‐grained will be key to developing predictive models to aid managers in designing timber sales that maintain high vole populations. Our results emphasize the importance of the spatial pattern and scale of disturbance in determining the response of vertebrates to landscape change and the need for more refined investigations of the consequences of deforestation.
Fire Regime Changes in La Michilía Biosphere Reserve, Durango, Mexico
Authors: Fulé Peter Z. , Covington W. Wallace
Published: March 2003

Abstract:The ability of reserves to maintain natural ecosystem processes such as fire disturbance regimes is central to long‐term conservation. Fire‐scarred tree samples were used to reconstruct fire regimes at five study sites totaling approximately 230 ha in pine (  Pinusspp.) and oak (Quercusspp.) forests of La Michilía Biosphere Reserve on the dry east slope of the Sierra Madre Occidental, Durango, Mexico. Study sites covered a 20‐km environmental gradient of elevation, topography, and human land uses. Plant communities ranged from oak‐pine to mixed conifer forests. Fires were frequent at all sites prior to 1930, when large‐scale grazing of domestic livestock was initiated. Widespread fires have been excluded from four of the five sites since 1945, with an essentially uninterrupted regime of frequent fires continuing only in the reserve core. Xeric sites had many, smaller fires, whereas mesic sites had fewer but larger fires. On a reserve‐wide scale, a fire burned on at least one site nearly every year, usually in the dry spring or early summer season, but fire years were rarely synchronous among the sites. Fire occurrence was weakly related to the Southern Oscillation climate pattern; major reserve‐wide fire years almost never coincided with wet Southern Oscillation extremes but only occasionally matched dry extremes. Maintenance of the long‐term frequent‐fire regime in the reserve core is one indicator that the biosphere reserve model has been successful in conserving natural processes, but the protected area is small ( 7000 ha). Because of the key role of frequent‐fire regimes in regulating ecosystem structure and function, restoration of the ecological role of fire disturbance is a desirable conservation strategy.
Coexistence between People and Elephants in African Savannas
Authors: Hoare Richard E. , Du Toit Johan T.
Published: March 2003

Abstract:The decline in the range and numbers of elephants as a result of expanding human activity in Africa is recognized as one of the continent’s more serious conservation problems. Understanding the relationship between human settlement patterns and elephant abundance is fundamental to predicting the viability of elephant populations. The prevailing model of human‐elephant interaction predicts a negative linear relationship between rising human density and declining elephant density at a coarse (national or subcontinental) scale. Using observed elephant densities and human population data, we tested this prediction in a study area of 15,000 km2in northwestern Zimbabwe. The results did not fit a linear model. Elephant and human coexistence occurs at various levels of human density, up to a threshold of human density beyond which elephant populations disappear. This threshold seems to be related to a particular stage in the process of agriculturally transformed land becoming spatially dominant over the natural woodland that constitutes elephant habitat. Within the contexts of conservation and sustainable development in African savannas, investigating spatial relationships between elephant and human abundance should be a priority topic for future research.
Threat Reduction Assessment: a Practical and Cost‐Effective Approach to Evaluating Conservation and Development Projects
Authors: Salafsky Nick , Margoluis Richard
Published: March 2003

Abstract: There is a growing debate over the extent to which integrated conservation and development projects are contributing to conservation. One of the chief reasons for this debate is that there are few if any standardized and cost‐effective methods for defining and measuring conservation success so that different projects can be assessed over time or compared to other projects in different ecological and socioeconomic contexts. Current biologically based approaches to measuring conservation outcome have a number of practical limitations that preclude their use by typical project teams. As a result, most project teams do not measure project outcome and thus find it difficult to determine whether their interventions are working. To address this problem, we have developed an approach called threat reduction assessment (TRA) that measures project outcome. We explore the background for this approach, focusing on program evaluation in other disciplines, including engineering and public health; next we develop a model of the conservation and development context. We then propose one way in which this approach might be implemented through the calculation of a TRA index. Finally, we present and analyze examples of the approach in use in projects from Papua New Guinea, Indonesia, and Madagascar. We found that although the TRA approach has the theoretical disadvantages of being a proxy measurement of biodiversity and is subject to bias, it has the theoretical advantages of being sensitive to changes over short time periods and throughout a project site, and of allowing comparison among projects in different settings. Furthermore, it is practical and cost‐effective because it is based on data collected through simple techniques, it is directly related to project interventions, it is readily interpreted by project staff, and it can be done in retrospect. Although the TRA approach will need further refinement, it could be an important complement to biological approaches to measuring conservation project success.
Time Lag between Deforestation and Bird Extinction in Tropical Forest Fragments
Authors: Brooks Thomas M. , Pimm Stuart L. , Oyugi Joseph O.
Published: March 2003

Abstract: Tropical forests are becoming increasingly fragmented, threatening the survival of the species that depend on them. Small, isolated forest fragments will lose some of their original species. What is uncertain is how long this process of faunal relaxation will take. We compiled data on birds in five tropical forest fragments in Kakamega Forest, Kenya, of known date of isolation. We then predicted the original and eventual species richness of these fragments and, from this difference, the eventual species losses. Expressing the losses to date as a fraction of eventual losses suggests that faunal relaxation approximates an exponential decay with a half‐life of approximately 50 years for fragments of roughly 1000 ha. In other words, in the first 50 years after isolation, tropical forest fragments of this size suffer half of the total number of extinctions that they are likely to experience. This result sets the time scale over which humanity must take conservation action in fragmented tropical forests, may aid efforts to set priorities, and indicates how high the future global extinction rate will be.
No Inbreeding Depression Observed in Mexican and Red Wolf Captive Breeding Programs
Authors: Kalinowski Steven T. , Hedrick Philip W. , Miller Philip S.
Published: March 2003

Abstract: Inbreeding depression is expected to affect populations of outbreeding mammals in inverse proportion to their population size and can affect whether small populations persist or go extinct. We used studbook records to examine the effect of inbreeding upon juvenile viability and litter size in two endangered species that have recently been reintroduced to the wild: the Mexican wolf (Canis lupus baileyi) and the red wolf (C. rufus). We found that neither juvenile viability nor litter size was lowered by inbreeding in either taxon. In fact, both captive breeding programs appear to have less lethal equivalents than the median estimate for mammals. We did find that year of birth was correlated with increasing viability in both taxa. We conclude that there is no evidence that inbreeding depression will prove a major obstacle to the success of either recovery effort.
Simulating Historical Variability in the Amount of Old Forests in the Oregon Coast Range
Authors: Wimberly Michael C. , Spies Thomas A. , Long Colin J. , Whitlock Cathy
Published: March 2003

Abstract:We developed the landscape age‐class demographics simulator ( LADS) to model historical variability in the amount of old‐growth and late‐successional forest in the Oregon Coast Range over the past 3,000 years. The model simulated temporal and spatial patterns of forest fires along with the resulting fluctuations in the distribution of forest age classes across the landscape. Parameters describing historical fire regimes were derived from data from a number of existing dendroecological and paleoecological studies. Our results indicated that the historical age‐class distribution was highly variable and that variability increased with decreasing landscape size. Simulated old‐growth percentages were generally between 25% and 75% at the province scale (2,250,000 ha) and never fell below 5%. In comparison, old‐growth percentages varied from 0 to 100% at the late‐successional reserve scale (40,000 ha). Province‐scale estimates of current old‐growth (5%) and late‐successional forest (11%) in the Oregon Coast Range were lower than expected under the simulated historical fire regime, even when potential errors in our parameter estimates were considered. These uncertainties do, however, limit our ability to precisely define ranges of historical variability. Our results suggest that in areas where historical disturbance regimes were characterized by large, infrequent fires, management of forest age classes based on a range of historical variability may be feasible only at relatively large spatial scales. Comprehensive landscape management strategies will need to consider other factors besides the percentage of old forests on the landscape, including the spatial pattern of stands and the rates and pathways of landscape change.
Influence of Habitat Patchiness on Genetic Diversity and Spatial Structure of a Serpentine Endemic Plant
Authors: Wolf Amy T. , Harrison Susan P. , Hamrick James L.
Published: March 2003

Abstract:Conservation of rare plant species often involves small, local populations dispersed within apparently suitable habitat. We used enzyme electrophoresis to study genotypic diversity in 32 populations ofCalystegia collina, a self‐incompatible clonal plant endemic to serpentine substrate in northern California's Coast Range. Genotypic diversity within a population was a good predictor of seed set by randomly marked flowers. Ramets from the most abundant genotypes in a population were most likely to produce flowers, but flowers from abundant genotypes were less likely to produce seed capsules than were flowers from rarer genotypes. These results are consistent with previous findings that reproductive success inC. collinais limited by the availability of compatible pollen. On small serpentine outcrops supporting only one or two populations,C. collinadid not show reduced genotypic diversity or heterozygosity compared with populations on large outcrops supporting many populations. Instead, genotypic diversity and outcrop size had strong but independent influences on reproductive success. Although large serpentine outcrops contain more populations and provide better conditions for flower and seed production, significant diversity of unique genotypes clearly exists in isolated serpentine outcrops. Our findings suggest that plant conservation strategies must take into account the natural distribution of populations. The effects of habitat fragmentation onC. collinaand other plant species that occur naturally in small, discrete patches may be unlike those that have been documented in more recently fragmented species.
Marten Habitat Selection in a Clearcut Boreal Landscape
Authors: Potvin François , Bélanger Louis , Lowell Kim
Published: March 2003

Abstract:To describe the forest mosaic suitable for marten (  Martes americana) in a clearcut boreal landscape, we studied habitat selection in an area (123 km2) located in western Québec, in which black spruce (  Picea mariana) was the predominant forest type. This block had been recently clearcut with the protection of regeneration cutting technique, a logging method that employs equally spaced harvesting trails. The resulting landscape had a center dominated by a cutover matrix (60% of the block) and surrounded by contiguous uncut forest. Over 2 years, 20 marten equipped with radio collars provided enough locations to delineate their winter home range. Habitat composition and spatial configuration were measured at both stand and landscape scales by means of a geographic information system database that included telemetry locations and home ranges, forest maps, and limits of clearcut areas. Inside their winter home ranges, animals avoided open regenerating stands composed mostly of recent clearcuts with sparse regeneration. They did not select coniferous stands, even those that were mature or overmature, but preferred deciduous and mixed stands, a large proportion of which had a dense coniferous shrub layer as a result of a spruce budworm (Choristoneura fumiferana) epidemic 15–20 years ago. At the landscape scale, winter home ranges differed from random mosaics because they had a larger proportion of uncut forest (>30 years), a smaller proportion of open regenerating stands, larger core area in forest habitat, and less edge between open regenerating stands and forest. Winter home ranges usually contained <30–35% open or closed regenerating stands and> 40–50% uncut forest. We conclude that marten and clearcutting may be compatible, provided that forest logging is adapted to that species at the landscape level. Where the objective is to maintain marten at a local scale in black spruce forest, we suggest that ≥50% uncut forest be preserved inside 10‐km2units and that <30% of the area be clearcut over a 30‐year period.
Review of Ecological Effects of Roads on Terrestrial and Aquatic Communities
Authors: Trombulak Stephen C. , Frissell Christopher A.
Published: March 2003

Abstract:Roads are a widespread and increasing feature of most landscapes. We reviewed the scientific literature on the ecological effects of roads and found support for the general conclusion that they are associated with negative effects on biotic integrity in both terrestrial and aquatic ecosystems. Roads of all kinds have seven general effects: mortality from road construction, mortality from collision with vehicles, modification of animal behavior, alteration of the physical environment, alteration of the chemical environment, spread of exotics, and increased use of areas by humans. Road construction kills sessile and slow‐moving organisms, injures organisms adjacent to a road, and alters physical conditions beneath a road. Vehicle collisions affect the demography of many species, both vertebrates and invertebrates; mitigation measures to reduce roadkill have been only partly successful. Roads alter animal behavior by causing changes in home ranges, movement, reproductive success, escape response, and physiological state. Roads change soil density, temperature, soil water content, light levels, dust, surface waters, patterns of runoff, and sedimentation, as well as adding heavy metals (especially lead), salts, organic molecules, ozone, and nutrients to roadside environments. Roads promote the dispersal of exotic species by altering habitats, stressing native species, and providing movement corridors. Roads also promote increased hunting, fishing, passive harassment of animals, and landscape modifications. Not all species and ecosystems are equally affected by roads, but overall the presence of roads is highly correlated with changes in species composition, population sizes, and hydrologic and geomorphic processes that shape aquatic and riparian systems. More experimental research is needed to complement post‐hoc correlative studies. Our review underscores the importance to conservation of avoiding construction of new roads in roadless or sparsely roaded areas and of removal or restoration of existing roads to benefit both terrestrial and aquatic biota.
Comparative Analysis of Management Regimes and Medicinal Plant Trade Monitoring Mechanisms for American Ginseng and Goldenseal
Authors: Robbins Christopher S.
Published: March 2003

Abstract: Two popular and profitable native North American medicinal plants, American ginseng (   Panax quinquefolius) and goldenseal (  Hydrastis canadensis), both of which are listed in Appendix 2 of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), are monitored under disparate domestic strategies that are designed to satisfy CITES requirements. The P. quinquefolius program has benefited the species by encouraging U.S. states to enact laws to protect wild populations and regulate collection, and by establishing a transparent system under which harvest, commerce, and export can be monitored, evaluated, and controlled routinely. But certain programmatic constraints, such as insufficient funding and gaps in biological monitoring, undermine its effectiveness as a management strategy for the species. The joint industry and government H. canadensis initiative is intended to give commercial traders more responsibility in monitoring plant trade and the federal government access to information that may otherwise be difficult to obtain without the help of traders. I examined the structure, successes, and deficiencies of the P. quinquefolius program, promising features of the evolving H. canadensis program, Turkey's management of geophytes, and other sources of information from federal agencies that might contribute to more effective management of medicinal plants in the United States. Although the main goal of domestic monitoring programs for P. quinquefolius and H. canadensis is to implement their CITES listings, it is conceivable that similar programs could be established for non–CITES medicinal plants, thereby minimizing or replacing the need for CITES protection.
Effects of a Proposed Ex Situ Conservation Program on In Situ Conservation of the Babirusa, an Endangered Suid
Authors: Clayton L. M. , Milner‐Gulland E. J. , Sinaga D. W. , Mustari A. H.
Published: March 2003

Abstract: Detailed data are rarely available to show how interventions such as captive breeding programs can create an uncontrolled demand for live specimens of endangered species. We present a case study of the effect of a planned, internationally recognized captive breeding program on trade in the endangered babirusa wild pig from July to December 1998. Although the program had not yet begun, international interest in the captive breeding of babirusas gave hunters and dealers the false impression that there was a potentially lucrative and officially sanctioned national and international demand for any live babirusas they might catch. Swift action by the Indonesian authorities halted this trade, but the study provides a warning about the damage that can be caused to the conservation of a species if management programs are instituted without a full understanding of the practicalities of its conservation, particularly interactions between the species and local people.
Bayesian Methods in Conservation Biology
Authors: Wade Paul R.
Published: March 2003

Abstract: Bayesian statistical inference provides an alternate way to analyze data that is likely to be more appropriate to conservation biology problems than traditional statistical methods. I contrast Bayesian techniques with traditional hypothesis‐testing techniques using examples applicable to conservation. I use a trend analysis of two hypothetical populations to illustrate how easy it is to understand Bayesian results, which are given in terms of probability. Bayesian trend analysis indicated that the two populations had very different chances of declining at biologically important rates. For example, the probability that the first population was declining faster than 5% per year was 0.00, compared to a probability of 0.86 for the second population. The Bayesian results appropriately identified which population was of greater conservation concern. The Bayesian results contrast with those obtained with traditional hypothesis testing. Hypothesis testing indicated that the first population, which the Bayesian analysis indicated had no chance of declining at >5% per year, was declining significantly because it was declining at a slow rate and the abundance estimates were precise. Despite the high probability that the second population was experiencing a serious decline, hypothesis testing failed to reject the null hypothesis of no decline because the abundance estimates were imprecise. Finally, I extended the trend analysis to illustrate Bayesian decision theory, which allows for choice between more than two decisions and allows explicit specification of the consequences of various errors. The Bayesian results again differed from the traditional results: the decision analysis led to the conclusion that the first population was declining slowly and the second population was declining rapidly.
Response of Avian Communities to Historic Habitat Change in the Northern Chihuahuan Desert
Authors: Pidgeon A. M. , Mathews N. E. , Benoit R. , Nordheim E. V.
Published: March 2003

Abstract:Throughout much of the northern Chihuahuan Desert, the grasslands that were widespread at the time of European settlement have been replaced by desert shrublands. Little is known about the effects of this change on avian communities. We analyzed historic U.S. Government Land Office records to assess large‐scale changes in vegetation cover from the 1880s to the present day. We studied vegetation and avian communities in one grassland habitat type and four desert shrubland habitat types to examine (1) how breeding‐bird communities may have changed in response to habitat conversion from grassland to desert shrubland and (2) whether breeding‐bird communities differ among the four desert shrubland habitat types that compose Chihuahuan Desert scrub in this region. To estimate the characteristics of 1880s black grama (   Bouteloua eriopoda) grassland, we focused on plots located within extensive patches of present‐day black grama and compared the avian communities found there with those in desert shrubland. Species richness was higher in desert shrubland than grassland. Among the desert shrubland habitat types, species richness was consistently highest in mesquite. Avian abundance patterns differed among the four desert shrubland habitat types. At least 30% of the avian community in each habitat pair was distinct. Conversion of grassland to shrubland in south‐central New Mexico has likely been accompanied by a major turnover in the avian community. Remaining tracts of black grama provide habitat for species that may be uniquely adapted to the northern Chihuahuan Desert and should be protected.
A Systematic Test of an Enterprise Strategy for Community‐Based Biodiversity Conservation
Authors: Salafsky N. , Cauley H. , Balachander G. , Cordes B. , Parks J. , Margoluis C. , Bhatt S. , Encarnacion C. , Russell D. , Margoluis R.
Published: March 2003

Abstract:A commonly held belief is that if people can benefit financially from enterprises that depend on nearby forests, reefs, and other natural habitats, then they will take action to conserve and sustainably use them. The Biodiversity Conservation Network brought together conservation and development organizations and local communities to systematically test this hypothesis across 39 conservation project sites in Asia and the Pacific. Each project implemented one or more community‐based enterprises such as setting up an ecotourism lodge, distilling essential oils from wild plant roots, producing jams and jellies from forest fruits, harvesting timber, or collecting marine samples to test for pharmaceutical compounds. Each project team collected the biological, enterprise, and social data necessary to test the network's hypothesis. We present the results of this test. We found that a community‐based enterprise strategy can lead to conservation, but only under limited conditions and never on its own. We summarize the specific conditions under which an enterprise strategy will and will not work in a decision chart that can be used by project managers to determine whether this strategy might make sense at their site. We also found that an enterprise strategy can be subsidized and still create a net gain that pays for conservation. Based on our experiences, we recommend developing “learning portfolios” that combine action and research to test other conservation strategies.
Temperate Terrestrial Vertebrate Faunas in North and South America: Interplay of Ecology, Evolution, and Geography with Biodiversity
Authors: Barnosky Anthony D. , Hadly Elizabeth A. , Maurer Brian A. , Christie Michael I.
Published: March 2003

Abstract: To help identify the factors that govern species richness in biological preserves, we performed a comparative study of terrestrial vertebrate species richness for two analogous montane areas critical for biodiversity conservation: the Greater Yellowstone region of the Rocky Mountains, United States, and the Nahuel Huapi region, Patagonia, around Bariloche, Argentina. We explored the ecological interactions of such factors as latitude, habitat heterogeneity, inferred productivity, geographic context, history of lineage, and history of environment in generating and maintaining species richness. Overall species richness of terrestrial vertebrates was higher in the Yellowstone area, but patterns were not uniform across vertebrate classes. Ectotherms (reptiles and amphibians) were more diverse in the Patagonian site, whereas endotherms (birds and mammals) were more diverse in the Yellowstone site. The higher diversity of Patagonian ectotherms is a result of abnormally high numbers of species within two specialized taxa: frogs and the lizard genus Liolaemus. There were high percentages of endemic species (68% of amphibians, 35% of reptiles, 15% of mammals) and feral, non‐native mammals (19%) in Patagonia. These results imply that (1) biodiversity is generated and maintained by a combination of local phenomena and by continental area and related historical constraints; (2) the relative weight of the various influences may differ for ectotherms (  fit latitudinal and related models) and endotherms (  fit history‐based models); and (3) because larger‐scale processes are so important for the maintenance of natural biological diversity, it is crucial that biological reserves be selected and managed with an understanding of the geographical and geological context of the continents on which they are located. Reserves located on large continents with connections to other continents preserve large numbers of species per given unit of geographic area and protect critical habitat for species such as migrants that require large areas for maintenance of persistent populations. In contrast, reserves located on relatively isolated continents protect a high number of evolutionarily unique species per given unit of geographic area and have a high potential for colonization by exotic species.
Predicting the Risk of Extinction through Hybridization
Authors: Wolf Diana E. , Takebayashi Naoki , Rieseberg Loren H.
Published: March 2003

Abstract:Natural hybridization threatens a substantial number of plant and animal species with extinction, but extinction risk has been difficult to evaluate in the absence of a quantitative assessment of risk factors. We investigated a number of ecological parameters likely to affect extinction risk, through an individual‐based model simulating the life cycle of two hybridizing annual plant species. All parameters tested, ranging from population size to variance in pollen‐tube growth rates, affected extinction risk. The sensitivity of each parameter varied dramatically across parameter sets, but, overall, the competitive ability, initial frequency, and selfing rate of the native taxon had the strongest effect on extinction. In addition, prezygotic reproductive barriers had a stronger influence on extinction rates than did postzygotic barriers. A stable hybrid zone was possible only when habitat differentiation was included in the model. When there was no habitat differentiation, either one of the parental species or the hybrids eventually displaced the other two taxa. The simulations demonstrated that hybridization is perhaps the most rapidly acting genetic threat to endangered species, with extinction often taking place in less than five generations. The simulation model was also applied to naturally hybridizing species pairs for which considerable genetic and ecological information is available. The predictions from these “worked examples” are in close agreement with observed outcomes and further suggest that an endemic cordgrass species is threatened by hybridization. These simulations provide guidance concerning the kinds of data required to evaluate extinction risk and possible conservation strategies.
Relationship between Coefficient of Inbreeding and Parasite Burden in Endangered Gazelles
Authors: Cassinello Jorge , Gomendio Montserrat , Roldan Eduardo R. S.
Published: March 2003

Abstract: We studied the effects of inbreeding depression on parasite infection in three species of endangered gazelles: Gazella cuvieri, G. dama, and G. dorcas. Coefficients of inbreeding were calculated for all individuals because complete genealogies were available. The levels of inbreeding differ both intra‐ and interspecifically. We collected samples of feces and determined nematode infection by counting nematode eggs in the samples. At the interspecific level, the species with the highest mean levels of inbreeding ( G. cuvieri) had the highest levels of gastrointestinal parasites. Analyses done at the intraspecific level revealed a positive relationship between individual coefficient of inbreeding and parasite infection in G. cuvieri, but not in the species with the intermediate and lowest levels of inbreeding. Our findings suggest that high levels of inbreeding may make individuals more susceptible to parasitism, even under favorable environmental conditions, so this factor should be taken into account by those managing endangered species.