bluuebunny/crossref_metadata_2025 huggingface dataset:
Eastern Hemlock Regeneration and Deer Browsing in the Northern Great Lakes Region: A Re‐examination and Model Simulation
Authors: MLADENOFF DAVID J. , STEARNS FOREST
Published: March 2003

Abstract: White‐tailed deer (Odocoileus virginianus) populations are currently extremely high in the upper Great Lakes region, and browsing may have severe negative effects on many forest species, including the eastern hemlock (Tsuga canadensis), a former forest dominant. We suggest that this problem must be examined in an expanded spatial and temporal context. It may be incorrect to generalize from limited evidence on one scale of observation (stand level) to explain a regional, long‐term failure of tree species regeneration. We reviewed hemlock life‐history characteristics, its long‐term behavior on a regional scale, and evidence from recent studies in the context of long‐term forest ecosystem processes. We then conducted 400‐year computer simulations within a neutral model framework (see Caswell 1976), relative to browsing, to test whether other factors might adequately explain the lack of hemlock regeneration in the northern lake states. The results suggest that browsing is not the critical step blocking hemlock forest re‐establishment on a regional scale. We suggest that the interaction of climate, disturbance, hemlock life history, ecosystem processes, and historical land use produce positive feedbacks that prevent hemlock regeneration usually before deer browsing can occur. There is need to modify current single‐species forest management and silviculture, and to manage forests at a landscape scale in a way that maintains regional biodiversity and sustainable forest ecosystems. These modifications should include reduced deer levels and maintenance of larger patches of mature ecosystems. But we caution against broadly invoking the negative effects of any single factor such as browsing as a basis for management changes without a thorough assessment of all factors.
Centers of High Biodiversity in Africa
Authors: POMEROY DEREK
Published: March 2003

Abstract: Species diversity is commonly used as a criterion for determining the most important sites for conservation. The simplest method is merely to use species richness, but more sophisticated methods weight species in various ways. Further refinements can be made by combining two or more methods for one or more taxonomic groups. Data for Africa are limited and of variable quality, but “hotspots” can be identified provisionally, the Albertine Rift (where Burundi, Rwanda, Uganda, and Zaire meet) coming up most consistently. But the varying resutls produced by different methods almost certainly reflect some real differences, as can be seen both regionally (endemism at the Cape is high for plants but not for other groups) and locally (the species richness of forest trees and forest birds in Uganda are only moderately correlated). Hence, overall conservation policies are likely to be improved by the use of more than one criterion.
Sex‐Biased Harvesting and Population Dynamics in Ungulates: Implications for Conservation and Sustainable Use
Authors: Ginsberg J.R. , Milner‐Gulland E.J.
Published: March 2003

The consumptive use of wildlife, in particular trophy hunting and game ranching of ungulates, has been advocated as a tool for conservation in Africa. We show that these methods of harvesting differ significantly from natural predation, with trophy hunting showing extreme selection for adult males and game ranching leading to disproportionate harvests of young males. Little information, either theoretical or empirical, exists concerning the effect of these harvesting regimes on the long‐term population dynamics of ungulate populations. Despite that, the potential effects of sex‐skewed harvests are numerous. In this paper, we investigate one potentially deleterious effect of sex‐skewed harvests. Both theory and experimental data suggest that male ungulates are limited in their absolute ability to inseminate females. Using a Leslie‐Matrix model and published data on impala, we show that the interaction between sperm limitation and harvests with highly male‐biased sex ratios can lead to greatly reduced female fecundity (defined as the number of young born) and population collapse. These results are robust and suggest that present methods of harvesting may not be optimal, or viable, in the long term.
Genetic Depletion in the European Bison (Bison bonasus) and the Significance of Electrophoretic Heterozygosity for Conservation
Authors: Hartl Günther B. , Pucek Zdzislaw
Published: March 2003

Starch gel electrophoresis was used to screen 35 lowland bison from the herd in the Biażlowieża Primeval Forest for genetic variation at 69 presumptive structural loci. Average heterozygosity (H = 1.2%) proved to be three times lower than that based on 20 loci (H = 3.5%) reported in a previous study by other authors. These earlier results were interpreted as evidence that the passage of the species through an extreme genetic bottleneck (12 founder genomes) had not had much influence on genetic variation. A comparison of estimates of H and the proportion of polymorphic loci (P) among different species or populations of Artiodactyla revealed that P was the only parameter to be significantly reduced in those that had experienced genetic bottlenecks. However, the data also show that, in spite of similar H values in species or populations with or without bottlenecks, average heterozygosity is only useful as an indicator of overall genetic variability in the latter. To draw conclusions about genetic depletion on the basis ofelectrophoretic data, we strongly recommend that H, together with its variance among a large number of loci, and additional parameters such as P and the ratio H:P be taken into account.
Quantitative Ethnobotany and Amazonian Conservation
Authors: Phillips O. , Gentry A.H. , Reynel C. , Wilkin P. , Galvez‐Durand B C.
Published: March 2003

We use quantitative ethnobotanical data to compare the usefulness of six floristically distinct forest types to mestizo people at Tambopata, southeast Peru. We aim to evaluate which forest types are most useful, and why. Ethnobotanical data were collected with informants in inventory plots and analyzed using a new technique that uses a two‐tier calculation process to derive an “informant indexed” estimate of each species’ use value. Use values are estimated based on the degree of consistency between repeated interviews of each informant and between different informants. We show that (1) in 6.1 ha, 94% of woody stems are “useful” to mestizos. (2) Based on percentages of useful plants per plot, there is little difference between each forest type. (3) Simply calculating the percent of useful plants is misleading, however, because most species have minor uses, and only a few are exceptionally useful. (4) Using the informant indexing technique, we demonstrate significant differences between each forest type’s utility. Mature forests of present and former floodplains are more useful than other forest types, mostly due to their importance as sources of construction materials and food. (5) Lower floodplain is more useful medicinally, swamp more important commercially, and terra firme sandy more important technologically; they are not easily substituted for some of these uses. (6) On average, 80% of the value of forest plant products to mestizos is subsistence value; only 20% is commercial. We conclude that (1) to maintain cultural autonomy, Amazonian people may need access to all local forest types, and (2) present and former floodplain forests in western Amazonia should be a conservation priority. We make these broad conclusions on the basis of evidence of: (1) ethnoecological similarities among mestizo cultures in Peruvian Amazonia; (2) the similarity of family‐level floristic composition at Tambopata and elsewhere in western Amazonia, (3) rapid floodplain deforestation; and (4) floodplain resource overextraction. Conservationists should focus on helping communities gain control of floodplain resources.
Avian Communities of Fragmented South‐Temperate Rainforests in Chile
Authors: Willson Mary F. , De Santo Toni L. , Sabag Carlos , Armesto Juan J.
Published: March 2003

The diversity and relative abundance of south‐temperate rainforest birds decreased as the size of the habitat patch decreased. Ecological categories, including endemics, mutualists (pollinators, seed dispersers), understory species, and species dependent on large trees, were not differentially sensitive to patch size. Nevertheless, most of the species with at least marginally significant declines were endemic (6 of 7 species), covered nesters (6 of 7 species), and understory dwellers (5 of 7 species). Some mutualists and big‐tree users were also affected. The losses will become more severe as clearing of the forest continues. Possible mitigation measures include leaving small stands of forest and corridors between habitat patches and, in certain circumstances, alternative agricultural practices.
Wildlife Association with Human‐Altered Water Sources in Semiarid Vegetation Communities
Authors: Burkett Douglas W. , Thompson Bruce C.
Published: March 2003

Based on common use in wildlife management, we hypothesized that human‐constructed water sources influence faunal communities detectably compared to similar habitats that lack water. We examined 20 wildlife water units and 20 paired comparison sites without water from April to August 1992 in semiarid southern New Mexico to assess animal species associations. We sampled sites by using small‐mammal live traps, herpetofaunal and invertebrate pitfall arrays, and 30‐minute time‐area counts. We compared animal species richness and species concordance among water units (rain catchments, earthen tanks, and windmills) and comparison sites in three vegetation communities (mixed scrub, grassland, and pinyon‐juniper). We detected 134 animal taxa during field sampling. Animal species richness did not differ between water units and comparison sites among vegetation communities. Amphibians were found only at water units but occur far from units during seasonal wet periods. Greater numbers of individual small mammals and herpetofauna at water units versus comparison sites likely related to debris and disturbed soil present near water units. Taxa detected at water units and comparison sites were 65% concordant overall; discordant taxa were those rarely detected. Our data implied that definitive effects of artificial water sources on native wildlife species were not detectable. Providing water sources may be a strategic management tool but must be viewed critically regarding effect on distribution of native, feral, and exotic animals. Water units should be developed only when and where clear objectives have been stated, natural water sources have been quantified, commitment exists to ensure continued function, and feral and exotic animals will not benefit to the detriment of native species.
Pollution, Habitat Destruction, and Biodiversity in Poland
Authors: Oleksyn Jacek , Reich Peter B.
Published: March 2003

In the past 50 years, Poland has experienced unprecedented deterioration of the environment and loss of biodiversity. Emissions of toxic gases, such as SO2, have reached 3 to 4 million tons annually, widely affecting flora, fauna, and human health. Almost all surface waters are heavily polluted. More than 75% of the water in the Vistula, Poland's largest river, is unsuitable even for industrial use. Environmental pollution, habitat loss and fragmentation, and industrialization of agricultural lands and forests have contributed to the loss of biodiversity. As many as 2500 plant species may be endangered (≈25% of all species) and approximately 228 (≈2%) have been extirpated from Poland. The largest losses of flora and fauna have occurred in wetland ecosystems. Among vertebrate species, 15 (≈2%) have been lost and more than 210 (another 30%) are endangered. Given the current economic uncertainty, it is difficult to predict future trends in pollutant emissions and their effects on Poland's biological diversity.
A Reassessment of Homozygosity and the Case for Inbreeding Depression in the Cheetah, Acinonyx jubatus: Implications for Conservation
Authors: Merola Michele
Published: March 2003

Preservation of genetic diversity within declining populations of endangered species is a major concern in the discipline of conservation biology. The endangered cheetah, Acinonyx jubatus, exhibits relatively little genetic variability (polymorphism = 0.02–0.04, heterozygosity = 0.0004–0.014). Since the discovery of the cheetah's relative homozygosity, this species has been frequently cited as an example of one whose survival may be compromised by the loss of genetic diversity. The cheetah's genetic uniformity is generally believed to be the result of an historical population bottle‐neck followed by a high level of inbreeding. Evidence offered in support of this hypothesis includes the cheetah's present low level of genetic variability and symptoms of inbreeding depression in captive populations. Using available data on fluctuating asymmetry and genetic variation in other carnivores, I question the assumption that the present level of genetic diversity in the cheetah is indicative of a loss of former variability. Carnivores exhibit significantly lower levels of genetic variation than other mammals, and several carnivores for which data are available exhibit lower levels of heterozygosity and polymorphism than the cheetah does. Measures of fluctuating asymmetry do not support the hypothesis that the cheetah is suffering an increased level of bomozygosity due to genetic stress. Many of the phenotypic effects attributed to inbreeding depression, such as infertility, reduced litter sizes, and increased susceptibility to disease, are limited to captive individuals and may be explained as physiological or behavioral artifacts of captivity. In sum, the genetic constitution of the cheetah does not appear to compromise the survival of the species. Conservation efforts may be more effectively aimed at a real, immediate threat to the cheetah's future: the loss of its natural habitat.
Conservation of the Grassy White Box Woodlands: Population Genetics and Fragmentation of Eucalyptus albens
Authors: Prober Suzanne M. , Brown A.H.D.
Published: March 2003

White box (Eucalyptus albens) woodlands once covered large parts of the fertile agricultural land of the wheat‐sheep belt of southeastern Australia. Populations of E. albens were almost continuous across much of this region, but clearing has left a mosaic of remnant populations, scattered trees, and treeless pastures or cropland. Using allozyme electrophoresis of remnant populations sampled from across the range of E. albens, we examined patterns of genetic variation in this species and the effects of fragmentation on its genetic diversity. Total genetic diversity in E. albens was higher than reported for any other eucalypt species (Ht = 0.306), while differentiation among populations from across its range was one of the lowest for eucalypts (Gst = 5.7%). Cluster analysis of the 10 largest populations sampled indicated that patterns of genetic variation in E. albens are generally consistent with geographic relationships, although no major genetic differentiation was detected. The relationship between genetic and geographic patterns was obscured with the inclusion of small populations in the analysis, suggesting a need for caution in the sampling of small populations for genetic studies. There was a significant, log relationship between remnant population size and all genetic diversity measures, with lower diversity in small populations of less than about 500 individuals. Some small populations had higher levels of diversity than would be expected from this simple relationship, and the deviants were best explained by low isolation from larger stands of E. albens (for total number of alleles) or lower than average levels of inbreeding (for observed beterozygosity). We recommend that for maximum conservation of genetic diversity in E. albens at the local scale, populations should either contain greater than 500 individuals or form a closely spaced mosaic to allow gene flow between smaller units. Reconstructed populations should be established from seed collected from local populations of greater than 500 individuals. At the broad scale, conservation of genetic diversity in E. albens would probably be maximized by a wide geographic spread of reserved populations.
Anadromous Fish as Keystone Species in Vertebrate Communities
Authors: Willson Mary F. , Halupka Karl C.
Published: March 2003

Many wildlife species feed on anadromous fishes of several life‐history stages. There is evidence for some wildlife species that the availability of anadromous fish is critically important for survival or reproduction. In some regions anadromous fishes in fresh water appear to be keystone food resources for vertebrate prediators and scavengers, forging an ecologically significant link between aquatic and terrestrial ecosystems. The spatial distribution of anadromous fish in fresh water, including the occurrence of runs in very small streams, has important consequences for wildlife biology (social interactions, distribution, activity patterns, possibly survivorship) and conservation of biodiversity.
Relation of Terrestrial‐Breeding Amphibian Abundance to Tree‐Stand Age
Authors: Dupuis Linda A. , Smith James N.M. , Bunnell Fred
Published: March 2003

There is a lack of research on the effects of logging on Canadian amphibians. We compared the abundance of terrestrial salamanders in old‐growth forests with that in young and mature post‐harvest stands. We also measured habitat features of amphibians and contrasted these with old‐growth and harvested stands to assess the effects of forest harvest. Quadrat searches demonstrated that clearcut harvesting reduces terrestrial amphibian populations by up to 70% in coastal old‐growth forests. We suggest that this reduction results from a decrease in availability of moist microhabitats. Salamander densities within 10 meters of streams in managed stands were similar to those near and away from streams in old growth. We recommend that forest managers recognize the needs of terrestrial amphibians and help maintain amphibian populations by preserving cool, moist habitats. This can be accomplished within cutblocks by (1) maintaining an even distribution of logs and snags as stable, moist microhabitats; (2) retaining some understory as sources of shade, and (3) preserving streamside buffers. Managers must also ensure some level of landscape connectivity to enable climate‐sensitive amphibians to disperse and recolonize marginal habitats.
Dispersal and Use of Corridors by Birds in Wooded Patches on an Agricultural Landscape
Authors: Haas Carola A.
Published: March 2003

Dispersal behavior has important effects on the persistence and recolonization of populations, but is one of the least understood traits of most organisms. Knowledge of patterns of fledgling, natal, and breeding dispersal of birds in a patchy environment will assist in decisions regarding reserve design and protection or construction of corridors. I present data on movement patterns of three migratory bird species, American Robin (Turdus migratorius), Brown Thrasher (Toxostoma rufum), and Loggerhead Shrike (Lanius ludovicianus). These birds are relatively common breeders in south‐central North Dakota (U.S.) in riparian woodlands and in shelterbelts (woodlots planted as windbreaks in the open agricultural environment). Field assistants and I individually marked and monitored the movements of more than 500 adults breeding in a network of shelterbelts across an 8 × 11 km study area. Most movement occurred at relatively short distances within a shelterbelt. Movements by adults between shelterbelt sites, although rare, occurred significantly more frequently between sites connected by a wooded corridor than between unconnected sites. For robins, there were on average 2.5 dispersal events between each pair of connected sites, but only 0.17 dispersal events between each pair of unconnected sites (Mann‐Whitney test, significant at p < 0.009). Because unconnected and connected sites were similar in average area (1.7 to 1.9 ha), distance to next wooded habitat, and tree‐species composition, this result provides a test of the hypothesis that organisms disperse preferentially along connecting corridors.
Patterns of Diversity of Neotropical Squamate Reptile Species with Emphasis on the Brazilian Amazon and the Conservation Potential of Indigenous Reserves
Authors: Da Silva Nelson Jorge , Sites Jack W.
Published: March 2003

We present new distibutional data for squamate reptiles (amphisbaenians, lizards, and snakes) from several Neotropical sites and estimate species (alpha) diversity at each site. Species compositions at all localities were used to estimate similarity in species richness within and between each of the major regions sampled: Central American lowland forests, Amazonia, and South American dryland forests. We used these estimates to derive maps summarizing overall regional patterns (beta diversity) of squamate richness. Both groups clearly reveal distinct faunal divisions among the three regions. Within Amazonia, lizards and snakes show a clear division in species composition between a “western edge” cluster of sites adjacent to eastern Andean slopes and all other localities in the central and eastern regions. Within this east‐central block of sites, a further division is evident between localities north and south of the main Amazon River channel. These general regions of squamate similarity were qualitatively assessed in Brazil’s portion of Amazonia within the context of the distribution of all state, federal, and Indian lands that are in principle afforded some level of protection and therefore offer potential for biodiversity conservation. We assess the potential for biodiversity conservation relative to the size of reserves needed to sustain populations of 500 individuals of the three largest species of snakes and to the distribution of potential conservation areas relative to the regional patterns of diversity identified by the statistical analysis. We conclude that the sizes and distributions of reserves are adequate to sustain viable populations of squamates if these areas can be counted on to play a major role in biodiversity conservation.
Across‐Country Analyses of Biodiversity Congruence and Current Conservation Effort in the Tropics
Authors: Balmford Andrew , Long Adrian
Published: March 2003

In identifying priorities for conservation action, it is critically important to assess how much current conservation initiatives are targeted toward key sites for biodiversity. Such analyses are greatly hampered, however, by lack of information about biological richness and existing conservation effort. We tried to address this problem by using data on one well‐known indicator group and by focusing solely on an international scale, which is the only level at which global information on certain aspects of conservation effort is so far available. Building on the results of a project that mapped the distribution of all bird species with breeding ranges of less than 50,000 km2, we found that the number of these restricted‐range birds in tropical countries was a useful predictor of national levels of endemism and, to a lesser extent, species richness and threat in other animal and plant groups. The relationships usually persisted after removing the effects of country area, confirming the utility of restricted‐range birds as biodiversity indicators. When we then compared national scores for restricted‐range bird species with measures of current conservation effort, we found that the extent of both protected areas and foreign funding for biodiversity conservation and research increased with this index of a country’s biological value. Thus, conservation efforts are generally greater in tropical countries with large numbers of restricted‐range birds. These results should be interpreted cautiously. When we controlled for area effects, although mean biodiversity spending per unit area of a country increased with area‐adjusted importance for restricted‐range birds, the percentage of a country covered by protected areas did not increase. Moreover, our indices of effort and biological richness are clearly limited in scope, quality, and resolution. Most important, the relationships between overall current effort and biological value are weak, and there are many ornithologically rich countries that receive relatively little conservation attention. These nations are in many cases important priorities for additional conservation action.
Decline of the Shasta Crayfish (Pacifastacus fortis Faxon) of Northeastern California
Authors: Light Theo , Erman Don C. , Myrick Chris , Clarke Jay
Published: March 2003

Native freshwater faunas in North America are declining, principally due to the combined effects of habitat degradation and introduced species. Relatively little attention has been directed to the decline of freshwater invertebrates, which may be even more threatened than fishes. This paper chronicles recent changes in the distribution and abundance of the Shasta crayfish (Pacifastacus fortis Faxon), a state and federally endangered species endemic to the midreaches of the Pit River system in northeastern California. We made snorkeling and SCUBA surveys for crayfish in 1990 and 1991 and examined various records for historic distributions. Shasta crayfish have been extirpated from much of their historic range by water impoundment and diversion, and they are further threatened by two introduced crayfish species (Pacifastacus leniusculus Dana and Orconectes virilis Hagen). By 1990 Shasta crayfish were restricted to seven isolated populations, mostly in the headwaters of spring‐fed tributaries to the Pit river. P. leniusculus had become established throughout much of the study area in about 12 years. In one site P. leniusculus probably contributed to the precipitous decline of Shasta crayfish, from 2000–3000 in 1980 to about 370 (± 135) in 1991. O. virilis, which occurred in only the most disturbed parts of the system, showed little range expansion in 30 years and had been replaced in a large stretch of the Pit River by P. leniusculus. P. leniusculus occupied sites with a broad range of habitat variables (temperature, pH, turbidity, substrate size) partly or wholly overlapping measures of sites with the other two species. The decline of the Shasta crayfish, like the extinction of its closest relative P. nigrescens in the San Francisco Bay area earlier this century, reflects the decline of its habitat and probably pressure from the aggressive exotic P. leniusculus.
Population History, Genetic Variability, and Horn Growth in Bighorn Sheep
Authors: FitzSimmons Nancy N. , Buskirk Steven W. , Smith Michael H.
Published: March 2003

Bighorn sheep (Ovis canadensis) are restricted in distribution and numbers relative to presettlement conditions. Some populations have alledgedly suffered losses of fitness resulting from small, insular populations and a breeding system that reduces effective population size. Large horns in rams, which confer breeding superiority, are absent from some populations, and this absence may result in part from loss of genetic variability. We investigated the relationship among allozyme variability, population history, and horn growth in bighorn sheep from the Rocky Mountains. Heterozygosity was higher for bighorn sheep than has been reported for Dall sheep (O. dalli). Heterozygosity and allelic variability were marginally related to effective population size for the proceeding 15 years. Horn growth was significantly higher in more heterozygous than in less heterozygous rams for years 6, 7, and 8 of life. By the end of year 8, more heterozygous rams had 13% higher horn volumes than less heterozygous rams. Most hunting of bighorn sheep involves selective removal of large‐horned rams, which we hypothesize may reduce genetic variability of these populations and contribute to losses in fitness.
Effects of Changes in Biodiversity on Ecosystem Function in Tropical Forests
Authors: Silver Whendee L. , Brown Sandra , Lugo Ariel E.
Published: March 2003

Changing land use in the tropics has resulted in vast areas of damaged and degraded lands where biodiversity has been reduced. The majority of research on biodiversity has been focused on population and community dynamics and has rarely considered the ecosystem processes that are intimately related. We present a framework for examining the effects of changes in biodiversity on ecosystem function in natural, managed, and damaged tropical forests. Using a whole‐ecosystem approach, the framework identifies key nutrient and energy cycling processes and critical junctures or pathways, termed interfaces, where resources are concentrated and transferred between the biotic and abiotic components of the ecosystem. Processes occurring at these interfaces, and the organisms or attributes participating in these processes, exert a strong influence on ecosystem structure. We use examples from Puerto Rico, Southern China, Dominica, and Nicaragua to illustrate how the functional diversity framework can be applied to critically examine the effects of changes in biodiversity on ecosystem function, and the relative success or failure of rehabilitation strategies. The few available data suggest that functional diversity, and not just species richness, is important in maintaining the integrity of nutrient and energy fluxes. High species richness, however, may increase ecosystem resiliency following disturbance by increasing the number of alternative pathways for the flow of resources. We suggest ways in which the framework of functional diversity can be used to design research to examine the effects of changes in biodiversity on ecosystem processes and in the design and evaluation of ecosystem management and land rehabilitation projects in the tropics.
Ranking Conservation and Timber Management Options for Leadbeater’s Possum in Southeastern Australia Using Population Viability Analysis
Authors: Lindenmayer David B. , Possingham Hugh P.
Published: March 2003

The conservation of the endangered Leadbeater’s Possum, Gymnobelideus leadbeateri, is one of the most contentious forestry issues in Australia. The challenge is to identify strategies to conserve the species in the significant portion of its range in the central highlands of Victoria (southeastern Australia) where timber harvesting occurs. We used ALEX, a simulation program for population viability analysis, to explore the effectiveness of potential forest management strategies to enhance the persistence of G. leadbeateri in areas of wood production. Our study focused on the relationship between the risk of metapopulation extinction and (1) the number and spatial arrangement of 50‐ha logging areas that could be reserved from timber harvesting and (2) the impacts of post‐fire salvage logging in reserved areas. We modeled complex patch structures within two forest blocks (Murrindindi and Steavenson) that were based on maps of both existing patches of suitable habitat for G. leadbeateri and the location of potential logging areas. We recorded high values for the probability of extinction of metapopulations of G. leadbeateri when existing strategies for the conservation of the species within the Murrindindi and Steavenson Forest Blocks were modeled. Exclusion of salvage logging operations from burned, old‐growth forests significantly improved the species’ prospects of survival in both the short and long term. Withdrawal of timber harvesting from some proposed logging coupes made a significant, positive long‐term contribution to metapopulation persistence. But there will be a delay of at least 150 years until areas set aside now make a significant contribution to metapopulation persistence. This is the time required for existing stands of regrowth to develop old‐growth characteristics that are an essential habitat component for G. leadbeateri. We examined the effectiveness of different designs for setting aside a total reserved area of 300 ha. These ranged from a single 300‐ha reserve to 12, 25‐ha reserves. Populations in smaller reserves were vulnerable to extinction from demographic stochasticity and environmental variability. Conversely, a small number of larger reserves were susceptible to destruction in a single, catastrophic wildfire, highlighting the need for several dispersed reserves. Analyses of the sensitivity of various management options to variations in fire frequency and extent, movement capability, and a wide range of other factors indicated that the conservation strategy that gave the best relative outcome for G. leadbeateri was both to set aside several 50 to 100‐ha reserves in every forest block and to preclude post‐fire salvage logging operations from these areas if they burned in a wildfire.
Pastoral Politics: Gaddi Grazing, Degradation, and Biodiversity Conservation in Himachal Pradesh, India
Authors: Saberwal Vasant K.
Published: March 2003

Two assumptions underlie the current conservation focus worldwide. The first is that democratic governments can restrict human resource use within protected areas, and the second is that human land use for subsistence leads to degradation and is incompatible with the maintenance of high levels of biological diversity. An examination of official policy documents over the past century indicates that Gaddi herders of Himachal Pradesh, northwestern Indian Himalaya, have used political influence to circumvent bureaucratic policies of exclusion and that there is an absence of scientific evidence to support the notion that Gaddi grazing leads to land degradation. Although grazing intensity has profoundly shaped the structure and composition of the Siwalik forests (the Gaddi winter grazing grounds), as demonstrated by transect‐based data presented here, deviations from a supposed “climax” community need not constitute degradation. A growing rather than declining cattle population attests to the regenerative capacities of these forests. Within the alpine meadows grazed by the Gaddi in summer, mean plant species richness increased along transects originating at herder camps and extending 250 m north of border camp sites. Intense grazing pressure or heavy manuring by livestock bedded at night are likely to be responsible for the observed low species diversity adjacent to the campsite, but the effect is insignificant at the level of the overall landscape. Interviews with borders also suggest the presence of a sizable, though hunted, mammalian fauna in these high altitude meadows. Recognition of the difficulties associated with implementing restrictive policies, and the fact that human land‐use practices need not lead to degradation or to a decline in biological diversity, should lead to more inclusive conservation policies within protected areas as well as an expansion of the conservation focus beyond protected‐area boundaries.
Effect of Forest Fragmentation on Genetic Diversity and Mating System in a Tropical Tree, Pithecellobium elegans
Authors: Hall Pamela , Walker Sarah , Bawa Kamaljit
Published: March 2003

Genetic diversity, population differentiation, and temporal variation in outcrossing rates were examined for Pithecellobium elegans, a Neotropical rain forest canopy tree. Several forest fragments and a large reserve (1500 ha) were compared for several population genetic parameters. For eight populations sampled on the Atlantic coastal plain of Costa Rica, allozyme heterozygosity (0.13), polymorphism (35%), and effective number of alleles (1.24) were similar to values reported for other tropical tree species that occur at similar densities of less than one individual per hectare. These measures of genetic variation were lowest in populations of the smallest size, farthest from the reserve, and more isolated from other populations. Differentiation among samples collected in small forest fragments and the reserve population accounted for 10% of the total genetic variation observed. There was a positive relationship between the level of differentiation of populations from the reserve population and their distance from the reserve. Though predominantly an annually flowering species, the number of trees in flower at any one time varied from 80% of observed trees to only 6%. Outcrossing rates did not differ for two episodes in which the proportions of flowering trees were 33% and 80%. But periods of low density of flowering adults resulted in poor seed crops or failure to set fruit for many individuals. Population size at many sites will be effectively decreased because of the variation in flowering. Fragmentation of what was once a large, continuous forested area is resulting in genetic erosion of small, isolated populations of Pithecellobium elegans.
Economic Development and the Conservation of Large Carnivores
Authors: Rasker Raymond , Hackman Arlin
Published: March 2003

Conserving large carnivores in North America hinges on protecting vast wildlands, a strategy often assumed to carry significant economic costs in terms of jobs and income foregone. Using case studies, we tested whether there is enough evidence to support the assertion that the protection of wildlands is detrimental to economic development in the northern U.S. Rocky Mountains and the Rocky Mountains of southern British Columbia and Alberta. We analyzed employment and income trends in northwestern Montana (U.S.A.) for counties with a high degree of wildland protection versus counties with high levels of resource extraction and little wildland protection. Employment and personal income levels in “wilderness” counties grew faster than in “resource‐extraction” counties. Wilderness counties also showed higher degrees of economic diversification and lower unemployment rates. No direct cause‐and‐effect relationship was established between wildlands protection and economic development, but to the assertion that protecting wildland habitat for large carnivores is detrimental to a region’s economy, enough counterevidence is presented to suggest an alternative hypothesis: the protection of wilderness habitat that sustains wild carnivores such as grizzly bears (Ursus arctos horribilis) and wolves (Canis lupus) does not have a detrimental effect on local or regional economies. Evidence presented suggests that economic growth is stimulated by environmental amenities. Further, case studies in southern British Columbia and Alberta in Canada and the Greater Yellowstone region, in the U.S., where environmental protection has been explicitly recognized as an economic development strategy, suggest that environmental protection and economic development are complementary goals. In some areas, however, “amenity‐based” economic growth is rapidly leading to urban sprawl and subsequent loss of wildlife habitat, and there is a need for growth management.
A Pragmatic Approach to Grizzly Bear Conservation
Authors: Primm Steven A.
Published: March 2003

Progress in grizzly bear (Ursus arctos horribilis) conservation in the Rocky Mountains of Canada and the United States is urgently needed. Human‐caused mortality is the appropriate focal point for understanding the problem. This issue has a number of dimensions, but the human dimensions are by far the most complex and difficult to analyze. Conducting analyses and implementing conservation plans at the site or local level makes optimal use of humans’ limited cognitive capabilities. Neither maintaining the status quo in grizzly bear conservation nor relying solely on major reform is a viable strategy. Instead, concerned people should take a pragmatic approach to developing innovative processes for forming reason‐based public opinions that in turn inform effective public policies. There are many benefits to such an approach and, given the lack of viable alternatives, it should be tested with a pilot project by the appropriate people and organizations.
Effect of Introduced Crayfish and Mosquitofish on California Newts
Authors: Gamradt Seth C. , Kats Lee B.
Published: March 2003

One goal of conservation biology is to explain population declines. We present field survey data and experimental evidence that implicate introduced predators as a possible cause of decline in the California newt (Taricha torosa). In 1994 and 1995 we surveyed 10 streams in the Santa Monica Mountains of southern California for amphibians. These streams contained California newts when surveyed between 1981 and 1986. Of the 10 streams surveyed in 1994, three contained introduced mosquitofish (Gambusia affinis) and/or crayfish (Procambarus clarkii). These three streams contained no California newt eggs, larvae, or adults. The seven streams without introduced predators contained California newts. We conducted laboratory and field experiments to determine if California newt larvae and egg masses are susceptible to predation by mosquitofish and crayfish. Results from these experiments indicate that crayfish consume California newt egg masses and that both mosquitofish and crayfish consume larval newts. In 24‐hour field experiments, no newt larvae survived in crayfish enclosures, and only 13% of the larvae survived with mosquitofish. Newt larvae are known to have antipredator adaptations for native predators. Apparently, these adaptations are not adequate for coexistence with introduced crayfish or mosquitofish. Heavy rains in 1995 removed introduced crayfish from one stream. We found newt egg masses, larvae, and adults in that stream the following spring. This same stream showed no evidence of California newts when crayfish were present in matched‐date surveys in 1994. These experiments and surveys present evidence that predation by mosquitofish and crayfish may cause localized decline of newts in mountain streams of southern California. Understanding the effects of nonnative species is an important step in preventing detrimental introductions in the future.
Training Conservation Biologists in Human Interaction Skills
Authors: Cannon John R. , Dietz James M. , Dietz Lou Ann
Published: March 2003

Questionnaires were sent to 298 graduate programs in conservation biology and other areas of the biological and agricultural sciences and to 702 public and private organizations that employ, or might employ, conservation biologists. The focus of the questionnaires was on the need for training conservation biologists in human interaction skills (e.g., interpersonal communication, leadership, group decision making). Respondents were asked to indicate the current availability of such training at their institutions or organizations. Questionnaires were returned by 28.5% of the graduate programs and 21.1% of the conservation organizations. A majority of both groups of respondents indicated a high need for training in the following seven areas: written and oral communication; explaining science and values of biodiversity to the lay public; group decision making; interpersonal skills; group planning; leadership; and advocacy. Despite the high level of perceived training need, relatively few academic institutions and even fewer conservation organizations offer or require courses in human interaction skills (with the exceptions of written and oral communication and foreign languages). Sixty‐four percent of the graduate faculty respondents and 78% of the employer organization respondents indicated that human interaction skills are equally important or more important to the work of conservation biologists than science knowledge and skill. We suggest that follow‐up research should be conducted to delineate further the need for human interaction skills training and to assess the relationship between specific human interactions skills and conservation outcomes. We also recommend that a curriculum on human interaction should be designed and developed for conservation biologists, perhaps through a cooperative effort of interested faculty and employers facilitated by the Society for Conservation Biology and conservation organizations.
Open Corridors Appear to Facilitate Dispersal by Ringlet Butterflies (Aphantopus hyperantus) between Woodland Clearings
Authors: Sutcliffe Odette L. , Thomas Chris D.
Published: March 2003

We studied the ringlet butterfly (Aphantopus hyperantus) in an area of woodland in eastern England. A. hyperantus occurs in open fields, rides (grassy tracks), and glades within the woodland. Mark‐recapture methods showed that exchange rates of adult A. hyperantus between fields and glades can be predicted better by distance‐via‐rides than by direct distance. Behavioral observations showed that A. hyperantus readily moved from glades into rides but rarely moved from glades into dense woodland. The rides are likely to be corridors that act as conduits between fields and glades. In the A. hyperantus system, connectivity could reduce local extinctions and increase rates of recolonization in the event of local extinction.
Effects of Social Structure and Prey Dynamics on Extinction Risk in Gray Wolves
Authors: Vucetich John A. , Peterson Rolf O. , Waite Thomas A.
Published: March 2003

Extinction models based on diffusion theory generally fail to incorporate two important aspects of population biology—social structure and prey dynamics. We include these aspects in an individual‐based extinction model for small, isolated populations of the gray wolf (Canis lupus). Our model predicts mean times to extinction significantly longer than those predicted by more general (diffusion) models. According to our model, an isolated population of 50 wolves has a 95% chance of surviving just 9 years and only a 30% chance of surviving beyond 100 years. Reflecting the influence of social structure, a wolf population initially comprising 50 individuals is expected to persist only a few years longer, on average (71 years), than is a population initially comprising just a single reproductive pair (62 years). In contrast, substantially greater average prey abundance leads to dramatically longer expected persistence times. Autocorrelated prey dynamics result in a more complex distribution of extinction times than predicted by many extinction models. We contend that demographic stochasticity may pose the greatest threat to small, isolated wolf populations, although environmental stochasticity and genetic effects may compound this threat. Our work highlights the importance of considering social structure and resource dynamics in the development of population viability analyses.
Ecological Sustainability as a Conservation Concept
Authors: Callicott J. Baird , Mumford Karen
Published: March 2003

Neither the classic resource management concept of maximum sustainable yield nor the concept of sustainable development are useful to contemporary, nonanthropocentric, ecologically informed conservation biology. As an alternative, we advance an ecological definition of sustainability that is in better accord with biological conservation: meeting human needs without compromising the health of ecosystems. In addition to familiar benefit‐cost constraints on human economic activity, we urge adding ecologic constraints. Projects are not choice‐worthy if they compromise the health of the ecosystems in which human economic systems are embedded. Sustainability, so defined, is proffered as an approach to conservation that would complement wildlands preservation for ecological integrity, not substitute for wildlands preservation.