bluuebunny/crossref_metadata_2025 huggingface dataset:
Restoration of Landscape Structure Altered by Fire Suppression
Authors: Baker William L.
Published: March 2003

There is increasing interest in applying landscape ecological research to the management of wildlands, particularly regarding the negative effects of fragmentation and the benefits of corridors. Patch‐producing large disturbances, such as fires and floods, produce a spatial mosaic structure in landscapes to which many species are sensitive. Management of the spatial structure of the patch mosaic has seldom been an explicit concern, however, in part because of insufficient knowledge about bow this spatial structure is affected by alterations in the disturbance regime. Yet the patch mosaic structure of many landscapes has been altered by disturbance control (such as fire suppression), and there is substantial interest in restoring natural disturbance regimes in some wildland landscapes. It has been proposed that, in landscapes subjected to decades of fire suppression, simple reinstatement of the natural fire regime may lead to adverse effects because fuel buildup during fire suppression may result in unusually large fires. It has also been proposed that the use of small prescribed fires may be an effective approach to restoration of landscapes subjected to fire suppression. Here I use a spatial GIS‐based simulation model to analyze the effects of reinstating a natural fire regime in the Boundary Waters Canoe Area, Minnesota, after 82 years of fire suppression. The simulation experiment suggests that suppression can be expected to significantly alter landscape structure, but landscape structure can generally be restored within 50–75 years by reinstating the natural fire regime. Unusually large fires would probably hasten the restoration of landscape structure, while small prescribed fires will not restore the landscape but instead will produce further alteration.
Effects of Habitat Area on the Distribution of Grassland Birds in Maine
Authors: Vickery Peter D. , Hunter Malcolm L. , Melvin Scott M.
Published: March 2003

We used multiple and logistic regression analysis to study the breeding‐area requirements of 10 species of grassland and early‐successional birds at 90 grassland‐barren sites in Maine. The incidence of six of the species was clearly sensitive to the area of grassland. Upland Sandpipers, the species with the largest area requirements, were infrequent at sites of less than 50 ha and reached 50% incidence at those of about 200 ha. Grasshopper Sparrows reached 50% incidence at about 100 ha, Vesper Sparrows at about 20 ha, and Savannah Sparrows at about 10 ha. Incidence for three edge species, Brown Thrasher, Common Yellowthroat, and Song Sparrow, was negatively correlated with open area, and incidence for Field Sparrows was not strongly influenced by grassland size. These results indicate that grasslands need to be approximately 200 ha in area if they are to be likely to support a diverse grass land bird fauna. However, large grasslands or grassland‐barrens are rare; random samples indicated that in Maine only 1% of hayfields and only 8% of grassland‐barrens were more than 64 ha in area. Conservation efforts seeking to protect habitat for rare grassland birds need to consider sites of at least 100 ha—and preferably 200 ha—in size, and these are notably rare in Maine and probably throughout New England and eastern North America. Airports provide some of the last extensive patches of grassland habitat in the northeast. To maintain viable populations of area‐sensitive grassland birds, management of these sites for nesting birds will become increasingly important.
Conservation or Commercial Management of Temperate Forests of Baja California Sur, Mexico
Authors: Arriaga Laura , Díaz Sara , Mercado Carmen
Published: March 2003

The current status of the oak and oak‐pine forests in the Sierra de La Laguna range of the Baja California peninsula is examined from four perspectives: (1) the structural analysis of the woodlands; (2) the natural regeneration of hurricane windfall clearings and its effect on the oak‐pine community; (3) the density, mortality, size, and commercial potential of the only pine species Pinus lagunae; and (4) the possible destruction of this endemic species by attack from moths. These factors were evaluated to make recommendations regarding the management and/or commercialization of the forest resources of this proposed Biosphere Reserve. Results show that the oak woodlands occurring at low elevations contain many tropical plants from the tropical dry forest that surrounds these woodlands, and that the tropical elements decrease at higher altitudes. In forest gaps, oaks were more abundant than pines. Gaps contained a lower diversity of perennial plants than mature oak‐pine forest. P. lagunae has a high adult mortality, which can be attributed to the joint effect of fire and insect attack. Results indicate that the forest in this region does not have timber‐yielding potential because of the small area it covers and because of the low tree diameters and volume, which are insufficient to carry out a continuous and income‐producing extraction of the pine resource of Baja California Sur. Finally, options for management are discussed and future studies are proposed to determine the life cycle and extent of the moth populations.
Amazonian Nature Reserves: An Analysis of the Defensibility Status of Existing Conservation Units and Design Criteria for the Future
Authors: Peres Carlos A. , Terborgh John W.
Published: March 2003

Many tropical nature reserves are woefully understaffed or exist only on paper. Without effective implementation, tropical reserves cannot count on in situ enforcement and consequently are subject to a wide range of invasive threats. Weak institutional structures are aggravated by reserve designs that facilitate rather than discourage unlawful human activities. Taking into account severe financial and institutional constraints, we consider the current status of forest reserves in lowland Amazonia. We ask how the criteria by which reserves are delimited may affect the efficiency with which the contained areas are defended. In a GIS analysis, we found that 40 to 100% of the area of all existing nature reserves in Brazilian Amazonia are directly accessible via navigable rivers and/or functional roads. Such access greatly facilitates the illegal harvest and conversion of forest resources in a region where each guard is responsible for protecting an area larger than the State of Delaware. Cost‐effective defense of large areas can be achieved through appropriate delimitation of reserves along watershed divides and by efficient deployment of limited infrastructure and personnel. Given current and probable future levels of financial resources allocated to reserve maintenance in Amazonia, any new nature reserves in this region should be designed and situated so that their defensibility is maximized. Defensibility criteria should complement site considerations based on biological criteria, such as presumed centers of diversity and endemism.
The Crumbling Infrastructure of Biodiversity: The Avian Example
Authors: Winker Kevin
Published: March 2003

The successful conservation of biodiversity depends in part upon an accurate assessment of the diversity to be preserved. This assessment is in the domain of systematics, taxonomy, and general comparative biology. Specimens play a central role in this science, and research collections thus represent the touchstone of biodiversity. The massive job of describing and understanding avian diversity is far from complete, yet the specimen basis for much‐needed work is not being added to our collections; current holdings are inadequate. The dwindling influx of specimens is due primarily to opposition to collecting, which is fueled by (1) focusing conservation at the level of the individual; (2) unfamiliarity with population biology; (3) misunderstanding of scientific research; (4) typological thinking; and (5) misplaced morality. Specimen‐based avian research has a long and scientifically strong history, and the benefits of this research have been extensive. Our research collections must serve as functional biological libraries. The majority of avian populations can easily withstand the relatively tiny levels of collecting required to keep this science vigorous. Insofar as avian conservation necessarily includes the preservation of a myriad of species comprising the ecosystems upon which birds rely, this problem has broad implications for the conservation of biodiversity.
Temporal Changes in Allele Frequencies and a Population’s History of Severe Bottlenecks
Authors: Richards Christine , Leberg Paul L.
Published: March 2003

Monitoring temporal changes in genetic variation has been suggested as a means of determining if a population has experienced a demographic bottleneck. Simulations have shown that the variance in allele frequencies over time (F) can provide reasonable estimates of effective population size (Ne). This relationship between F and Ne suggests that changes in allele frequencies may provide a way to determine the severity of recent demographic bottlenecks experienced by a population. We examined allozyme variation in experimental populations of the eastern mosquitofish (Gambusia holbrooki) to evaluate the relationship between the severity of demographic bottlenecks and temporal variation in allele frequencies. Estimates of F from both the fish populations and computer simulations were compared to expected rates of drift. We found that different methods for estimating F had little effect on the analysis. The variance in estimates of F was large among both experimental and simulated populations experiencing similar demographic bottlenecks. Temporal changes in allele frequencies suggested that the experimental populations had experienced bottlenecks, but there was no relationship between observed and expected values of F. Furthermore, genetic drift was likely to be underestimated in populations experiencing the most severe bottlenecks. The weak relationship between F and bottleneck severity is probably due to both sampling error associated with the number of polymorphic loci examined and the loss of alleles during the bottlenecks. For populations that may have experienced severe bottlenecks, caution should be used in making evolutionary interpretations or management recommendations based on temporal changes in allele frequencies.
Reproductive Stages Limiting Productivity of the Endangered Attwater’s Prairie Chicken
Authors: Peterson Markus J. , Silvy Nova J.
Published: March 2003

An important concern of conservation biologists is determining what conditions most limit the number of individuals in endangered populations. Because time is a constraint, narrowing the search for such factors is beneficial. Toward this end we used broad spatial and temporal data, to test the hypothesis that reproductive success (as measured by juvenile‐to‐adult ratios) of the endangered Attwater’s Prairie Chicken (Tympanuchus cupido attwateri) was not equal to that of the nonendangered Greater Prairie Chicken (T. c. pinnatus). We then tested the hypotheses that mean clutch size, egg hatchability, nesting success, and number of chicks per brood prior to brood breakup for Attwater’s Prairie Chicken were not equal to those of the Greater Prairie Chicken. We found that the mean ratio of juveniles to adults among Attwater’s Prairie Chicken was less than that of the Greater Prairie Chicken (p < 0.011), as would be predicted if reproductive success controls proportional changes in prairie‐grouse numbers among years. Mean nesting success (32.2%) and number of chicks per brood prior to brood breakup (4.2) of Attwater’s Prairie Chicken were both less than those of the Greater Prairie Chicken (49.5 %, p = 0.0425, and 6.0 p = 0.0001, respectively). We suggest that researchers focus on determining what proportion of Attwater’s Prairie Chicken broods survive and why Attwater’s Prairie Chicken nesting and brood‐rearing success are so poor relative to those of the Greater Prairie Chicken.
Patterns of the Remnant Cichlid Fauna in Southern Lake Victoria
Authors: Seehausen Ole , Witte Frans , Katunzi Egid F. , Smits Jan , Bouton Niels
Published: March 2003

During the years 1984–1987 Lake Victoria in East Africa experienced what is probably the largest mass extinction of contemporary vertebrates. Within a decade about 200 endemic species of haplochromine cichlids disappeared. The extinctions that occurred in the 1980s have been documented predominantly on species of offshore and sub‐littoral waters in the Mwanza Gulf of southern Lake Victoria. Although the littoral fauna of southern Lake Victoria had not been examined in detail, their diversity seemed less affected by the changes in the ecosystem. We give results of the first comprehensive inventory of the littoral cichlid fauna in southern Lake Victoria and discuss its conservation status. We also report on new developments in the sub‐littoral fauna after 1990. More than 50 littoral and 15 sub‐littoral stations were sampled between the years 1991 to 1995. Of the littoral stations, 34 were sampled for the first time. One hundred sixty three species of haplochromines were collected. Of these, 102 species were previously unknown. About two thirds of them live in rocky areas that were sampled for the first time. Littoral rocky habitats harbored the highest diversity. Since 1990, however, 13 more species disappeared from established sampling stations in littoral habitats. Fishing practices, spreading of exotic fishes, water hyacinth, and eutrophication are considered important threats to the littoral fauna. Also in the upper sub‐littoral the number of species declined further. On deeper sub‐littoral mud bottoms individual and species numbers increased again, although they are nowhere close to those found before the Nile perch (Lates niloticus) upsurge. This fauna differs from the well studied pre‐Nile perch fauna. At well‐established sampling stations, the sub‐littoral zone is dominated by previously unknown species, and some known species have performed dramatic habitat shifts.
Effects of Land‐Use and Tsetse Fly Control on Bird Species Richness in Southwestern Ethiopia
Authors: Wilson Cathleen J. , Reid Robin S. , Stanton Nancy L. , Perry Brian D.
Published: March 2003

Successful control of tsetse (Glossina spp.)‐transmitted trypanosomiasis in the Ghibe Valley, Ethiopia, appears to have accelerated conversion of wooded grassland into cropland. Land conversion, in turn, may have fragmented wildlife habitat. Our objective was to assess the influence of the expansion of agricultural land‐use, brought about by tsetse control, on ecological properties by using bird species richness and composition as indicators of environmental impacts. We sampled bird species richness and composition (using Timed‐Species counts) and habitat structure (using field sampling and remote sensing) in four land cover/land‐use types in areas subjected to tsetse fly control and adjacent areas without control. At the height of the growing season bird species numbers and vegetative complexity were greater in the small‐holder, oxen‐plowed fields and riparian woodlands than in wooded grasslands or in large‐holder, tractor‐plowed fields. Species composition was highly dissimilar (40–70% dissimilarity) comparing among land‐use types, with many species found only in a single type. This implies that trypanosomiasis control that results in land conversion from wooded grasslands to small‐holder farming in this region may have no adverse impacts on bird species numbers but will alter composition. These results also suggest that moderate land‐use by humans (e.g., small‐holder field mosaics) increases habitat heterogeneity and bird species richness relative to high levels of use (e.g., tractor‐plowed fields). Tsetse control may be indirectly maintaining species richness in the valley by encouraging the differential spread of these small‐scale, heterogeneous farms in place of large‐scale, homogeneous farms. Nevertheless, if the extent of small‐holder farms significantly exceeds that of present levels, negative impacts on bird species richness and large shifts in species composition may occur.
Population Genetic Structure in the Black Rat Snake: Implications for Management
Authors: Prior K. A. , Gibbs H. L. , Weatherhead P. J.
Published: March 2003

Assessments of population genetic structure and diversity can be of value in formulating management plans for threatened species. Using randomly amplified polymorphic DNA markers, we found evidence of significant genetic structure among black rat snakes (  Elaphe obsoleta) sampled at three spatial scales. Highly isolated (1500–1900 km apart) populations were strongly divergent (  FST = 0.242–0.323), whereas populations more proximal ( 465 km apart) although currently isolated, exhibited far less divergence (  FST = 0.019). A considerable proportion (80%) of total genetic diversity was due to differences among individuals within populations, although differences among populations (8%) also were significant. At the scale of sub‐populations ( local populations 15–50 km apart), differentiation was generally moderate (  FST = 0.058). Our estimates of Nei’s genetic distance for sub‐populations (0.014) approximated (mean = 0.044) those obtained in other studies that have assessed differentiation between snake populations based on variation in allozymes. The majority (ca. 86%) of total genetic variance across five sub‐populations was attributable to differences among individuals, although differences among sub‐populations (ca. 13%) also were significant. We found little evidence of genetic structure (  FST = 0.006) between pairs of hibernacula, our finest spatial scale (samples 1–2 km apart), if they were located in natural habitats. In contrast, a pair of hibernacula sampled in an urban area exhibited genetic structure equivalent to some sub‐population differences (  FST = 0.039), suggesting interrupted gene flow related to urban development. Our results have direct implications for ranking populations in terms of their conservation value and the genetic management of threatened snakes.
Genetic Structure and Migration in Native and Reintroduced Rocky Mountain Wolf Populations
Authors: Forbes Stephen H. , Boyd Diane K.
Published: March 2003

Gray wolf (Canis lupus) recovery in the Rocky Mountains of the U.S. is proceeding by both natural recolonization and managed reintroduction. We used DNA microsatellite analysis of wolves transplanted from Canada to two reintroduction sites in the U.S. to study population structure in native and reintroduced wolf populations. Gene flow due to migration between regions in Canada is substantial, and all three recovery populations in the U.S. had high genetic variation. The reintroduced founders were moderately genetically divergent from the naturally colonizing U.S. population. These findings corroborate that the reintroduction more than meets generally accepted genetic guidelines. Maintaining this variation, however, will depend on ample reproduction in the first few generations. In the long term genetic variation will best be retained if migration occurs among the recolonizing and the two transplanted populations. Evidence from field observation and genetic studies shows extensive dispersal by wolves, and we conclude that exchange among these groups due to natural dispersal is likely if public tolerance and legal protection are adequate outside lands designated for wolf recovery.
Predicting Invasiveness of Plant Species Based on Biological Information
Authors: Goodwin Brett J. , McAllister Andrew J. , Fahrig Lenore
Published: March 2003

Abstract:
Previous studies suggest that, within particular groups of plant species, biological attributes can be used to predict the potential invasiveness of species that are intentionally introduced for horticultural or agricultural purposes. We examined the broad question of whether commonly available biological information can predict the invasiveness of a wide range of intentionally and accidentally introduced species. We collected information from published floras on 165 pairs of plant species. In each pair, one species originated in Europe and successfully invaded New Brunswick, Canada, and the other was a congeneric species that has not invaded North America. Only three biological characters—lifeform, stem height, and flowering period—and European geographic range were known for all species. We conducted multiple logistic regression analyses using two‐thirds (110) of the species pairs and tested the predictive ability of resulting models using the remaining 55 pairs. Although a significant logistic regression model was obtained using the biological attributes, the model could not predict invasiveness of the test species pairs. In contrast, a model using only European range successfully predicted invasiveness in 70% of the test species. The importance of geographic range suggests that prediction of invasiveness on a species‐by‐species basis is not likely to help stem the flow of accidentally introduced invasive species. Species that are inadvertently picked up and moved to a new location due to their wide distribution are the same species that are likely to succeed in a new environment due to their wide environmental tolerances.
Forest Restoration in Abandoned Agricultural Land: a Case Study from East Africa
Authors: Chapman Colin A. , Chapman Lauren J.
Published: March 2003

Abstract: Millions of hectares of tropical forests have been converted to agricultural land and abandoned, so it is important that we understand the process of forest recovery and comprehend how pathways are modified by different types of disturbance in different geographic regions. In a 4‐year case study, we quantified the pattern of forest recovery following clearing and 3 years of cultivation of a moist‐evergreen forest in Uganda. Long‐term observation ( 746 hours) of frugivore visitation to the regenerating area demonstrated that birds were frequent visitors (5.8 birds/hour), whereas large mammalian frugivores rarely used the area. Frugivore visitation rates facilitated seedling recruitment that averaged 0.51 seedlings/m 2 from 22 tree species by the end of the study. Recruitment included species with large seeds, despite the fact that seed‐eating rodents were almost twice as abundant in the regenerating area than in mature forest. By the end of the study, however, only 20 trees were ≥0.5 m tall, and no trees were ≥2 m tall. This slow recruitment reflected high seedling mortality and dominance of the area by elephant grass ( Pennisetum purpureum) and the herb Acanthus pubescens. After 4 years, trees ≥0.5 m tall attained a biomass of only 8.92 kg/ha, whereas the biomass of P. purpureum and A. pubescens had reached 35,500 kg/ha and 18,100 kg/ha respectively. We provide an initial assessment of two programs designed to enhance restoration of abandoned agricultural lands: planting of cuttings to act as dispersal foci and sowing of seeds. Our results showed that density of seedlings growing in the management plot where we sowed seeds (0.35 seedlings/m 2) and in the plot where we established cuttings (0.30 seedling/m 2) was lower than in the control plot (0.51 seedlings/m 2). This East African site was only lightly disturbed, yet tree recovery was occurring slower than in heavily degraded sites described from South America. The rate of recovery seemed to be strongly determined by interactions between tree seedlings and P. purpureum and A. pubescens.
Trends in Wildlife Management and the Appropriateness of Australian University Training
Authors: Baxter G. S. , Hockings M. , Carter R. W. , Beeton R. J. S.
Published: March 2003

Abstract: That the greatest challenges in conservation are often not technical but rather economic or sociological has been expressed for at least the last 20 years. This raises the question of whether the training offered to tomorrow's conservation practitioners prepares them sufficiently to deal with the human dimensions of conservation. We analyzed 747 papers from seven wildlife management and conservation biology journals to determine the trends in this area of conservation management between 1985 and 1995. We found that over that time the emphasis stayed on single‐species issues with a science focus, but there was a marked shift toward conservation biology issues, management‐oriented research, and discussion of economic and social factors relevant to management. We also examined the handbooks of 11 Australian universities to analyze the content of 439 compulsory subjects in 12 degrees that we judged could produce wildlife managers. More than 68% of subjects were from a basic science or technology discipline, 16% from resource management, and only 13% from economics, humanities, communications, or planning. Thus, many of the skills required by contemporary wildlife managers must be learned in postgraduate training or on the job. Much of the undergraduate training syllabus, in Australia at least, does not reflect trends in the practice of wildlife management today and will not provide tomorrow's managers with the range of disciplinary understanding required. We were able, however, to identify three types of undergraduate training—ecological system managers, environmental managers, and human system managers—and we found that the curricula in human‐system management contained increased emphasis on socioeconomic issues relevant to management.
Sample Size for the Diagnosis of Conservation Units
Authors: Walsh Peter D.
Published: March 2003

Abstract: Use of the phylogenetic species concept in defining conservation units is based on the assumption that the fixation of a particular character state in a population is diagnostic of a long history of reproductive isolation. In practice, diagnosis is usually based on the character states of a small sample of individuals rather than the states of the entire population. Unfortunately, when sample sizes are small, samples in which all individuals share one character state can easily be drawn from populations that are actually polymorphic. I describe statistical methods for examining how much confidence can be placed in the diagnosis of a conservation unit, given the operative sample size. The methods estimate the probability of drawing a sample in which all individuals show the same state, if individuals with unsampled ( hidden) states actually exist in the population at some hypothetical frequency (e.g., 0.05). I considered finite and infinite population‐size models. The infinite population‐size model suggests that in order to reject with 95% confidence the hypothesis that 5% of individuals carry hidden character states, a sample of 59 individuals is necessary. Finite population‐size models give slightly smaller critical sample sizes for diagnosis with 95% confidence. I describe methods for including the effect of uncertainty in estimating population size when calculating critical sample size, and I discuss extensions to multiple characters and the impact of spatial structuring of character states. My results suggest that confident diagnosis requires sample sizes much larger than those commonly used when the phylogenetic species concept is applied to defining conservation units.
Avian Nesting Success in a Selectively Harvested North Temperate Deciduous Forest
Authors: Robinson Scott K. , Robinson W. Douglas
Published: March 2003

Abstract:Predators and parasites of bird nests often reach maximum abundance near ecotonal edges, potentially causing reproductive failure for birds breeding near edges. Timber‐harvesting methods in which single or small groups of trees are removed from forested lands may maximize amounts of edge created within forest tracts. We evaluated the effect of internal edges created by timber harvest in Trail of Tears, a deciduous forest in southern Illinois ( U.S.A.). We measured the nesting‐success and brood‐parasitism rates of four songbird species, the Acadian Flycatcher (Empidonax virescens), Kentucky Warbler (Oporornis formosus), Wood Thrush (Hylocichla mustelina), and Northern Cardinal (Cardinalis cardinalis). Each species bred in each of three forest management units: compartments selectively harvested within the previous 6 years (recent cuts); compartments 10 to 15 years post‐harvest (older cuts); and compartments remaining uncut for at least the last 40 years. Levels of brood parasitism by Brown‐headed Cowbirds (    Molothrus ater) were high throughout the forest but were significantly higher in the selectively harvested compartments for Acadian Flycatchers and Kentucky Warblers. Nest predation differed among compartments in species‐specific patterns. None of the four species suffered consistently greater losses of nests in cut than uncut forest in Trail of Tears. For three of the four species, however, rates of nest failure were consistently higher in Trail of Tears than in two other large tracts of uncut forest in the southern Illinois region, suggesting that predator populations may be greater in Trail of Tears than in other large forest tracts. Overall, the results suggest that selective logging added little to existing fragmentation effects in this landscape in which levels of nest predation and brood parasitism are chronically high. Although the creation of internal edges appeared to have few detrimental effects on these two measures of songbird productivity, effects may differ in landscapes with greater forest cover or different predator and brood‐parasite assemblages.
Beyond Kyoto: Forest Management in a Time of Rapid Climate Change
Authors: Noss Reed F.
Published: March 2003

Abstract: Policies to reduce global warming by offering credits for carbon sequestration have neglected the effects of forest management on biodiversity. I review properties of forest ecosystems and management options for enhancing the resistance and resilience of forests to climate change. Although forests, as a class, have proved resilient to past changes in climate, today's fragmented and degraded forests are more vulnerable. Adaptation of species to climate change can occur through phenotypic plasticity, evolution, or migration to suitable sites, with the latter probably the most common response in the past. Among the land‐use and management practices likely to maintain forest biodiversity and ecological functions during climate change are (1) representing forest types across environmental gradients in reserves; (2) protecting climatic refugia at multiple scales; (3) protecting primary forests; (4) avoiding fragmentation and providing connectivity, especially parallel to climatic gradients; (5) providing buffer zones for adjustment of reserve boundaries; (6) practicing low‐intensity forestry and preventing conversion of natural forests to plantations; ( 7) maintaining natural fire regimes; (8) maintaining diverse gene pools; and (9) identifying and protecting functional groups and keystone species. Good forest management in a time of rapidly changing climate differs little from good forest management under more static conditions, but there is increased emphasis on protecting climatic refugia and providing connectivity.
Income and Price Elasticities of Bushmeat Demand in Lowland Amerindian Societies
Authors: Wilkie David S. , Godoy Ricardo A.
Published: March 2003

Abstract: Consumption of bushmeat is an important component of household economies in most tropical forested regions of the world and is resulting in unsustainable levels of hunting, even in relatively isolated regions. We conducted standardized surveys of household consumption, income, wealth, and education level among Amerindian societies in Central and South America. Results suggest 1) demand for bushmeat may follow an inverted ∪ pattern with income, 2) consumers, particularly the most well‐off, reduce their consumption of bushmeat as the price increases; and 3) a small decrease in the price of meat from domesticated animals is likely to lead to a large decrease in the consumption of fish but not of bushmeat. Policy makers may be able to reduce demand for bushmeat by raising the price of bushmeat, by increasing the direct and opportunity costs of hunting, and by raising household income.
Genetic Variability in mtDNA of the Silvery Gibbon: Implications for the Conservation of a Critically Endangered Species
Authors: Andayani Noviar , Morales Juan Carlos , Forstner Michael R. J. , Supriatna Jatna , Melnick Don J.
Published: March 2003

Abstract:The silvery gibbon (  Hylobates moloch), endemic to the island of Java, relies on closed‐canopy, lowland evergreen forest for its survival. Because Java has lost over 91% of its original forest, silvery gibbons currently occupy small, isolated forest fragments and are threatened with extinction. To contribute to a comprehensive conservation strategy for this species, we analyzed the mtDNA control region of 31 silvery gibbons representing most remaining populations. Our results suggest the presence of at least two genetically differentiated lineages: a “western” lineage, represented by the largest remaining natural population in Gunung Halimun National Park and a “central” lineage, consisting of smaller, more isolated populations in and around the Gunung Masigit/Simpang/Tilu complex, Gunung Gede/Pangrango, and Gunung Slamet. These two lineages, at a minimum, represent different management units that should, except in the most dire circumstances, be managed separately.
Effects of Grazing on the Demography and Growth of the Texas Tortoise
Authors: Kazmaier Richard T. , Hellgren Eric C. , Ruthven Donald C. , Synatzske David R.
Published: March 2003

Abstract: Considerable effort has been exerted in attempts to understand the complex ecological effects of grazing. North American tortoises, by virtue of their distribution, provide a good model taxon through which to study how grazing effects vary with grazing regime, habitat, and climate. We studied the Texas tortoise ( Gopherus berlandieri ), which is restricted primarily to privately owned rangelands of southern Texas and northeastern Mexico. Management of this species is hampered by a lack of information on the effects of common land‐use practices. We evaluated the effects of moderate grazing by cattle (short‐duration, winter‐spring rotational grazing regime; 6–28 animal‐unit days/ha/year) on this tortoise by comparing two grazed and two ungrazed sites in the Western Rio Grande Plains, Texas ( U.S.A.), from April 1994 to October 1997. We made 132 captures of 106 individuals in the ungrazed pastures and 324 captures of 237 individuals in the grazed pastures. We also radiotracked 22 tortoises in the ungrazed pastures and 25 tortoises in the grazed pastures. Comparisons of relative abundance, body‐size distribution, age distribution, body mass, sex ratio, adult survival, proportion of juveniles, and growth rates revealed no differences ( p> 0.05 for all parameters) between tortoises on grazed and ungrazed areas. Based on these results, we suggest that moderate grazing by cattle is not incompatible with maintenance of Texas tortoise populations. Our data were consistent with a general model of tortoise biogeography and tolerance of disturbance which suggests that Texas tortoises are tolerant to intermediate levels of disturbance. Generalities about the effect of cattle grazing on the four North American tortoises should be avoided unless they can be placed in the context of grazing regime, precipitation, habitat quality, and tortoise requirements.
Conservation Applications of Astronaut Photographs of Earth: Tidal‐Flat Loss ( Japan), Elephant Effects on Vegetation (Botswana), and Seagrass and Mangrove Monitoring (Australia)
Authors: Robinson Julie A. , Lulla Kamlesh P. , Kashiwagi Minoru , Suzuki Maggie , Nellis M. Duane , Bussing Charles E. , Long Warren J. Lee , McKenzie Len J.
Published: March 2003

Abstract: National Aeronautics and Space Administration ( NASA) photographs taken by astronauts from low Earth orbit can provide information relevant to conservation biology. This data source is now more accessible because of improvements in digitizing technology, Internet file transfer, and availability of image processing software. We present three examples of conservation‐related projects that benefited from the use of astronaut photographs. First, NASA scientists requested that astronauts photograph the area of the controversial Isahaya Bay reclamation project in Japan. Japanese researchers used photographs from before and after the reclamation as a tool for communication with the public about the effects of tidal‐flat loss. The newly acquired images and the availability of high‐resolution digital images from NASA archives provided timely public information on the observed changes. Second, we digitally classified and analyzed a Space Shuttle photograph of Chobe National Park in Botswana to identify the locations of woodlands affected by elephants. Field validation later confirmed that areas identified on the image showed evidence of elephant damage. Third, we used a summary map from intensive field surveys of seagrasses in Shoalwater Bay, Australia, as reference data for a supervised classification of a digitized photograph taken from orbit. The classification distinguished seagrasses, sediments, and mangroves with accuracy approximating that in studies using other satellite remote‐sensing data. Astronaut photographs are in the public domain, and the database of nearly 400,000 photographs from the late 1960s to the present is available at a single searchable location on the Internet ( http://eol.jsc.nasa.gov/sseop). These photographs can be used by conservation biologists as a source of general information about the landscape and for quantitative mapping.
Science, Power, and System Dynamics: the Political Economy of Conservation Biology
Authors: Song Samantha J. , M'Gonigle R. Michael
Published: March 2003

Abstract:Frustration with the lack of action on conservation issues by governments has sparked debate around the policy role of conservation biologists. We analyzed the political economy of conservation biology, that is, of the dynamics of the political and economic structures within which conservation biology operates, and we suggest more productive means for conservation biologists to achieve conservation goals. Within the modern state, conservation goals are marginalized because the growth needs of industrial capital have the highest priority. Environmental advocacy within this system largely addresses only proximate concerns and has limited success. Science is a product of modern society, but scientists now need to foster novel institutional arrangements in which humans can function within the limits of natural systems. This entails a larger recognition of the inherent contradictions residing within current institutions that themselves depend on unsustainably high resource flows. As one critical counterbalance to these institutions, we discuss community‐based management and research as primary institutions through which sustainable use of natural resources might be achieved.
An Ecological and Economic Assessment of the Nontimber Forest Product Gaharu Wood in Gunung Palung National Park, West Kalimantan, Indonesia
Authors: Paoli Gary D. , Peart David R. , Leighton Mark , Samsoedin Ismayadi
Published: March 2003

Abstract: Ecological and economic data are essential to the identification of tropical nontimber forest products with the potential for sustainable and profitable extraction in a managed system. We studied the demographic effect and economic returns of harvesting aromatic gaharu wood from fungus‐infected trees of Aquilaria malaccensis Lam. at Gunung Palung National Park, Indonesia, to evaluate the management potential of gaharu wood. Aquilaria malaccensis trees openface> 20 cm in diameter occurred at low preharvest densities (0.16–0.32 ha) but were distributed across five of six forest types surveyed. During a recent harvest, 75% of trees were felled, with harvest intensities ranging from 50% to 100% among forest types. Overall, 50% of trees contained gaharu wood, but trees at higher elevations contained gaharu wood more frequently ( 73%) than trees at lower elevation (27%). The mean density of regeneration ( juveniles> 15 cm in height) near adult trees (3–7 m away) was 0.2/m2, 200 times greater than at random in the forest (10/ha), but long‐term data on growth and survivorship are needed to determine whether regeneration is sufficient for population recovery. Gaharu wood extraction from Gunung Palung was very profitable for collectors, generating an estimated gross financial return per day of US $8.80, triple the mean village wage. Yet, the estimated sustainable harvest of gaharu wood at natural tree densities generates a mean net present value of only $10.83/ha, much lower than that of commercial timber harvesting, the dominant forest use in Kalimantan. Returns per unit area could be improved substantially, however, by implementing known silvicultural methods to increase tree densities, increase the proportion of trees that produce gaharu wood, and shorten the time interval between successive harvests. The economic potential of gaharu wood is unusual among nontimber forest products and justifies experimental trials to develop small‐scale cultivation methods.
Dynamics and Viability of a New Zealand Robin Population Reintroduced to Regenerating Fragmented Habitat
Authors: Armstrong Doug P. , Ewen John G.
Published: March 2003

Abstract: New Zealand Robins (   Petroica australis) were reintroduced to Tiritiri Matangi, a highly modified island undergoing an extensive revegetation program. The island had only 13 ha of fragmented forest likely to be suitable for robins. We wished to determine whether the population was likely to persist until additional habitat became available through maturation of the revegetation and, therefore, whether it was sensible to reintroduce this species early in the restoration program. We used an information‐theoretic approach to model survival, fecundity, sex ratio, and juvenile dispersal for this population, based on data collected in the first 6 years after reintroduction. This involved nominating a limited set of plausible models for each process and then selecting the models that best explained the data based on Akaike's information criterion. We used mark‐recapture analysis on survey data to model survival and general linear modeling on fecundity data. The best models were as follows: (1) juvenile survival declined as population size increased, whereas adult survival was constant among years; (2) fecundity was substantially lower for females in their first year after translocation and varied among forest patches, but did not vary among age classes or years; (3) the expected sex ratio of recruits was 50:50; (4) the distribution of recruits depended on the number of existing residents in patches and patch sizes, but not on patch isolation. We used VORTEX to simulate the dynamics of the population based on these models and associated parameter estimates. The population was predicted to have negligible chance of extinction over several decades under current conditions, and this prediction was not sensitive to uncertainty in parameter estimates or model structure. Maturation of the planted matrix should allow the population to expand to several hundred birds over the next few decades, preventing extreme loss of genetic variation. We therefore conclude that the early reintroduction of this species was reasonable, despite the limited habitat available at the time. Our results show that it is critical to obtain data for the first few years after reintroduction if habitat is likely to be limited, because it is otherwise impossible to detect density‐dependent processes critical to population viability. Results also show that the first year after reintroduction may be misleading if considered alone.
Effects of Dry Tropical Forest Fragmentation on the Reproductive Success and Genetic Structure of the TreeSamanea saman
Authors: Cascante Alfredo , Quesada Mauricio , Lobo Jorge J. , Fuchs Eric A.
Published: March 2003

Abstract:Tropical trees are particularly vulnerable to forest fragmentation because of their low densities, self‐incompatibilty system, and high rates of outbreeding. Forest fragmentation is likely to decrease gene flow, increase endogamy, and eventually produce a high differentiation among remnant populations. Our objectives were to evaluate the effect of forest fragmentation on the reproductive success, progeny vigor, and genetic variation of the tropical dry‐forest treeSamanea saman. We conducted our study in the dry forest of Costa Rica and compared two tree conditions to evaluate forest fragmentation: (1) isolated, individual trees more than 500 m from the nearest conspecific and surrounded by agricultural fields, pastures, or small remnant forest patches and (2) trees in continuous populations of 10 or more individuals per hectare and surrounded by undisturbed forest. We compared the probability of natural pollination, seed production, genetic variation, and progeny vigor of trees in isolation and in continuous populations. The probability of flowers receiving more than 23 pollen tubes at the base of styles (the flowers more likely to produce a mature fruit) was significantly greater for trees in continuous populations (2.1%) than for trees in isolation (0.4%). However, flowers from the two tree conditions received similar pollen loads on their stigmas. Fruits of trees from continuous populations produced similar numbers of seeds as isolated trees did and had a similar probability of seed abortion. The probability of seed predation by bruchid beetles was significantly greater in continuous populations (30%) than in isolated trees (20%). The number of undamaged seeds (  potentially viable) was similar for both tree conditions. A genetic analysis of progeny showed that levels of genetic diversity in trees in isolation and in continuous populations were comparable. The effective self‐fertilization rate and inbreeding coefficient of the progeny were slightly higher for isolated trees than for trees in continuous populations. In addition, there was more genetic similarity in the progeny of isolated trees, within and between fruits. Seeds produced by different fruits within a tree were more likely to be related in an isolated tree than in a tree from continuous populations. Seeds produced by trees from continuous populations were more likely to germinate and to produce greater leaf area and biomass as seedlings than progeny from isolated trees. We concluded that the fragmentation of tropical dry forests affects the genetic variation and vigor ofS. samanprogeny. Isolated trees showed high reproductive capacity, however, in spite of their habitat condition.
Effects of National Conservation Spending and Amount of Protected Area on Species Threat Rates
Authors: McKinney Michael L.
Published: March 2003

Abstract:Red‐list data from non‐island nations show that a greater proportion of protected area is correlated with significantly lower percentages of threatened birds, mammals and plants, and especially overharvested birds and mammals, once the effects of endemism, human population size, and other confounding variables are removed. Proportion, number and size of areas protected are among the reserve traits correlated with reduced threat. Per‐capita conservation spending strongly correlates with per‐capita income and with proportion of area protected, number of reserves, and proportion of partially protected area. Although most reserve traits are positively correlated among themselves, median reserve size is significantly inversely correlated with other reserve traits and with conservation spending, indicating that wealthier nations have more numerous but smaller and less protected reserves than poorer nations. These findings represent correlation rather than causation, but they do support studies at finer scales which suggest that even poorly protected “paper parks” are better than no parks at all for the reduction of threat among species.