bluuebunny/crossref_metadata_2025 huggingface dataset:
Composition Changes in a Subandean Avifauna after Long‐Term Forest Fragmentation
Authors: Renjifo Luis Miguel
Published: March 2003

Abstract:Current understanding of the effects of forest fragmentation is based largely on studies in temperate regions, Australia, and Neotropical lowlands. In contrast, the consequences of anthropogenic forest fragmentation for Andean avifaunas are poorly understood, despite large‐scale habitat loss and fragmentation. I assessed the effects of long‐term fragmentation on a subandean avifauna in Colombia by comparing the occurrence of bird species in forest fragments isolated over 50–90 years with the original avifauna. Prefragmentation bird composition was based on historical records and current species composition in continuous forest. The original avifauna had approximately 139 forest species and 45 species of open habitats. Among forest species, 30% were currently extinct in fragmented forest and 4% were regionally extinct. At least 23 nonforest species colonized the region from the lowlands following deforestation. Species with small geographic ranges and those that were locally scarce or rare throughout their ranges were likely to be locally extinct. Forest raptors, terrestrial insectivores, and large frugivores were highly extinction prone, whereas nectarivores, small frugivores, and aerial insectivores were highly resilient; other guilds were intermediate. Antbirds (Formicariidae, Thamnophilidae), Cotingas, and, especially, Icterids were highly extinction prone. Large body size was not a determinant of vulnerability except among frugivores. Sixty‐two percent of the species of special conservation concern were extinct in fragments. These results suggest that only large forest tracts will ensure the survival of a large proportion of subandean avifaunas. Fragments of mature forest, however, may support a diverse avifauna, including small populations of globally endangered species several decades after isolation. These fragments could play an important role in the restoration of local avifaunas. A good understanding of the mechanisms that allow persistence in such fragments may prove essential for the conservation of those species for which no large tracts of suitable habitat remain.
Effects of Landscape Composition and Wetland Fragmentation on Frog and Toad Abundance and Species Richness in Iowa and Wisconsin, U.S.A.
Authors: Knutson Melinda G. , Sauer John R. , Olsen Douglas A. , Mossman Michael J. , Hemesath Lisa M. , Lannoo Michael J.
Published: March 2003

Abstract:Management of amphibian populations to reverse recent declines will require defining high‐quality habitat for individual species or groups of species, followed by efforts to retain or restore these habitats on the landscape. We examined landscape‐level habitat relationships for frogs and toads by measuring associations between relative abundance and species richness based on survey data derived from anuran calls and features of land‐cover maps for Iowa and Wisconsin. The most consistent result across all anuran guilds was a negative association with the presence of urban land. Upland and wetland forests and emergent wetlands tended to be positively associated with anurans. Landscape metrics that represent edges and patch diversity also had generally positive associations, indicating that anurans benefit from a complex of habitats that include wetlands. In Iowa the most significant associations with relative abundance were the length of the edge between wetland and forest ( positive) and the presence of urban land (negative). In Wisconsin the two most significant associations with relative abundance were forest area and agricultural area ( both positive). Anurans had positive associations with agriculture in Wisconsin but not in Iowa. Remnant forest patches in agricultural landscapes may be providing refuges for some anuran species. Differences in anuran associations with deep water and permanent wetlands between the two states suggest opportunities for management action. Large‐scale maps can contribute to predictive models of amphibian habitat use, but water quality and vegetation information collected from individual wetlands will likely be needed to strengthen those predictions. Landscape habitat analyses provide a framework for future experimental and intensive research on specific factors affecting the health of anurans.
Local Extinctions of Terrestrial Insectivorous Birds in a Fragmented Landscape near Manaus, Brazil
Authors: Stratford Jeffrey A. , Stouffer Philip C.
Published: March 2003

Abstract:We examined the distributions of nine species of terrestrial insectivorous birds in 4‐ to 14‐year‐old rainforest fragments north of Manaus, Brazil. We surveyed 11 fragments of 1, 10, and 100 ha, 95 ha of secondary vegetation, and nine continuous forest plots (controls) of 1–100 ha. We augmented standard spot‐mapping with extensive playback surveys. The fragments had been sampled with mist nets before isolation, so our results could be compared with the pre‐isolation distribution. For the nine species, there were 55 cases of local extinction in the 11 fragments between about 1 year after isolation and the time of our surveys. This corresponds to 74% extinction of the local populations in fragments. These extinctions occurred despite the second‐growth connection of some fragments to continuous forest as little as 70 m away. Three apparent colonization events by species not detected before isolation also occurred, but these may also reflect inadequate sampling before isolation. Our comparison of fragments and similar‐sized control plots in continuous forest showed an area effect on species richness in both fragments and control plots, but fragments had fewer species than control plots of equal size. In a fragmented Amazonian landscape, the full suite of terrestrial insectivores would persist in the short term only in large fragments ( >100 ha), although much larger areas are probably necessary for the long‐term persistence of their populations.
Accounting for Uncertainty in Risk Assessment: Case Study of Hector's Dolphin Mortality due to Gillnet Entanglement
Authors: Slooten Elisabeth , Fletcher David , Taylor Barbara L.
Published: March 2003

Abstract: Uncertainties about biological data and human effects often delay decisions on management of endangered species. Some decision makers argue that uncertainty about the risk posed to a species should lead to precautionary decisions, whereas others argue for delaying protective measures until there is strong evidence that a human activity is having a serious effect on the species. We have developed a method that incorporates uncertainty into the estimate of risk so that delays in action can be reduced or eliminated. We illustrate our method with an actual situation of a deadlock over how to manage Hector's dolphin (Cephalorhychus hectori). The management question is whether sufficient risk is posed to the dolphins by mortalities in gillnets to warrant regulating the fisheries. In our quantitative risk assessment, we use a population model that incorporates both demographic ( between‐individual) and environmental ( between‐year) stochasticity. We incorporate uncertainty in estimates of model parameters by repeatedly running the model for different combinations of survival and reproductive rates. Each value is selected at random from a probability distribution that represents the uncertainty in estimating that parameter. Before drawing conclusions, we perform sensitivity analyses to see whether model assumptions alter conclusions and to recommend priorities for future research. In this example, uncertainty did not alter the conclusion that there is a high risk of population decline if current levels of gillnet mortality continue. Sensitivity analyses revealed this to be a robust conclusion. Thus, our analysis removes uncertainty in the scientific data as an excuse for inaction.
An Evaluation of Management Objectives for Canada's Commercial Harp Seal Hunt, 1996‐1998
Authors: Johnston D. W. , Meisenheimer P. , Lavigne D. M.
Published: March 2003

Abstract: The largest existing hunt for marine mammals is Canada's commercial hunt for Northwest Atlantic harp seals (Pagophilus groenlandicus). From 1995 to 1998, the total allowable catch was set at a level that the Canadian Department of Fisheries and Oceans calculated would not cause the population to decline, consistent both with its stated management objectives of maintaining stable seal populations while allowing a sustainable harvest and with its stated policy of taking a precautionary approach to management. During those years, Canada's total allowable catch was progressively increased from 186,000 harp seals per year (1995) to 250,000 (1996) to 275,000 (1997 & 1998). We examined whether the government's management objectives were achieved using the conventional approach of comparing landed catches with the replacement yield estimated from a biological population model. We then conducted a second assessment, using a more modern and precautionary approach recently implemented for marine mammal management in the United States which incorporates uncertainty into management models to estimate sustainable “potential biological removal levels.” From 1996 to 1998, landed catches from Canada and Greenland exceeded Canada's estimated replacement yield. Over the same period, estimated total human‐caused mortality exceeded potential biological removal levels by 1.5 to 5.9 times. Given such levels of reported catches and estimated total human‐caused mortality, Canada's management of its harp seal hunt did not achieve its objectives. It is likely, therefore, that the population is now declining and, if recent levels of killing continue, the population will stabilize only at levels below (and possibly far below) its maximum net productivity level. Viewed from this perspective, Canada's approach to harp seal management between 1996 and 1998 cannot be deemed precautionary or risk‐averse.
Regional Turnover and Fluctuation in Populations of Five Plants Confined to Serpentine Seeps
Authors: Harrison Susan , Maron John , Huxel Gary
Published: March 2003

Abstract: Spatial patterns in population turnover were analyzed for five plant species confined to a patchy and isolated habitat, serpentine seeps: annuals Helianthus exilis and Mimulus nudatus and perennials Senecio clevelandii, Astragalus clevelandii, and Delphinium uliginosum. A 3‐year survey showed that, over a preceding 15‐year period, 32 of 132 known populations in a 4200‐ha area disappeared, and 65 new populations appeared. Populations that disappeared were significantly more isolated from conspecific populations than were surviving populations. Populations that disappeared were also marginally significantly closer to human‐caused disturbances than were populations that survived. Vacant sites in which new populations appeared were significantly less isolated from conspecific populations than sites remaining vacant. Spatial patterns in population density were analyzed for three of the species for 3 years at 50 sites in a 20 × 40 km region. From 1997 to 1998, population densities of each species changed synchronously throughout the region. From 1998 to 1999, one species (  Mimulus nudatus) again showed synchrony, and populations of the other two species (  Helianthus exilis, Delphinium uliginosum) remained asynchronous and spatially uncorrelated. The five species we studied all appear to be persisting well at the regional scale, despite recent disturbance to the study region. These results suggest that for rare plants in isolated habitats, the spatial configuration of populations may have an important influence on local population persistence.
Prescribing Flood Regimes to Sustain Riparian Ecosystems along Meandering Rivers
Authors: Richter Brian D. , Richter Holly E.
Published: March 2003

Abstract: The composition and structure of native riverine ecosystems are tightly linked to natural hydrologic variability. By managing river flows for water supplies and power generation, water management agencies have inadvertently caused considerable degradation of riverine ecosystems and associated biodiversity. New approaches for meeting human needs for water while conserving the ecological integrity of riverine ecosystems are greatly needed. We describe an approach for identifying the natural flooding characteristics that must be protected or restored to maintain riparian (  floodplain) ecosystems along meandering rivers. We developed a computer model to simulate flood‐driven changes in the relative abundance of riparian patch types along the Yampa River in Colorado ( U.S.A.). The model is based on research suggesting that the duration of flooding at or above 209 m3 per second (125% of bankfull discharge) is particularly important in driving lateral channel migration, which is responsible for initiating ecological succession in the Yampa's riparian forest. Other hydrologic variables, such as the magnitude of annual peak flows, were not as strongly correlated with lateral channel migration rates. Model simulations enabled us to tentatively identify a threshold of alteration of flood duration that could lead to substantial changes in the abundance of forest patch types over time should river flows be regulated by future water projects. Based on this analysis, we suggest an ecologically compatible water management approach that avoids crossing flood alteration thresholds and provides opportunity to use a portion of flood waters for human purposes. Recommended improvements to the Yampa model include obtaining additional low‐elevation aerial photographs of the river corridor to enable better estimation of channel migration rates and vegetation changes. These additional data should greatly improve the model's accuracy and predictive capabilities and therefore its management value.
Genetics, Taxonomy, and Conservation of the Threatened California Gnatcatcher
Authors: Zink Robert M. , Barrowclough George F. , Atwood Jonathan L. , Blackwell‐Rago Rachelle C.
Published: March 2003

Abstract:The California Gnatcatcher (   Polioptila californica) has become a flagship species in the dispute over development of southern California's unique coastal sage scrub habitat, a fragile, geographically restricted ecosystem with high endemism. One aspect of the controversy concerns the status of the subspecies of this bird in southern California coastal sage scrub that is currently listed as threatened under the U.S. Endangered Species Act. To investigate the recent population history of this species and the genetic distinctiveness of subspecies and to inform conservation planning, we used direct sequencing of mitochondrial DNA (mtDNA) for 64 individuals from 13 samples taken throughout the species' range. We found that coastal sage scrub populations of California Gnatcatchers are not genetically distinct from populations in Baja California, which are dense and continuously distributed throughout the peninsula. Rather, mtDNA sequences from this species contain the signatures of population growth and support a hypothesis of recent expansion of populations from a southern Baja California refugium northward into the southern coastal regions of California. During this expansion, stochastic events led to a reduction in genetic variation in the newly occupied range. Thus, preservation of coastal sage scrub cannot be linked to maintaining the genetic diversity of northern gnatcatcher populations, despite previous recognition of subspecies. Our study suggests that not all currently recognized subspecies are equivalent to evolutionarily significant units and illustrates the danger of focusing conservation efforts for threatened habitats on a single species.
Status of Marine Mammals in the United States
Authors: Read Andrew J. , Wade Paul R.
Published: March 2003

Abstract: The 1994 amendments to the U.S. Marine Mammal Protection Act required, for the first time, an assessment of the status of every marine mammal stock in the United States. We draw conclusions about the status of marine mammals from assessments of 153 stocks conducted to meet the requirements of these amendments. We found important regional differences in the status of stocks. Most stocks in the Atlantic and Pacific experience human‐induced mortality (takes), primarily from gill‐net fisheries. The proportion of stocks with takes was lower in the Gulf of Mexico and Hawaii, areas with few gill‐net fisheries. Estimated takes exceeded removal limits for 29% of stocks in the Atlantic, 14% in the Pacific, 8% in Alaska, 7% in the Gulf of Mexico, and 0% in Hawaii. Twenty‐eight stocks are listed as threatened or endangered under the U.S. Endangered Species Act. Most, but not all, baleen whale stocks are recovering after cessation of commercial harvests. Many species of pelagic cetaceans, including beaked and sperm whales, are vulnerable to mortality in pelagic drift‐net fisheries. Most pinniped stocks experience takes, but none of these takes exceeds removal limits, and all pinniped stocks on mainland coasts of the United States are increasing in abundance. Quantitative data on trends in abundance are available for few cetacean stocks, emphasizing the difficulty of monitoring trends in these species. These stock assessments have greatly advanced our understanding of the status of marine mammals in the United States, but information gaps remain, particularly regarding stock structure and possible mortality in unmonitored fisheries.
Effects of Forest Roads on Macroinvertebrate Soil Fauna of the Southern Appalachian Mountains
Authors: Haskell David G.
Published: March 2003

Abstract:Many forested landscapes are fragmented by roads, but our understanding of the effects of these roads on the function and diversity of the surrounding forest is in its infancy. I investigated the effect of roads in otherwise continuous forests on the macroinvertebrate fauna of the soil. I took soil samples along transects leading away from the edges of unpaved roads in the Cherokee National Forest in the Southern Appalachian mountains of the United States. Roads significantly depressed both the abundance and the richness of the macroinvertebrate soil fauna. Roads also significantly reduced the depth of the leaf‐litter layer. These effects persisted up to 100 m into the forest. Wider roads and roads with more open canopies tended to produce steeper declines in abundance, richness, and leaf‐litter depth, but these effects were significant only for canopy cover and litter depth. The macroinvertebrate fauna of the leaf litter plays a pivotal role in the ability of the soil to process energy and nutrients. These macroinvertebrates also provide prey for vertebrate species such as salamanders and ground‐foraging birds. The effect of roads on the surrounding forest is compounded by the sprawling nature of the road system in this and many other forests. My data suggest that even relatively narrow roads through forests can produce marked edge effects that may have negative consequences for the function and diversity of the forest ecosystem.
Fishing‐Gear Restrictions and Conservation of Benthic Habitat Complexity
Authors: Kaiser Michel J. , Spence Fiona E. , Hart Paul J. B.
Published: March 2003

Abstract: When two commercially important marine species coexist in the same habitat, conflict may arise between different sectors of the fishing industry. A good example of this situation is when fishers using towed bottom‐fishing gear ( scallop dredges, beam trawls, and otter trawls) operate in the same areas in which fixed‐bottom gear ( crab pots) are deployed. We examined an area subject to a voluntary agreement between these two sectors of the fishing industry such that some areas are used exclusively by fixed‐gear fishers, some are shared seasonally by both sectors, and others are open to all methods of fishing all year. This agreement was enacted to resolve conflict between the two sectors of the industry. An additional possible benefit of this agreement is the protection of the seabed from towed bottom‐fishing gear, which is one of the greatest sources of anthropogenic disturbance of seabed habitats worldwide. Previous studies have demonstrated that complex emergent epifaunal communities are substantially altered by such activities. This habitat alteration in turn influences closely associated species, some of which may be of commercial importance. We undertook comparative surveys of the benthic habitat and communities within the area covered by the agreement and compared different areas subjected to a range of fishing disturbance regimes. Communities found within the areas closed to towed fishing gears were significantly different from those open to fishing either permanently or seasonally. Abundance‐biomass curves demonstrated that the communities within the closed areas were dominated by higher biomass and emergent fauna that increased habitat complexity. Areas fished by towed gear were dominated by smaller‐bodied fauna and scavenging taxa. Scallop dredges and beam trawls used on more stable habitats appear to have greater impacts on the environment than lighter otter trawls used in shallower water with less stable sediments. It would appear from our data that conflict management in the form of gear‐restriction measures has the added benefit of conserving habitats and benthic fauna sensitive to bottom‐fishing disturbance.
Analysis and Conservation Implications of Koala Genetics
Authors: Sherwin William B. , Timms Peter , Wilcken Jonathan , Houlden Bronwyn
Published: March 2003

Abstract:Koalas are the only living member of their family and therefore deserve serious conservation consideration. Koalas have low levels of genetic variation within and among populations in the southern part of their range, where they have experienced many relocations and population crashes since European colonization of Australia. The importance of this change in variation is underlined by preliminary indications that levels of genetic variation may affect fitness in koalas. Techniques have been developed to help identify and monitor genetic problems in koalas and to provide the information and tools to make genetic management an integral part of koala conservation. The koala is currently at an appropriate point for conservation intervention: there is clear evidence of decline in some populations, but the existence of other robust populations offers the possibility of a variety of creative solutions to their conservation problems. Managers should aim to maintain this species' current ecological amplitude (the range of environments in which populations are found) and minimize the loss, fragmentation, or decline of populations. There are no data to suggest that any population requires genetic supplementation. The concepts of evolutionarily significant unit ( ESU) and management unit (MU) can be useful in the genetic management of koalas, including monitoring and management regimes. But ESUs and MUs can also be misleading if they are not interpreted carefully in terms of population history and the ultimate goal of management. Translocations should not involve extensive use of stock from a single source, especially those with low genetic variation, and they require careful management to avoid possible problems when individuals encounter novel strains of the pathogenChlamydia pecorum, because several genetically distinct strains have been found in koalas, some of which may derive from introduced species. Genetic indicators can and must make considerable contributions to koala management, but they require careful interpretation.
Population Trends and the Koala Conservation Debate
Authors: Phillips Stephen S.
Published: March 2003

Abstract: A critical issue affecting the long‐term management of koalas is their perceived conservation status. Koalas still occur in many areas throughout their historical range, but numbers of animals are estimated to vary from <100,000 to at least one order of magnitude higher. Complex factors limit free‐ranging koala populations, including food tree preferences, history of disturbance, and Chlamydia infection, all of which make longer‐term population trends of many populations difficult to predict. Lack of consensus regarding the size and viability of remaining populations and regarding the extent of and reasons for decline, overabundance or in some instances, hinders the conservation task. A reappraisal of population trends suggests that, notwithstanding localized management issues in Victoria and South Australia, overall the species is “vulnerable” on the basis of current World Conservation Union criteria. Recommendations for more effective conservation of koalas include (1) acknowledging the legitimacy of differing perspectives, (2) recognizing the uncertainty and assumptions inherent in population estimates and trends, (3) applying greater rigor and developing better standards for monitoring population trends, and (4) being cautious in assigning conservation status to national, state, and regional populations.
Forest Edges as Nutrient and Pollutant Concentrators: Potential Synergisms between Fragmentation, Forest Canopies, and the Atmosphere
Authors: Weathers Kathleen C. , Cadenasso Mary L. , Pickett Steward T. A.
Published: March 2003

Abstract: Forest fragmentation leads to a dramatic increase in forest edge, and these edges may function as traps and concentrators for wind‐borne nutrients and pollutants. We assessed the influence of forest edges on atmospheric deposition and subsequent inputs to the forest floor in deciduous‐forest fragments in the eastern United States. To quantify these inputs, we collected throughfall—water that has passed through the forest canopy—from edge and interior zones of forests adjacent to open fields. During the 1995 growing season, atmospheric input (wet and dry deposition) of sulfur to forest edge zones was elevated compared with input to forest interiors. Throughfall fluxes of dissolved inorganic nitrogen and calcium were also greater at edges than interiors. The mean edge increases ranged from 17% to 56% for the nutrients and pollutants we measured. When we manipulated the structure of forest edges by removing all vegetation below half the canopy height, throughfall flux in the edge zone declined sharply and was less than that of the respective interior zone. Changing the vegetation structure of the edge also shifted the zone of highest throughfall flux farther into the interior of the forest. Our data suggest that forest edges can function both as significant traps for airborne nutrients and pollutants from adjoining agricultural or urban landscapes and effective concentrators of below‐canopy chemical fluxes. These enhanced fluxes may have cascading effects on soil‐nutrient cycling, microbial activity, seedling dominance, and other ecological processes near forest edges.
A Method for Setting the Size of Plant Conservation Target Areas
Authors: Burgman Mark A. , Possingham Hugh P. , Lynch A. Jasmyn J. , Keith David A. , McCarthy Michael A. , Hopper Stephen D. , Drury Wendy L. , Passioura Jason A. , Devries Robert J.
Published: March 2003

Abstract: Realistic time frames in which management decisions are made often preclude the completion of the detailed analyses necessary for conservation planning. Under these circumstances, efficient alternatives may assist in approximating the results of more thorough studies that require extensive resources and time. We outline a set of concepts and formulas that may be used in lieu of detailed population viability analyses and habitat modeling exercises to estimate the protected areas required to provide desirable conservation outcomes for a suite of threatened plant species. We used expert judgment of parameters and assessment of a population size that results in a specified quasiextinction risk based on simple dynamic models. The area required to support a population of this size is adjusted to take into account deterministic and stochastic human influences, including small‐scale disturbance, deterministic trends such as habitat loss, and changes in population density through processes such as predation and competition. We set targets for different disturbance regimes and geographic regions. We applied our methods to Banksia cuneata, Boronia keysii, and Parsonsia dorrigoensis, resulting in target areas for conservation of 1102, 733, and 1084 ha, respectively. These results provide guidance on target areas and priorities for conservation strategies.
Maximum Plant‐Community Endemism at Intermediate Intensities of Anthropogenic Disturbance in Bolivian Montane Forests
Authors: Kessler Michael
Published: March 2003

Abstract:I compared the endemism of four plant groups (Araceae, Bromeliaceae, Palmae, Pteridophyta) along gradients of increasing anthropogenic forest disturbance, from undisturbed mature forest to disturbed forest (logged, grazed, or burned), secondary forest, secondary scrub, and finally pasture, at 16 sites in the Bolivian Andes. I measured endemism as the mean inverse range size (number of 1° cells) of all species per study group encountered in each habitat and site. Overall, endemism was significantly higher in disturbed forest than in mature forest, but it declined in more strongly disturbed habitats. To explain the relationship of range size to habitat disturbance, I propose that endemic species are somewhat competitively inferior to other co‐occurring taxa, limited in their ability to establish and maintain new populations following dispersal and thus to expand their ranges. Within their established ranges, endemic species depend on natural habitat disturbances to prevent their competitive exclusion by other species, so they profit from a certain level of anthropogenic disturbance. This pattern and the explanatory hypotheses should be subjected to critical evaluation. Although the pattern does not apply to every endemic tropical plant species, it indicates that conservation of part of the endemic tropical forest flora may be achieved in forest areas subject to sustainable forest use without the need to completely exclude human activities.
Effects of Economic Prosperity on Numbers of Threatened Species
Authors: Naidoo Robin , Adamowicz Wiktor L.
Published: March 2003

Abstract:We used data from over 100 countries to investigate the link between numbers of threatened species and per‐capita gross national product. We corrected for factors that might otherwise confound such a relationship. Our study was motivated by the continuing debate over the relationship between environmental degradation and per‐capita income. Proponents of the environmental Kuznets‐curve hypothesis argue that although environmental degradation may increase initially, increases in per‐capita income will eventually result in greater environmental quality. Theoretical objections and the lack of widespread empirical evidence recently have thrown doubt on the existence of such a pattern. Treating threat to biodiversity as one potential indicator of environmental degradation, we divided threatened species into seven taxonomic groups ( plants, mammals, birds, amphibians, reptiles, fishes, and invertebrates) and analyzed each group separately. Count‐data regression analysis indicated that the number of threatened species was related to per‐capita gross national product in five of seven taxonomic groups. Birds were the only taxonomic group in which numbers of threatened species decreased throughout the range of developed countries' per‐capita gross national product. Plants, amphibians, reptiles, and invertebrates showed increasing numbers of threatened species throughout this same range. If these relationships hold, increasing numbers of species from several taxonomic groups are likely to be threatened with extinction as countries increase in prosperity. A key challenge is to understand the interactions among consumer preferences, biology, and institutions that lead to the relationship observed for birds and to see whether this knowledge can be applied to conservation of other taxa.
Long‐Term Effects of Forestry on Birds of the Eastern Canadian Boreal Forests: a Comparison with Fennoscandia
Authors: Imbeau Louis , Mönkkönen Mikko , Desrochers André
Published: March 2003

Abstract: Logging is considered the most important threat to species in boreal forests. In contrast to eastern Canada, where most boreal forests remain largely untouched, in Fennoscandia it is possible to assess the cumulative, long‐term effects of intensive forestry on wildlife. But harvesting of stands is rapidly changing Canadian boreal forests, which represent an important proportion of the world's boreal forests. We show that Fennoscandia and eastern Canada present striking similarities in terms of forest‐age structure, natural‐disturbance regime, and structure of bird assemblages, and we provide an assessment of the long‐term effects of forestry on eastern Canadian birds of the boreal forest. We used life‐history traits from habitat, nesting site, and geographical range to calculate an index of sensitivity to changes induced by modern forestry for boreal species of each region. Tropical migrants commonly found in eastern Canadian boreal forests have life‐history traits that are not threat factors in relation to changes caused by modern forestry. Therefore, the general belief that tropical migrants in North America are more sensitive to landscape changes than those in Europe may not hold for species found in the boreal coniferous forests of eastern Canada. Nine Fennoscandian species present high levels of sensitivity, and at least eight eastern Canadian species are of similar concern. In both regions, most of the sensitive species are resident cavity nesters. Given the important similarities between the two regions, the northern expansion of commercial forestry in eastern Canada is likely to result in the significant decline of several resident species, as has occurred in Fennoscandia.
Global Habitat Protection: Limitations of Development Interventions and a Role for Conservation Performance Payments
Authors: Ferraro Paul J.
Published: March 2003

Abstract:Conservation biologists, policy makers, and citizens have identified the protection of native ecosystems in low‐income nations as a global social objective. Among the more popular initiatives toward this objective is the use of development interventions in the peripheral areas of endangered ecosystems. Such interventions indirectly provide desirable ecosystem services by redirecting labor and capital away from activities that degrade ecosystems (e.g., agricultural intensification) and by encouraging commercial activities that supply ecosystem services as joint products (e.g., ecotourism). I examined the economics of such interventions and the available empirical evidence and concluded that development interventions are hindered by (1) the indirect and ambiguous conservation incentives that they generate, (2) the complexity of their implementation, and (3) their lack of conformity with the temporal and spatial dimensions of ecosystem conservation objectives. In contrast, paying individuals or communities directly for conservation performance may be a simpler and more effective approach. In recent years there has been widespread experimentation with contracting approaches to ecosystem conservation. Conservation contracting can (1) reduce the set of critical parameters that practitioners must affect to achieve conservation goals, (2) permit more precise targeting and more rapid adaptation over time, and (3) strengthen the links between individual well‐being, individual actions, and habitat conservation, thus creating a local stake in ecosystem protection. In situations where performance payments are unlikely to work, indirect development interventions are also unlikely to work. Thus, despite the potential barriers to developing a system of conservation contracts in low‐income nations, my analysis suggests that performance payments have the potential to improve the way in which ecosystems are conserved in these nations.
Effect of the Introduced Common Slipper Shell on the Suprabenthic Biodiversity of the Subtidal Communities in the Bay of Saint‐Brieuc
Authors: Vallet Carole , Dauvin Jean‐Claude , Hamon Dominique , Dupuy Christine
Published: March 2003

Abstract:Our study compared the suprabenthic fauna collected in the Bay of Saint‐Brieuc (western English Channel) in September 1995 and May 1996 at two sites colonized byCrepidula fornicatawith that of one site where it was absent (site 23–0). WhereCrepidulawas present, no species dominated and abundance remained low. At the site withoutCrepidula, abundance was higher and the mysidHaplostylus lobatusdominated the suprabenthic community. Swimming activity of most suprabenthic species was increased by the presence ofC. fornicata. The differential abundance and swimming activity of certain species are linked to the conversion of the formerly soft substrate to now hard, shelled substrate.
Refining the Whooping Crane Studbook by Incorporating Microsatellite DNA and Leg‐Banding Analyses
Authors: Jones Kenneth L. , Glenn Travis C. , Lacy Robert C. , Pierce James R. , Unruh Natalie , Mirande Claire M. , Chavez‐Ramirez Felipe
Published: March 2003

Abstract:We sought to refine genetic management of the endangered Whooping Crane ( Grus americana) population by developing comprehensive genetic pedigrees for the captive population. Improvements to the studbook were accomplished by addition of pedigree information derived from leg‐banding data on wild juvenile and founder similarity coefficients calculated from microsatellite DNA profiles to the original studbook pedigree. Incorporation of pedigrees derived from data on leg‐banding of wild juveniles did not greatly alter the previous relatedness structure of the captive population, but incorporation of microsatellite similarity coefficients produced a substantially different view of the population structure. Microsatellite data provided new information on shared founder genotypes and provided a new DNA–based studbook pedigree that will assist in genetic management of the Whooping Crane population.
Use of Fragmented Landscapes by Marbled Murrelets for Nesting in Southern Oregon
Authors: Meyer C. B. , Miller S. L.
Published: March 2003

Abstract:As old‐growth forest becomes more fragmented in the Pacific Northwest (  U.S.A.), species dependent on large patches of old‐growth forest may be at greater risk of extinction. The Marbled Murrelet (   Brachyramphus marmoratus), a seabird whose populations are declining in North America, nests in such old‐growth forests or forests with large remnant trees. Using logistic regression models on landscapes in southern Oregon, we addressed (1) whether old‐growth forest fragmentation was associated with use of an area by murrelets and (2) whether proximity to certain marine features was associated with use of forest fragments by murrelets. On a geographic information system vegetation map derived from satellite imagery, we placed circular plots of 400‐, 800‐, 1600‐, and 3200‐m radius over surveyed inland areas occupied or unoccupied by murrelets. Within each plot, spatial and other land‐ and seascape habitat variables were calculated and regressed against murrelet occupancy. Murrelets generally occupied low‐elevation inland sites in landscapes with relatively low fragmentation and isolation of old‐growth forest patches, and these sites were close to the coast, river mouths, and a major bay. Almost all occupied landscapes occurred in a fog‐influenced vegetation zone. Because nesting habitat with large amounts of interior forest is currently scarce in southern Oregon, management efforts should focus on protecting or creating large, contiguous blocks of old‐growth forest, especially in areas near the coast.
Bushmeat Exploitation in Tropical Forests: an Intercontinental Comparison
Authors: Fa Julia E. , Peres Carlos A. , Meeuwig Jessica
Published: March 2003

Abstract: We calculated extraction and production rates of bushmeat species in two main tropical, moist‐forest regions, the Amazon and Congo basins. Extraction was estimated from the average number of animals consumed per person per year from anthropological studies that reported animal kills brought into settlements in the regions. We calculated extraction rates ( kg / km 2/year) for 57 and 31 mammalian taxa in the Congo and Amazon, respectively. We then examined the sustainability of these extraction rates by basin and by taxa, using extraction‐to‐production (   E:P) mass‐balance equations. Production (tonnes/year) was calculated as the product of rmax (the intrinsic rate of natural increase), mammal biomass, and total area of forest in each region. Species exploitation rates at specific body masses were significantly greater in the Congo than in the Amazon. The E :P ratio for the Congo was 2.4, 30 times the Amazon's ratio of 0.081. Thus, Congo Basin mammals must annually produce approximately 93% of their body mass to balance current extraction rates, whereas Amazonian mammals must produce only 4% of their body mass. We calculated sustainability levels derived from Robinson and Redford's harvest model for each taxa. On a basin‐wide level, 60% and none of the mammal taxa in the Congo and Amazon basins, respectively, were exploited unsustainably. To evaluate the effect of error on the estimates of E :P, we conducted a sensitivity analysis, which suggests that the mass‐balance was most sensitive to error in standing stock but that our results are robust. We estimated that over 5 million tons of wild mammal meat feed millions in Neotropical (0.15 million) and Afrotropical (4.9 million) forests annually. Our Congo basin estimates are four times higher than those calculated for the region by other workers, and we conclude that the current situation of bushmeat extraction in African rain forests is more precarious than previously thought.
Effects of Rock Climbing on the Vegetation of the Niagara Escarpment in Southern Ontario, Canada
Authors: McMillan Michele A. , Larson Douglas W.
Published: March 2003

Abstract:The cliffs of the Niagara Escarpment support unique and diverse plant communities. Although recreational rock climbing has become extremely popular in North America over the past two decades, little is known about the effect of this sport on the natural biota. We examined the ecological effects of rock climbing on vascular plant, bryophyte, and lichen communities along the Niagara Escarpment in southern Ontario. We made comparisons among randomly selected climbed and unclimbed rock outcrops by sampling from three positions: plateau (or cliff edge), cliff face, and talus (or cliff base). Density, percent cover, species richness, and species diversity of vascular plants were lower on climbed outcrops than on unclimbed outcrops. In addition, the proportion of alien plants was three times greater in climbed areas than in unclimbed areas. The frequency and richness of bryophyte species were also significantly lower in climbed areas. The frequency of lichens was the same on climbed and unclimbed cliffs, but species richness was significantly lower in climbed areas, and community composition differed between climbed and unclimbed areas. Our results suggest that rock climbing has significant negative effects on all aspects of the vegetative community on cliffs. Therefore, we recommend that conservation plans be modified to include specific policies regarding recreational rock climbing for lands containing exposed cliffs. For example, we suggest that the establishment of new climbing routes be banned in protected areas along the Niagara Escarpment.
Relative Sensitivities of Mammalian Carnivores to Habitat Fragmentation
Authors: Crooks Kevin R.
Published: March 2003

Abstract: I examined the effects of habitat fragmentation on the distribution and abundance of mammalian carnivores in coastal southern California and tested the prediction that responses to fragmentation varied with the body size of carnivore species. I conducted track surveys for nine native and two exotic carnivore species in 29 urban habitat fragments and 10 control sites. Fragment area and isolation were the two strongest landscape descriptors of predator distribution and abundance. Six species were sensitive to fragmentation, generally disappearing as habitat patches became smaller and more isolated; three species were enhanced by fragmentation, with increased abundance in highly fragmented sites; and two species were tolerant of fragmentation, with little to no effect of landscape variables on their distribution and abundance. Within urban habitat fragments, the carnivore visitation rate increased at sites with more exotic cover and closer to the urban edge, a pattern driven largely by the increased abundance of fragmentation‐enhanced carnivores at edge sites. Finally, body size, in conjunction with other ecological characteristics, partially accounted for the heterogeneity in responses to fragmentation among carnivore species. These differential sensitivities are useful criteria for choosing appropriate focal species for ecological research and conservation planning, a choice that depends on the scale of fragmentation in a region and the commensurate responses of carnivore populations at that scale.
Zoning Marine Protected Areas through Spatial Multiple‐Criteria Analysis: the Case of the Asinara Island National Marine Reserve of Italy
Authors: Villa Ferdinando , Tunesi Leonardo , Agardy Tundi
Published: March 2003

Abstract: As the role of marine protected areas as conservation tools becomes better understood and more sophisticated, their planning becomes more complicated. Systematic, objective approaches to site selection and design can help reconcile conflicting interests, represent stakeholders' viewpoints fairly and evenly, and extend the scope of planning studies from single reserves to networks. We illustrate the use of spatial multiple‐criteria analysis for determining the suitability of marine areas for different uses and levels of protection. This technique couples geographic information systems (GIS) for land assessment and evaluation with a formal statement of the design priorities as seen from the different viewpoints of all involved stakeholders. The planning process, while staying focused on the main purposes of conservation and feasibility, involves all the main interest groups in the definition of priorities so that conflicts and tensions are kept under control. We used multiple‐criteria analysis to integrate objective data with the contrasting priorities of different stakeholders in the planning of a marine protected area. The results of the analysis can be used to define an optimal spatial arrangement of different protection levels. As a case study, we developed a zoning plan for one of the first marine protected areas in Italy, the Asinara Island National Marine Reserve.