bluuebunny/crossref_metadata_2025 huggingface dataset:
Causes of Extirpations in the Wadden Sea, an Estuarine Area in The Netherlands
Authors: Wolff Wim J.
Published: March 2003

Abstract:The various causes of extirpation of marine and estuarine species were investigated for the Dutch Wadden Sea to gain an impression of their relative importance. I obtained data from geological, archaeological, historical, and biological publications. At least 10 species of algae, 10 invertebrates, 13 fishes, 5 birds, and 4 marine mammals became extinct during the past 2000 years. Habitat destruction played a part in at least 26 cases, overexploitation in at least 17, and pollution in at least 3. Causes of the disappearance of two species are unknown. Introduction of exotic marine species was not involved in any of the extirpations. I compared this pattern of extinction to that of worldwide extinctions of marine and estuarine species, which have been attributed to overexploitation, habitat destruction, and in two cases to the introduction of terrestrial predators to the breeding habitats of marine birds. The results imply that conservation of marine species should address overexploitation and habitat destruction as the main causes of extinction.
Choice of Species‐Area Function Affects Identification of Hotspots
Authors: Veech Joseph A.
Published: March 2003

Abstract: I tested the reliability of species‐area curves for use in identifying hotspots, political or geographical regions of high species richness. On a species‐area plot, hotspots are points (regions) that appear above the curve to a greater extent than other points. Because several different curves can be fit to species‐area data, identification of hotspots may differ depending on the curve‐fitting function used. I tested this hypothesis by comparing hotspots identified by the power function, the extreme value function, a linear function, and the exponential function. I examined several species‐area data sets varying in size and in the presence of endemics. I defined hotspots as the highest 25% for small data sets and highest 10% and 25% for large data sets of standardized residuals from each function fitted to each data set. For some data sets, the functions agreed in identification of hotspots in that they identified 75% or more of the same hotspots. The extreme value function tended to identify hotspots not identified by the other three functions. For most data sets, the functions did not agree completely in identifying hotspots. Therefore, species‐area curves should not be used as the sole means of identifying hotspots of species richness, although they can be used to examine the effect hotspot area has on richness for hotspots identified by other methods.
The Ecological Road‐Effect Zone of a Massachusetts (U.S.A.) Suburban Highway
Authors: Forman Richard T. T. , Deblinger Robert D.
Published: March 2003

Abstract:Ecological flows and biological diversity trace broad patterns across the landscape, whereas transportation planning for human mobility traditionally focuses on a narrow strip close to a road or highway. To help close this gap we examined the “road‐effect zone” over which significant ecological effects extend outward from a road. Nine ecological factors—involving wetlands, streams, road salt, exotic plants, moose, deer, amphibians, forest birds, and grassland birds—were measured or estimated near 25 km of a busy four‐lane highway west of Boston, Massachusetts. The effects of all factors extended>100 m from the road, and moose corridors, road avoidance by grassland birds, and perhaps road salt in a shallow reservoir extended outwards>1 km. Most factors had effects at 2–5 specific locations, whereas traffic noise apparently exerted effects along most of the road length. Creating a map of these effects indicates that the road‐effect zone averages approximately 600 m in width and is asymmetric, with convoluted boundaries and a few long fingers. We conclude that busy roads and nature reserves should be well separated, and that future transportation systems across landscapes can provide for ecological flows and biological diversity in addition to safe and efficient human mobility.
Non‐Native Fish Introductions and the Decline of the Mountain Yellow‐Legged Frog from within Protected Areas
Authors: Knapp Roland A. , Matthews Kathleen R.
Published: March 2003

Abstract: One of the most puzzling aspects of the worldwide decline of amphibians is their disappearance from within protected areas. Because these areas are ostensibly undisturbed, habitat alterations are generally perceived as unlikely causes. The introduction of non‐native fishes into protected areas, however, is a common practice throughout the world and may exert an important influence on amphibian distributions. We quantified the role of introduced fishes (several species of trout) in the decline of the mountain yellow‐legged frog (  Rana muscosa) in California's Sierra Nevada through surveys openface> 1700 sites in two adjacent and historically fishless protected areas that differed primarily in the distribution of introduced fish. Negative effects of fishes on the distribution of frogs were evident at three spatial scales. At the landscape scale, comparisons between the two protected areas indicated that fish distribution was strongly negatively correlated with the distribution of frogs. At the watershed scale, the percentage of total water‐body surface area occupied by fishes was a highly significant predictor of the percentage of total water‐body surface area occupied by frogs. At the scale of individual water bodies, frogs were three times more likely to be found and six times more abundant in fishless than in fish‐containing waterbodies, after habitat effects were accounted for. The strong effect of introduced fishes on mountain yellow‐legged frogs appears to result from the unique life history of this amphibian which frequently restricts larvae to deeper water bodies, the same habitats into which fishes have most frequently been introduced. Because fish populations in at least some Sierra Nevada lakes can be removed with minimal effort, our results suggest that the decline of the mountain yellow‐legged frog might be relatively easy to reverse.
Making Consistent IUCN Classifications under Uncertainty
Authors: Akçakaya H. Reşit , Ferson Scott , Burgman Mark A. , Keith David A. , Mace Georgina M. , Todd Charles R.
Published: March 2003

Abstract:The World Conservation Union (IUCN) defined a set of categories for conservation status supported by decision rules based on thresholds of parameters such as distributional range, population size, population history, and risk of extinction. These rules have received international acceptance and have become one of the most important decision tools in conservation biology because of their wide applicability, objectivity, and simplicity of use. The input data for these rules are often estimated with considerable uncertainty due to measurement error, natural variation, and vagueness in definitions of parameters used in the rules. Currently, no specific guidelines exist for dealing with uncertainty. Interpretation of uncertain data by different assessors may lead to inconsistent classifications because attitudes toward uncertainty and risk may have an important influence on the classification of threatened species. We propose a method of dealing with uncertainty that can be applied to the current IUCN criteria without altering the rules, thresholds, or intent of these criteria. Our method propagates the uncertainty in the input parameters and assigns the evaluated species either to a single category (as the current criteria do) or to a range of plausible categories, depending on the nature and extent of uncertainties.
Evidence of Natural Reproduction of Aquaculture‐Escaped Atlantic Salmon in a Coastal British Columbia River
Authors: Volpe John P. , Taylor Eric B. , Rimmer David W. , Glickman Barry W.
Published: March 2003

Abstract: We present evidence of the first successful natural spawning of Atlantic salmon (  Salmo salar) documented on the Pacific coast of North America. Twelve juvenile Atlantic salmon composed of two year classes were captured in the Tsitika River, British Columbia. We analyzed restriction‐length polymorphisms of PCR‐amplified 5S rDNA and mtDNA to confirm that these individuals were Atlantic salmon. Scale analysis strongly suggested they were the products of natural spawning by feral adults. The gut contents, size, and condition of these individuals suggest that Atlantic salmon are successfully maturing in the Tsitika River, British Columbia. This event has raised concerns that the presence and possible establishment of feral Atlantic salmon may further jeopardize the continued persistence of already fragile native Pacific salmonids through competition for resources and occupation of niches that are currently underutilized.
Shrubsteppe Bird Response to Habitat and Landscape Variables in Eastern Washington, U.S.A.
Authors: Haegen W. Matthew Vander , Dobler Frederick C. , Pierce D. John
Published: March 2003

Abstract:The landscape of the intermountain west has changed dramatically in the last 150 years, particularly in the state of Washington, where over half the native shrubsteppe ecosystem has been converted to agricultural lands, resulting in a fragmented landscape with few extensive tracts of shrubsteppe. We examined the historical and current distribution of shrubsteppe on different soil types in eastern Washington, and we censused bird communities at 78 sites in shrubsteppe from 1991 to 1993. We compared abundance of species among soil types and range conditions and developed models of species occurrence using site‐specific vegetation and landscape variables. The pattern of shrubsteppe conversion has resulted in a disproportionate loss of deep soil communities. Eight bird species showed strong relationships with soil type and three with range condition. These associations likely resulted from the influence of soil type and range history on the vegetation of these communities. Brewer's Sparrows ( Spizella breweri) and Sage Sparrows (Amphispiza belli) reached their highest abundances in deep, loamy soils, whereas Loggerhead Shrikes (  Lanius ludovicianus) were most abundant in deep, sandy soils. Sage Sparrows occurred more frequently in landscapes dominated by shrubsteppe, indicating a negative relationship with fragmentation. Our results suggest that fragmentation of shrubsteppe and the pattern of agricultural conversion among soil types have had detrimental effects on numerous shrubsteppe species. The landscape for species with an affinity for deep, loamy soil communities has changed considerably more than the overall loss of shrubsteppe would indicate. Conservation practices that emphasize retention of shrubsteppe communities on deep soils and that reduce further fragmentation will be critical to the maintenance of avian biological diversity in this system.
Overview, Critical Assessment, and Conservation Implications of Koala Distribution and Abundance
Authors: Melzer Alistair , Carrick Frank , Menkhorst Peter , Lunney Daniel , John Barbara ST.
Published: March 2003

Abstract: Regional and national surveys provide a broadscale description of the koala's present distribution in Australia. A detailed understanding of its distribution is precluded, however, by past and continuing land clearing across large parts of the koala's range. Koala population density increased in some regions during the late 1800s and then declined dramatically in the early 1900s. The decline was associated with habitat loss, hunting, disease, fire, and drought. Declines are continuing in Queensland and New South Wales. In contrast, dense koala populations in habitat isolates in Victoria and South Australia are managed to reduce population size and browse damage. Current understanding of koala distribution and abundance suggests that the species does not meet Australian criteria as endangered or vulnerable fauna. Its conservation status needs to be reviewed, however, in light of the extensive land clearing in New South Wales and Queensland since the last (1980s) broadscale surveys. Consequently, we recommend that broadacre clearing be curtailed in New South Wales and Queensland and that regular, comprehensive, standardized, national koala surveys be undertaken. Given the fragmentation of koala habitat and regional differences in the status of the koala, we recommended that studies on regional variation in the koala be intensified and that koala ecology in fragmented and naturally restricted habitats be developed. More generally, the National Koala Conservation Strategy should be implemented.
Designing Species Translocation Strategies When Population Growth and Future Funding Are Uncertain
Authors: Haight Robert G. , Ralls Katherine , Starfield Anthony M.
Published: March 2003

Abstract: When translocating individuals to found new populations, managers must allocate limited funds among release and monitoring activities that differ in method, cost, and probable result. In addition, managers are increasingly expected to justify the funding decisions they have made. Within the framework of decision analysis, we used robust optimization to formulate and solve different translocation problems in which both population growth and future funding were uncertain. Performance criteria included maximizing mean population size and minimizing the risk of undesirable population‐size outcomes. Robust optimization provided several insights into the design of translocation strategies: (1) risk reduction is obtained at the expense of mean population size; (2) as survival of released animals becomes more important, funds should be allocated to release methods with lower risks of failure, regardless of costs; (3) the performance gain from monitoring drops as the proportion of a fixed budget required to pay for monitoring increases; and (4) as the likelihood of obtaining future funding increases, more of the existing budget should be spent on building release capacity rather than saved for future operating costs. These relationships highlight the importance of performance criteria and economic costs in determining optimal release and monitoring strategies.
Patterns of Genetic Diversity in Remaining Giant Panda Populations
Authors: Lu Zhi , Johnson Warren E. , Menotti‐Raymond Marilyn , Yuhki Naoya , Martenson Janice S. , Mainka Susan , Shi‐Qiang Huang , Zhihe Zheng , Li Guanghan , Pan Wenshi , Mao Xiarong , O'Brien Stephen J.
Published: March 2003

Abstract: The giant panda (Ailuropoda melanoleuca) is among the more familiar symbols of species conservation. The protection of giant panda populations has been aided recently by the establishment of more and better‐managed reserves in existing panda habitat located in six mountain ranges in western China. These remaining populations are becoming increasingly isolated from one another, however, leading to the concern that historic patterns of gene flow will be disrupted and that reduced population sizes will lead to diminished genetic variability. We analyzed four categories of molecular genetic markers (mtDNA restriction‐fragment‐length polymorphisms [RFLP], mtDNA control region sequences, nuclear multilocus DNA fingerprints, and microsatellite size variation) in giant pandas from three mountain populations (Qionglai, Minshan, and Qinling) to assess current levels of genetic diversity and to detect evidence of historic population subdivisions. The three populations had moderate levels of genetic diversity compared with similarly studied carnivores for all four gene measures, with a slight but consistent reduction in variability apparent in the smaller Qinling population. That population also showed significant differentiation consistent with its isolation since historic times. From a strictly genetic perspective, the giant panda species and the three populations look promising insofar as they have retained a large amount of genetic diversity in each population, although evidence of recent population reduction—likely from habitat loss—is apparent. Ecological management to increase habitat, population expansion, and gene flow would seem an effective strategy to stabilize the decline of this endangered species.
Conservation Value of Private Lands for Crested Caracaras in Florida
Authors: Morrison Joan L. , Humphrey Stephen R.
Published: March 2003

Abstract: In southcentral Florida, where agricultural lands are being converted rapidly to urban development, much of the remaining nonurban habitat occurs on privately owned cattle ranches. We studied the Crested Caracara (Caracara cheriway), a threatened bird of prey, to learn the role of private lands in sustaining the population. We investigated patterns of distribution and reproductive activity of breeding pairs of caracaras in relation to patterns of land ownership and use. Eighty‐two percent of 73 active nest sites found were on privately owned cattle ranches. We rarely found breeding pairs on publicly owned lands, most of which are managed as natural areas (no agricultural production and limited livestock grazing) to support native plant and animal communities. In 46 breeding areas with 4 years of known histories of occupancy and reproduction, pairs nesting on lands where the major land use was cattle ranching exhibited higher rates of breeding‐area occupancy, attempted breeding during more years, initiated egg laying earlier, exhibited higher nesting success, and attempted a second brood after successfully fledging a first brood more often than pairs nesting on lands managed as natural areas. Compositional analysis suggested nonrandom selection of habitats by breeding pairs of caracaras in their establishment of a home range in the current landscape of southcentral Florida. Compared with random areas and available habitat in the overall study area, caracara home ranges had higher proportions of improved pasture and lower proportions of forest, woodland, oak scrub, and marsh. Which management activities favor and do not favor caracaras is uncertain, and hypotheses should be formulated and tested to guide future conservation applications. Particular grazing and fire management practices on privately and publicly owned lands may affect the structure of vegetation and prey communities in ways that influence caracaras. Or, replacement of native by exotic grasses may retain structurally suitable plant communities, whereas fertilization and grazing may increase productivity and nutrient cycling in ways that favor caracaras. Given continued conversion of natural habitats and agricultural lands to urban development, it is important to recognize that cattle ranches may provide important resources for wildlife conservation. Although cattle ranching is not likely to benefit all species historically associated with the native prairie ecosystem in Florida, finding ways to retain this land use may be important for the conservation of Florida's population of Crested Caracaras and other organisms of Florida's dry prairies.
Climate Warming and Calling Phenology of Frogs near Ithaca, New York, 1900–1999
Authors: Gibbs James P. , Breisch Alvin R.
Published: March 2003

Abstract: Because ambient temperature strongly influences reproduction in frogs, the seasonal timing of frog calling provides a sensitive index of biotic response to climate change. Over the last century, daily temperatures increased during 5 of the 8 months key to gametogenesis in frogs and toads near Ithaca, New York ( U.S.A.). Earliest dates of calling frogs recorded by Albert Hazen Wright between 1900 and 1912 near Ithaca were compared to those from the New York State Amphibian and Reptile Atlas Project for 1990–1999 for the three counties surrounding Ithaca. Four species are now calling 10–13 days earlier, two are unchanged, and none is calling later. The data suggest that climate has warmed in central New York State during this century and has resulted in earlier breeding in some amphibians—a possible first indication of biotic response to climate change in eastern North America.
Indices of Grassland Biodiversity in the Chihuahuan Desert Ecoregion Derived from Remote Sensing
Authors: Muldavin Esteban H. , Neville Paul , Harper Glenn
Published: March 2003

Abstract: We used a relatively simple and direct remote‐sensing approach to determine biodiversity values in arid ecosystems and thus identify potential conservation sites. We developed indices based on regression models between grass, shrub, litter, exposed‐soil groundcover components, and Landsat thematic mapper satellite imagery reflectance values over a reference site in the northern Chihuahuan Desert in New Mexico. This site supports low‐disturbance desert grasslands that have been excluded from livestock grazing for 55 years and moderate‐disturbance grasslands that have been under a continuous grazing regime for over 100 years. Greater richness and abundance of noninvasive and nonruderal plant species were associated with the low‐disturbance grasslands that had lower shrub abundance, increased litter and grass cover, and lower exposed soil. Using the thematic mapper indices, we computed an additive grassland biodiversity index such that, as exposed soil and shrub values go down, litter and grass values go up, as does the biodiversity index. When the biodiversity index was applied to the reference‐site landscape, grasslands previously identified for their high conservation value were detected. As a further test, we applied the indices to a site in Chihuahua, Mexico, that supports similar grasslands but for which there are few other data on condition and conservation values. The soil, grass, and shrub indices were moderately effective in describing the range of variation at the Mexico site, but the litter equation was not. Still, higher biodiversity value in terms of nonruderal plant diversity tended to correspond to higher grass cover and lower soil exposure and a higher overall biodiversity index. Some localized calibration with geologic substrate may be required along with an assessment of the temporal constraints, but generally the index shows promise for quickly and efficiently detecting desert grasslands of high biodiversity conservation value.
Examining Fragmentation and Loss of Primary Forest in the Southern Bahian Atlantic Forest of Brazil with Radar Imagery
Authors: Saatchi S. , Agosti D. , Alger K. , Delabie J. , Musinsky J.
Published: March 2003

Abstract: The Atlantic rainforest of southern Bahia is one of the last remnants of the lowland forest of eastern Brazil that once covered the entire coastal area from Rio Grande do Norte to Rio Grande do Sul ( lat 8°–28° S) and has been deforested to a small fraction of its original cover (1–12%). All recent vegetation surveys have been based on optical satellite data, which is hampered by cloud cover and by southern Bahia's intricate mix of forest patches with other tree crops, especially cocoa. We describe the application of radar remote‐sensing data to distinguish forest patches from cocoa planted in the shade of natural‐forest trees. Radar, unlike optical sensors, is not obstructed by cloud cover and can acquire information about forest structure by penetrating into the vegetation canopy. The vegetation map generated from radar data clearly separates forest patches based on the degree of structural disturbance such as the density of shaded trees, the openness of the canopy, and the density of the monodominant Erythyrina shaded trees. The structural classification based on the radar data, and shown on the map, can help researchers assess the degree of fragmentation of the original Atlantic coastal forest and delineate areas of less disturbance with higher potential for conservation of biodiversity. This information can then be applied to conservation planning, especially the design and monitoring of nature reserves and the modeling of biological corridors.
Evaluating Ultraviolet Radiation Exposure with Satellite Data at Sites of Amphibian Declines in Central and South America
Authors: Middleton Elizabeth M. , Herman Jay R. , Celarier Edward A. , Wilkinson John W. , Carey Cynthia , Rusin Robert J.
Published: March 2003

Abstract:Many amphibian species have experienced substantial population declines or have disappeared altogether during the last several decades at a number of amphibian survey sites in Central and South America. Our study addresses the use of trends in solar UV‐B radiation exposure (280–320 nm) at these sites over the last two decades, derived from the Total Ozone Mapping Spectrometer satellite data. It is intended to demonstrate a role for satellite observations in determining whether UV‐B radiation is a contributing factor in amphibian declines. We used these data to calculate the daily erythemal (sunburning) UV‐B, or UV‐Bery , exposure at the latitude, longitude, and elevation of each of 20 survey sites. The annually averaged UV‐Berydose, as well as the maximum values, have been increasing in both Central and South America, with higher levels reached at the Central American sites. The annually averaged UV‐Beryexposure increased significantly from 1979–1998 at all 11 Central American sites we examined (r 2= 0.60–0.79;p≤ 0.015), with smaller but significant increases at five of the nine South American sites (r 2= 0.24–0.42;p≤ 0.05). The number of days having the highest UV‐B exposure (≥6.75 kJ/m2/day) increased in both regions from <40 days per year to approximately 58 days per year in 1998 (r2= 0.24–0.42;p≤ 0.001). In Central America, the contribution of these very high UV‐Beryexposure levels to the annual UV‐Berytotal increased from approximately 5 to approximately 15% over the 19‐year period, but actual daily exposures for each species are unknown. A UV‐B ratio, the highest monthly UV‐B exposure relative to the annual average for the highest UV‐B category (≥6.75 kJ/m2), increased in both regions over this time period (r 2= 0.73;p≤ 0.001). This UV index was consistently higher for Central America, where species declines have been the most severe. These results should justify further research into whether UV‐Beryradiation plays a role in amphibian population declines and extinctions. We discuss synergy among UV‐B radiation and other factors, especially those associated with alterations of water chemistry (e.g., acidification) in aqueous habitats.
Landscape Ecology Approaches to Wetland Species Conservation: a Case Study of Two Turtle Species in Southern Maine
Authors: Joyal Lisa A. , McCollough Mark , Hunter Malcolm L.
Published: March 2003

Abstract:We investigated the habitat use and movements of two turtle species to assess the importance of conserving multiple wetlands and the upland matrix in which they occur. Spotted turtles ( Clemmys guttata) and Blanding's turtles (  Emydoidea blandingii) are considered threatened and endangered, respectively, in Maine where they are near the northeastern periphery of their geographic range. We used resightings of marked individuals (69 spotted, 16 Blanding's) and radiotelemetry (13 spotted, 9 Blanding's, radiotagged for one or two seasons) to investigate the movements and habitat use of both species. Individuals of both species used multiple wetlands throughout the year, including permanent and seasonal pools, forested swamps, and wet meadows. Pools occupied by spotted and Blanding's turtles were small (<0.4 ha), and they were less isolated from other wetlands than pools that did not contain turtles. Both species used uplands extensively for nesting, dormancy, and traveling between wetlands. Turtles traveled 70–570 m (spotted) and 100–1620 m ( Blanding's) to nest, and nests were located 1–120 m (spotted) and 70–410 m ( Blanding's) from the nearest wetland. Spotted and Blanding's turtles entered relatively dormant stages for 15–89 and 3–21 consecutive days, respectively, and upland dormancy sites were 12–80 m (spotted) and 30–110 m ( Blanding's) from the nearest wetland. Total distance traveled overland throughout a season was 0–1680 m and 0–6760 m for radiotagged spotted and Blanding's turtles, respectively. Most spotted turtles followed a seasonal pattern of habitat use: pools for spring activity, upland forest for relative dormancy during part of the summer, and wet meadows or forested swamps for overwintering. A seasonal pattern in the habitat use of Blanding's turtles was not as evident. Our study suggests that protecting small wetlands, maintaining generous terrestrial buffers around individual wetlands, and conserving wetlands in groups are important components of a landscape approach to species conservation.
Relationship of Effective to Census Size in Fluctuating Populations
Authors: Kalinowski Steven T. , Waples Robin S.
Published: March 2003

Abstract:The effective size of a population (   Ne   ) rather than the census size (   N) determines its rate of genetic drift. Knowing the ratio of effective to census size,Ne  /  N, is useful for estimating the effective size of a population from census data and for examining how different ecological factors influence effective size. Two different multigenerational ratios have been used in the literature based on either the arithmetic mean or the harmonic mean in the denominator. We clarify the interpretation and meaning of these ratios. The arithmetic meanNe  /  Nratio compares the total number of real individuals to the long‐term effective size of the population. The harmonic meanNe  /  Nratio summarizes variation in theNe  /  Nratio for each generation. In addition, we show that the ratio of the harmonic mean population size to the arithmetic mean population size provides a useful measure of how much fluctuation in size reduced the effective size of a population. We discuss applications of these ratios and emphasize how to use the harmonic meanNe  /  Nratio to estimate the effective size of a population over a period of time for which census counts have been collected.
Extinction Debt at Extinction Threshold
Authors: Hanski Ilkka , Ovaskainen Otso
Published: March 2003

Abstract:To allow for long‐term metapopulation persistence, a network of habitat fragments must satisfy a certain condition in terms of number, size, and spatial configuration of the fragments. The influence of landscape structure on the threshold condition can be measured by a quantity called metapopulation capacity, which can be calculated for real fragmented landscapes. Habitat loss and fragmentation reduce the metapopulation capacity of a landscape and make it less likely that the threshold condition can be met. If the condition is not met, the metapopulation is expected to go extinct, but it takes some time following habitat loss before the extinction will occur, which generates an extinction debt in a community of species. We show that extinction debt is especially great in a community in which many species are close to their extinction threshold following habitat loss because the metapopulation‐dynamic time delay is especially long in such species. A corollary is that landscapes that have recently experienced substantial habitat loss and fragmentation are expected to show a transient excess of rare species, which represents a previously overlooked signature of extinction debt. We consider a putative example of extinction debt on forest‐inhabiting beetles in Finland. At present, the few remaining natural‐like forests are distributed evenly throughout southern Finland, but the number of regionally extinct old‐growth forest beetles is much greater in the southwestern coastal areas, where human impact on forests has been lengthy, than in the northeastern inland areas, where intensive forestry started only after World War II. Ignoring time delays in population and metapopulation dynamics will lead to an underestimate of the number of effectively endangered species.
Conservation Where People Live and Work
Authors: Miller James R. , Hobbs Richard J.
Published: March 2003

Abstract: Effective conservation planning requires information from well‐designed studies across a spectrum of land uses, ranging from wildlands to highly modified production landscapes and large cities. There is currently a lack of such information about human settlement, even though this is a major source of land‐use change with serious implications for biodiversity. Fewer than 6% of the papers in recent volumes of Conservation Biology described work conducted in urban, suburban, or exurban areas or studies in which human settlement was considered explicitly. For a variety of reasons, conservation has tended to focus on lands with a relatively small human presence, often dominated by resource extraction and agriculture. Urbanization is occurring in numerous biodiversity hotspots worldwide, however, and has been identified as a primary cause of declines in many threatened and endangered species. Suburban and exurban growth are affecting biodiversity in many places once thought of as too remote to attract such levels of development. Conservation biologists must address the issue of human settlement to enhance the habitat value of unreserved lands for native species, to increase landscape connectivity between reserves, and to mitigate adverse influences on reserves from adjacent lands. Conservation and restoration of native habitats in densely settled areas also have social and educational value. We therefore suggest a more balanced approach in conservation biology to addressing the effects of human land use through increased attention to areas where people live and work.
Effects of the Size of Prescribed Fire on Insect Predation of Northern Blazing Star, a Rare Grassland Perennial
Authors: Vickery Peter D.
Published: March 2003

Abstract: Loss of native grassland habitat in New England has reached>90%. Consequently, remaining grasslands persist as small, geographically isolated fragments, and populations of many plants and animals have declined or disappeared. Given the rarity of the fauna and flora of these habitats, ecological management of many of the remaining native grassland fragments in a manner that attempts to mimic natural processes has been intensive, and the effects of this management on some taxa, such as grassland birds, are now well understood. But the effects of management, especially prescribed fire, on native plants and invertebrates are less well known. I studied the effects of prescribed fire on northern blazing star (   Liatris scariosa var. novae‐angliae), a rare grassland perennial endemic to the northeastern United States. Once distributed from southern Maine to northern New Jersey, northern blazing star has disappeared from 69% of the sites where it formerly occurred. Seed predation appears to be a critical proximate factor limiting recruitment of juveniles into local populations. Seven of 8 study sites in Maine and Massachusetts had a 65% average rate of seed predation, and there was no evidence of juvenile recruitment at these sites. None of these sites had been burned in the past 5 years. Experimental research at Kennebunk, Maine, demonstrated that, in the absence of fire, seed viability of northern blazing star was low, the result of larval microlepidopteran ( moth) predators in the flower heads. Prescribed fire temporarily reduced seed predation from approximately 90% to approximately 16% for 1 year following fire, but seed‐predation levels once again approached 90% within 2 years. Prescribed fires larger than 13 ha helped reduce predation rates, but fires smaller than 6 ha did not, suggesting that dispersal of adult moths from unburned source areas was spatially limited. Preferably, prescribed burns should be larger than 10 ha, large enough to have core areas larger than 100 m from adjoining unburned units. My results suggest that prescribed fire should be an important component of habitat management for northern blazing star, and they emphasize the need to carefully study the effects of the spatial scale of prescribed fires in other geographic regions and for a broad range of taxa.
Critical Elements for Biologically Based Recovery Plans of Aquatic‐Breeding Amphibians
Authors: Semlitsch Raymond D.
Published: March 2003

Abstract:The global loss of biodiversity and the increasing number of threatened or endangered species have focused attention on conservation and species‐recovery strategies. Because current evidence indicates that some amphibians are experiencing population declines, range constrictions, or extinctions, and federal and state agencies have listed many species as threatened or endangered, it is essential to develop sound principles upon which to base recovery plans for different ecosystems, amphibian communities, or species if we are to balance the conservation of amphibian diversity with economic development and a growing human population. I present a framework of biologically based principles that can be used for current species conservation efforts. My goal is to provide the critical elements needed to develop biologically based recovery plans for aquatic‐breeding amphibians in any region. This paper is organized in three parts: (1) an overview of critical local population and landscape processes required to maintain amphibian species and threats, (2) the critical elements associated with successful recovery plans, and (3) considerations for measuring success and long‐term habitat management. Clearly, we need more basic data on life‐history requirements, special adaptations, habitat use, dispersal behavior, and population biology, especially factors influencing long‐term persistence for many species. Nevertheless, because some species are in urgent need of conservation action, we cannot afford to wait for additional data; the most important critical elements required to initiate effective recovery efforts for amphibians are known. I hope my discussion will help managers understand the importance of incorporating local population and metapopulation factors into their recovery and restoration plans. I also hope managers begin to think about ultimate recovery and restoration strategies that consider connectivity among populations across regions and state boundaries. Only through such coordinated efforts can we really be certain that species are conserved and biodiversity is maintained.
Focal Species, Community Representation, and Physical Proxies as Conservation Strategies: a Case Study in the Amphibolite Mountains, North Carolina, U.S.A.
Authors: Kintsch Julia A. , Urban Dean L.
Published: March 2003

Abstract:Conservation organizations are increasingly employing representative‐based conservation strategies to overcome the limits of a species‐by‐species approach and to expand the focus of conservation to include overall biodiversity and ecosystem processes. To compare focal‐species, community‐level, and physical‐proxy approaches in terms of their ability to predict vegetation communities and capture rare species, we used plot‐level data from the Amphibolite Mountains of North Carolina. We identified diagnostic species via indicator‐species analysis to calculate predictability and capture rates at the focal‐species and community levels. We performed classification and regression‐tree analysis to determine whether the biotic communities could effectively be characterized by their physical environment and to assess community predictability at this scale. At both the focal‐species level and the community level, common indicator species were most reliable when the indicator species were themselves habitat specialists occurring in distinct sites. In most cases, rare‐species capture was maximized with a focal‐species approach, but this approach required high levels of investment. Alternatively, conservation strategies based on physical proxies were not dependent on intense field surveys, but were less effective in capturing rare species. This approach may still provide an important first cut for narrowing down the number of sites requiring intense field surveys and finer‐scale analysis. Both coarse‐filter approaches provided effective mechanisms for targeting and protecting large‐scale ecological processes and overall biodiversity, and community‐level conservation also recognized the inherent value of communities beyond their capacity as representative indicators. An effective and efficient conservation‐design strategy might employ each of these three conservation targets in a multistage approach. Conservation efforts could also benefit from further research into the ecological characteristics that regulate the distribution of rare species and the implications for species capture with these different conservation approaches.
Catch and Bycatch of Sea Birds and Marine Mammals in the Small‐Scale Fishery of Punta San Juan, Peru
Authors: Majluf Patricia , Babcock Elizabeth A. , Riveros Juan Carlos , Schreiber Milena Arias , Alderete William
Published: March 2003

Abstract: Between 1991 and the present, we have had observers stationed at the port of San Juan in southern Peru to interview fishers as they landed their catch. They observed the landings of 922 Humboldt Penguins (  Spheniscus humboldti), 510 dusky dolphins (   Lagenorhynchus obscurus), 214 Burmeister's porpoises (   Phocaena spinnipinnis), and 75 bottlenose dolphins (   Tursiops truncatus) between November 1991 and June 1998, although the retention of penguins and small cetaceans is banned by Peruvian law. Most of these animals were captured in 1992–1994, when the fishers were mainly using surface‐drift gillnets to target a pelagic schooling fish called cojinova (  Seriolella violacea). Capture rates were much lower in 1995–1998, when fishers were mostly using fixed demersal gillnets and shellfish diving, due apparently to a lack of surface‐schooling cojinova in the vicinity. We used generalized linear models to examine the effect of year, gear type, area, and target fish species on the probability of capturing either penguins or dolphins. We found that the probability of a fishing vessel capturing a penguin or a dolphin increased when drift gillnets were used instead of fixed gillnets. Fishing area, year, and the species of fish caught also significantly affected the probability of capture. A population model (  Vortex) applied to Humboldt Penguins showed that the high levels of mortality seen in the early 1990s are not sustainable and could lead to local extinction in a few years. The mortality levels seen in the late 1990s are more likely to be sustainable, but a return to the use of drift gillnets would rapidly result in unsustainable levels of mortality.
Biogeographic Crossroads as Priority Areas for Biodiversity Conservation
Authors: Spector Sacha
Published: March 2003

Abstract: Threats to biodiversity outpace the resources of the conservation community and necessitate careful prioritization of conservation actions. I suggest that targeting the regions where biogeographic assemblages intersect—“biogeographic crossroads”—is a strategy that may achieve significant conservation economy by focusing on areas that satisfy many conservation criteria. I used a combination of data on Scarabaeine beetles in Bolivia and on other taxa and locations from the literature to consider the short‐ and long‐term benefits of conserving these biogeographic crossroads. Biogeographic crossroads are areas of high species richness and beta diversity, often across many taxonomic groups. They are also regions where representativeness can be achieved with relative efficiency. Recent evidence that ecotones may be loci of evolution suggests that evolutionary processes such as speciation and coevolution may be conserved at biogeographic crossroads. Biogeographic crossroads appear to be areas of high conservation priority and opportunity in both the short and long term and require increased attention in the process of setting conservation priorities.
Importance of Coarse Woody Debris to Avian Communities in Loblolly Pine Forests
Authors: Lohr Steven M. , Gauthreaux Sidney A. , Kilgo John C.
Published: March 2003

Abstract:To investigate the importance of standing (snags) and down coarse woody debris ( DCWD) to bird communities in loblolly pine (  Pinus taeda) forests, we compared breeding (1997–1999) and nonbreeding (1997–1998, 1998–1999) responses of birds among two coarse woody debris (CWD) removal and control treatments. In each of four blocks, we established four experimental units: (1) DCWD removed, (2) snags and DCWD removed, and (3) and (4) unmodified control plots. We quantified vegetation layers to determine their effects on the experimental outcome. Total breeding bird abundance, abundance of resident species, breeding bird diversity, breeding species richness, and abundance of Great Crested Flycatchers (   Myiarchus crinitus) were reduced by the removal of DCWD and snags. Total woodpecker and Carolina Wren (   Thryothorus ludovicianus) breeding territories were reduced by snag removal. Weak excavating and secondary cavity‐nesting species, Neotropical migrants, and Eastern Towhees (   Pipilio erythrophthalmus) had fewer breeding territories on plots where DCWD was removed. Red‐headed Woodpeckers (   Melanerpes erythrocephalus) and midstory and canopy‐nesting species were at lowest densities on plots where all CWD had been removed. The CWD removal had no effect on the nonbreeding bird community. Most breeding and nonbreeding species used habitats with sparse midstory and well‐developed understory, whereas sparse canopy cover and dense midstory were important to some nonbreeding species. Snag and DCWD retention, and practices that maintain a dense understory and sparse midstory and canopy, will create favorable breeding habitat for many bird species of loblolly pine forests.
The Landscape Ecology of Invasive Spread
Authors: With Kimberly A.
Published: March 2003

Abstract: Although habitat loss, fragmentation, and invasive species collectively pose the greatest threats to biodiversity, little theoretical or empirical research has addressed the effects of landscape structure—or spatial pattern more generally—on the spread of invasive species. Landscape ecology is the study of how spatial pattern affects ecological process. Thus, a landscape ecology of invasive spread involves understanding how spatial pattern, such as habitat fragmentation or resource distributions, affects the various stages of the invasion process. Landscape structure may affect the spread of invasive species and the invasibility of communities by (1) enhancing spread above some threshold level of landscape disturbance directly, or indirectly through landscape effects on dispersal vectors; (2) affecting the various stages of the invasion process (e.g., dispersal vs. population growth) in different, potentially contrasting, ways; (3) interacting with the distribution of invasive species to facilitate spread (e.g., nascent foci); (4) promoting or altering species interactions in ways that enhance the invasibility of communities (e.g., edge effects); (5) compromising the adaptive potential of native species to resist invasion, or—alternatively—enhancing the adaptive response of invasive species, in fragmented landscapes; and (6) interacting with the dynamics of the disturbance architecture to create spatiotemporal fluctuations in resource availability, which enhance system invasibility. Understanding the landscape ecology of invasive spread may thus afford new insights and opportunities for managing and restoring landscapes so as to control the spread of invasive species and minimize the invasibility of communities.