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Geology topics

Sarah J. Converse

Publications and source records attributed to Sarah J. Converse.

At least 73 records · Page 4Linked to original sources
USGS2019

Linking demographic and food-web models to understand management trade-offs

Alternatives in ecosystem-based management often differ with respect to trade-offs between ecosystem values. Ecosystem or food-web models and demographic models are typically employed to evaluate alternatives, but the approaches are rarely integrated to uncover conflicts between values. We applied multi-state models to a capture-recapture dataset on common guillemots Uria aalge breeding in the Baltic Sea to identify factors influencing survival. The estimated relationships were employed together with Ecopath-with-Ecosim food-web model simulations to project guillemot survival under six future scenarios incorporating climate change. The scenarios were based on management alternatives for eutrophication and cod fisheries, issues considered top priority for regional management, but without known direct effects on the guillemot population. Our demographic models identified prey quantity (abundance and biomass of sprat Sprattus sprattus) as the main factor influencing guillemot survival. Most scenarios resulted in projections of increased survival, in the near (2016-2040) and distant (2060-2085) future. However, in the scenario of reduced nutrient input and precautionary cod fishing, guillemot survival was projected to be lower in both future periods due to lower sprat stocks. Matrix population models suggested a substantial decline of the guillemot population in the near future, 24% per 10 years; and a smaller reduction, 1.1% per 10 years, in the distant future. To date, many stakeholders and Baltic Sea governments have supported reduced nutrient input and precautionary cod fishing and implementation is underway. Negative effects on non-focal-species have previously not been uncovered, but our results show that the scenario is likely to negatively impact the guillemot population. Linking model results allowed identifying trade-offs associated with management alternatives. This information is critical to thorough evaluation by decision-makers, but not easily obtained by food-web models or demographic models in isolation. Appropriate datasets are often available, making it feasible to apply a linked approach for better-informed decisions in ecosystem-based management.

Ecology and Evolution↗
USGS2019

Future directions to escalate benefits of stepping-stone approach for conservation translocations

Through a reintroduction case study on the critically endangered Vancouver Island marmot (Marmota vancouverensis), we introduced a ‘stepping-stone’ approach which utilizes the transition of released individuals among populations to maximize demographic growth potential (Lloyd et al. 2019). We greatly appreciate and hereby reflect on the thoughtful commentaries by Chauvenet (2019), Hayward (2019) and Thévenin (2019) to propose 3 key topics for future exploration.

Animal Conservation↗
USGS2019

The dilemma of pest suppression in the conservation of endangered species

In the conservation of endangered species, active suppression of a population of one native species to benefit another native species poses particular challenges. Obvious examples include predator control and nest parasite reduction. Less obvious is the control of blood-feeding arthropods. We present a case study on the effect of blood-feeding black flies (Simulium spp.) on reintroduced Whooping Cranes (Grus americana). Our intent is to provide a transferrable, science-driven approach for determining the effects of blood-feeding arthropods on endangered vertebrates, and demonstrate an approach for guiding selection of management actions for managers faced with competing objectives. A multi-year experiment demonstrated that black flies reduce nest success in reintroduced cranes by driving the birds off their nests during incubation. Deciding how to respond, however, is complicated because the target black flies are native species that serve important ecological functions. We suggest that a decision-analytic approach can inspire the development of creative management alternatives and facilitate a transparent process that evaluates trade-offs among competing objectives. Recognizing that these decisions involve trade-offs, which must be weighed in the context of each case, is crucial to identifying alternatives that best balance multiple management objectives. Given the uncertainty about the population dynamics of blood-feeding arthropods, an adaptive management approach will offer substantial benefits.

Wisconsin↗
USGS2019

Whooping Cranes past and present

The Whooping Crane ( Grus americana ), endemic to North America, is the rarest of all crane species. It is believed that in the early 1800s, the Whooping Crane was widespread in North America, though it was never very abundant. Whooping Crane numbers decreased precipitously as westward migration of Euro-American settlers converted prairie to cropland and the birds were hunted. By the early 1940s the total population was as low as 21 individuals; the migratory Aransas-Wood Buffalo Population, from which all extant Whooping Cranes are descended, dwindled to 16 in 1941. The threat of extinction was very real. These dire circumstances excited the interest of ornithologists and conservationists in the United States and Canada, and much has been accomplished since to conserve the species. To describe the historical and ongoing conservation activities for Whooping Cranes, we distinguish two eras of Whooping Crane Conservation: before 1950 and after 1950. The first era was characterized by publicizing the plight of the Whooping Crane and halting hunting and habitat destruction. The second era, continuing to the present, has been characterized by development of information about cranes through scientific study, conservation efforts of governmental and nongovernmental organizations, protection of the species under the Endangered Species Act in the United States and the Species at Risk Act in Canada, habitat protection, and reintroduction of new populations of Whooping Cranes. Publication of the monograph, The Whooping Crane by Robert Porter Allen, in 1952 stimulated much of the work of the second era, and still stands as the definitive work on the biology of Whooping Cranes. The remnant Aransas Wood Buffalo Population, which is crucial to species recovery, has grown to over 430 birds as of winter 2016–17. Four reintroduced populations were started in the second era; two are currently active efforts (the Eastern Migratory population and the Louisiana Nonmigratory Population), although neither population is selfsustaining. This volume gathers together the current scientific information about Whooping Cranes and the experiences of various reintroduction and management operations, to provide a baseline from which a third era of Whooping Crane conservation may be launched.

Book chapter↗
USGS2019

Population dynamics of reintroduced Whooping Cranes

Because of the small size and restricted range of the Aransas-Wood Buffalo Population, reintroduction is a prominent element of the recovery effort to ensure persistence of Whooping Cranes ( Grus americana ). A fundamental objective of all Whooping Crane reintroduction efforts is the establishment of a self-sustaining population. Therefore, success of reintroduction efforts will ultimately be determined by demography: births and deaths of Whooping Cranes in the released population. We present a detailed review of the demographic modeling efforts for two reintroduced populations of Whooping Cranes: the Florida Nonmigratory Population and the Eastern Migratory Population. Both of these populations have struggled with poor demographic performance, and the Florida Nonmigratory Population is now nearly extirpated. The focus of our review is on the models used to represent Whooping Crane population dynamics and the major uncertainties that still exist about population dynamics in reintroduced Whooping Cranes. We also discuss the centrality of population models to the management of reintroduced Whooping Cranes, and the use of decision analysis to navigate multiple-objective decisions made under uncertainty. Development of demographic models, and articulation and testing of hypotheses about the causes of poor demographic performance in reintroduced populations, will continue to be research areas of importance in support of Whooping Crane reintroduction.

Book chapter↗
USGS2019

Reproductive failure in the Eastern Migratory Population: The interaction of research and management

The reintroduction of the Eastern Migratory Population of Whooping Cranes ( Grus americana ) has shown the most promise of any effort to date toward the establishment of a self-sustaining population. However, reproduction – including both nest success and chick survival – has been a major challenge. Here, we review the research and management efforts deployed to identify and address this challenge. While there is evidence that a proximal cause of nest failure is harassment by blood-feeding black flies ( Simulium spp. ), this is not likely to be the only contributing factor, and we present alternative hypotheses. There is less understanding of the causes of poor chick survival, and we present hypotheses for factors that may be contributing to chick mortality, including environmental, genetic, and behavioral factors. For both nest success and chick survival, we carried out a value of information analysis, using expert judgment, which allowed us to prioritize the alternative hypotheses for evaluation based on the expected management benefit of addressing each hypothesis. On the horizon are multiple opportunities to explore hypotheses about environmental factors as well as genetic and behavioral characteristics of the birds themselves that may contribute to poor reproduction. If bird-specific characteristics, such as genetics or rearing methods, are hindering reproduction, this has important implications for all efforts to restore Whooping Crane populations.

Book chapter↗
USGS2019

Reproduction and reproductive strategies relevant to management of Whooping Cranes ex situ

Due to the small population size (∼400 birds) and continuing threats to wild Whooping Cranes ( Grus americana ), an ex situ (captive) population is maintained to contribute to the recovery of the species. The goals of the captive breeding program are to provide opportunity for research and birds for reintroduction. However, reproduction among captive birds is far from optimal. Specifically, whooping cranes maintained ex situ experience delayed onset of reproduction as well as low rates of egg production and egg fertility when compared to wild populations. To improve the contribution of the captive population to Whooping Crane recovery, there is a need to (1) advance the understanding about the mechanisms regulating ovarian function and egg production, especially the influence of males (their presence and behavior) on endocrine and reproductive behavior in females, as well as (2) identify the underlying cause(s) of poor reproduction in Whooping Cranes housed ex situ. In this chapter, we summarize current knowledge of Whooping Crane reproduction with a focus on egg production and fertility. We also discuss management strategies, such as environmental management, and reproductive technologies, including artificial insemination and sperm cryopreservation that may benefit captive reproduction, and finish with a discussion of future research priorities.

Book chapter↗
USGS2019

A three-pipe problem: Dealing with complexity to halt amphibian declines

Natural resource managers are increasingly faced with threats to managed ecosystems that are largely outside of their control. Examples include land development, climate change, invasive species, and emerging infectious diseases. All of these are characterized by large uncertainties in timing, magnitude, and effects on species. In many cases, the conservation of species will only be possible through concerted action on the limited elements of the system that managers can control. However, before an action is taken, a manager must decide how to act, which is, if done well, not easy. In addition to dealing with uncertainty, managers must balance multiple potentially competing objectives, often in cases when the management actions available to them are limited. Guidance in making these types of challenging decisions can be found in the practice known as decision analysis. We demonstrate how using a decision-analytic approach to frame decisions can help identify and address impediments to improved conservation decision making. We demonstrate the application of decision analysis to two high-elevation amphibian species. An inadequate focus on the decision-making process, and an assumption that scientific information is adequate to solve conservation problems, must be overcome to advance the conservation of amphibians and other highly threatened taxa.

Biological Conservation↗
USGS2018

Integrated population modeling provides the first empirical estimates of vital rates and abundance for polar bears in the Chukchi Sea

Large carnivores are imperiled globally, and characteristics making them vulnerable to extinction (e.g., low densities and expansive ranges) also make it difficult to estimate demographic parameters needed for management. Here we develop an integrated population model to analyze capture-recapture, radiotelemetry, and count data for the Chukchi Sea subpopulation of polar bears ( Ursus maritimus ), 2008–2016. Our model addressed several challenges in capture-recapture studies for polar bears by including a multievent structure reflecting location and life history states, while accommodating state uncertainty. Female breeding probability was 0.83 (95% credible interval [CRI] = 0.71–0.90), with litter sizes of 2.18 (95% CRI = 1.71–2.82) for age-zero and 1.61 (95% CRI = 1.46–1.80) for age-one cubs. Total adult survival was 0.90 (95% CRI = 0.86–0.92) for females and 0.89 (95% CRI = 0.83–0.93) for males. Spring on-ice densities west of Alaska were 0.0030 bears/km 2 (95% CRI = 0.0016–0.0060), similar to 1980s-era density estimates although methodological differences complicate comparison. Abundance of the Chukchi Sea subpopulation, derived by extrapolating density from the study area using a spatially-explicit habitat metric, was 2,937 bears (95% CRI = 1,552–5,944). Our findings are consistent with other lines of evidence suggesting the Chukchi Sea subpopulation has been productive in recent years, although it is uncertain how long this will continue given sea-ice loss due to climate change.

Scientific Reports↗
USGS2018

Optimizing release strategies: A stepping-stone approach to reintroduction

Evaluation of alternative management strategies enables informed decisions to accelerate species recovery. For reintroductions, post-release survival to reproductive age is a key parameter influencing population growth. Here we trial a ‘stepping-stone’ method to maximize the success of captive-bred animals when the availability of more suitable wild-born release candidates is limited. Our approach makes use of relatively safe and established wild populations to prepare captive-bred individuals for eventual translocation to a final release destination, thus building resilience through establishment of multiple populations over time. We developed a novel multievent model integrating encounter history and biotelemetry data to evaluate reintroduction strategies for the critically endangered Vancouver Island marmot (Marmota vancouverensis). We compared post-release survival of 176 individuals (52 wild-born, 47 captive-bred marmots released directly to destinations, and 77 captive-bred marmots released with a stepping-stone approach). Survival estimates to prime breeding-age (PBA), were then used to quantify expected success of potential release strategies. Our analysis indicates that post-release survival varies by source population and release method, as well as age, season, year, and years since release. Conditional on an objective of maximizing survival to PBA, our results suggest that using wild-born marmots for translocations as often as possible, and stepping-stone captive-bred marmots prior to final release, will result in the best outcomes. There was a 0.86 probability that survival to PBA was greater for captive-bred marmots released as yearlings using a stepping-stone approach (survival to PBA mode = 0.13, 95% CRI = 0.05-0.30) than for captive-bred animals that were directly released to destination sites as one-year-olds (survival to PBA mode = 0.04, 95% CRI = 0.01-0.24). Consequently, the stepping-stone approach yields much higher population establishment or growth potential than previous release strategies that used captive-bred marmots. Optimizing the combination of release candidates, sites, and timing can thereby increase the effectiveness of reintroductions.

British Columbia↗
USGS2018

Analysis of population change and movement using robust design removal data

In capture-mark-reencounter studies, Pollock’s robust design combines methods for open populations with methods for closed populations. Open population features of the robust design allow for estimation of rates of death or permanent emigration, and closed population features enhance estimation of population sizes. We describe a similar design, but for use with removal data. Data collection occurs on secondary sampling occasions clustered within primary sampling periods. Primary sampling periods are intervals of brief enough duration that it can be safely assumed that the population is unchanged by births, deaths, immigration or emigration during them; all population change and movement occurs between primary sampling periods. Our model provides a basis for inference about population size, changes in population size, and movement rates among sample locations between primary sampling periods. Movement rates are modeled as functions of distance and time. Capture probabilities are modeled as a function of effort. We apply the model to data obtained in attempting to eradicate an introduced population of veiled chameleons ( Chamaeleo calyptratus ) on the island of Maui in Hawaii.

Journal of Agricultural, Biological, and Environme↗
USGS2018

Improving conservation policy with genomics: A guide to integrating adaptive potential into U.S. Endangered Species Act decisions for conservation practitioners and geneticists

Rapid environmental change makes adaptive potential—the capacity of populations to evolve genetically based changes in response to selection—more important than ever for long-term persistence of at-risk species. At the same time, advances in genomics provide unprecedented power to test for and quantify adaptive potential, enabling consideration of adaptive potential in estimates of extinction risk and laws protecting endangered species. The U.S. Endangered Species Act (ESA) is one of the most powerful environmental laws in the world, but so far, the full potential of genomics in ESA listing and recovery decisions has not been realized by the federal agencies responsible for implementing the ESA or by conservation geneticists. The goal of our paper is to chart a path forward for integrating genomics into ESA decision making to facilitate full consideration of adaptive potential in evaluating long-term risk of extinction. For policy makers, managers, and other conservation practitioners, we outline why adaptive potential is important for population persistence and what genomic tools are available for quantifying it. For conservation geneticists, we discuss how federal agencies can integrate information on the effect of adaptive potential on extinction risk—and the related uncertainty—into decisions, and suggest next steps for advancing understanding of the effect of adaptive potential on extinction risk. The mechanisms and consequences of adaptation are incredibly complex, and we may never have a complete understanding of adaptive potential for any organism. Nevertheless, we argue that the best available evidence regarding adaptive potential should be incorporated by federal agencies into modeling and decision making processes now, while at the same time conserving genome-wide variation and striving for a deeper understanding of adaptive potential and its effects on population persistence to improve decision-making into the future.

Conservation Genetics↗
USGS2018

The importance of early life experience and animal cultures in reintroductions

Even within a single population, individuals can display striking differences in behavior, with consequences for their survival and fitness. In reintroduced populations, managers often attempt to promote adaptive behaviors by controlling the early life experiences of individuals, but it remains largely unknown whether this early life training has lasting effects on behavior. We investigated the behavior of reintroduced whooping cranes ( Grus americana ) trained to migrate using two different methods to see whether their migration behavior remained different or converged over time. We found that the behavior of the two groups converged relatively rapidly, indicating that early life training may not produce lasting effects, especially in species that display lifelong learning and behavioral adaptation. In some cases, managers may consider continual behavioral interventions after release if desired behaviors are not present. Understanding the roles early life experience and animal cultures play in determining behavior is crucial for successful reintroduction programs.

Conservation Letters↗
USGS2018

Implicit decision framing as an unrecognized source of confusion in endangered species classification

Legal classification of species requires scientific and values‐based components, and how those components interact depends on how people frame the decision. Is classification a negotiation of trade‐offs, a decision on how to allocate conservation efforts, or simply a comparison of the biological status of a species to a legal standard? The answers to problem‐framing questions such as these influence decision making in species classifications. In our experience, however, decision makers, staff biologists, and stakeholders often have differing perspectives of the decision problem and assume different framings. In addition to differences between individuals, in some cases it appears individuals themselves are unclear about the decision process, which contributes to regulatory paralysis, litigation, and a loss of trust by agency staff and the public. We present 5 framings: putting species in the right bin, doing right by the species over time, saving the most species on a limited budget, weighing extinction risk against other objectives, and strategic classification to advance conservation. These framings are inspired by elements observed in current classification practices. Putting species in the right bin entails comparing a scientific status assessment with policy thresholds and accounting for potential misclassification costs. Doing right by the species adds a time dimension to the classification decision, and saving the most species on a limited budget classifies a suite of species simultaneously. Weighing extinction risk against other objectives would weigh ecological or socioeconomic concerns in classification decisions, and strategic classification to advance conservation would make negotiation a component of classification. We view these framings as a means to generate thought, discussion, and movement toward selection and application of explicit classification framings. Being explicit about the decision framing could lead decision makers toward more efficient and defensible decisions, reduce internal confusion and external conflict, and support better collaboration between scientists and policy makers.

Conservation Biology↗
USGS2018

Examination of multiple working hypotheses to address reproductive failure in reintroduced Whooping Cranes

Understanding multiple challenges that restrict conservation success is a central task of applied ecology, especially when resources are limited and actions are expensive, such as with reintroduction programs. Simultaneous consideration of multiple hypotheses can expedite identification of factors that most limit conservation success. Since 2001, reintroduction of a migratory population of Whooping Cranes ( Grus americana ) has been under way in eastern North America. Hatching success, however, has been extremely low. In our study area, in and near Necedah National Wildlife Refuge in central Wisconsin, USA, we simultaneously tested 3 hypotheses explaining poor hatching success: harassment of incubating birds by black flies (Simuliidae), effects of captivity, and inexperience of breeders. When black flies were experimentally suppressed, hatching probability doubled. Daily nest survival for Whooping Cranes was strongly and negatively related to an index of black fly abundance, particularly of Simulium annulus . Daily nest survival was negatively but only weakly related to the number of generations that ancestors of breeding Whooping Cranes had been in captivity and was not related to nesting experience. We also examined whether Whooping Cranes were nesting later to avoid stress from black flies. Phenology shifted earlier with more growing degree days and greater nesting experience and was only weakly related to year. Overall, improved hatching success did not lead to better reproductive success. Although effects of black flies on hatching success can be mitigated through management, such actions would not be adequate to generate satisfactory population growth. Recognition of this limitation was hastened through experimentation.

Wisconsin↗
USGS2017

A projection of lesser prairie chicken ( Tympanuchus pallidicinctus ) populations range-wide

We built a population viability analysis (PVA) model to predict future population status of the lesser prairie-chicken ( Tympanuchus pallidicinctus , LEPC) in four ecoregions across the species’ range. The model results will be used in the U.S. Fish and Wildlife Service's (FWS) Species Status Assessment (SSA) for the LEPC. Our stochastic projection model combined demographic rate estimates from previously published literature with demographic rate estimates that integrate the influence of climate conditions. This LEPC PVA projects declining populations with estimated population growth rates well below 1 in each ecoregion regardless of habitat or climate change. These results are consistent with estimates of LEPC population growth rates derived from other demographic process models. Although the absolute magnitude of the decline is unlikely to be as low as modeling tools indicate, several different lines of evidence suggest LEPC populations are declining.

Colorado, Kansas, New Mexico, Oklahoma, Texas↗