The Prairie Pothole Region (PPR) of the north-central U.S. and south-central Canada contains millions of small prairie wetlands that provide critical habitat to many migrating and breeding ...waterbirds. Due to their small size and the relatively dry climate of the region, these wetlands are considered at high risk for negative climate change effects as temperatures increase. To estimate the potential impacts of climate change on breeding waterbirds, we predicted current and future distributions of species common in the PPR using species distribution models (SDMs). We created regional-scale SDMs for the U.S. PPR using Breeding Bird Survey occurrence records for 1971-2011 and wetland, upland, and climate variables. For each species, we predicted current distribution based on climate records for 1981-2000 and projected future distributions to climate scenarios for 2040-2049. Species were projected to, on average, lose almost half their current habitat (-46%). However, individual species projections varied widely, from +8% (Upland Sandpiper) to -100% (Wilson's Snipe). Variable importance ranks indicated that land cover (wetland and upland) variables were generally more important than climate variables in predicting species distributions. However, climate variables were relatively more important during a drought period. Projected distributions of species responses to climate change contracted within current areas of distribution rather than shifting. Given the large variation in species-level impacts, we suggest that climate change mitigation efforts focus on species projected to be the most vulnerable by enacting targeted wetland management, easement acquisition, and restoration efforts.
Climate change poses major challenges for conservation and management because it alters the area, quality, and spatial distribution of habitat for natural populations. To assess species' ...vulnerability to climate change and target ongoing conservation investments, researchers and managers often consider the effects of projected changes in climate and land use on future habitat availability and quality and the uncertainty associated with these projections. Here, we draw on tools from hydrology and climate science to project the impact of climate change on the density of wetlands in the Prairie Pothole Region of the USA, a critical area for breeding waterfowl and other wetland-dependent species. We evaluate the potential for a trade-off in the value of conservation investments under current and future climatic conditions and consider the joint effects of climate and land use. We use an integrated set of hydrological and climatological projections that provide physically based measures of water balance under historical and projected future climatic conditions. In addition, we use historical projections derived from ten general circulation models (GCMs) as a baseline from which to assess climate change impacts, rather than historical climate data. This method isolates the impact of greenhouse gas emissions and ensures that modeling errors are incorporated into the baseline rather than attributed to climate change. Our work shows that, on average, densities of wetlands (here defined as wetland basins holding water) are projected to decline across the U.S. Prairie Pothole Region, but that GCMs differ in both the magnitude and the direction of projected impacts. However, we found little evidence for a shift in the locations expected to provide the highest wetland densities under current vs. projected climatic conditions. This result was robust to the inclusion of projected changes in land use under climate change. We suggest that targeting conservation towards wetland complexes containing both small and relatively large wetland basins, which is an ongoing conservation strategy, may also act to hedge against uncertainty in the effects of climate change.
Conserving wide‐ranging large carnivores in human‐dominated landscapes is contingent on acknowledging the conservation value of human‐modified lands. This is particularly true for tigers (Panthera ...tigris), now largely dependent on small and fragmented habitats, embedded within densely populated agroecosystems in India. Devising a comprehensive conservation strategy for the species requires an understanding of the temporal patterns of space use by tiger within these human‐modified areas. These areas are often characterized by altered prey communities, novel risks resulting from high human densities and seasonally dynamic vegetative cover. Understanding space use within these areas is vital to devising human‐tiger conflict prevention measures and for conserving landscape elements critical to maintain functional connectivity between populations. We documented seasonal space‐use patterns of tigers in agricultural lands surrounding protected areas in the Central Terai Landscape (CTL) in northern India. We estimated the probability of space use and its drivers by applying dynamic occupancy models that correct for false‐positive and false‐negative errors to tiger detection\non‐detection data within agricultural areas. These data were generated by conducting local interviews, sign surveys, and camera trapping within 94 randomly selected 2.5‐km2 grid cells. We found that agricultural areas were used with high probability in the winter (0.64; standard error SE 0.08), a period of high vegetative cover availability. The use of agricultural lands was lower in the summer (0.56; SE 0.09) and was lowest in the monsoon season (0.21; SE 0.07), tracking a decline in vegetative cover and available habitat across the landscape. Availability of vegetative cover and drainage features positively influenced space use, whereas use declined with increasing distance to protected areas and the extent of human settlements. These findings highlight the role of agricultural areas in providing seasonal habitats for tigers and offer a basis for understanding where tigers and humans co‐occur in these landscapes. These findings help expand our current understanding of what constitutes large carnivore habitats to include human‐dominated agricultural areas. They underscore the need for greater integration of land‐sharing and land‐sparing initiatives to conserve large carnivores within human‐dominated agroecosystems.
In order to contribute to conservation planning efforts for golden eagles (Aquila chrysaetos) in the western U.S., we developed nest site models using >6,500 nest site locations throughout a ...>3,483,000 km2 area of the western U.S. We developed models for twelve discrete modeling regions, and estimated relative density of nest sites for each region. Cross-validation showed that, in general, models accurately estimated relative nest site densities within regions and sub-regions. Areas estimated to have the highest densities of breeding golden eagles had from 132-2,660 times greater densities compared to the lowest density areas. Observed nest site densities were very similar to those reported from published studies. Large extents of each modeling region consisted of low predicted nest site density, while a small percentage of each modeling region contained disproportionately high nest site density. For example, we estimated that areas with relative nest density values <0.3 represented from 62.8-97.8% (Formula: see text = 82.5%) of each modeling area, and those areas contained from 14.7-30.0% (Formula: see text = 22.1%) of the nest sites. In contrast, areas with relative nest density values >0.5 represented from 1.0-12.8% (Formula: see text = 6.3%) of modeling areas, and those areas contained from 47.7-66.9% (Formula: see text = 57.3%) of the nest sites. Our findings have direct application to: 1) large-scale conservation planning efforts, 2) risk analyses for land-use proposals such as recreational trails or wind power development, and 3) identifying mitigation areas to offset the impacts of human disturbance.
The northern spotted owl (Strix occidentalis caurina) was listed as threatened under the U.S. Endangered Species Act (ESA) in 1990. We applied modern spatial conservation theory and models to ...evaluate several candidate critical habitat networks, and sought an efficient conservation solution that encompassed the highest value lands for spotted owl recovery rather than maximizing the total area of potential critical habitat. We created a map of relative habitat suitability, which served as input to the spatial conservation prioritization program Zonation. We used the spatially-explicit individual-based population model HexSim to estimate and compare simulated spotted owl population outcomes among a suite of candidate critical habitat networks that varied in size and spatial arrangement under alternative scenarios of future habitat suitability and barred owl (S. varia) effects. We evaluated simulated spotted owl population outcomes, including total population size, and extinction and quasi-extinction likelihoods for 108 combinations of candidate critical habitat networks by habitat change by barred owl scenarios, both range-wide and within 11 distinct portions of the owl's range. Barred owl encounter rates and the amount and suitability of habitat had substantial effects on simulated spotted owl populations. When barred owl encounter rates were high, changes in the amount and suitability of habitat had minimal impacts on population performance. Under lowered barred owl encounter rates, candidate critical habitat networks that included most existing high suitability habitat supported a high likelihood of long-term population persistence. Barred owls are currently the primary driving force behind poor population performance of NSOs; however, our models demonstrated that a sufficient area of high suitability habitat remains essential for recovery when effects of barred owls can be reduced. The modeling approach we employed is sufficiently flexible to incorporate new information about spotted owls as it becomes available and could likely be applied to conservation planning for other species.
Ecological systems can change substantially in response to small shifts in environmental conditions. Such changes are characterized by a nonâlinear relationship between the value of the response ...variable and one or more explanatory variables. Documenting the magnitude of change and the environmental conditions that give rise to these threshold responses is important for both the scientific community and the agencies charged with ecosystem management. A threshold is defined as a substantial change in a response variable, given a marginal change in environmental conditions. Here, we demonstrate the usefulness of a derivativeâbased method for detecting ecological thresholds along a single explanatory variable. The âsignificant zero crossingsâ (SiZer) approach uses a nonâparametric method to approximate the response function and its derivatives and then examines how those functions change across the range of the explanatory variable. SiZer makes fewer assumptions than conventional threshold models and explores a full range of smoothing functions. We believe SiZer is a useful technique for the exploratory analysis of many ecological datasets.
Conserving tigers in working landscapes Chanchani, Pranav; Noon, Barry R.; Bailey, Larissa L. ...
Conservation biology,
06/2016, Volume:
30, Issue:
3
Journal Article
Peer reviewed
Tiger (Panthera tigris) conservation efforts in Asia are focused on protected areas embedded in human-dominated landscapes. A system of protected areas is an effective conservation strategy for many ...endangered species if the network is large enough to support stable metapopulations. The long-term conservation of tigers requires that the species be able to meet some of its life-history needs beyond the boundaries of small protected areas and within the working landscape, including multiple-use forests with logging and high human use. However, understanding of factors that promote or limit the occurrence of tigers in working landscapes is incomplete. We assessed the relative influence of protection status, prey occurrence, extent of grasslands, intensity of human use, and patch connectivity on tiger occurrence in the 5400 km² Central Terai Landscape of India, adjacent to Nepal. Two observer teams independently surveyed 1009 km of forest trails and water courses distributed across 60 166-km² cells. In each cell, the teams recorded detection of tiger signs along evenly spaced trail segments. We used occupancy models that permitted multiscale analysis of spatially correlated data to estimate cell-scale occupancy and segment-scale habitat use by tigers as a function of management and environmental covariates. Prey availability and habitat quality, rather than protected-area designation, influenced tiger occupancy. Tiger occupancy was low in some protected areas in India that were connected to extensive areas of tiger habitat in Nepal, which brings into question the efficacy of current protection and management strategies in both India and Nepal. At a finer spatial scale, tiger habitat use was high in trail segments associated with abundant prey and large grasslands, but it declined as human and livestock use increased. We speculate that riparian grasslands may provide tigers with critical refugia from human activity in the daytime and thereby promote tiger occurrence in some multiple-use forests. Restrictions on human-use in high-quality tiger habitat in multiple-use forests may complement existing protected areas and collectively promote the persistence of tiger populations in working landscapes. Los esfuerzos de conservación del tigre (Panthera tigris) en Asia están enfocados en las áreas protegidas enclavadas en los paisajes dominados por el hombre. Un sistema de áreas protegidas es una estrategia efectiva de conservación para muchas especies en peligro si es lo suficientemente extenso para mantener metapoblaciones estables. La conservación a largo plazo de los tigres requiere que la especie sea capaz de satisfacer algunas de sus necesidades de desarrollo más allá de las fronteras de las pequeñas áreas protegidas y dentro de los paisajes de trabajo, incluyendo a los bosques de usos múltiples con tala de árboles y mucho uso humano. Sin embargo, el entendimiento de los factores que promueven o limitan la presencia de los tigres en los paisajes de trabajo está incompleto. Evaluamos la influencia relativa del estado de protección, la presencia de presas, la extensión del pastizal, la intensidad del uso humano y la conectividad entre fragmentos sobre la presencia de tigres en los 5400 km² del Paisaje de Terai Central en la India, adjunto a Nepal. Dos equipos de observadores censaron independientemente los 1009 km de senderos de bosque y cursos de agua distribuidos en 60 celdas de 166 km². En cada celda, los equipos registraron la detección o no detección de señales de tigres a lo largo de segmentos de sendero espaciados uniformemente. Usamos modelos de ocupación que permitieron un análisis multiescala de datos correlacionados espacialmente para estimar la ocupación a escala de celda y el uso de hábitat por los tigres a escala de segmento como funciones de manejo y covarianzas ambientales. La disponibilidad de presas y la calidad del hábitat, en lugar de la designación de áreas protegidas, influyeron sobre la ocupación por tigres. La ocupación por tigres fue baja en algunas áreas protegidas de India que estaban conectadas a áreas extensas de hábitat de tigres en Nepal, lo que cuestiona la eficiencia de las estrategias actuales de manejo y protección tanto en India como en Nepal. A una escala espacial más fina, el uso de hábitat por tigres fue alto en los segmentos de senderos asociados a presas abundantes y pastizales extensos, pero declinó conforme incrementó el uso por humanos y ganado. Especulamos que los pastizales ribereños pueden proporcionarles a los tigres refugios fundamentales de la actividad humana diurna y así promover la presencia de tigres en algunos bosques de usos múltiples. Las restricciones sobre el uso humano de los hábitats de alta calidad de los tigres en bosques de usos múltiples pueden complementar a las áreas protegidas existentes y promover colectivamente la recuperación de las poblaciones de tigres en los paisajes de trabajo.
Monitoring the population trends of multiple animal species at a landscape scale is prohibitively expensive. However, advances in survey design, statistical methods, and the ability to estimate ...species presence on the basis of detection-nondetection data have greatly increased the feasibility of species-level monitoring. For example, recent advances in monitoring make use of detection-nondetection data that are relatively inexpensive to acquire, historical survey data, and new techniques in genetic evaluation. The ability to use indirect measures of presence for some species greatly increases monitoring efficiency and reduces survey costs. After adjusting for false absences, the proportion of sample units in a landscape where a species is detected (occupancy) is a logical state variable to monitor. Occupancy monitoring can be based on real-time observation of a species at a survey site or on evidence that the species was at the survey location sometime in the recent past. Temporal and spatial patterns in occupancy data are related to changes in animal abundance and provide insights into the probability of a species' persistence. However, even with the efficiencies gained when occupancy is the monitored state variable, the task of species-level monitoring remains daunting due to the large number of species. We propose that a small number of species be monitored on the basis of specific management objectives, their functional role in an ecosystem, their sensitivity to environmental changes likely to occur in the area, or their conservation importance. El monitoreo de las tendencias poblacionales de múltiples especies animales en la escala de paisaje es prohibitivamente costoso. Sin embargo, los avances en el diseño de muestreo, métodos estadísticos y la habilidad para estimar la presencia de especies con base en datos de detección-no detección han aumentado considerablemente la factibilidad del monitoreo a nivel de especie. Por ejemplo, avances recientes en el monitoreo hacen uso de datos de detección-no detección que son relativamente baratos, datos de muestreo históricos, y nuevas técnicas de evaluación genética. La habilidad para utilizar medidas indirectas de la presencia de algunas especies incrementa enormemente la eficiencia del monitoreo y reduce costos de muestreo. Después de ajustes por ausencias falsas, la proporción de unidades de muestreo en un paisaje en los que una especie es detectada (ocupación) es una variable de estado lógica a monitorear. El monitoreo de la ocupación se puede basar en observaciones en tiempo real de una especie en un sitio de muestreo o en la evidencia de que la especie estuvo en la localidad de muestreo en algún momento del pasado reciente. Los patrones temporales y espaciales de los datos de ocupación están relacionados con cambios en la abundancia de animales y proporciona ideas de la probabilidad de persistencia de una especie. Sin embargo, aun con la eficiencia obtenida cuando la ocupación es la variable de estado monitoreada, la tarea del monitoreo a nivel de especie sigue siendo desalentador debido al gran número de especies. Proponemos que un reducido número de especies sea monitoreado con base en objetivos de manejo específicos, en su papel funcional en el ecosistema, su sensibilidad a cambios ambientales que probablemente ocurran en el área o en su importancia para la conservación.
Sex ratio, and the extent to which it varies over time, is an important factor in the demography, management, and conservation of wildlife populations. Greater sage‐grouse Centrocercus urophasianus ...populations in western North America are monitored using counts of males at leks in spring. Population estimates derived from lek‐count data typically assume a constant, female‐biased sex ratio, yet few rigorous, empirically derived estimates of sex ratio are available to test that assumption. We estimated pre‐breeding sex ratio of greater sage‐grouse in a peripheral, geographically isolated population in northwestern Colorado during two consecutive winters using closed‐population, robust‐design, multi‐state, genetic mark–recapture models in program MARK. Sex ratio varied markedly between years, with estimates of 3.29 (95% CI: 2.36–4.59) females per male in winter 2012–2013 and 1.54 (95% CI: 1.22–1.95) females per male in winter 2013–2014. Rather than assuming a constant sex ratio, biologists should consider the potential for large annual variation in sex ratio of greater sage‐grouse populations when estimating population size or trend from male lek‐count data.
Species distribution models (SDMs) have become an essential tool for the management and conservation of imperiled species. However, many at‐risk species are rare and characterized by limited data on ...their spatial distribution and habitat relationships. This has led to the development of SDMs that integrate multiple types and sources of data to leverage more information and provide improved predictions of habitat associations. We developed a novel integrated species distribution model to predict habitat suitability for jaguars (Panthera onca) in the border region between northern Mexico and the southwestern USA. Our model combined presence‐only and occupancy data to identify key environmental correlates, and we used model results to develop a probability of use map. We adopted a logistic regression modeling framework, which we found to be more straightforward and less computationally intensive to fit than Poisson point process‐based models. Model results suggested that high terrain ruggedness and the presence of riparian vegetation were most strongly related to habitat use by jaguars in our study region. Our best model, on average, predicted that there is currently 25,463 km2 of usable habitat in our study region. The United States portion of the study region, which makes up 38.6% of the total area, contained 40.6% of the total usable habitat. Even though there have been few detections of jaguars in the southwestern USA in recent decades, our results suggest that protection of currently suitable habitats, along with increased conservation efforts, could significantly contribute to the recovery of jaguars in the USA.
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