Ainley D.G.,H.T. Harvey and Associates |
Ballard G.,PRBO Conservation Science
Polar Biology | Year: 2012
Recent research has clearly shown that the fear of predation, i. e. aversion to taking risks, among mesopredators or grazers, and not merely flight from an apex predator to avoid predation, is an important aspect of ecosystem structuring. In only a few, though well-documented cases, however, has this been considered in the marine environment. Herein, we review studies that have quantified behavioral responses of Adélie penguins Pygoscelis adeliae and emperor penguins Aptenodytes forsteri to the direct presence of predators, and question why the penguins avoid entering or exiting the water at night. We also show, through literature review and new analyses of Adélie penguin diving data, that Antarctic penguins are capable of successful prey capture in the dark (defined here as <3.4 lux). Finally, we summarize extensive data on seasonal migration relative to darkness and prey availability. On the basis of our findings, we propose that penguins' avoidance of foraging at night is due to fear of predation, and not to an inability to operate effectively in darkness. We further propose that, at polar latitudes where darkness is more a seasonal than a year-round, daily feature, this "risk aversion" affects migratory movements in both species, consistent with the "trade-off" hypothesis seen in other marine vertebrates weighing foraging success against predation risk in their choice of foraging habitat. Such non-consumptive, behavioral aspects of species interactions have yet to be considered as important in Southern Ocean food webs, but may help to explain enigmatic movement patterns and choice of foraging grounds in these penguin species. © 2011 Springer-Verlag.
Kelly M.,University of California at Berkeley |
Tuxen K.A.,P.O. Box 7092 |
Stralberg D.,PRBO Conservation Science
Ecological Indicators | Year: 2011
Tidal salt marshes in the San Francisco Estuary region display heterogeneous vegetation patterns that influence wetland function and provide adequate habitat for native or endangered wildlife. In addition to analyzing the extent of vegetation, monitoring the dynamics of vegetation pattern within restoring wetlands can offer valuable information about the restoration process. Pattern metrics, derived from classified remotely sensed imagery, have been used to measure composition and configuration of patches and landscapes, but they can be unpredictable across scales, and inconsistent across time. We sought to identify pattern metrics that are consistent across spatial scale and time - and thus robust measures of vegetation and habitat configuration - for a restored tidal marsh in the San Francisco Bay, CA, USA. We used high-resolution (20 cm) remotely sensed color infrared imagery to map vegetation pattern over 2 years, and performed a multi-scale analysis of derived vegetation pattern metrics. We looked at the influence on metrics of changes in grain size through resampling and changes in minimum mapping unit (MMU) through smoothing. We examined composition, complexity, connectivity and heterogeneity metrics, focusing on perennial pickleweed (Sarcocornia pacifica), a dominant marsh plant. At our site, pickleweed patches grew larger, more irregularly shaped, and closely spaced over time, while the overall landscape became more diverse. Of the two scale factors examined, grain size was more consistent than MMU in terms of identifying relative change in composition and configuration of wetland marsh vegetation over time. Most metrics exhibited unstable behavior with larger MMUs. With small MMUs, most metrics were consistent across grain sizes, from fine (e.g. 0.16 m2) to relatively large (e.g. 16m2) pixel sizes. Scale relationships were more variable at the landcover class level than at the landscape level (across all classes). This information may be useful to applied restoration practitioners, and adds to our general understanding of vegetation change in a restoring marsh. © 2010 Elsevier Ltd. All rights reserved.
Goodman R.E.,San Francisco State University |
Lebuhn G.,San Francisco State University |
Seavy N.E.,PRBO Conservation Science |
Gardali T.,PRBO Conservation Science |
Bluso-Demers J.D.,San Francisco Bay Bird Observatory
Global Change Biology | Year: 2012
There has been a growing interest in whether established ecogeographical patterns, such as Bergmann's rule, explain changes in animal morphology related to climate change. Bergmann's rule has often been used to predict that body size will decrease as the climate warms, but the predictions about how body size will change are critically dependent on the mechanistic explanation behind the rule. To investigate change in avian body size in western North America, we used two long-term banding data sets from central California, USA; the data spanned 40 years (1971-2010) at one site and 27 years (1983-2009) at the other. We found that wing length of birds captured at both sites has been steadily increasing at a rate of 0.024-0.084% per year. Although changes in body mass were not always significant, when they were, the trend was positive and the magnitudes of significant trends were similar to those for wing length (0.040-0.112% per year). There was no clear difference between the rates of change of long-distance vs. short-distance migrants or between birds that bred locally compared to those that bred to the north of the sites. Previous studies from other regions of the world have documented decreases in avian body size and have used Bergmann's rule and increases in mean temperature to explain these shifts. Because our results do not support this pattern, we propose that rather than responding to increasing mean temperatures, avian body size in central California may be influenced by changing climatic variability or changes in primary productivity. More information on regional variation in the rates of avian body size change will be needed to test these hypotheses. © 2011 Blackwell Publishing Ltd.
Ballard G.,PRBO Conservation Science |
Jongsomjit D.,PRBO Conservation Science |
Veloz S.D.,PRBO Conservation Science |
Ainley D.G.,983 University Avenue
Biological Conservation | Year: 2012
Designation of an effective marine protected area (MPA) requires substantial knowledge of the spatial use of the region by key species, particularly those of high mobility. Within the Ross Sea, Antarctica, the least altered marine ecosystem on Earth, unusually large and closely interacting populations of several marine bird and mammal species co-exist. Understanding how that is possible is important to maintaining the ecological integrity of the system, the major goal in designating the Ross Sea as an MPA. We report analyses of niche occupation, two-dimensional habitat use, and overlap for the majority (9) of mesopredator species in the Ross Sea considering three components: (1) diet, (2) vertical distribution and (3) horizontal distribution. For (1) and (2) we used information in the literature; for (3) we used maximum entropy modeling to project species' distributions from occurrence data from several ocean cruises and satellite telemetry, correlated with six environmental variables. Results identified and ranked areas of importance in a conservation prioritization framework. While diet overlapped intensively, some spatial partitioning existed in the vertical dimension (diving depth). Horizontal partitioning, however, was the key structuring factor, defined by three general patterns of environmental suitability: (1) continental shelf break, (2) shelf and slope, and (3) marginal ice zone of the pack ice surrounding the Ross Sea post-polynya. In aggregate, the nine mesopredators used the entire continental shelf and slope, allowing the large populations of these species to co-exist. Conservation prioritization analyses identified the outer shelf and slope and the deeper troughs in the Ross Sea shelf to be most important. Our results substantially improve understanding of these species' niche occupation and imply that a piecemeal approach to MPA designation in this system is not likely to be successful. © 2011 Elsevier Ltd.
Wiens J.A.,PRBO Conservation Science |
Bachelet D.,Oregon State University |
Bachelet D.,Conservation Biology Institute
Conservation Biology | Year: 2010
To anticipate the rapidly changing world resulting from global climate change, the projections of climate models must be incorporated into conservation. This requires that the scales of conservation be aligned with the scales of climate-change projections. We considered how conservation has incorporated spatial scale into protecting biodiversity, how the projections of climate-change models vary with scale, and how the two do or do not align. Conservation planners use information about past and current ecological conditions at multiple scales to identify conservation targets and threats and guide conservation actions. Projections of climate change are also made at multiple scales, from global and regional circulation models to projections downscaled to local scales. These downscaled projections carry with them the uncertainties associated with the broad-scale models from which they are derived; thus, their high resolution may be more apparent than real. Conservation at regional or global scales is about establishing priorities and influencing policy. At these scales, the coarseness and uncertainties of global and regional climate models may be less important than what they reveal about possible futures. At the ecoregional scale, the uncertainties associated with downscaling climate models become more critical because the distributions of conservation targets on which plans are founded may shift under future climates. At a local scale, variations in topography and land cover influence local climate, often overriding the projections of broad-scale climate models and increasing uncertainty. Despite the uncertainties, ecologists and conservationists must work with climate-change modelers to focus on the most likely projections. The future will be different from the past and full of surprises; judicious use of model projections at appropriate scales may help us prepare. © 2009 Society for Conservation Biology.
Holmes A.L.,Oregon State University |
Miller R.F.,PRBO Conservation Science
Journal of Wildlife Management | Year: 2010
The combination of ecological site descriptions and state-and-transition models (STMs) describes potential vegetation, plant composition, and plant community dynamics and thus can be used to classify and understand dynamics of wildlife habitats across landscapes or home ranges. Numerous studies have evaluated effects of plant community dynamics on diversity and abundance of wildlife populations, but we could find no studies that examined changes in wildlife populations with respect to STMs. We compared abundance of grasshopper sparrows (Ammodramus savannarum) across 5 community phases representing 2 different ecological states in the Columbia Basin, Oregon, USA, to evaluate utility of STMs for understanding and predicting potential changes in habitat use by wildlife species. We measured grasshopper sparrow abundance in 165 100-m fixed-radius point counts distributed across 17 study plots within 5 plant community phases: native perennial grassland, sagebrush-steppe, depleted sagebrush-steppe, sagebrush-steppe with an annual grass understory, and annual grassland. We used a general estimating equation with a Poisson distribution to model relative abundance and estimate differences in this abundance index between linked pairs of community phases. Grasshopper sparrows showed clear differences in abundance among community phases and were most numerous in perennial grasslands and least abundant in depleted sagebrush and sagebrush annual grass community phases. As a management tool, STM provides information that predicts the direct and indirect cumulative impacts of various management actions on vegetation composition and structure (and thus habitat). Ecological site descriptions and STMs enable land managers and scientists to assess potential and current wildlife habitat suitability and to predict potential response of wildlife populations to vegetation dynamics based on the ecological potential of the site. © 2010 The Wildlife Society.
Wiens J.A.,PRBO Conservation Science |
Wiens J.A.,University of Western Australia
Landscape Ecology | Year: 2013
The world is changing rapidly, challenging the sustainability of landscapes and the resources and ecosystem services they provide to people and to plants and animals. Changes in land use and climate will alter the structure and composition of landscapes, and landscape functions may also be disrupted if the changes drive systems past thresholds into novel, no-analog configurations. Although landscapes will persist in some form, it is unlikely that they will provide the same values to people or habitat for wildlife that are the focus of current sustainability efforts. Tradeoffs among services to people or resources for wildlife will be inevitable. For the concept of sustainability to be relevant under these conditions, we must ask, "Sustainability of what, for whom?" Landscapes cannot be all things to all people (or organisms). Decisions about how to balance competing needs and goals and set priorities requires an understanding of landscape structure, function, and change-the foundation elements of landscape ecology. © 2012 Springer Science+Business Media Dordrecht.
Wiens J.A.,PRBO Conservation Science |
Wiens J.A.,University of Western Australia |
Seavy N.E.,PRBO Conservation Science |
Jongsomjit D.,PRBO Conservation Science
Biological Conservation | Year: 2011
Protected areas for conservation are intended to contain the environmental conditions that enable species and ecosystems to persist. The locations of such areas are fixed, but the environment within them may change, especially with climate change. To illustrate how multiple climate factors may change in relation to protection status, we used Principal Components Analysis to construct a climate space for California based on eight climate variables assessed at an 800-m resolution. We used projections of future climate derived from a downscaled regional climate model in conjunction with the IPCC SRES A2 scenario to assess how the climate space might shift under future conditions and to identify the combinations of conditions that may no longer occur in the state (disappearing climates) or that will be new to the state (novel climates). Disappearing climates, which were generally toward cooler and/or wetter extremes of the climate space, represented only 0.5% of California's land area but occurred disproportionately more often in conservation areas that were fully protected. Novel climates (5.8% of California) also occurred disproportionately in fully protected areas; in most cases these climates were characterized by hotter and drier combinations with more seasonal precipitation. The disproportionate occurrence of both novel and disappearing future climates in currently protected areas may create challenges to conservation of the status quo, but such areas may also be " hotspots of opportunity" for responding to the extremes of climate change. © 2011 Elsevier Ltd.
Record S.,Harvard University |
Fitzpatrick M.C.,University of Maryland Center for Environmental Science |
Finley A.O.,Michigan State University |
Veloz S.,PRBO Conservation Science |
Ellison A.M.,Harvard University
Global Ecology and Biogeography | Year: 2013
Aim: The distributions of many organisms are spatially autocorrelated, but it is unclear whether including spatial terms in species distribution models (SDMs) improves projections of species distributions under climate change. We provide one of the first comparative evaluations of the ability of a purely spatial SDM, a purely non-spatial SDM and a SDM that combines spatial and environmental information to project species distributions across eight millennia of climate change. Location: Eastern North America. Methods: To distinguish between the importance of climatic versus spatial explanatory variables we fit three Bayesian SDMs to modern occurrence data for Fagus and Tsuga, two tree genera whose distributions can be reliably inferred from fossil pollen: a spatially varying intercept model, a non-spatial model with climatic variables and a spatially varying intercept plus climate model. Using palaeoclimate data with a high temporal resolution, we hindcasted the SDMs in 1000-year time steps for 8000 years, and compared model projections with palynological data for the same periods. Results: For both genera, spatial SDMs provided better fits to the calibration data, more accurate predictions of a hold-out validation dataset of modern trees and higher variance in current predictions and hindcasted projections than non-spatial SDMs. Performance of non-spatial and spatial SDMs according to the area under the receiver operating curve varied by genus. For both genera, false negative rates between non-spatial and spatial models were similar, but spatial models had lower false positive rates than non-spatial models. Main conclusions: The inclusion of computationally demanding spatial random effects in SDMs may be warranted when ecological or evolutionary processes prevent taxa from shifting their distributions or when the cost of false positives is high. © 2013 John Wiley & Sons Ltd.
Gardali T.,PRBO Conservation Science |
Holmes A.L.,PRBO Conservation Science
Environmental Management | Year: 2011
With limited financial resources available for habitat restoration, information that ensures and/or accelerates success is needed to economize effort and maximize benefit. In the Central Valley of California USA, riparian habitat has been lost or degraded, contributing to the decline of riparian-associated birds and other wildlife. Active restoration of riparian plant communities in this region has been demonstrated to increase local population sizes and species diversity of landbirds. To evaluate factors related to variation in the rate at which bird abundance increased after restoration, we examined bird abundance as a function of local (restoration design elements) and landscape (proportion of riparian vegetation in the landscape and riparian patch density) metrics at 17 restoration projects within five project areas along the Sacramento River. We developed a priori model sets for seven species of birds and used an information theoretic approach to identify factors associated with the rate at which bird abundance increased after restoration. For six of seven species investigated, the model with the most support contained a variable for the amount of riparian forest in the surrounding landscape. Three of seven bird species were positively correlated with the number of tree species planted and three of seven were positively correlated with the planting densities of particular tree species. Our results indicate that restoration success can be enhanced by selecting sites near existing riparian habitat and planting multiple tree species. Hence, given limited resources, efforts to restore riparian habitat for birds should focus on landscape-scale site selection in areas with high proportions of existing riparian vegetation. © 2011 Springer Science+Business Media, LLC.