LaRue
Michelle
LaRue
Michelle
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ArticleThe call of the emperor penguin: legal responses to species threatened by climate change(Wiley, 2021-08-03) Jenouvrier, Stephanie ; Che-Castaldo, Judy ; Wolf, Shaye ; Holland, Marika M. ; Labrousse, Sara ; LaRue, Michelle ; Wienecke, Barbara ; Fretwell, Peter T. ; Barbraud, Christophe ; Greenwald, Noah ; Stroeve, Julienne ; Trathan, Phil N.Species extinction risk is accelerating due to anthropogenic climate change, making it urgent to protect vulnerable species through legal frameworks in order to facilitate conservation actions that help mitigate risk. Here, we discuss fundamental concepts for assessing climate change risks to species using the example of the emperor penguin (Aptenodytes forsteri), currently being considered for protection under the US Endangered Species Act (ESA). This species forms colonies on Antarctic sea ice, which is projected to significantly decline due to ongoing greenhouse gas (GHG) emissions. We project the dynamics of all known emperor penguin colonies under different GHG emission scenarios using a climate-dependent meta-population model including the effects of extreme climate events based on the observational satellite record of colonies. Assessments for listing species under the ESA require information about how species resiliency, redundancy and representation (3Rs) will be affected by threats within the foreseeable future. Our results show that if sea ice declines at the rate projected by climate models under current energy system trends and policies, the 3Rs would be dramatically reduced and almost all colonies would become quasi-extinct by 2100. We conclude that the species should be listed as threatened under the ESA.
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ArticleThe emperor penguin - vulnerable to projected rates of warming and sea ice loss(Elsevier, 2019-10-08) Trathan, Phil N. ; Wienecke, Barbara ; Barbraud, Christophe ; Jenouvrier, Stephanie ; Kooyman, Gerald L. ; Le Bohec, Céline ; Ainley, David G. ; Ancel, André ; Zitterbart, Daniel ; Chown, Steven L. ; LaRue, Michelle ; Cristofari, Robin ; Younger, Jane ; Clucas, Gemma V. ; Bost, Charles-Andre ; Brown, Jennifer A. ; Gillett, Harriet J. ; Fretwell, Peter T.We argue the need to improve climate change forecasting for ecology, and importantly, how to relate long-term projections to conservation. As an example, we discuss the need for effective management of one species, the emperor penguin, Aptenodytes forsteri. This species is unique amongst birds in that its breeding habit is critically dependent upon seasonal fast ice. Here, we review its vulnerability to ongoing and projected climate change, given that sea ice is susceptible to changes in winds and temperatures. We consider published projections of future emperor penguin population status in response to changing environments. Furthermore, we evaluate the current IUCN Red List status for the species, and recommend that its status be changed to Vulnerable, based on different modelling projections of population decrease of ≥50% over the current century, and the specific traits of the species. We conclude that current conservation measures are inadequate to protect the species under future projected scenarios. Only a reduction in anthropogenic greenhouse gas emissions will reduce threats to the emperor penguin from altered wind regimes, rising temperatures and melting sea ice; until such time, other conservation actions are necessary, including increased spatial protection at breeding sites and foraging locations. The designation of large-scale marine spatial protection across its range would benefit the species, particularly in areas that have a high probability of becoming future climate change refugia. We also recommend that the emperor penguin is listed by the Antarctic Treaty as an Antarctic Specially Protected Species, with development of a species Action Plan.
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ArticleQuantifying the causes and consequences of variation in satellite-derived population indices: a case study of emperor penguins(Wiley Open Access, 2021-08-11) Labrousse, Sara ; Iles, David T. ; Viollat, Lise ; Fretwell, Peter T. ; Trathan, Phil N. ; Zitterbart, Daniel ; Jenouvrier, Stephanie ; LaRue, MichelleVery high-resolution satellite (VHR) imagery is a promising tool for estimating the abundance of wildlife populations, especially in remote regions where traditional surveys are limited by logistical challenges. Emperor penguins Aptenodytes forsteri were the first species to have a circumpolar population estimate derived via VHR imagery. Here we address an untested assumption from Fretwell et al. (2012) that a single image of an emperor penguin colony is a reasonable representation of the colony for the year the image was taken. We evaluated satellite-related and environmental variables that might influence the calculated area of penguin pixels to reduce uncertainties in satellite-based estimates of emperor penguin populations in the future. We focused our analysis on multiple VHR images from three representative colonies: Atka Bay, Stancomb-Wills (Weddell Sea sector) and Coulman Island (Ross Sea sector) between September and December during 2011. We replicated methods in Fretwell et al. (2012), which included using supervised classification tools in ArcGIS 10.7 software to calculate area occupied by penguins (hereafter referred to as ‘population indices’) in each image. We found that population indices varied from 2 to nearly 6-fold, suggesting that penguin pixel areas calculated from a single image may not provide a complete understanding of colony size for that year. Thus, we further highlight the important roles of: (i) sun azimuth and elevation through image resolution and (ii) penguin patchiness (aggregated vs. distributed) on the calculated areas. We found an effect of wind and temperature on penguin patchiness. Despite intra-seasonal variability in population indices, simulations indicate that reliable, robust population trends are possible by including satellite-related and environmental covariates and aggregating indices across time and space. Our work provides additional parameters that should be included in future models of population size for emperor penguins.
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ArticleSpatio-temporal transferability of environmentally-dependent population models: Insights from the intrinsic predictabilities of Adélie penguin abundance time series(Elsevier, 2023-04-19) Şen, Bilgecan ; Che-Castaldo, Christian ; Krumhardt, Kristen M. ; Landrum, Laura ; Holland, Marika M. ; LaRue, Michelle A. ; Long, Matthew C. ; Jenouvrier, Stéphanie ; Lynch, Heather J.Ecological predictions are necessary for testing whether processes hypothesized to regulate species population dynamics are generalizable across time and space. In order to demonstrate generalizability, model predictions should be transferable in one or more dimensions, where transferability is the successful prediction of responses outside of the model data bounds. While much is known as to what makes spatially-oriented models transferable, there is no general consensus as to the spatio-temporal transferability of ecological time series models. Here, we examine whether the intrinsic predictability of a time series, as measured by its complexity, could limit such transferability using an exceptional long-term dataset of Adélie penguin breeding abundance time series collected at 24 colonies around Antarctica. For each colony, we select a suite of environmental variables from the Community Earth System Model, version 2 to predict population growth rates, before assessing how well these environmentally-dependent population models transfer temporally and how reliably temporal signals replicate through space. We show that weighted permutation entropy (WPE), a model-free measure of intrinsic predictability recently introduced to ecology, varies spatially across Adélie penguin populations, perhaps in response to stochastic environmental events. We demonstrate that WPE can strongly limit temporal predictive performance, although this relationship could be weakened if intrinsic predictability is not constant over time. Lastly, we show that WPE can also limit spatial forecast horizon, which we define as the decay in spatial predictive performance with respect to the physical distance between focal colony and predicted colony. Irrespective of intrinsic predictability, spatial forecast horizons for all Adélie penguin breeding colonies included in this study are surprisingly short and our population models often have similar temporal and spatial predictive performance compared to null models based on long-term average growth rates. For cases where time series are complex, as measured by WPE, and the transferability of biologically-motivated mechanistic models are poor, we advise that null models should instead be used for prediction. These models are likely better at capturing more generalizable relationships between average growth rates and long-term environmental conditions. Lastly, we recommend that WPE can provide valuable insights when evaluating model performance, designing sampling or monitoring programs, or assessing the appropriateness of preexisting datasets for making conservation management decisions in response to environmental change.
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ArticleWhere to live? Landfast sea ice shapes emperor penguin habitat around Antarctica(American Association for the Advancement of Science, 2023-09-27) Labrousse, Sara ; Nerini, David ; Fraser, Alexander D. ; Salas, Leonardo ; Sumner, Michael ; Manach, Frederic Le ; Jenouvrier, Stephanie ; Iles, David ; LaRue, MichellePredicting species survival in the face of climate change requires understanding the drivers that influence their distribution. Emperor penguins (Aptenodytes forsteri) incubate and rear chicks on landfast sea ice, whose extent, dynamics, and quality are expected to vary substantially due to climate change. Until recently, this species’ continent-wide observations were scarce, and knowledge on their distribution and habitat limited. Advances in satellite imagery now allow their observation and characterization of habitats across Antarctica at high resolution. Using circumpolar high-resolution satellite images, unique fast ice metrics, and geographic and biological factors, we identified diverse penguin habitats across the continent, with no significant difference between areas with penguins or not. There is a clear geographic partitioning of colonies with respect to their defining habitat characteristics, indicating possible behavioral plasticity among different metapopulations. This coincides with geographic structures found in previous genetic studies. Given projections of quasi-extinction for this species in 2100, this study provides essential information for conservation measures.
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ArticleEmperor Penguins on thin sea ice(Frontiers Media, 2023-11-02) Jenouvrier, Stephanie ; LaRue, Michelle ; Trathan, Philip ; Barbraud, ChristopheEmperor penguins are tough birds that breed on sea ice, which is the frozen surface of the ocean. They are famous for walking across the sea ice, to and from the open ocean, to get food for their chicks. Their bodies and behaviors help them live in the cold, dark winters of Antarctica. However, though they live far away from people, human actions are not always good for emperor penguins. Humans are causing the world to warm. With warmer temperatures, sea ice around Antarctica will melt. For emperor penguins, this means their homes might disappear. We know so much about emperor penguins because scientists and explorers have been studying them for over 70 years. In this article, we will tell you about what is likely to happen to emperor penguins—and what their future can tell us about our own future.
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ArticleAdvances in remote sensing of emperor penguins: First multi-year time series documenting trends in the global population(The Royal Society, 2024-03-13) LaRue, Michelle ; Iles, David T. ; Labrousse, Sara ; Fretwell, Peter T. ; Ortega, David ; Devane, Eileen ; Horstmann, Isabella ; Viollat, Lise ; Foster-Dyer, Rose ; Le Bohec, Celine ; Zitterbart, Daniel ; Houstin, Aymeric ; Richter, Sebastian ; Winterl, Alexander ; Wienecke, Barbara ; Salas, Leo ; Nixon, Monique ; Barbraud, Christophe ; Kooyman, Gerald L. ; Ponganis, Paul J. ; Ainley, David G. ; Trathan, Philip ; Jenouvrier, StephanieLike many polar animals, emperor penguin populations are challenging to monitor because of the species' life history and remoteness. Consequently, it has been difficult to establish its global status, a subject important to resolve as polar environments change. To advance our understanding of emperor penguins, we combined remote sensing, validation surveys and using Bayesian modelling, we estimated a comprehensive population trajectory over a recent 10-year period, encompassing the entirety of the species’ range. Reported as indices of abundance, our study indicates with 81% probability that there were fewer adult emperor penguins in 2018 than in 2009, with a posterior median decrease of 9.6% (95% credible interval (CI) −26.4% to +9.4%). The global population trend was −1.3% per year over this period (95% CI = −3.3% to +1.0%) and declines probably occurred in four of eight fast ice regions, irrespective of habitat conditions. Thus far, explanations have yet to be identified regarding trends, especially as we observed an apparent population uptick toward the end of time series. Our work potentially establishes a framework for monitoring other Antarctic coastal species detectable by satellite, while promoting a need for research to better understand factors driving biotic changes in the Southern Ocean ecosystem.