Trathan Phil N.

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Trathan
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Phil N.
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0000-0001-6673-9930

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The call of the emperor penguin: legal responses to species threatened by climate change

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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Quantifying the causes and consequences of variation in satellite-derived population indices: a case study of emperor penguins

2021-08-11 , Labrousse, Sara , Iles, David T. , Viollat, Lise , Fretwell, Peter T. , Trathan, Phil N. , Zitterbart, Daniel , Jenouvrier, Stephanie , LaRue, Michelle

Very 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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The emperor penguin - vulnerable to projected rates of warming and sea ice loss

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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Spectral reflectance of whale skin above the sea surface: a proposed measurement protocol

2020-03-10 , Cubaynes, Hannah C. , Rees, W. Gareth , Jackson, Jennifer A. , Moore, Michael J. , Sformo, Todd L. , McLellan, William A. , Niemeyer, Misty E. , George, John C. , van der Hoop, Julie , Forcada, Jaume , Trathan, Phil N. , Fretwell, Peter T.

Great whales have been detected using very‐high‐resolution satellite imagery, suggesting this technology could be used to monitor whales in remote areas. However, the application of this method to whale studies is at an early developmental stage and several technical factors need to be addressed, including capacity for species differentiation and the maximum depth of detection in the water column. Both require knowledge of the spectral reflectance of the various whale species just above the sea surface, as when whales bodies break the surface of the water to breath, log or breach, there is, at times, no sea water between the whale's skin and the satellite sensor. Here we tested whether such reflectance could be measured on dead whale tissue. We measured the spectral reflectance of fresh integument collected during the bowhead subsistence harvest, and of thawed integument samples from various species obtained following strandings and stored at −20°C. We show that fresh and thawed samples of whale integument have different spectral properties. The reflectance of fresh samples was higher than the reflectance of thawed samples, as integument appears to darken after death and with time, even under frozen conditions. In this study, we present the first whale reflectance estimates (without the influence of sea water and for dead tissue). These provide a baseline for additional work, needed to advance the use of satellite imagery to monitor whales and facilitate their conservation.

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