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  • VHR imagery  (1)
  • population projections  (1)
  • 2020-2023  (2)
  • 1
    Publication Date: 2022-05-27
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Jenouvrier, S., Judy, C.-C., Wolf, S., Holland, M., Labrousse, S., LaRue, M., Wienecke, B., Fretwell, P., Barbraud, C., Greenwald, N., Stroeve, J., & Trathan, P. N. The call of the emperor penguin: legal responses to species threatened by climate change. Global Change Biology, 27, (2021): 5008– 5029, https://doi.org/10.1111/gcb.15806.
    Description: 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.
    Description: We acknowledge support of NASA (80NSSC20K1289) to SJ, MH, and of NSF—OPP (1744794) to SJ, ML.
    Keywords: climate risk assessments ; Endangered Species Act ; foreseeable future ; population projections ; resiliency, redundancy and representation (3Rs) ; sea ice projections ; species distribution ; treatment of scientific uncertainty
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
    Publication Date: 2022-10-21
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Labrousse, S., Iles, D., Viollat, L., Fretwell, P., Trathan, P. N., Zitterbart, D. P., Jenouvrier, S., & LaRue, M. Quantifying the causes and consequences of variation in satellite-derived population indices: a case study of emperor penguins. Remote Sensing in Ecology and Conservation, (2021), https://doi.org/10.1002/rse2.233.
    Description: 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.
    Description: Geospatial support for this work was provided by the Polar Geospatial Center under NSF-OPP awards 1043681 and 1559691. NCAR- PPC visitor funds and Ian Nisbet that supported the internship of LV. WWF-UK supported PNT and PTF under grant GB095701. DZ was supported by The Penzance Endowed Fund and The Grayce B. Kerr Fund in Support of Assistant Scientists. To SJ, ML, SL, LV, NSF OPP 1744794.
    Keywords: Emperor penguin ; Intra-seasonal variability ; Population estimates ; Population trend ; Satellite imagery ; VHR imagery
    Repository Name: Woods Hole Open Access Server
    Type: Article
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