Vulnerability to climate change of United States marine mammal stocks in the western North Atlantic, Gulf of Mexico, and Caribbean
Authors: Lettrich Matthew D. , Asaro Michael J. , Borggaard Diane L. , Dick Dorothy M. , Griffis Roger B. , Litz Jenny A. , Orphanides Christopher D. , Palka Debra L. , Soldevilla Melissa S. , Balmer Brian , Chavez Samuel , Cholewiak Danielle , Claridge Diane , Ewing Ruth Y. , Fazioli Kristi L. , Fertl Dagmar , Fougeres Erin M. , Gannon Damon , Garrison Lance , Gilbert James , Gorgone Annie , Hohn Aleta , Horstman Stacey , Josephson Beth , Kenney Robert D. , Kiszka Jeremy J. , Maze-Foley Katherine , McFee Wayne , Mullin Keith D. , Murray Kimberly , Pendleton Daniel E. , Robbins Jooke , Roberts Jason J. , Rodriguez- Ferrer Grisel , Ronje Errol I. , Rosel Patricia E. , Speakman Todd , Stanistreet Joy E. , Stevens Tara , Stolen Megan , Moore Reny Tyson , Vollmer Nicole L. , Wells Randall , Whitehead Heidi R. , Whitt Amy 
Published: September 2023

Climate change and climate variability are affecting marine mammal species and these impacts are projected to continue in the coming decades. Vulnerability assessments provide a framework for evaluating climate impacts over a broad range of species using currently available information. We conducted a trait-based climate vulnerability assessment using expert elicitation for 108 marine mammal stocks and stock groups in the western North Atlantic, Gulf of Mexico, and Caribbean Sea. Our approach combined the exposure (projected change in environmental conditions) and sensitivity (ability to tolerate and adapt to changing conditions) of marine mammal stocks to estimate vulnerability to climate change, and categorize stocks with a vulnerability index. The climate vulnerability score was very high for 44% (n = 47) of these stocks, high for 29% (n = 31), moderate for 20% (n = 22), and low for 7% (n = 8). The majority of stocks (n = 78; 72%) scored very high exposure, whereas 24% (n = 26) scored high, and 4% (n = 4) scored moderate. The sensitivity score was very high for 33% (n = 36) of these stocks, high for 18% (n = 19), moderate for 34% (n = 37), and low for 15% (n = 16). Vulnerability results were summarized for stocks in five taxonomic groups: pinnipeds (n = 4; 25% high, 75% moderate), mysticetes (n = 7; 29% very high, 57% high, 14% moderate), ziphiids (n = 8; 13% very high, 50% high, 38% moderate), delphinids (n = 84; 52% very high, 23% high, 15% moderate, 10% low), and other odontocetes (n = 5; 60% high, 40% moderate). Factors including temperature, ocean pH, and dissolved oxygen were the primary drivers of high climate exposure, with effects mediated through prey and habitat parameters. We quantified sources of uncertainty by bootstrapping vulnerability scores, conducting leave-one-out analyses of individual attributes and individual scorers, and through scoring data quality for each attribute. These results provide information for researchers, managers, and the public on marine mammal responses to climate change to enhance the development of more effective marine mammal management, restoration, and conservation activities that address current and future environmental variation and biological responses due to climate change.