Effects of sea-level rise on northern elephant seal (Mirounga angustirostris) and Pacific harbor seal (Phoca vitulina richardii) haul-outs at Point Reyes Peninsula, California.

Environmental changes associated with global warming can challenge marine mammals that may not be capable of adapting to significant changes to marine and coastal environments.In California, northern elephant seals (Mirounga angustirostris) and Pacific harbor seals (Phoca vitulina Linnaeus) are natural indicator species of coastal change as they rely heavily on terrestrial habitats for hauling-out.Though there has been previous research identifying suitable haul-out areas for northern elephant seals and Pacific harbor seals within central and northern California, as well as the effects of sea-level rise (SLR) on those habitats, advancements in mapping technology provide more detailed analysis on prior and future predictions.We investigated a series of SLR scenarios to assess the effects on haul-out sites for northern elephant seals and Pacific harbor seals at Point Reyes National Seashore (PRNS), California.From known and established haul-out locations, 5 categorical variables (slope, aspect, distance to water, distance to human access points, and vegetation type) were used to describe local habitat preference based on pinniped ecology, availability of data, literature and expert opinion.Using raster surface layers to describe the categorical variables a habitat suitability analysis (HSA) using a geographic information system (GIS) (ESRI 2022) was developed.SLR impacts on the two pinniped species were projected using the resulting HSA under current baseline conditions and then calculating changes in haul-out suitability from different SLR scenarios for the years 2040, 2060, 2080, and 2100.By 2100, highly suitable haul-outs for Pacific harbor seals are project to decrease by 38% from baseline, and by 63% for northern elephant seals.For both species, by 2080, models indicated that over half of the highly suitable areas would be inundated from SLR. Management at PRNS will need to be able to adapt to rising sea level and the subsequent change in available haul-outs for pinnipeds.The results of this study will be used to better understand pinniped responses to SLR and contribute to the effective management of pinnipeds at PRNS.