Projected changes to the extent and seasonality of seabird habitat in the California current and implications for marine spatial planning

Climate-induced changes in ocean conditions are likely to affect species habitat use across current management boundaries (e.g., marine protected areas). Therefore, it is important to identify potential future risks that may reduce the effectiveness of fixed boundaries or cause negative interactions between wildlife and human ocean-use sectors. Here, we used presence and absence records from a compilation of > 132,000 ship-based and aerial at-sea visual survey transect segments collected from 1980-2017 to fit species distribution models (SDMs) for five abundant and ecologically important seabird species in the California Current Ecosystem (CCE), including both resident (common murre, Cassin’s auklet, and rhinoceros auklet) and seasonal migrant (sooty shearwater, black-footed albatross) species with different life-histories. We then projected their daily habitat suitability from 1980-2100 using an ensemble of three dynamically downscaled, high-resolution (0.1°) climate projections for the CCE. We compared long-term changes in both mean conditions and intra-annual (seasonal) variability within four National Marine Sanctuaries and four proposed areas for offshore wind energy development in the CCE. Sea surface temperature, bottom depth, daylength, and biogeographic province were the most important variables, with relative importance being species-specific. Each species displayed a negative relationship with increasing temperatures that was most pronounced in the two auklet species. Accordingly, habitat suitability scores declined across the CCE, most prominently south of Point Conception, emerging from historical variability for all species except sooty shearwater. Despite long-term negative trends in habitat suitability, we identified extensive species-specific seasonal refugia, highlighting potential changes in the intra-annual occurrence of suitable habitat. Our results suggest that perceptions of conservation benefits of marine sanctuaries and potential interactions between seabirds and new ocean-use development could be notably different by 2100, and that many impacts may occur by mid-century. Thus, it is critical to consider future projections of species habitat suitability within marine spatial management and planning processes.