Projecting the Impacts of Climate Change on Species Occupying Aquatic Habitats in Southern California

Climate change will impact aquatic habitats in southern California through novel precipitation and temperature regimes, as well as higher sea levels. The dense urbanization of southern California has already drastically reduced the extent of these habitats through land conversion to hardscapes and harbors, which makes them more vulnerable to changing conditions. These aquatic habitats support several native species listed under the federal and/or state Endangered Species Acts, which means management of these habitats for species protection is not simply a moral or environmental issue, but an issue with legal and economic implications. In this research we evaluate the impacts of climate change on riparian and coastal salt marshes and the species that depend on those habitats. Species occurrence data is combined with hydrology, temperature, water level, and precipitation data to model species distributions. We use projections from climate models to predict future stream conditions, which are used in the species distribution models to predict changing habitat suitability with climate change. We project that streams in the region will become hotter by an average of 3�C, with more intense warming occurring in high elevation streams. We also project that streamflow conditions will become more extreme with approximately one additional storm each year, a larger magnitude of high flow, and an increased duration of dry- or low-flow conditions. We project that riparian species in high elevations will lose suitable habitat due to temperature increases, but that species in low elevations will gain suitable habitat driven by both streamflow and temperature. We find that an endangered salt marsh bird has habitat associations which may make it particularly vulnerable to climate change. First, it uses the entire marsh, which suggests that the rapid loss of upper marsh habitat projected due to sea level rise, could exacerbate conditions for the bird despite nesting in the low marsh. Second, breeding population is generally negatively associated with high streamflows, suggesting that additional storms from the watershed could decrease breeding pairs. This research can be used in climate change planning to prioritize vulnerable habitats and species for additional protection, restoration, and/or monitoring efforts