Combined impacts of sea level rise and invasive species on Cordylanthus maritimus (Salt Marsh Bird’s Beak) in Upper Newport Bay, California

Abstract

Abstract Salt Marsh Bird’s Beak (Cordylanthus maritimus subsp. maritimus) is a hemiparasitic halophyte that is endemic to coastal salt marshes of southern California and is both state and federally endangered. By the year 2100, sea level is projected to rise by up to 3 meters, which will decrease the biodiversity of salt marshes and lead to changes in plant community assemblages, impacting the narrow ecological niche of C. maritimus. Here, we address how sea level rise will impact the habitable range of C. maritimus, and we examine how these impacts will be compounded by the presence of an invasive plant species, Algerian sea lavender (Limonium ramosissimum). We used LiDAR data, plant distributions, and sea level rise projections for the Upper Newport Bay Ecological Reserve to create species distribution models and map current and future ranges for both species. The areas of these ranges and the area of overlap between both species were calculated for 2020, 2050, and 2100 under varying sea level rise scenarios. Although overlap between the two species’ ranges currently exists, C. maritimus inhabits a smaller area at relatively lower elevations than L. ramosissimum. Across all 2050 and 2100 scenarios, we project L. ramosissimum will occupy at least 161% and 292% more habitable area than C. maritimus, respectively. More than 96% of the projected habitable area for C. maritimus may also be suitable for L. ramosissimum, increasing competition between the two species and highlighting a critical need to strategically control invasive L. ramosissimum in Upper Newport Bay.