Modeled Sea Level Rise Impacts on Coastal Vegetation and Infrastructure at Lake Earl Wildlife Area and Tolowa Lagoon, Northern California: Implications for Management and Adaptive Planning

Abstract

Few ecosystems remain untouched by sea-level rise along the Pacific coast of North America. This process has facilitated reduction in the range of ecosystem responses and promoted loss of biological diversity at a scale relevant to local populations of plants and animals. Even fewer studies have evaluated the extent of rising sea levels on coastal ecosystems at finer scales. Here, I quantified the projected impacts of rising sea level on the vulnerability of plant communities at the Lake Earl-Tolowa Lagoon System (Lake Earl Wildlife Area) using a Static Vegetation Model. I also evaluated use of a recent regional coastal Marsh-migration Model fitted to the same study area. Results showed the Static Model predicted 100% of Estuarine Brackish Emergent habitat, 34.0% of Coastal Dune habitat, 80.7% of Freshwater Emergent Wetland, 48.9% of Forest Wetland, 21.0% of Grassland/Pasture, 8.0% of Coastal Maritime Forest, and 3.4% of Urban infrastructure would be inundated by salt-water at ~3.0m (~9.8 ft) of sea-level rise. Conversely, categories of marsh-types used in the Marsh-migration Model were inconsistent with the type of vegetation mapped within the study area, and impacts to these categories did not materialize until ~14 m (~45.9 ft) of sea-level rise. At this level Estuarian Wetland, Emergent Wetland, and Unconsolidated Shore exhibited slight increases in area, while other categories declined. The Marsh-migration Model also proved insufficient at identifying any major alteration in the extent of marsh-types for future planning or conservation by land managers, which was the primary goal of this model at conception. Identifying the potential impact of future sea-level rise on biological communities necessitates extensive data collection, quantification of plant and animal communities, updating existing vegetation maps, modeling the potential for migration inland, and establishing a comprehensive, multi-scale coastal-change modeling framework at spatiotemporal scales unique to the particular wildlife area. These actions are necessary to identify, assess, mitigate, and alleviate any potential future stressors in rising sea-level on natural resources on managed lands along the coast of northern California and elsewhere.