Remote Sensing Tools for Mapping and Monitoring Kelp Forests along the West Coast

Kelp forests grow in nearshore rocky subtidal areas along the Pacific Coast from Alaska to Baja California, and within four federal marine protected areas along the West Coast: Olympic Coast, Greater Farallones, Monterey Bay, and Channel Islands national marine sanctuaries. Kelp forests are highly dynamic ecosystems with growth and distribution influenced greatly by ocean conditions, ecological dynamics, environmental stressors, and anthropogenic impacts. There is a critical need to better understand regional variations of kelp forest response to certain stressors, particularly to increasing frequency, duration, and intensity of marine heatwaves, which may elicit large-scale ecosystem threshold shifts and changes in species range and distribution along the West Coast.

Management agencies are tasked with understanding these dynamics and planning effective adaptive management strategies for resource protection, conservation, and restoration. Bull kelp and giant kelp, two main foundational species, form canopy layers at the ocean’s surface that are detectable by various remote sensing tools.

Remote sensing technology is a valuable tool on both a broad and fine scale, with varying spatial and temporal capabilities. These technologies can measure kelp canopy extent to analyze past ecosystem dynamics, evaluate status and trends, and assess response to management efforts. Analyzing kelp forest dynamics at a local level is valuable for fine-scale restoration and conservation efforts, yet there are significant benefits to developing adaptive management of kelp forests and associated resources at a regional level with a coordinated and complementary approach facilitated between resource managers.

Accessibility of remote sensing technologies has vastly improved in recent years, yet there is a limited understanding among resource managers of the capabilities of each platform, including coverage, resolution, cost, practical applications, and availability of data on kelp canopy cover. This report highlights several tools and data portals that are available to resource managers to effectively communicate and collaborate across the West Coast for timely and efficient decisionmaking. We will also evaluate the capabilities and practical applications of satellite imagery, plane-based aerial imagery, and uncrewed aerial systems, with specific recommendations to increase the capacity of resource managers to acquire data and support analysis conducive to adaptive management of kelp forests. These data will be presented through remote sensing case studies of three national marine sanctuaries in California while highlighting important applications and key areas of coordination between management agencies and partners relevant to the West Coast Region.

Key Words

kelp forest, kelp canopy, bull kelp, giant kelp, remote sensing, drone, uncrewed aerial systems, satellite imagery, Landsat, PlanetScope, Olympic Coast National Marine Sanctuary, Greater Farallones National Marine Sanctuary, Monterey Bay National Marine Sanctuary, Channel Islands National Marine Sanctuary, California Department of Fish and Wildlife, The Nature Conservancy