11:30–11:45 | ABSTRACT 1275
Global kelp forest dynamics over four decades revealed by satellite remote sensing
Kelp forests provide three-dimensional structure that supports diverse coastal ecosystems, fisheries, and tourism, yet most kelp forest research has focused on a subset of the global distribution (e.g., the northeastern Pacific and southwestern Australia) due to limited research funding and high monitoring costs. Regional studies have documented declines tied to marine heatwaves and localized increases in turbidity, alongside instances of resilience, but a coherent global synthesis has been lacking. Here we leverage the Landsat archive to scale up from a patchwork of regional investigations and present the first global-scale time series of kelp forest extent spanning more than four decades. Automated satellite detection of floating kelp canopy is based, in part, on the amplification of near-infrared (NIR) reflectance of kelp fronds relative to seawater, supplemented with spatial (e.g., position relative to the coast) and temporal (e.g., covariation between NIR anomalies and tidal state) context. Matchups to expert classifications yield strong area agreement (RMSD < 2% in 1 km coastal bins), and field matchups indicate a detection sensitivity of approximately 13% intrapixel cover. The global time series reveals highly variable dynamics: persistent declines are confirmed in some regions, but a substantial proportion of forests are stable or increasing in extent. Synchrony among regional populations suggests basin-scale climate modes account for a substantial portion of the changes previously reported in regional studies. Data access and visualization are supported through Kelpwatch.org, which is actively used by resource managers and the research community.
Thomas Bell, Woods Hole Oceanographic Institution, [email protected], https://orcid.org/0000-0002-0173-2866
Henry Houskeeper, Woods Hole Oceanographic Institution, [email protected]
Kyle Cavanaugh, UCLA, [email protected]
