This article examines how maritime regulation affects one of the most important aquatic ecosystems along the California coast: kelp forests. Combining satellite measures of kelp canopy and biomass with AIS vessel trajectories, we exploit variation in pre-policy shipping exposure across kelp cells. After California’s Ocean-Going Vessel Fuel Rule (2009), kelp improves disproportionately where maritime traffic was highest, with estimated gains of approximately 15–17% per unit of log shipping exposure. Event studies show no differential pre-trends, with the treatment effect appearing sharply at implementation. We apply the same design to the 2011 boundary modification around the Channel Islands, which re-concentrated vessel traffic in specific corridors. Kelp declined most in the cells that had the highest pre-modification shipping exposure.
Keywords: kelp forests, maritime regulation, emission control areas, difference-in-differences, ecosystem services, AIS, shipping behaviour
JEL: Q57, R41, F18
Candau, F. and Lafferrere, F. (2026). “The Hidden Cost of Globalization in the Underwater World: Evidence from California’s Kelp Forests.” Working paper, HAL hal-05655884.
@unpublished{CandauLafferrere2026Kelp,
author = {Candau, Fabien and Lafferrere, Florian},
title = {The Hidden Cost of Globalization in the Underwater World: Evidence from California's Kelp Forests},
year = {2026},
note = {Working paper, HAL hal-05655884},
url = {https://hal.science/hal-05655884}
}