Cumulative Human Impacts to California Current Marine Ecosystems, 2008

Quantitative assessment of spatial patterns of all human uses of the oceans and their cumulative effects is needed for implementing ecosystem-based management, marine protected areas, and ocean zoning. Researchers applied methods developed to map cumulative impacts globally to the California Current using more comprehensive and higher-quality data for 25 human activities and 19 marine ecosystems. They first surveyed experts in six sub-regions of the California Current to explore geographic variation in the effects of threats. A workshop was held to use decision theory to evaluate the tradeoffs of using expert opinion to assess threats and associated impacts. Data on ecosystems and threats were gathered at resolutions of approximately one square kilometer. By synthesizing information and inferences regarding anticipated impacts of threats, project participants developed a spatially-explicit understanding of the distribution and magnitude of human threats in the California Current. The analysis indicates where protection and threat mitigation are most needed in the California Current and reveals that coastal ecosystems near high human population density and the continental shelves off Oregon and Washington are the most heavily impacted. Climate change is the top threat, and impacts from multiple threats are ubiquitous. Remarkably, these results were highly spatially correlated with the global results for this region (R2=.92), suggesting that the global model provides guidance to areas without local data or resources to conduct similar regional-scale analyses. This dataset contains raster layers for the 25 human activities and 19 ecosystems used to build the cumulative impact model in the California Current marine ecosystems. A zip file for all impacts, a zip file for all ecosystems, and a raster of the final model are included along with the individual impacts and ecosystems raster layers. For more information on methods, see Halpern et al, Mapping cumulative human impacts to California Current marine ecosystems. Conservation Letters, 2009. https://doi.org/10.1111/j.1755-263X.2009.00058.x