A site selection decision framework for effective kelp restoration

We present a decision support framework as a spatially explicit site classification scheme to prioritize locations for conducting kelp restoration. The framework was created for the coast of California, where restoration projects are increasingly proposed. We first created spatial distribution models using two decades of in situ kelp forest monitoring data and a suite of environmental and biological variables, and estimated the historical stability of kelp forests prior to a marine heatwave (MHW). We then used kelp canopy abundance data derived from satellite imagery to measure the extent of forest loss after the MHW and the recent state of kelp forests. We integrated these three site-specific kelp metrics to construct a classification tree for prioritizing restoration sites. To further refine the classification we show the current trend of increase or decrease for each site. We found that within each region of California, sites had a range of priority classes, but the south region had the highest proportion of sites with high and mid priority for kelp restoration, followed by the north region. The central region had the lowest proportion of sites in these categories. Outputs of site prioritization are mapped across the study region, readily usable for managers and restoration practitioners with class-specific recommendations for restoration approaches. The framework can be updated over time, as new data become available, as well as adapted to other species and regions with similar data sets. This regional site selection framework is intended to be used in addition to socio-ecological, socio-economic, and administrative considerations.