By Alex Young, GIS Manager

For the past several months Sonoma Ecology Center has been mapping invasive weed Arundo donax throughout the Sacramento San Joaquin Delta. The first phase of mapping was to identify large stands of the water-loving weed from aerial photos and record their locations in GIS (Geographic Information Systems). Next, we went out in the field and verified what we had mapped using GPS and tablet computers to double-check our work.

Once we were satisfied with our results we finalized the data layer again in GIS. We found that Arundo is spread throughout the Delta concentrated mostly along the navigable stream network and colonized in narrow bands close to water, and along levees. Since Arundo is expensive to remove, and funding for eradication is limited, we needed a way to prioritize sites for eradication. For this we used an Index based Multi-species Conservation Value (IMCV)approach. In the GIS we assembled habitat distribution data for over 20 endangered or threatened species and combined them into a single layer that shows us where the highest concentration of quality habitat exists for the greatest number of species. We then overlayed our map of Arundo points to show which sites fall within the high value sites. We recommended that these sites get the highest priority for eradication.

We have finished the mapping for the whole Delta, we are now finalizing the prioritization for the Cache Slough Complex, an area in the northwest side of the Delta in Solano County. This is where our eradication
efforts will begin. We have been working with Solano RCD to help identify willing landowners and securing permits to work in the area.

The restoration work includes removing the Arundo and revegetation with native plants. Native plant seeds were collected in the Cache Slough area and propagated in our Native Plant Nursery at the Sonoma Garden Park. These seedlings will be ready to plant in late fall 2015.