Playing in the mud is one of many unique facets of marshland restoration work. Bay mud is most commonly a deep black, with hues that include rust, mocha, and ebony, and textures ranging from custard, to wet clay, and even cookie batter. This mud is a key substrate of the intertidal zone of north San Francisco Bay, where DU is partnering with Sonoma Land Trust and US Fish and Wildlife Service on large-scale native cordgrass restoration efforts to accelerate wetland development at both Sears Point and Cullinan Ranch in San Pablo Bay National Wildlife Refuge. These efforts were selected both for their habitat benefits and to stabilize eroding levee slopes buffeted by successive years of winter storms causing erosion on the newly constructed levee slopes.
Following Sonoma Land Trust’s plantings in 2019 at Sears Point, DU’s planting crew waded into the mud last fall to establish native cordgrass in areas returned to tidal influence in 2015. At these sites the land had sunk nearly seven feet over the past century after being disconnected from the tides by constructed earthen berms that allowed the wetlands to be pumped dry and farmed. Planting native grass is one of many strategies to regain soil elevation by trapping sediment that flows in with the tides. This work scales up the efforts of planting marsh mounds at Sears Point by then graduate student Margot Buchbinder, and Sonoma Land Trust-led cordgrass plantings at Sears Point in 2019 planned by plant ecologist Dr. Peter Baye.
Pacific cordgrass grows in continuous swaths several feet wide at channel edges. Cordgrass beds have remarkable capacity to attenuate wind-wave energy, stabilize the shoreline, and facilitate sediment deposition—critical attributes for speeding restoration outcomes.
Establishing cordgrass at unvegetated sites involves transplanting plugs harvested from local native cordgrass stands. The planting crew dug up vegetative shoots, with roots and rhizomes embedded in bay mud, and planted them in the low marsh zone below recently constructed levee slopes. Wind and wave erosion, soil type, transplant desiccation, and grazing pressure from Canada Geese can all impede successful propagation. At both Sears Point and Cullinan Ranch, DU and partners are taking a phased approach, planting in successive years depending on the prior season’s survival rates.