Publication Date

Spring 2022

Degree Type


Degree Name

Master of Science (MS)


Environmental Studies


Rachel O'Malley

Subject Areas

Environmental studies


Urban coastal wetlands protect humans from sea-level rise while providing valuable habitat for wildlife. Degradation and loss of these wetlands threaten urban infrastructure such as wastewater treatment facilities. Nature-based adaptive solutions with the combined purposes of bioremediation, coastal defense, and habitat creation are being tested to make communities safer and more resilient. The current research examines a 6-year-old experimental horizontal levee at the Oro Loma Sanitary District in San Lorenzo, California. Using horizontal transects and quadrat sampling, I compare the success of two planting strategies – a wet meadow and a riparian scrub community – on an ecotone slope. I document the effects of fragmentation and dominant plant species on plant diversity and abundance in the wet meadow. Although most planted species survived from 2015 to 2021, plant diversity decreased over time in both plant communities. Fragmentation was also associated with encroachment by invasive nonnative species in the wet meadow. Both fragmentation and the presence of native dominants willow (Salix lasiolepis) and cattails (Typha) correlated with reduced planted native species diversity and cover in the wet meadow community. In the absence of natural disturbance processes, created wetlands, especially fragmented wetlands with substantial edge, may progress to a successional state dominated by a few species. Future projects might benefit from specifying habitat creation goals in addition to wastewater treatment goals, selecting native plant palettes that inhibit succession or incorporate natural disturbance to break dominance cycles and planting larger patches with lower edge ratios.

Available for download on Saturday, August 23, 2025