Comparison of Invertebrates on Restored and Unrestored Coastal Dunes in Northern California

We evaluated the effectiveness of coastal dune restoration work in northern California for invertebrates with an emphasis on pollinators. Coastal dune restoration increases plant diversity by replacing just a few invasive, nonnative plants with several native plants, so we predicted that invertebrate abundance and diversity would increase in response. We employed multiple methods, including pan traps, pitfall traps, sweep netting, aerial netting, and light traps to conduct a comprehensive inventory and comparison of invertebrate community abundance, representation, and richness, evenness, and diversity at the family level. We collected significantly more invertebrates (F = 10.94, df = 1, P = 0.01) and pollinators (F = 14.25, df = 1, P < 0.01) on restored sites compared to unrestored sites in both 2018 and 2021. Similarly, we found significantly higher family richness for all invertebrates (F = 18.29, df = 1, P < 0.01) and for pollinators (F = 15.49, df = 1, P < 0.01) on restored sites compared to unrestored sites in both years. In general, we found higher family diversity and evenness indices on unrestored sites compared to restored sites for all invertebrates and only pollinators in 2018 and 2021, however only some of these differences were significant. The diversity and evenness results were driven by just a few families (especially Scarabaedae, Ephydridae, and Lauxaniidae) dominating the numbers of specimens collected on restored sites in particular. Overall, our results highlight the importance of dune restoration efforts with respect to invertebrate conservation.