COS 88-1 - The impact of non-native European sea lavender removal on the population and pollination of rare Salt Marsh Bird's Beak (1B.2)

Abstract: California Coastal Salt Marsh communities are intact only in a few areas along the coast and are threatened by human development and sea level rise. Salt Marsh Bird’s Beak (Chloropyron maritimum maritimum) is a rare plant found in salt marshes, that is additionally threatened by non-native plant invasion and the potential loss of pollinators. Salt Marsh Bird’s Beak is hemi-parasitic, so it relies on having neighboring plants to obtain nutrients. European sea-lavender (LIDU) often occupies the same areas as Salt Marsh Bird’s Beak in abundance, sometimes forming large vegetative mats which may compete for limited pollinators. Salt Marsh Bird’s Beak is self-compatible, but pollinator visitation benefits seed set. We wanted to understand what was visiting Salt Marsh Bird’s Beak flowers and how often, if the presence of European sea lavender impacts Salt Marsh Bird’s Beak floral visitation, and how the experimental removal of European sea lavender would impact floral visitation. To address this, we conducted before-after control-impact experiment, observing pollinators before and after the experimental removal of the non-native European sea-lavender in 30 2x2m plots between the years 2017-2022. Over the five-year period, all floral visitors within each plot were recorded, including visits to the Salt Marsh Bird’s Beak, non-native European sea-lavender, and other co-occurring salt marsh flowers. Our experiment took place at the UC NRS Carpinteria Salt Marsh Reserve in Carpinteria, California.



We found that visitation to Salt Marsh Bird’s Beak was overall very low, only 41 individuals of 4 taxa were observed over 3,965 minutes of observation. Non-native European sea-lavender was mostly visited by two non-native insect visitors, the European honey bee (Apis mellifera) and the Common Lagoon Fly (Eristalinus aeneus), neither of which were ever recorded visiting Salt Marsh Bird’s Beak. Conversely, the 4 taxa that visited Salt Marsh Bird’s Beak also visited European sea-lavender. After the removal of European sea-lavender, there was significantly higher visitation to native plants in removal plots than control plots (Kruskal-Wallis, p=0.038). However, we also found there was significantly less Salt Marsh Bird’s Beak flowering in removal plots than control plots (Kruskal-Wallis, p< 0.001) after removal, possibly due to less vegetation cover in removal plots (p < 0.001). In conclusion, this work shows that non-native plants can impact communities’ services, and the removal of them can have adverse effects. Further studies could look at how the low visitation is impacting the reproductive success of Salt Marsh Bird’s Beak at Carpinteria Salt Marsh.