Invasive Species Removal Management Plan for the invasive species Ammophila arenaria and Carpobrotus edulis within the Samoa Dunes and Wetlands Conservation Area

Coastal sand dunes are invaluable ecosystems throughout the world, as they protect coastal communities (Gomez-Pina, 2002), store sand, and serve as important habitat for unique flora and fauna. Coastal sand dunes are key dynamic “natural structures which protect the coastal environment by absorbing energy from wind, tide and wave action” (AB, 1999). These ecosystems are composed of a beach berm, located closest to the water, then the incipient dune, the foredune(s), and then the backdune(s) (NSW DLWC, 2001). Dynamic systematic sand movement along and between the dune structure is key to a thriving coastal dune ecosystem (U.S. Fish and Wildlife Service, 2020). Coastal dunes aid in preventing coastal water intrusion, flooding, and structural damage through their ability to absorb the impacts of wind and water, acting as a natural barrier against storms and high tides (Gomez-Pina, 2002). They also act as sand storage sites, supplying sand to eroded beaches through their natural movements, and provide critical habitat for a variety of plants and animals (NSW DLWC, 2001). As humans increased their travel and migration, invasive plant species too became more widespread; two species particularly impactful to the coastal dunes in Humboldt County (California) are Ammophila arenaria and Carpobrotus edulis (Pickart, 1997). The introduction of invasive Ammophila arenaria, also known as European beachgrass, and Carpobrotus edulis, or ice plant, among other species, was a direct result of the European colonization of North America (Friends of the Dunes, 2021). Both species were planted intentionally along the west coast of North America, including Humboldt County, as a stabilizing aid. Ammophila arenaria was planted along the North Spit of Humboldt Bay to stabilize the sand along the railroad tracks (Pickart, 1997). The colonization of Turtle Island, known today as North and Central America, by both humans and plants has hugely changed and damaged the coastal dunes along the west coast of the United States. From the southernmost coastal dunes of California to the northern dunes in Washington, Ammophila arenaria restricts natural dune movements and threatens the native coastal dune mat vegetation (Pickart, 1997). While various other invasive species negatively impact coastal dune ecosystems, the colonizing and stabilizing nature of Ammophila arenaria and Carpobrotus edulis make their management and removal critical to restoring and rehabilitating invaded coastal dunes such as the Samoa Dunes and Wetlands Conservation Area. The Samoa Dunes and Wetlands Conservation Area is a 357-acre property that lies within the unceded current and ancestral homeland of the Indigenous Wiyot people (Figure 1) (Friends of the Dunes, 2021). The site is called Twaya’t in the native language of the Wiyot people, often referred to in English as the North Spit; and lies between Wigi: the Humboldt Bay and shou’r: the Pacific Ocean (Butler, 2012). Along the Samoa Peninsula, the Samoa Dunes and Wetlands Conservation Area property is directly west of the Samoa Bridge and immediately south of the Manila Dunes Recreation Area (Friends of the Dunes, 2021). The site may be familiar to some local community members as it is on the path of the Kinetic Grand Championship race, and the area includes what was formerly known as Dead Man’s Drop Forest and Dog Ranch within its boundaries (Evans, 2021). The property consists of an abandoned home structure, various other outbuildings, a ranch facility, multiple stretches of coastal dune habitats and a rare old-growth coastal dune forest (Greenson, 2020). The acquisition of this property by Friends of the Dunes creates a continuous stretch of over 1,600 acres of native coastal dune habitat, dedicated and protected exclusively for conservation efforts and recreational usage (Kemp, 2020)