Ma-le’l Dunes, a National Natural Landmark, lie between the Mad River Slough and the Pacific Ocean at the base of the Samoa Peninsula, which partially encloses the northern part of Humboldt Bay, about 1 mile (1.6 km) north of Manila and 3.5 miles (5.6 km) west of Arcata, California. The dunes divide into northern and southern sections. The northern section forms part of the Humboldt Bay National Wildlife Refuge, managed by the US Fish and Wildlife Service; the southern section is overseen by the Bureau of Land Management. They take their name from a historic Wiyot village or seasonal camp. Humboldt Bay, named for naturalist Alexander von Humboldt, is 14 miles (23 km) long and 4.5 miles (7 km) wide, making it California’s second-largest enclosed bay. The coastal geology north of Cape Mendocino is driven by interactions among the oceanic Gorda and Pacific plates and the continental North American plate, known as the Mendocino Triple Junction. The Coast Ranges arose from deformation caused by accretion and subduction beneath the continental margin, combined with northward motion along the San Andreas Fault. They consist mainly of accreted Mesozoic and Cenozoic Franciscan Complex rocks— graywacke sandstones, shales, and conglomerates that have undergone low-grade metamorphism—overlain by uplifted marine and fluvial sediments. Fluvial terraces are well developed along major rivers such as the Mad, Eel, Van Duzen and Mattole, while marine terrace consist of coarse gravels, cobble berms and dune sands on uplifted Holocene and Pleistocene platforms. Ma-le’l Dunes form part of a coastal barrier complex that migrated up the marine shelf with rising sea levels after the Last Glacial Maximum, reaching their present location about 7,000 years ago. The dunes comprise quartz and feldspar from rivers and basalt from coastal headlands, deposited by nearshore, wave-generated currents. In summer, southward currents deposit sand; in winter, northward, high-energy storms erode the beaches.

Wiyot people have inhabited the Humboldt Bay area for thousands of years, using the north and south spit dunes for fishing, hunting, and annual huckleberry gathering. Their traditional homeland stretched from the Mad River in the north to the lower Eel River in the south, primarily along a coastal fringe of dunes and tidal marshes. They were among the last native Californians to encounter white settlers, as Spanish missions reached only San Francisco Bay. In 1806, Captain Jonathan Winship, employed by the Russian-American Company in the maritime fur trade, recorded the first ship entry into Humboldt Bay, though Russian traders mostly bypassed it in search of better sea otter habitat. By the mid‑1800s, gold and timber lured Euro-American settlers to the region. Josiah Gregg and an expedition from the interior reached Humboldt Bay in 1849 by crossing the Coast Ranges. After returning to San Francisco, news of the discovery spurred several ships north; in 1850, Lieutenant Douglass Ottinger on the Laura Virginia became the first American to enter the bay. In 1853, the US Army established Fort Humboldt under Brevet Lieutenant Colonel Robert C. Buchanan of the 4th Infantry Regiment to shield the Wiyot from gold‑seekers and settlers. Competition for land and resources led to violent clashes, and diseases such as smallpox and influenza decimated the Wiyot. Humboldt Bay later became a major transport hub for the logging industry, aided by railroads. Settlements grew into towns while marshlands were drained and diked for cattle pasture. Homesteads dotted the dunes, where European beachgrass was planted to stabilize shifting sands, and sand mining continued until the 1990s. Conservation efforts began in the 1940s. In 1976, Hortense and William Lanphere donated land to The Nature Conservancy, establishing the Lanphere-Christensen Dunes Preserve. In 1997, the preserve joined the Humboldt Bay National Wildlife Refuge, and in 2004, the Ma‑le’l Dunes were added to create the Lanphere Ma-le’l Dunes.

European beachgrass was commonly planted on West Coast dunes during the first half of the 20th century. It was first introduced at Golden Gate Park in San Francisco in the late 1800s to stabilize shifting sands. Thousands of acres of dunes were stabilized during this period, mostly along the Oregon coast. As a result, Oregon and Washington now largely lack intact native dune plant communities. The introduction and spread of European beachgrass on the North Spit dunes of Humboldt Bay have been well studied since 1901. The grass accumulates sand more efficiently than native dune grass, forming higher, steeper foredunes that reduce aeolian sand transport to interior dunes. Perhaps its most significant impact is displacing entire native plant communities. Once common along major West Coast dune systems north of Monterey, California, the native dune grass community now survives only at Point Reyes and Humboldt Bay. This invasive species has altered natural dune dynamics and diminished biodiversity. European beachgrass currently or potentially affects six federally listed endangered plants on California’s coastal dunes. It also harms the threatened western snowy plover, a shorebird that nests in open strand areas. Dense stands of European beachgrass displace snowy plover nesting sites and provide cover for predators, lowering nesting success. Recent coastal dune restoration has focused on removing these invasive plants. Although interest in controlling European beachgrass emerged around 1980, large-scale control efforts did not begin until the 1990s. Current control methods include manual, mechanical, and chemical approaches, used singly or in combination. Manual removal of nonnative plants was conducted at Ma‑le’l Dunes from 2005 to 2010; however, European beachgrass is now so widespread on the U.S. West Coast that eradication remains impractical without a more cost‑effective method of control. The ecological changes wrought by European beachgrass underscore the challenges of managing invasive species on fragile coastal ecosystems. Its transformation of dune landscapes has prompted a rethinking of restoration strategies, balancing economic practicality with ecological preservation. Efforts to control the spread remain a priority. Read more here and here. Explore more of the Ma-le’l Dunes and Humboldt Bay here: