Restoring the Dunes

Dune systems depend on constant change. Invasive plants have upset the ecological balance by inhibiting sand movement, changing soil chemistry and crowding out native plants. Many invasive plants were first introduced to the dunes for the purpose of stabilizing the shifting sands in the early 1900’s.

The study of dune restoration first began at the Lanphere Dunes in the late 1970’s. Since then a lot has been learned about the practices of restoring dunes and how dunes react to the removal of invasive plants. Restoration of the dunes on the North Spit in Humboldt County focuses on hand removal of non-native, invasive plant species. With minimal disturbance to the land during restoration activities, the ecosystem is able to regenerate quickly. Native plants are able to increase in number and reclaim areas once invaded. This helps restore native biodiversity and return natural processes to the dune ecosystem.

You can learn more and get involved in restoring local dunes by participating in one of our volunteer restoration programs.

Invasive Plants

European beachgrass (Ammophila arenaria)

Native to Europe, this grass was planted along the north spit in 1901 to stabilize the sand along the railroad. The Latin name Ammophila means "sand-loving" as the grass thrives on being buried. This grass spreads by deep, tough, buried stems (rhizomes) and forms dense, continuous stands.

Dune Impacts – European beachgrass traps blowing sand and does not allow it to continue through the dunes system, causing dune stabilization. Sand movement is a critical part of the dynamic dune system and over stabilization creates an unnatural condition on the dunes. The thick stands that it forms crowds out native plants.

Control – European beachgrass is removed with hands and shovels. Although this is labor intensive, it is the most effective method locally. Because this grass is constantly being buried with sand its root systems grow deep in the sand. This makes it virtually impossible to remove the entire root. Portions of root remaining after initial removal efforts will re-sprout and will require 4-8 follow-up treatments before being starved of nutrients and die. Beachgrass is piled up and left to dry before being burned.

Iceplant (Carpobrotus chilensis and Carpobrotus edulis)

Iceplant is native to South Africa. It is believed that it was introduced to local dunes as early as the 1500’s in sand used as ship’s ballasts. The origin of Carpobrotus chilensis is not clearly understood, and some biologists believe it is native to California. This species is far less invasive than C. edulis. However, when C. chilensis hybridizes with C. edulis, it takes on more aggressive traits and should be controlled.

Dune Impacts - Iceplant is a succulent which stores water in swollen leave or stems enabling it to survive after being uprooted. It grows low to the ground and blankets the dunes, crowding out native plants, and stabilizing sand.

Control - Iceplant is easily controlled with manual removal. Large clones can be rolled up like a carpet with the roots being cut with shovels underneath as it is rolled. Small patches are piled up and left to dry. After a few months piles are revisited and any pieces of the plant that are touching the ground and growing are removed and placed on the top of the pile until all of the pile is dead and dry.

Yellow Bush Lupine (Lupinus arboreus)

Yellow bush lupine is native to central California, but this species is not native to Humboldt County. There are two other species of lupine that are considered to be native here, but are smaller and less commonly seen on the dunes. Yellow bush lupine was introduced to the North Spit in the early 1900’s when the railroad was being used to transport rock to construct the north jetty. Five women were hired by the Army Corps of Engineers to plant the lupine seeds along the railroad to prevent unwanted sand burial. The seeds were obtained by the Presidio in San Francisco.

Dune Impacts – Yellow bush lupine is a large shrub that creates a new microclimate by providing shade and moisture to surround plants. The roots have nodules which contain nitrogen-fixing bacteria that increase nutrients and organic matter in the sand, creating a condition where other weedy plants can become established.

Control – Small yellow bush lupines are removed by physically pulling up the entire plant, including the deep tap root. Larger bushes are removed using an axe to chop the plant off at the base. Shrubs are then piled, dried and burned. Lupines have long lasting seed banks, so removal efforts must be continuous as new plants will emerge from seeds that have previously been dispersed.