Invasive Species: European Beachgrass

Visit a beach in California, particularly in the northern half of the state, and you are likely to come across stands of European Beachgrass (Arundo arenaria).  It looks so innocuous, picturesque even, waving in the Pacific breeze and blurring the line between land and sea.  But this grass, a plant you've probably never thought twice about, is much more than it seems.  Innocuous it is not.  European Beachgrass is one of California's most wanted offenders: an introduced, aggressive invasive species.

This picturesque photo of the California's Pacific Coast has a secret...  Most people won't notice that the grass seen
here is an imposter; it's not native to the area, but a species that doesn't belong in this ecosystem.

The main crime this grass is guilty of is being too good at its job.  In 1869, European Beachgrass was planted around Golden Gate Park in San Francisco, and since 1900, it has been introduced to other parts of California's coast in an effort to stabilize sand dunes.  But sand dunes are by nature fluid, ever-changing, ephemeral.  ("Shifting sands" is a saying for a reason.) 

Unfortunately, this unique quality of sand dunes and the distinct habitat that they create was recognized too late: the exotic grass had been introduced, and found California's climate more than suitable.  Where it has been introduced, European Beachgrass has spread vigorously, to the point that native vegetation is choked out and the dunes are cemented firmly in place by the tenacious clumps of grass.  Dunes are no longer able to shift, build and re-shape with the winds.  Dunes covered in European Beachgrass re-form to become parallel to the coast, rather than perpendicular, creating foredunes that are so high and steep, the sand supply to the rest of the dune system is effectually cut off.

European Beachgrass near Watsonville, California

European Beachgrass spreads by creeping rhizomes, underground stems that are capable of producing roots and shoots (just like the pesky Bermuda grass in your garden: every tiny piece will develop into a whole new plant).  Pieces of rhizomes that have been dislodged by crashing waves are easily carried to new sites, where they wash ashore and root.  The ability of rhizomes to sprout makes removal of European Beachgrass extremely difficult.

Threatened Western Snowy Plovers require the open spaces of beaches and dunes for breeding and for survival as a
species.

Beaches and dunes with extensive stands of European Beachgrass have lower biodiversity than those with native plant cover.  The thick growth of European Beachgrass excludes native plants, including dune wildflowers that provide a food source for native butterflies and other pollinators.  The lack of open spaces on dunes choked with the introduced grass severely reduces nesting habitat for threatened Western Snowy Plovers (Charadrius alexandrinus nivosus).  To make matters worse, thick beachgrass provides cover for plover predators, diminishing the success of breeding pairs nearby.  Our native perennial dune grass, American Dune Grass (Elymus mollis) grows with ample open space between clumps.  Other natives that are excluded by European Beachgrass include Yellow Sand Verbena (Abronia latifolia) and the endangered Menzie's Wallflowers (Erysimum menziesii).  Dune systems that have been extensively stabilized by European Beachgrass may then be colonized further by lupine and coyote bush, transforming the dune community entirely.

Endangered Menzie's Wallflower, one of many native species that is choked out by aggressive European Beachgrass

Comments

  1. BanyanWandererDecember 9, 2020 at 6:11 AM

    Interestingly enough, here in the East Coast a grass from the same genus called Ammophila breviligulata (American Beach Grass) is planted en masse for the goal of stabilizing dunes and protecting the beach. Without that grass the beach would disappear over time due to erosion, is the thinking.

    https://poasession.blogspot.com/2019/10/american-beach-grass-ammophila.html

    ReplyDelete
    Replies
    1. Siera NystromDecember 9, 2020 at 11:41 AM

      Thank you for your comment and for sharing your blog! On my first visit to an Atlantic Coast beach during the summer of 2019, I noticed the native grasses on the dunes - beautiful and totally different from what I'm used to! I wonder if someone in the 19th century was familiar with the grasses of the Atlantic Coast and thought, hey, we should plant something like that on the Pacific Coast too... since it looks like it belongs on the dunes, even though it's not native and the Pacific Coast dunes host an entirely different assemblage of plants... But hey, this introduced grass should do the trick... And the trouble with invasives began!
      Thanks again for sharing!

      Delete
    2. BanyanWandererDecember 10, 2020 at 4:30 AM

      Interesting hypothesis, although it turns out A. arenaria has been known to be an excellent ecosystem engineer in Europe for hundreds of years. The English naturalist John Leonard Knapp for example, considered it to be a great terraformer. One other interesting thing is that it seems the eastern species (A. breviligulata) was actually tested in Oregon in the 1930s, where it became invasive and has actually been supplanting A. arenaria ;-) Karma in a way I suppose.

      Delete
    3. Siera NystromDecember 10, 2020 at 11:07 AM

      That is interesting! Thanks for sharing!

      Delete

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