Abbotts plan (Point Reyes Light, 03.12.2009)
Point Reyes National Seashore has plans for a $2 million restoration of 300 acres of coastal dunes south of Abbotts Lagoon. It will use excavators to dig up European beachgrass and bury it in deep pits under at least three feet of sand.
“Dunes have been highly developed in California, and rare dune species are moving towards extinction,” said Ellen Hamingson, a vegetation biologist for the park.
The last remaining intact dune habitat in the park is south of Abbotts Lagoon, and it includes some of the largest expanses of rare native plant communities, such as the American dune grass and beach pea.
“Native dunes are becoming a rare thing on the coast,” said Cicely Muldoon, interim superintendent for the park. “It’s extraordinary habitat and any opportunity to restore it is good.”
The dunes are critical habitat to 11 species federally listed as endangered or threatened, including the Western snowy plover, Myrtle’s silverspot butterfly, which is golden brown with black spots, and the endangered plants beach layia and Tidestrom’s lupine.
“It’s an intersection of rare species and invasive species,” Hamingson said. The fleshy beach layia, with white and yellow flowers, and the Tidestrom’s lupine, with whorls of purple peaflowers, are overwhelmed by invasive plants.
Over 70 percent of these coastal dunes are dominated by two nonnative plants—European beachgrass and ice plant. Together, they are aggressively spreading in solid mats, making it hard for native annual plants to germinate. “It’s acres and acres of a few species,” Hamingson said. “There’s no species diversity.” The park began small patches of eradication in 2001.
European beachgrass—the tall perennial grasses rising up to six feet on the sand—and the ice plant—a succulent with daisy-like purple flowers—were both introduced to California in the late 19th century to help stop sand dunes from blowing onto roads and houses. Beachgrass roots reach 10 to 20 feet deep into the sand, and the stalks continue to grow even if covered by sand. Together with the ice plant, the beachgrass holds onto the sand, making it into a solid wall of dunes instead of the regularly spaced dunes that occur naturally.
“The nonnative plants have been reshaping the dune,” Hamingson said. “They change the structure of the dunes, making them higher and parallel to the beach, creating a solid wall that prevents the flow of sand.”
These dunes naturally occur perpendicular to the shoreline, with high and low areas. Dunes that are high and parallel to the shoreline prevent the opening of new areas available for native dune annuals, which, along with the plover, need open sand movement.
“Once we remove those two problematic invasives, the dunes will naturally move back into a more perpendicular alignment,” Hamingson said.
Dense swaths of nonnative plants take up nesting space for plovers, whose nests are just tiny indentations in open areas of sand where vegetation is usually absent. Removing the invasive plants would increase unvegetated dunes for nesting, increase corridors for foraging and protection of young and decrease predation by ravens and red foxes, according to park ecologist Lorraine Parsons, who presented on the project at the Red Barn on Wednesday night. Clearing out the invasive species will also increase dune habitat and foraging sources for the silverspot butterfly.
“The environmental assessment is dense, partly because of all the different kinds of mitigations for plants, butterflies, frogs, snowy plovers, wetlands, where we can or can’t work, when we can work where,” Hamingson said.
The report listed three options for restoring site, with work expected to begin in 2010. One alternative is to take no new action, to only continue the current small-scale techniques used on increments of land. Another alternative would cost about $21 million and would combine treatments including prescribed burning, herbicide, hand removal and mechanical excavation.
The preferred alternative is mechanical excavation and deep burial, with potential treatment of resprouts with targeted herbicide use. Excavators will dig out clean sand and create a pit at least nine feet deep. Beachgrass and its roots will be dug up, the invasive mass will be dumped into the pit and buried under at least three feet of clean sand. Bulldozers could be used to level the cap of clean sand.
Treatment would last 160 days, but maintenance could take about five years. Should there be resprouts, they would be removed by hand or spot-sprayed with herbicide. “That would be one person going out with a backpack and spraying directly on a plant,” Hamingson said.
“There will be negligible to minor adverse impacts to rare plants, with minor to major long term benefits,” Parsons said.
Four years ago, park staff experimented with various methods on a patch of 50 acres. “Using hands to dig up roots that deep is challenging,” said Hamingson. “And the level of follow-up needed is hard to manage because of regrowth.” With hand removal, staff had to return 17 times. “In smaller areas or newer patches, it might work, but there are things you can’t scale up to 300 acres.” These experiments indicated that the most effective treatment for restoring dunes is to remove all the invasive biomass and bury it underneath clean sand.
Restrictions will apply. No heavy motorized equipment may be used within 500 feet of nesting plovers. “The park has been intensively surveying and monitoring the beach for plover nests for years,” Hamingson said. Should herbicides be used, it would only be in areas with wind speeds less than 10 mph and with buffers to wetlands, nesting areas and rare plants.
Snowy plovers breed, nest and rear between March and September, the silverspot butterfly adults actively feed between June through August. “There isn’t a lot of flexibility with these sensitive species in terms of their timelines,” Parsons said.
Public comments on any aspect of the report and proposal will be accepted until March 20. Comments can be submitted online at http://parkplanning.nps.gov, emailed to pore_planning@nps.gov or faxed to 663.8132, or mailed to Superintendent, Point Reyes National Seashore, 1 Bear Valley Road, Point Reyes Station, CA 94956.
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