Herbicides are the best option for killing invasive beachgrass and iceplant on 600 acres of coastal dunes in the Point Reyes National Seashore, according to an environmental assessment for a new management plan released last week. The park says the low cost of herbicide will both allow the park to cover a much wider area and minimize the dunes’ migration onto nearby ranches, making it the seashore’s preferred alternative. The public comment period for the assessment ends on Feb. 9.
The park is keen to rout invasive plants from the dunes to make way for endangered native plants and wildlife such as the endangered Western snowy plover. The environmental assessment includes alternatives that focus on mechanical and manual restoration, but both would cost at least 10 times as much per acre. The high cost of manual and mechanical removal undertaken around Abbotts Lagoon in recent years has precluded essential retreatment efforts—resulting in the regrowth of invasives—and led to smaller target areas. For now, the park has secured enough funds to cover chemical control on about 82 acres of the 600 outlined in the new plan .
If the park moves forward with the preferred alternative, it would spot spray invasives in three separate dune areas—near North Beach and F Ranch, A and B Ranch, and Limantour—with a mixture of Roundup Custom (or glyphosate) and imazapyr, which requires approval and oversight from the regional park office as well as buffers ranging from 10 to 500 feet from fragile wildlife, wetlands and organic pastures. (The seashore would also use a low-dose formulation that does not include certain agents sometimes present in Roundup that make the product more lethal.)
About 360 acres in the project area are federally designated wilderness. Herbicides can be used in those areas, but any project undertaken in wilderness—whether mechanical or chemical—requires additional evidence that chemical use is necessary to the project’s success. (It’s possible, for example, that pre-burning or pre-mowing a restoration area—a technique sometimes used to bolster the chances of success with an herbicide—might not be allowed because it may not be deemed essential for success.)
The proposal to restore more dunes drew criticism from seashore ranchers when it was announced in late 2012. Based on past mechanical work, they worried that without the stabilizing effects of invasives, dunes would migrate inland to ranches. But park wetland and vegetation ecologist Lorraine Parsons said herbicides leave dead beachgrass roots inside the dunes, providing some stabilization. The park will also actively revegetate dunes to help anchor them.
“We heard them loud and clear. We can still meet our goals for restoration…. yet not impact their operations,” Ms. Parsons said.
The ranchers will discuss the plan at their next meeting, said Ted McIsaac, the president of the Point Reyes Seashore Ranchers Association.
Crowding out natives
European beachgrass and iceplant were planted in California on purpose, starting over a century ago, to fortify dunes. It doesn’t entirely prevent migration, and the plan cites data that, for instance, dune areas have expanded near B Ranch by 27 percent between 1943 and 2007. Still, in the seashore, the grasses help ranchers whose operations abut the sandy mounds; in other areas along the coast, infrastructure such as railroads or homes benefit from more stable dunes.
But the plants crowd out endangered natives and eliminate habitat for endangered wildlife, the park says.
European beachgrass, one of the two primary targets of the seashore’s plan, is virile: it can grow six feet in six months, and its rhizomes—the root structure through which it primarily spreads—lie anywhere from three to 12 feet deep. It essentially thrives on being buried by sand. Thick mats of the grass, a fairly common site to people recreating along Point Reyes beaches, leave natives with no place to grow. Iceplant has a shallower root structure, but it still spreads widely and displaces other flora.
One struggling native is Tidestrom’s lupine, a crawling perennial that sports lilac blossoms in the spring. A federally and state listed endangered species, it ranges from Monterey to Sonoma Counties, and 10 of 19 known populations grow in the seashore. Unlike the invasives, it grows in discrete bushes, allowing the dunes more mobility. (Mobility, the plan says, should help the shoreline respond to climate change, since frozen dunes can’t move in response to sea level rise.)
Researchers from Washington University in St. Louis found that deer mice, which are prevalent among the tall, protective beachgrass, are a major challenge for Tidestrom’s lupine in the seashore. They munch on lupine seeds, further inhibiting the plant’s chances for survival. In some areas, particularly around B Ranch and the former Ben Davis property, the lupine could be headed for obliteration.
Beach layia, a diminutive plant in the daisy family, is also federally endangered, and its population has dropped almost 50 percent in the seashore since 2004, according to park data.
Dunes hardened by mats of invasives also impact wildlife. The Western snowy plover, an endangered shorebird, is left with little area to nest, since it nests in divots in sand dunes. The beachgrass, the park says, also creates steeper slopes on dunes closer to the ocean, further shrinking potential nesting habitat. (The park says it will maintain 500-foot buffers between plovers and herbicide spray.)
Last November, the seashore’s wildlife biologist, Dave Press, told the Light that six plover chicks fledged in 2014 in dunes restored around Abbotts Lagoon, the first time chicks had successfully hatched there since restoration began. (Fifteen chicks fledged in the entire seashore.) The seashore has no data on the area before the restoration, but Mr. Press said in an email this week that “The area was so choked with non-native dunegrass that it no longer functioned as snowy plover habitat.” The last time plovers could have nested there would have been decades ago, he added.
The dune plan also spotlights the endangered Myrtle’s silverspot butterfly, which needs nectar from natives like curlyleaf monardella. That plant occurs “in considerable numbers” in seashore dunes but is threatened by the continuing spread of European beachgrass, the plan says. The United States Fish and Wildlife Services says European beachgrass and iceplant are one of the butterfly’s “most serious present-day threats.”
Challenges of removal
The seashore first seriously began restoring dunes around the mouth of Abbotts Lagoon in 2000, when 70 percent of dunes in the seashore hosted the two nonnative plants.
Back then removal was entirely manual. But it was difficult, and not always productive. “If you’ve ever built a sand castle, you know that’s difficult,” Ms. Parsons said. The sand kept caving in. Even digging three feet proved troublesome. She said they came back 10 to 20 times a year, clearing out the same area.
Because it was virtually impossible to clear the plant manually without constant upkeep, in 2005 the park decided to try mechanical removal. (Exceptions were made for wetlands, which continued to be restored manually.) In mechanical removal, big excavators dig up dunes and bury the grasses under huge piles of clean sand. It’s still down there, and a few shoots can make their way up, but they die in their exhausting attempt to reach the surface.
In some ways, it worked quite well. In one excavated area, Tidestrom’s lupine returned to 16 of 80 acres in the first phase of the lagoon project, with 15,000 plants. Now there are 75,000, a healthy—and speedy—recolonization.
But mechanical removal comes with a high price tag. Part of the expense, Ms. Parsons said, came from contractors charging high prices because there was little information about dune restoration, and they worried about unknowns they might encounter along the way. That spurred the park to scale back the scope of restoration efforts around Abbotts Lagoon. Additionally, in some areas that were mechanically treated, substantial money was used up on the initial removal and little was left for follow up. Around 2009, Ms. Parsons said, beachgrass returned to an area the park had mechanically restored due to a lack of retreatment.
One alternative in the environmental assessment focuses on mechanical work, and estimates the cost at $52,000 per acre, over 10 times the expense of the preferred alternative.
Herbicide compromise
Around Abbotts Lagoon, mechanical removal dug deposited so much untethered sand on the surface that the dunes, in Ms. Parson’s eyes, became “primordial.” Free to migrate inland, sand buried some grasslands and fences, a serious issue for ranchers who are responsible for keeping their cattle contained.
According to aerial imagery cited in the assessment, dunes have been migrating inland around ranches since the 1940s. Recent restoration projects spurred about 10 acres to migrate inland, and though the park says only about an acre of that was grazeable pasture, more mechanical work could trigger even more migration.
In their comments during the plan’s scoping period, ranchers said dunes the seashore had dug up covered fences and filled up stockponds.
In subsequent phases of the Abbotts Lagoon restoration, the park applied some herbicides. Workers spot-sprayed plants, leaving a blue dye so they know what ground they have covered.
The mixture of RoundUp Custom and imazapyr worked well in decimating beachgrass at a lesser cost, and it also left dead rhizomes underground. Those dunes weren’t prone to migration, Ms. Parsons said.
“We thought, aha! It allowed native plants to come in and recruit among sprayed beachgrass. It may be the ticket to holding the dunes in place,” she said.
Although the purpose of the restoration is to allow for the natural movement of dunes, there have to be trade offs, she added. The plan outlines other methods to try to mitigate impacts on ranches: active revegetation of the dunes and the restoration of dunes closest to ranches in sections rather than in one fell swoop, allowing time for new vegetation to take root.
Herbicides aren’t popular in West Marin, and many might fear the potential drift of chemicals onto other flora and fauna. The environmental assessment says that concerns about birds such as the snowy plover arise from whether they might eat “contaminated vegetation or insects.” It adds that studies “suggest that the formulation is not highly toxic to birds… although decreased body weight was observed in the two studies involving dietary exposure.”
The plan says it will mitigate for potential impacts to habitat by not spraying on windy or rainy days and maintaining 25-foot buffers between herbicides and wetlands and organic pastures. Marin County also recommends 25-foot buffers for organic pastures; it’s less than the plovers, which get 500 feet, and other nesting birds, which get 100 feet, though more than rare plants, which get 10. (In these buffer areas, the park might use manual or mechanical methods to remove the invasives.)
The park also says it will use a lower concentration of glyphosate than is typically recommended for beachgrass, citing past successes.
The seashore has secured around $350,000 to undertake a two-and-a-half-year project that would include retreatment at one site within one of the three proposed areas. Since the herbicide alternative costs about $4,500 per acre, it would cover about 82 acres; with manual or mechanical, that funding would cover just a few acres. Clearing the remaining acreage from invasive plants would be contingent on securing more money. That ongoing spread, the plan admits, “[counters] at least some of the benefits from restoration at a localized scale.” But, it says, it’s better than the alternative.
The comment period for the Coastal Dune Restoration Environmental Assessment ends on Monday, Feb. 9. To comment visit parkplanning.nps.gov/projectHome.cfm?projectID=44082 or mail or hand-deliver comments to “Coastal Dune Restoration EA” c/o Superintendent, Point Reyes National Seashore, 1 Bear Valley Road, Point Reyes Station, CA 94956.