The complex relationship among snowy plovers, Washington beaches and invasive grass highlights a paradigm shift in some scientists' thinking about exotic species. A new generation of scientists now argues that our view of nuisance species is too simple.
GRAYLAND, Pacific County —
Cyndie Sundstrom trudges through thickets of knee-high grass in search of one of Washington’s most endangered birds — and that’s the problem.
Along this ribbon of Southwest Washington beach, the bird researcher is hunting for western snowy plovers, palm-size tufts of white and brown that need vast reaches of sand to survive.
But great expanses of blowing sand are vanishing from this coast. Instead, these beaches are hemmed in by giant dunes matted with forests of invasive grasses.
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“Plovers prefer it flat and open so they can scan for predators in all directions,” said Sundstrom, with the Washington Department of Fish and Wildlife.
For years government agencies have bulldozed these meddlesome weeds to give the troubled shorebirds more sand.
But new research from Oregon State University now shows those efforts also have unwelcome side effects. Bulldozing wipes out native plants and can further change the ecology of the beach.
The complex relationship among plovers, beaches and grass highlights a new sophistication in some scientists’ thinking about exotic species.
The introduction of invasive plants and animals — from tree-killing gypsy moths to river- and lake-destroying zebra mussels — has long been one of the planet’s greatest threats. They cause more than $100 billion a year in damage just in the United States. They’re often the reason species go extinct.
But a new generation of researchers now argues that our view of nuisance species is too simple.
“There’s a variety of work coming out that’s stepping away from the party line, which is that exotic species are always bad,” said Dov Sax, a Brown University assistant professor of biology. In reality, “there’s a lot more nuance to the story.”
For example, millions of dollars have been spent in the southwest eradicating the woody invasive tamarisk plant, which sucks up water and drives out native trees where endangered willow flycatchers nest. But flycatchers now nest in tamarisks, too. In Hawaii, invasive birds that helped kill off native crows, thrushes and honeycreepers are now the primary way important plants spread their seeds.
“If you’re going to remove a particular exotic species, you have to think about how that plays out ecologically,” Sax said. “There’re a bunch of cases, particularly on islands, where removing problem invaders trashed the system even worse.”
That’s what plover experts hope to avoid.
No one disputes that some exotics are trouble and need to go.
On a rare sunny spring day with the surf roiling behind her, Sundstrum knelt in a patch of green and showed off how unnatural Washington’s beach landscape had become.
She plucked a blade of grass and peeled it back to confirm her identification — Ammophila arenaria, better known as European beachgrass.
“If you were here 100 years ago, you wouldn’t have seen this at all,” she said. But here it is, up and down this coast, spread in clumps as thick as Douglas fir in the Cascades.
Unlike beaches along the eastern seaboard, where dunes bristle with waving grasses, the West Coast was never meant to be so pastoral. Beaches here were dotted by a select few low-growing plants that let sand blow freely, forming and reforming dunes with shifting winds and tides.
But beginning in the late 1800s, California settlers planted invasive grasses to stabilize dunes. The practice continued up the coast into the 1970s. The plant’s ability to spread did the rest.
The new vegetation set down thick horizontal and vertical roots that kept sand intact, so it no longer filled homes and communities. It let beach dunes reach heights of 45 feet, offering protection from crashing storm waves.
But by the 1980s it was clear this change had a cost. Beach grasses crowded out native plants and knocked down populations of tiny crabs and insects that fed birds and other nearshore creatures. Snowy plovers, normally camouflaged by sand, their eggs the size and color of polished shells, were forced to nest near stark green grass, which hid the foxes, ravens, crows and coyotes that like to eat their eggs.
Plover populations crashed, though bird experts made great efforts to save them, killing invasive grasses by any means necessary. In Oregon they also wrapped wire fences around nests to keep predators from eggs. But ravens and crows learned to wait and watch.
“We had increased hatching success, but instead of eating eggs, predators just fed on chicks,” said Scott Pearson, a Washington Department of Fish and Wildlife biologist. “When new chicks ran through the fence to the beach, they got gobbled up.”
These days government snipers with guns keep Oregon crows away from nests.
Sundstrom squinted into a lens, whipped out a recorder and whispered like a cop taking notes during surveillance
“All right, plover one, plover two, plover three, plover four,” she said. “At 11:44, southwest of the barn house about midspan of the open area, we’ve got four plovers in the same area where I located them this morning.”
During spring Sundstrom regularly surveys these birds, to keep tabs on locations — and how many are nesting. One of them this day had blue, orange and brown leg bands — research tags marking it as an Oregon bird that had come up last year, too.
“She had her nest right smack dab in the middle of what used to be a road,” Sundstrom said, shaking her head.
Today fewer than 65 of the birds nest in Washington — along the tip of the Long Beach Peninsula, and here at Midway-Grayland Beach. From the 23 nests scratched out here last year, only five young survived.
But things are improving.
Phoebe Zarnetske, an Oregon State researcher, and colleagues found that plover populations increased as a result of hand pulling, bulldozing and killing invasive grasses with herbicides. But the bulldozing, while faster than other methods, also mows down the native plants that let sand dunes blow and move around more naturally.
“The plover would probably become extinct in this region if not for these restoration areas,” Zarnetske said. “But if we keep bulldozing we also have the potential to lose a lot of plants.
“What we really need to start thinking about is not just targeting the plover, but targeting the ecosystem as a whole,” she said.
No one disputes that to save plovers Washington and Oregon’s invasive grasses still need to be removed from selective areas. But no one believes it’s practical — or even possible — to eliminate them all. For now, the new focus is on trying to remove them more delicately.
But other dramatic transitions are under way, too. Zarnetske said shifts in the way sand moves around these beaches is also helping pine forests slowly march toward the sea.
“We’re so focused on that plover, we’re not seeing how much the entire system is changing, too,” she said.
Craig Welch: 206-464-2093 or firstname.lastname@example.org