Wish you weren’t here
On a summer day in 1988, in a shallow, heart-shaped lake near Detroit, two Canadian university students found the future. While searching for native mussels to use in a research project, the students fished up a rock, and on that rock was an unfamiliar striped mussel, no larger than a fingernail. “We had no idea what it was, except that it was something new and very strange,” recalls biologist Paul Hebert, who supervised the project. “So I took a picture of it. I figured it’d be the last and only one I’d ever see.” Experts soon identified the specimens from Lake St. Clair as zebra mussels, a species native to the rivers around the Black and Caspian seas. In a matter of months, the diminutive mussels had conquered the lake, coating hard surfaces with solid layers of sharp shells. They even encrusted the lake’s large native mussels, eventually killing them all. “The poor things starved to death,” says Hebert. The zebra mussels hitched rides in boats, bait buckets and river currents, and within five years, they had established themselves in the five Great Lakes and in seven major rivers, including the Mississippi, Tennessee, Hudson and Ohio. Their ecological and economic misdeeds were soon infamous: Zebra mussels can rip apart native food webs, clog water intakes with tons of shells and mussel meat, foster the growth of noxious algae, and turn sugar-sand beaches into treacherous, stinking expanses of jagged shells. Three years after Hebert snapped his photograph, scientists discovered another species of invasive mussel in the Great Lakes, a close relative of the notorious zebra. The quagga mussel, named after an extinct zebra (“It was a jovial moment in the lab,” remembers researcher Ellen Marsden), soon proved more than a match for its predecessor. In the Great Lakes, many areas once dominated by the zebra now face quagga rule.Biologists sometimes compare the movement of invasive species to a series of hubs and spokes. Successful invaders radiate outward until, through feats of endurance or gifts of luck, they leap into new territory, establishing new hubs – and soon, new spokes.The quagga mussel made its first major leap in the late 1980s, when scientists believe it stowed away on a Black Sea ship and traveled nonstop to North America. Within the last two or three years – no one knows exactly when – the quagga leapt again. This time, the pioneers might have taken refuge in a persistent puddle on a fishing boat, or inside a rubber boot. They rode the freeways across hostile territory, surviving the plains and deserts. Finally, they found a new home in Lake Mead, the Colorado River reservoir just east of Las Vegas. The mussels settled deep beneath the surface of the reservoir, and did what they do best: They multiplied, quickly and quietly. Lake Mead staff estimate that by the time they were discovered, on Jan. 6, 2007, they numbered in the millions.Nearly eight years of drought in the Southwest have reduced Lake Mead to its lowest level in more than 40 years, and the reservoir’s exposed, dusty shoreline gives the Las Vegas Boat Harbor a makeshift air. But even on this late January weekend, the harbor is busy, and its gently bobbing docks are packed with boats of every description and provenance.
Wen Baldwin retired, more or less, to the Lake Mead area from Colorado 18 years ago, and he’s treated as a local here at the harbor; at its café, he greets the waitress and his fellow customers with cheerful teasing – despite his despondence over recent events. “I feel like I’ve been hit by a stick by this thing,” he says, shaking his head over a cup of coffee. Baldwin led the crusade to keep invasive mussels out of the Lake Mead National Recreation Area, and it’s clearly no fun to be routed by bivalves. “They snuck right in underneath me,” he says, in a tone salted with genuine anger. Baldwin first learned of zebra mussels about five years ago, when he heard an ecologist from Glen Canyon National Recreation Area – which encompasses Lake Powell, the next reservoir upstream from Lake Mead – speak about the likelihood of invasive mussel introduction in the Colorado River. “Whoa, it really got my attention,” Baldwin says. “Lake Mead was right in line. I could just visualize … well, I could just visualize it all happening here.” In their native neighborhoods around the Black Sea, zebra and quagga mussels – both members of the genus Dreissena – are reined in by natural competitors and predators. But in the early 1800s, new canal systems allowed zebra mussels to invade Western Europe, where they became a widespread pest. Quaggas – which can tolerate deeper depths, cooler temperatures, and softer surfaces than the zebras and are generally a few hairbreadths bigger, averaging about the size of a pinto bean – seem to spread more slowly than their cousin mussels. But the quaggas have also made their way upstream from their native range. Back in 1893, nearly a century before the zebra mussel crossed the Atlantic, English naturalist Harry Kew called Dreissena “one of the most successful molluscan colonists in the world.” Little did he know how right he was. The problems caused by zebra and quagga mussels are intricate and far-flung, but they all start with sex: Though some adult zebra and quagga mussels are as small as grains of rice, each female can produce a million eggs each year. Each mussel that survives to maturity can filter a liter or more of water every day, taking in algae and other edible particles and spewing out water clear enough to use in a swimming pool. This talent for purification sounds positive; it’s anything but. The particulates the mussels strain from their environment feed an array of aquatic invertebrates, which in turn feed fish, which in turn … you get the idea. Zebra and quagga mussels, by dint of their huge numbers and impressive industry, can disrupt food webs and, therefore, entire ecosystems. In the Great Lakes, the clearer water produced by zebra and quagga mussels allows sunshine to reach deeper into the lake than it would otherwise, encouraging the bloom of new species of algae; in fact, many local residents met the zebra mussel through a distasteful change in their drinking water. Before water suppliers changed their treatment regimes to deal with the algae growth, “the water had an organic taste, like an infusion of lawn clippings,” says Paul Hebert. “Imagine a grass shake.” Steve Yancho, chief of natural resources for Sleeping Bear Dunes National Lakeshore, 35 miles of still-scenic beaches and sand mountains on Lake Michigan, remembers when visitors started complaining about large mats of sewage – at times bigger than a car – floating near the beach. The mats smelled revolting, and their texture was even worse. “We went out to grab some samples of the stuff with a boat hook,” says Yancho, “and it was like we were passing the hook through warm petroleum jelly.” When park staff could bear to get closer, they realized the gunk had come not from a passing ship but from the bottom of the lake. It was the remnants of algae beds – fostered by the extra light and fertilized by mussel waste – that had died and decayed below the surface. Scientists are still trying to understand the extent of the biological mischief caused by zebra and quagga mussels. In the Great Lakes, the mussels changed the migration patterns of ducks, some of which now snack on mussels all winter rather than fly south. (Zebra and quagga mussels have no North American predators capable of controlling their spread, but ducks and some species of fish, including the invasive round goby, do eat them.) Die-offs of loons and other birds – including 180 loon casualties at the Sleeping Bear lakeshore last summer – are blamed on the rare type E botulism, probably nurtured in the oxygen-poor conditions caused by rotting algae and mussel waste. The mussels’ filtering prowess can then concentrate the botulism toxin – and countless other contaminants – in their tissues and wastes, likely opening a new route for contamination in the Great Lakes food web. The human costs are direct and enduring. “Anyone with a pipe in the water has reason to worry,” says Charles Ramcharan, an aquatic ecologist at Laurentian University in Ontario. In late 1989 and early 1990, the water supply for the Michigan town of Monroe was interrupted three times – once for more than two days – when mussels, drawn to the municipal water intakes by the flow of water and nutrients, mobbed the structures inside and out. Throughout the Great Lakes, power plants have fought off infestations of their cooling water systems, and in 1991, besieged Monroe hosed and vacuumed 30 tons of mussels out of a single water-intake structure. Municipalities and industries along the Great Lakes have tried to defend their equipment with tactics ranging from electric currents to anti-mussel paint, but most now protect their intakes by installing feed lines for chlorine or potassium permanganate, which kill larvae and settling adult mussels. The horrifying initial costs have abated somewhat, but ongoing maintenance is required. Charles O’Neill Jr., an invasive-species specialist with New York Sea Grant, a university-based research and education program, estimates that zebra and quagga mussels have cost the region between $1 billion and $1.5 billion.
Baldwin has never fished in Lake Mead – he prefers to fly-fish the mountain streams of Colorado – but he loves the lake nevertheless, and often makes the 10-mile trip to the Las Vegas Boat Harbor from his home in Henderson. “I go out in the middle of the lake, shut my boat off, and sit back and relax,” he says. “Or maybe I’ll get out on the beach, go climb in the hills. That’s how I get away from the rest of the world, let it go on by.” The prospect of the lake’s degradation – and the associated risk to the city of Las Vegas, which gets about 90 percent of its drinking water from the lake – kept Baldwin interested in zebra mussels. His attention is notable, considering that his career has included stints as a rancher, hunting guide, design engineer and, most recently, slots floorman at the Rio in Las Vegas. “Every time it gets routine, it’s time to change,” he says. “This never gets routine.” Though Baldwin likes to insist on his scientific illiteracy, he learned enough mussel biology to deliver a forceful stump speech about the species and took his message into state and federal offices. In some quarters, his cause was a difficult sell: With plenty of immediate crises to worry about, public agencies had little time or money to spare for a theoretical problem, even one as reality-based as the zebra mussel. The Bureau of Reclamation, for example, funded an extensive zebra mussel monitoring program at its Western reservoirs for several years in the early 1990s, only to abandon the effort when the threat failed to materialize. But Baldwin found allies in Lake Mead staff and other members of the 100th Meridian Initiative, a publicly funded consortium of state and federal agencies dedicated to keeping the zebra mussel – and other aquatic invasives – on the far side of the 100th meridian, the historic border of the West. They surveyed recreational boaters, the most likely cross-continental mussel carrier, and mounted educational campaigns to keep infested boats out of Western waters. Baldwin was soon volunteering 10 to 15 hours a week on zebra mussel prevention. He talked to groups of boaters, agency staffers, and others about effective boat cleaning and inspection. “The best way to get their attention is to get in their knickers,” he says. “Tell them how it’s going to cost them personally.” He learned to build zebra mussel samplers out of PVC pipe and lengths of nylon cord and installed them at six Lake Mead marinas. He checked them monthly for evidence and reported his results to a mussel data clearinghouse at Portland State University in Oregon. Whenever he could, he talked to marina workers about zebra mussels, describing what to look for as they went about their business. “Wen just kept after us,” says Gail Kaiser, whose family runs the Las Vegas Boat Harbor. But what is one person’s persistence, compared with the powers of zebra and quagga mussels?Invasion biologists like to talk about “propagule pressure,” or the number of times an invasive species enters an unfamiliar environment. The more numerous the propagules, the more likely the species will take hold. The propagule pressure of zebra and quagga mussels on Lake Mead was, and is, formidable. The lake hosts some 8 million visitors each year, and on a summer weekend, as many as 5,000 boats launch on Lake Mead and its neighboring reservoir, Lake Mohave. While a small survey of boaters at the lakes in 2002 suggested that little more than 1 percent come from mussel-infested states, any one of those boats could carry enough live mussels or mussel larvae – vanishingly small bits of life known as veligers – to seed a new population.Spot inspections at Lake Mead since May 2004 caught at least nine boats infected with invasive mussels, almost certainly a small percentage of the contaminated boats that entered the park. Officials for various agencies have also nabbed mussels in transit in Washington, California and elsewhere, and assume that many more have slipped by unseen. In the West, mussel propagules are present, persistent and resistant to detection; to settle in, all they need is a bit of good fortune. The quaggas also had the advantage of anonymity. Baldwin and the biologists he talked to expected zebra mussels, which are now established in the Mississippi River and range as far west as Kansas and Oklahoma, to lead any invasion of Lake Mead. While the scientists were aware of quagga mussels, the species has only a small outpost on the Mississippi. The closest substantial population is in Lake Michigan, some 1,000 miles away from Lake Mead. Baldwin, playing the odds, designed his samplers for the shallower waters preferred by zebra mussels. In February of last year, Baldwin dragged a plankton net through the Las Vegas harbor and turned up a microscopic globe of jelly that looked worryingly like a zebra mussel larva. Before taxonomists decreed it was benign, Park Service divers inspected the cables and mooring blocks at the harbor. They found nothing.
On Jan. 6 of this year, Baldwin got the call he dreaded. Eric Virgin, Gail Kaiser’s son-in-law and a member of the Las Vegas harbor staff, had found something suspicious while repairing an underwater cable. “It just seemed wrong,” he says now. Baldwin drove to the harbor, where the marina workers showed him one of the “Zap the Zebra” educational pamphlets they’d been handing out to visitors. Taped to it was the mussel Virgin had plucked off the steel cable. Later that day, divers found more mussels in the harbor, and at the nearby Lake Mead Marina. Over the next week, they found mussels at other locations throughout Boulder Basin, the western lobe of Lake Mead. The Lake Mead fish hatchery, a Nevada Department of Wildlife operation that stocks the lake with trout, was quarantined on Jan. 11 after workers discovered quagga mussels on the edges of the boards damming the fishponds. Robert McMahon, a mussel expert at the University of Texas-Arlington, soon confirmed that the invaders weren’t zebras, but quaggas. Size measurements suggested that the population was at least two years old, though some researchers speculate that the lake’s warmer waters could lead to fast growth; the timing of the invasion remains uncertain. While the evidence of infestation proliferated, so did its implications. The Southern Nevada Water Authority found quaggas on the outside of one of its Lake Mead intakes, some 90 feet below the surface. On Jan. 17, downstream from Lake Mohave in Lake Havasu, divers for the Metropolitan Water District of southern California found mussels attached to the outside of an intake for the Colorado River Aqueduct, the pipeline that waters Los Angeles. The following week, divers found mussels at the Central Arizona Project intakes in Lake Havasu. Later surveys turned up about a dozen mussels on an intake structure for Davis Dam, the plug for Lake Mohave, and another handful on the spillway gates for Parker Dam below Havasu. And in mid-February, an estimated 2,000 mussels were found on a “trash rack” protecting one of the intakes for Hoover Dam. Park Service divers, more accustomed to pulling drowning victims out of the lakes than searching for mussels, spent most of January scouring lakes Mead and Mohave. During the weekend of Jan. 20, they found more quaggas, this time stuck to docks and houseboats at the south end of Lake Mohave. Baldwin even discovered one of the lake’s largest quagga mussel specimens – the size of a hefty grape – stuck to the bottom of his own boat hoist. Lake Mead resource management chief Kent Turner says that given the number of mussel finds in Boulder Basin, and the density of mussels found at each location, it’s reasonable to assume that the quaggas in the reservoir already number in the millions. At the Las Vegas Boat Harbor, more than three weeks after the initial discovery, Baldwin is still distressed. “I feel like I’ve been hit by a stick,” he says again. He crosses the floating dock platforms, heading for the quiet boat slips on the northern edge of the marina. There, he unrolls his newest mussel sampler from a white plastic bucket. Redesigned to pick up quaggas, it extends his standard 6-foot samplers by 20 feet, and carries a doubled set of PVC tubing. He dunks its concrete anchor into the clear green water, and watches the nylon cord and its sampling tubes spin into the depths. Just a few feet away, gaggles of overfed carp, another import with a global reach, gather near the dock. Squirm-ing over one another to reach the surface, they push their mouths skyward, gaping for handouts. The quagga mussel discoveries in January set off a flurry of calls and meetings among park staff, state game officials, and scientists of all sorts, but definitive answers were hard to find. There are plenty of experts on invasive mussels in the Great Lakes; there are experts on the inner workings of Lake Mead. But the invasion of quagga mussels into the Colorado River Basin began an unintentional experiment, and no one is sure of the results. “I think we have about a year before we’re going to really find out,” says Jim LaBounty, a lake ecologist for the Southern Nevada Water Authority and a longtime student of Lake Mead. “But we’ve got an ideal set of conditions.” Lake Mead isn’t nearly as rich in algae as the Great Lakes. But reservoirs are, of course, rivers trapped within lakes, and LaBounty surmises that the constant flow of water in Lake Mead will carry plenty of nutrients to the reservoir’s newest filter feeders.No one could call Lake Mead pristine. Held in place by Hoover Dam, the reservoir is dominated by introduced sport fish, such as striped and largemouth bass. But it and Lake Mohave still harbor a handful of endangered razorback suckers, and Mohave is also home to a few endangered bonytail chub. Exactly how the mussels will affect them and the rest of the food web in the Colorado Basin remains largely unknown, especially since most research on invasive mussels has focused on zebras. Paul Hebert, the biologist whose students discovered zebra mussels in Lake St. Clair, supplies a rule of thumb: “You should prepare for broader consequences than you expect.” Though zebra and quagga mussels can be controlled at water intakes with chemical treatments, and driven out of very limited areas with poisons, high-pressure hoses, and other shock-and-awe tactics, eradication on any scale is expensive: Last winter, state officials in Virginia spent more than $400,000 on potassium chloride treatments for a 12-acre quarry. There is still some talk of eradication at Lake Mead, despite its enormous size and complex topography. “I don’t think we know enough to say it’s impossible,” says Andrew Cohen, a senior scientist at the San Francisco Estuary Institute and a member of the lake’s quagga mussel advisory team. While the park will never eliminate every mussel, he says, a well-funded effort could bury, overheat or poison enough mussels to interfere with the species’ famous fecundity. Considering the potential future costs of the mussel’s spread, such an undertaking could even make economic sense. But most agree that the lake’s primary concern is containment.
“Some lakes, because they receive so much boat traffic, can become what epidemiologists call super-spreaders,” says David Lodge, a researcher at the University of Notre Dame who works with the 100th Meridian Initiative. “Lake Mead will become such a lake.” Lake Powell, which many expected would be first in line for a mussel invasion, now requires boats fresh from mussel-infested states to get a free hot-water wash, courtesy of park concessionaires. But these thorough scrubdowns won’t be practical this summer, when visitors begin hauling their boats from one Southwestern reservoir to the next. “Last year, we washed 45 high-risk boats. This year, we could easily be dealing with 4,500,” says Glen Canyon National Recreation Area aquatic ecologist Mark Anderson. Quaggas could already be headed overland from Lake Mead to the West Coast. Two houseboat-rental operations on lakes Mead and Mohave also rent boats on lakes Trinity and Shasta in Northern California, and workers do move boats between the Nevada and California reservoirs. That means the quaggas might already have access to salmon watersheds, a prospect that worries many in the Pacific Northwest. The Columbia River could easily host a mussel infestation, and researchers foresee a raft of problems for the region’s salmon, ranging from disruption of the food web to encrustation of the ladders designed to allow salmon to migrate around dams. In San Francisco Bay, which Cohen and his colleague James Carlton have called “the most invaded aquatic ecosystem in North America,” the precipitous recent decline of several fish species has been blamed on another invasive bivalve, a type of Asian clam that dominates the northern reaches of the bay. With the industrious clam consuming much of the algae and other plant matter in the bay itself, many species rely on an infusion of nutrients from the Sacramento-San Joaquin river delta. But if the quagga mussel were to invade the delta’s fresh waters, it could vacuum up the bay’s remaining food supply. “The thought of another massively filter-feeding bivalve upstream, in the delta, is causing great concern,” says Cohen. “We might end up with a system that’s good for a couple species of clams, and things that feed on clams, but not much else.” The 100th Meridian Initiative’s Colorado Basin Team meeting in late January draws about 80 people – a record crowd – to Las Vegas from all over the region, including the Pacific Northwest. Wen Baldwin displays an extra-large jug of quagga mussels, newly scraped from a submerged metal cart in the Las Vegas Boat Harbor, and Lake Mead staff and state agency representatives report their discoveries and progress. California has assembled a three-person “incident command” team, the same authority structure it uses for earthquakes and oil spills. Emergency funding is keeping three of its state agricultural inspection stations near the Colorado River open around the clock, an effort – some say a quixotic one – to resist the continuing propagule pressure from Lake Mead. With only two findings of quagga mussels within its borders so far, and no quagga carriers nabbed at its inspection stations, California officials remain optimistic that its mussels will get out and stay out. The Metropolitan Water District, whose board recently approved $180,000 for quagga decontamination and sampling equipment, hopes that a previously scheduled draining of the Colorado River Aqueduct in March will dry up any resident mussels. But quagga monitoring in California has already taken a tragic turn: On Feb. 7, two Department of Water Resources divers drowned while searching for quagga mussels at a pumping plant along the California Aqueduct. State officials are investigating the deaths, and as of Feb. 22, diver surveys at the department’s facilities remained suspended. Throughout the Colorado Basin, most of the early response to the mussel invasion is underfunded and overtaxed. “We’re all dealing with very small pots of money,” says Tina Proctor, an aquatic nuisance species coordinator for the Fish and Wildlife Service. Press coverage has been spotty, and political attention is inconsistent: Arizona Gov. Janet Napolitano, a Democrat, is receiving regular briefings on the issue, but a spokesperson for Utah Gov. Jon Huntsman Jr., a Republican, indicates that it isn’t high on his agenda, pointing out that “Lake Mead isn’t actually in Utah.” So while “there’s an immediate need to do something,” as one audience member at the 100th Meridian meeting puts it, well-provisioned, strongly coordinated action is scarce. Yet quagga mussels aren’t likely to choke off Southern California’s water supply, or otherwise reprise the worst deeds of zebra mussels in the Great Lakes. Western managers can draw on the painful experience of their Midwestern counterparts to deal with mussels earlier and more aggressively. And some Western waters are too shallow, too warm, or otherwise unfriendly to quagga and zebra mussels. Cohen and his colleagues, for instance, found that at many sites in California, calcium levels are too low to support a viable population of zebra mussels, though whether these findings apply to quaggas is uncertain. The fact remains, however, that mussels and infrastructure don’t mix. Mussel defense is an expensive, eternal, and – as California has already shown – occasionally dangerous business. On the Great Lakes, chemical feed lines for water intakes have cost anywhere from $50,000 for a small facility to upwards of $1 million. Such outlays, along with ongoing costs for treatment and monitoring, are inevitably passed on to consumers. The only way to keep the price down is to contain, and keep containing, quagga and zebra mussels. Researcher David Lodge, observing the current crisis around Lake Mead from a safe distance, expects the Western quagga response will come to resemble a more rigorous version of the 100th Meridian Initiative, with a concerted campaign of public education and a prioritized system for boat inspections. (Inspections could employ legal as well as moral authority, since importation and transportation of nuisance species, including invasive mussels, is against the law in most states.) These humble tactics are credited with slowing the spread of zebra mussels in the Great Lakes, and so far, they’re the best tools on hand in the Colorado Basin and beyond. “If you break the invasion down into components – if you look at the most likely ways for the mussel to move – then you can start to do something about it,” Lodge says. “Boaters, by and large, are people who care about the environment. You just have to give them an incentive to practice better boat hygiene.”
Of course, the 100th Meridian Initiative’s only success was in delay. Just as the quagga began turning up in Lake Mead, biologists in the Great Lakes announced that the bloody red mysid, an omnivorous half-inch-long shrimp from the Baltic and Black seas, had become the 185th invasive species to take hold in the lakes. Exotic species are continually introduced into the Great Lakes through ships arriving via the St. Lawrence Seaway, with a new species establishing itself once or twice a year. Many are capable of hitching cross-continental rides. Though some state and federal regulations aim to stem the flow of invaders into the Great Lakes and other U.S. waters, requiring incoming ships to exchange or treat their ballast water at sea, existing rules are notoriously inadequate. James Carlton, the first researcher to document and draw attention to ballast-water invasions, has described the global-transport network as “ecological roulette.” Westerners “could be forgiven for thinking that they don’t need to care about invasions in the Great Lakes,” says Lodge, “but it’s clear now that the desert is no barrier, and the Great Plains are no barrier, at least not an insurmountable one. The invasions from the Great Lakes are not going to stop with quagga mussels, unless effective policies are put in place.” The real problem, of course, is not these species themselves but modern human behavior, which makes it possible for mussels and shrimp to move around the planet as never before. Carlton has pointed out that the number of “vectors” carrying invasive aquatic species – ranging from ships to offshore rigs to the aquarium trade – has roughly doubled every 100 years. On the shores of Lake Mead, where modern vectors delivered the quagga mussel to an environment already profoundly altered by Hoover Dam, human ingenuity collided with itself. “I suppose it’s a different situation if you’re dealing with a synthetic water body rather than one that’s been sitting there for X thousand years,” Paul Hebert says with a touch of acidity. “One could argue that you created a home for invasive species, so it’s only fair that the quagga mussel took advantage of it.” And invasions may beget more invasions, some researchers say, by customizing the environment for other exotic species. Steve Yancho of Sleeping Bear Dunes National Lakeshore remembers surveying for piping plovers on one of Lake Michigan’s small islands. “We looked down, and in this bed of zebra mussel shells that was a foot or foot-and-a-half deep, there was a Canada thistle, a fairly aggressive invasive plant,” he says. “We pulled the thing out, and there was no part of the root that was actually touching the soil. One invasive species was entirely supporting another.” So is our future filled with thistles, quagga mussels, cockroaches, and hordes of popcorn-fattened carp? Afloat on the rising global wave of invasions and extinctions, it’s easy to envision a monstrous, post-apocalyptic fauna, a homogenous cast capable of shredding nature’s diversity. Scientific wags call it the McBiota. Julie Lockwood, a researcher who studies biological homogenization at Rutgers University in New Jersey, says that humans have certainly ratcheted up the rate of invasions and extinctions, but points out that not all invasive species have equal homogenizing powers. While some, like the zebra and quagga mussel, resemble global fast-food chains, others are more like regional franchises, still dominating, but on a smaller scale. “If we make an effort to contain the species that spread a long way, like the zebra and quagga mussels, nature does better than we might think,” she says. Lockwood and her colleagues found that in California’s freshwater fisheries, for example, some remnants of regional diversity have – at least for the time being – survived a long history of intentional introductions and losses of native species. “We haven’t McDonaldized the whole place,” she says. “Some things do hang on in the face of invasions, partly because we want them to.” Habitat protection, pollution control and other strategies, she notes, can still help fend off the McBiota: “The conservation work we do matters.” At the close of the 100th Meridian meeting, the attendees set out for their various parks and states throughout the Colorado River Basin and beyond, newly charged with both containing the quagga and keeping its brethren at bay. They disperse, like so many propagules, into the currents of rush-hour traffic. As evening falls on the northbound freeway, a loaded boat trailer with Colorado plates climbs out of the glittering Las Vegas Valley with them, carrying its cargo upstream.Michelle Nijhuis is High Country News contributing editor. This article was made possible with support from the William C. Kenney Watershed Protection Foundation and the Jay Kenney Foundation.
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Denver has moved to safer-at-home Level 3 status, which is one step away from a full-fledged lockdown.