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Invasive Species, Past and Present

National Museum of Natural History
As our Museum writers, scientists, and exhibition developers produce the script for the new Fossil Hall, they’re discovering lots of fascinating stories about how life evolved. We’ll be sharing some of our favorites here. Passing cargo ships are a common sight at one of the fossil dig sites along the...

Are Humans an Invasive Species?

Smithsonian Magazine

Removing Invasive Species from Ballast Water

Office of Public Affairs
Smithsonian Environmental Research Center Marine Biologist George Smith discusses how scientists are trying to prevent invasive species from hitching a ride to new ecosystems aboard ships.

EU Releases Its First Invasive Species Blacklist

Smithsonian Magazine

Volunteers and land managers in the United States spend thousands of hours and billions of dollars each year trying to fight invasive species like buckthorn, garlic mustard, kudzu, starlings and hundreds of others. But invasive species are decimating ecosystems around the world. That’s why the EU recently enacted its first list of invasive species, which blacklists 23 animals and 14 plant species.

The new regulations state that the species “cannot be imported, kept, bred, transported, sold, used or exchanged, allowed to reproduce, grown or cultivated, or released into the environment.”

Government affairs officer for Great Britain’s Wildfowl & Wetlands Trust, Hannah Freeman, tells Jessica Aldred at The Guardian that the regulations are more than welcome for Britain whether its part of the EU or not. “This European regulation is a no-brainer that will save wildlife and also save our economy millions of pounds each year,” she says. “It’s important that we continue to make those savings and keep managing harmful alien species once we leave the EU.”

Many of the prohibited species are common in North America. In the States, the gray squirrel are known to mess with bird feeders in its native range. But Erik Stokstad at Science reports that in Great Britain, gray squirrels are pushing native red squirrels toward extinction by taking over their habitat and spreading squirrelpox. The squirrels are also spreading in northern Italy, and if not dealt with could invade France and Switzerland.

Conversely, skunk cabbage, a perennial large-leafed wetland plant found east of the Mississippi, is usually a sign of high-quality habitat in the United States. In the U.K., they have encroached on wild lands, Aldred reports, heavily impacting native plant populations in Scottish marshes.

Another threat? Raccoons. The critters were imported to Germany in the 1930s, reports Henry Chu at The Los Angeles Times, and in less than a century, the animals have increased to over one million strong, and are colonizing the countryside, towns and cities.

Other species on the list include kudzu, water hyacinth, the sacred ibis, ruddy duck, North American bullfrog, several species of crayfish, two other squirrel species and the small Indian mongoose.

Aisling Irwin at New Scientist reports that nations aren’t obligated to eradicate species that have already spread, but must keep them from expanding their territory or crossing borders. Invasive species kept as pets, like the coatimundi, a raccoon-like mammal from central and South America, will be allowed to live out their natural lives, but cannot breed or be imported.

Invasive species researcher Sven Bacher from the University of Fribourg in Switzerland says he hopes the list will soon expand. “We are all a bit concerned with the low numbers of species on the list,” he says. “We estimate there are around 1,000 to 1,500 invasive alien species in Europe and this is only a very poor selection.”

But as Irwin writes, Karmenu Vella, EU's environment commissioner, says that the blacklist is not fixed and will continue to be updated over time.

How Yellowstone Scientists Really Combat Invasive Species

Smithsonian Channel
Yellowstone cutthroat trout are on the brink of extinction as invasive lake trout continue to eat them. With the park's ecosystem at risk, it's up to scientists to figure out where these predators came from and how to contain them. From: MYSTERY IN YELLOWSTONE

Five Summer Activities That Can Spread Invasive Species

Smithsonian Environmental Research Center
By Joe Dawson Nothing seems to draw people outside like a beautiful summer weekend. A rain-free Saturday could mean taking the boat out on the water for some fishing or a family camping trip. Conservationists have found, however, that many summer activities carry the risk of spreading invasive species. A species gets the name “invasive” […]

Five Summer Activities That Can Spread Invasive Species

Smithsonian Environmental Research Center
By Joe Dawson Nothing seems to draw people outside like a beautiful summer weekend. A rain-free Saturday could mean taking the boat out on the water for some fishing or a family camping trip. Conservationists have found, however, that many summer activities carry the risk of spreading invasive species. A species gets the name “invasive” […]

The Global Price of Invasive Species

Smithsonian Magazine

It’s the stuff of environmental horror stories: Exotic species invades new shores, and swiftly lays ruin to the native ecosystem and its inhabitants. And it's so common it's become almost a trope. Think of kudzu vines strangling trees and shrubs in the South, Asian longhorned beetles decimating hardwood forests in the Northeast and prolific Asian carp outcompeting native fish (and terrifying boaters) in the Great Lakes.

But the devastation wrought by these invasions isn’t just environmental—it’s economic. Alien insects and pathogens cost an estimated $40 billion annually in the United States alone, in terms of the harm they wreak on crops and forests. As disparate parts of the world grow increasingly connected and thus face increased risk of new invasions, those costs will only rise.

Despite these scary stakes, researchers haven’t yet assessed the worldwide costs that these invasions cause as a whole. Instead, most research on invasive species has only been done on a singlecountry basis. That means we’ve been missing out on capturing the global nature of the problem: trade links virtually all countries, and thus all would-be invaders in a network of possible pathways into a new country.

Now, a new study attempts to fill that knowledge gap by using complex computer models to quantify the cumulative threat of 1,300 insect pests and fungal pathogens to crop production in 124 countries. The results are stark: almost a third of the countries studied had a high likelihood of imminent invasion. Developing countries stand to experience the worst impacts, while major agricultural producers like China and the U.S. pose the greatest risk as sources of invasive species, according to the findings, which were published this week in Proceedings of the National Academy of Sciences.

While the results reaffirm what researchers suspected, “this is the first work that has shown it quantitatively and at the global level,” says Dean Paini, a senior research scientist at the Commonwealth Scientific and Industrial Research Organization in Australia, and lead author of the study. Having a better idea of the risks “presents us with an opportunity to do something about it,” he adds.   

One of the key connections that enabled Paini and his colleagues to come to their conclusions was knowing the link between invasive species and global trade. While there are myriad ways by which invaders can sneak into a new port, past studies consistently found that the number of invasive species in a given country was related to that country’s trade levels. Knowing this, the researchers examined the proportion of total imports from each country’s trading partners to calculate the probability of an invasive species arriving in a given country.

Next, they estimated the chance of those pests actually establishing themselves in a new country by analyzing worldwide distributions using an artificial intelligence algorithm. That method generates likelihood indices of pests settling down and proliferating in areas where they do not already occur, based on where they are found already and how they interact with other species. Finally, researchers looked at annual crop production in each country and calculated the invasion threat to those crops, depending on which pests eat what and who trades with whom.

The results indicated that a third of the 124 countries faced a very high risk of being invaded, while only 10 countries faced a very low risk of invasion. In terms of absolute cost, countries that are major agricultural producers—the U.S., China, India and Brazil—stand to lose the most. But in terms or relative cost, developing countries, particularly those in sub-Saharan Africa, including Malawi, Burundi, Guinea, Mozambique and Ethiopia, were the most vulnerable. Trade patterns, pest presence and species analyses also revealed that the U.S. and China pose the greatest threat in terms of unintentionally delivering their potential invaders on other countries.

While Paini and his colleagues ran statistical tests to confirm that their results were robust, uncertainty always surrounds work with computer models. “I think the study was conducted well as an overview of the global threat to agriculture,” says Daniel Simberloff, an environmental scientist at the University of Tennessee, Knoxville who was not involved in the study. Simberloff adds that follow-up studies should delve more deeply into the impact of specific crop pests. “This will take a lot of work, but it will be much more definitive in terms of the real probability of the various threats,” he says.

For now, Paini and others hope that the paper will prompt countries to deploy the necessary resources to protect their own environments and economies, as well as encourage more affluent countries to prevent invasive species from spreading to developing ones. The paper’s conclusions “highlight the need for a world body to address, in a comprehensive manner, the continued threat of plant pests and pathogen invasions that result in enormous economic losses in the affected countries,” says Harold Mooney, an environmental biologist at Stanford University who was not involved in the work.

Mooney, for his part, is optimistic. “There is a lot being done internationally, which is cause for hope,” he says. This new research could help: After all, perhaps the best way to get people to care about their environments is to attach a dollar amount to it.

Making the Best of Invasive Species

Smithsonian Magazine

The lowly garlic mustard had never seen so much love.

This prolific invasive plant—cursed by home gardeners and park and wildlife managers alike—is routinely wrenched from the ground or spritzed with herbicide in an attempt to keep it from taking over. But on April 14 at Cleveland’s Shaker Lakes Nature Center, garlic mustard was the guest—or rather, pest—of honor.

“Pestival 2011” featured seven of Cleveland’s most notable chefs making garlic mustard a gourmet treat. They rose to the occasion deliciously: garlic mustard sauce over thin slices of roast beef, garlic mustard pesto on pork tenderloin crostinis, garlic mustard chutney on wonton-skin ravioli stuffed with tofu and paneer cheese, garlic mustard dip for thick-cut potato chips, and garlic mustard relish on chèvre cheesecake. The 125 attendees clustered around the chefs’ silvery platters, then carried artfully arranged portions of the garlic-mustard creations back to white-linen draped tables.

Would all this culinary artfulness persuade people to cook up some garlic mustard on their own, or at least recognize it when they see it along a path in a public park and yank it out?

“We hope so!” says Terri Johnson, the nature center’s special events manager. “We look forward to the day when garlic mustard is eradicated. Then we’ll hold Pestival as a victory celebration.”

Garlic mustard is just one of 50,000 alien plant and animal species that have arrived in the United States. These invaders flourish in the absence of their native competitors and predators. European settlers brought garlic mustard here for their kitchen gardens. An attractive plant with heart-shaped leaves and tiny white flowers, it outcompetes native plants for light, moisture, nutrients, soil and space. It propagates at a fierce speed, producing thousands of seeds that spread by sticking to animals’ fur.

“If you don’t control it, woods filled with native species can be completely taken over by garlic mustard in five years,” says Sarah Cech, the nature center’s naturalist.

When the nature center first conceived Pestival six years ago—the first one was a simpler event in which the staff prepared a garlic-mustard pesto served with spaghetti for 80 guests—they didn’t realize they were part of a national trend. The United States spends around $120 billion each year to control invasive species, according to Cornell University ecologist David Pimentel. But in the past decade or so, a growing number of people have decided to view the crisis of surging alien populations as an opportunity to expand the American palate. If these species are out of control because they have no natural predators, then why not convince the fiercest predator of all—human beings—to eat them? The motto of these so-called invasivores is, “If you can’t beat ’em, eat ’em.”

Take the Asian carp (please!). Imported from China in 1973 to clean algae from Southern ponds, the carp soon broke from their confines and infested Mississippi River waterways. Gobbling up the phytoplankton that support native species, the carp can grow four feet long and weigh 100 pounds. They continue to swim north and could establish themselves in the Great Lakes, the world’s largest freshwater system, and decimate native fish populations there.

Wildlife managers have tried to prevent Asian carp and other invasive species from reaching the Great Lakes by installing electric underwater fences and, occasionally, poisoning the water. But chefs from New Orleans to Chicago have also tried to put a dent in the population by putting the fish on their menu. Now, a researcher at the Aquaculture Research Center at Kentucky State University is trying to figure out how to harvest and promote carp as a food source. Currently, a few processing plants are converting Asian carp into ingredients for fertilizer or pet food. “That’s a shame, because the meat quality is excellent,” says Siddhartha Disgupta, an associate professor at the center.

Image by Winfred Wisniewski; Frank Lane Picture Agency / Corbis. Garlic mustard is just one of 50,000 alien plant and animal species that have arrived in the United States. These invaders flourish in the absence of their native competitors and predators. (original image)

Image by Jim Weber / ZUMA Press / Corbis. Asian carp, imported from China in 1973 to clean algae from Southern ponds, broke from their confines and infested the Mississippi River waterways. (original image)

Image by Kristin Ohlson. "Pestival 2011" featured seven of Cleveland's most notable chefs making garlic mustard a gourmet treat. Shown here is Chef Scott Kim and his assistant of SASA. They prepared wonton skin ravioli filled with garam masala seasoned tofu with paneer cheese served with garlic mustard chutney and cucumber salsa. (original image)

Image by Kristin Ohlson. Jonathon Sawyer is the owner of the Greenhouse Tavern and was named Best New Chef of 2010 by Food and Wine magazine. He plans to include garlic mustard as a regular part of his menu. (original image)

Image by Kristin Ohlson. Chef Britt-Marie Culey of Coquette Patisserie made chevre cheescake with garlic mustard relish. (original image)

Disgupta argues that the carp has all the health benefits associated with eating fish and, since it eats low on the food chain, has few contaminants such as mercury that tend to be concentrated in the flesh of other fish species. He says he’s eaten Asian carp in various preparations and found it delicious. But even though this species of carp is prized as a tasty fish in China, Americans usually grimace at the idea of eating it.

“There’s a negative prejudice to the name,” Disgupta says. “People think they’re bottom feeders. They get them mixed up with suckers, which look similar but are from a different biological family.”

In Florida, George Cera has trained his fork on a different invasive creature: the spiny-tailed black iguana, which was imported as an exotic pet, then escaped and proliferated. Cera was hired by the town of Boca Grande on Gasparilla Island to hunt and kill the iguanas, which feast on endangered plants as well as the eggs of protected sea turtles, gopher tortoises and burrowing owls. “They grab and eat them like we’d eat a cherry tomato,” Cera says.

In two years, Cera bagged 12,000 iguanas, his conscience soothed as he found parts of protected species inside them. But it bothered him to kill an animal without eating it. Then, he met some Central and South American tourists who told him that iguanas are considered a delicacy back home, where they’re a native species. They gave Cera recipes. He tracked down more on his own and produced an iguana cookbook.

“I thought it would be a fun way to educate the public,” Cera says. “Now, people come and ask me where they can get some of this meat.”

Perhaps no one tackles the issue of eating invasives with as much gusto as Jackson Landers, author of The Locavore Hunter blog. Over the past year, he’s traveled the country hunting invasives and gathering material for his new book, Eating Aliens. Landers has hunted and eaten feral pigs in Georgia, green iguanas in the Florida Keys, pigeons in New York City, Canada geese in Virginia and European green crabs in Massachusetts, among others.

“As a systematic approach to invasives, eating them should be a major component,” Landers says. “After all, human beings have eaten other species to extinction.”

Not everyone agrees with this approach, however. Sarah Simons, executive director of the Global Invasive Species Programme, echoes the thoughts of some wildlife managers, saying, “There is currently no evidence whatsoever to demonstrate a reduction in population size, or effective management, of invasive species by consuming them. More often, it is quite the reverse which occurs—promoting the consumption of an invasive species can actually create a market, which in turn increases the spread or introduction of invasive species.”

The organizers of Cleveland’s Pestival are well aware of the fine and dangerous line between educating people about garlic mustard—including its edibility—and inadvertently inspiring them to cultivate it in their backyards. But there seemed to be little cause for worry at the event. Most of the preparations offered an array of flavors, and it was hard for the diners to isolate the particular taste of garlic mustard. Some of the chefs only shrugged when asked if they planned to make the wayward green a regular part of their menu.

The exception was Jonathon Sawyer, owner of the Greenhouse Tavern and named a Best New Chef of 2010 by Food and Wine magazine. Sawyer loves to forage the ring of parks around Cleveland and has been carrying garlic mustard back to use in his restaurant and home for five years. In the springtime, he likes to eat the leaves raw, comparing their taste and bite to arugula. As the plants get older, he blanches and eats them like mustard greens.

“Dude, it’s the ultimate food!” Sawyer exclaimed as he passed out his artichoke and spinach dip with crème fraiche, garlic mustard and thick-cut potato chips. “It’s free, and nature wants us to get rid of it.”

How Yellowstone Scientists Really Combat Invasive Species

Smithsonian Magazine
Yellowstone cutthroat trout are on the brink of extinction as invasive lake trout continue to eat them

Natural Gas Trade Opens Door for Invasive Species

Smithsonian Environmental Research Center
by Kristen Minogue The U.S. is on the brink of a natural gas boom—but that could expose its shores to more invasive species, Smithsonian marine biologists report in a new study published this winter. Over the last decade, U.S. natural gas imports have dropped as the country tapped into its own resources. Now, thanks to […]

Two invasive species have Hawaiian reunion after 80-year separation

Smithsonian Insider

Fat, toxic and nocturnal, cane toads (Rhinella marina) are abundant today in Hawaii, even though they are South American natives. Released on the Hawaiian Islands […]

The post Two invasive species have Hawaiian reunion after 80-year separation appeared first on Smithsonian Insider.

Bite Back Against Invasive Species at Your Next Meal

Smithsonian Magazine

The Midwest has an Asian carp problem. The invasive species has a tendency to jump out of the water, bludgeon fisherman and destroy boats, and they’ve been found throughout the region. Scientists worry that they’ll eventually decimate the local fishing industry, disrupt the ecosystem and destroy up to 37 percent of native species in bodies of water like the Great Lakes.

Will the fish eventually take over? Chefs across the United States aren’t waiting to find out. Rather, they’re putting invasive species like Asian carp in their own dishes—and on restaurant menus.

In Washington, D.C., Chef Seng Luangrath at Thip Khao cooks with snakehead and blue catfish from the Potomac River for a special invasive species menu. At Miya’s Sushi in Connecticut, chefs serve invasive seaweed in a pumpkin miso soup; head chef Bun Lai is currently in Florida readying a pop-up restaurant that will feature even more types of invasive foods. Lionfish has appeared on menus in New Orleans (at GW Fins), New York City (at Norman’s Cay) and in at least a dozen restaurants in Florida.

It’s all part of a growing push to mitigate the effects of rapidly growing, non-native plants and animals on the ecosystem, drawing attention to the dangers of invasive species. For foodies, there’s a big bonus: Many invasive species taste great, too. When Eat MO Carp, a Missouri-based marketing initiative run by University of Missouri associate professor Mark Morgan, conducted a blind taste test pitting Asian carp against Missouri’s state fish, catfish, the carp won by a landslide.

Morgan’s organization considers Asian carp a menu item instead of a just a local pest. In a 2015 editorial for the Missourian, Morgan called using local carp a “win-win” that both creates demand and addresses a dire ecological issue. Morgan has served carp chili and tacos to Mizzou students, offered free samples at a grocery store, served as a food vendor for a bowfishing tournament and even persuaded a local brewery to throw an Asian carp-themed food event.

Eat MO Carp is just one of many invasive species-eating organizations nationwide. This August, visitors to Corvallis, Oregon can partake in Eradication by Mastication’s annual Invasive Species Cook-Off, a fundraiser for the Institute for Applied Ecology. Last year’s competition featured a docket of esteemed chefs, a Chopped-like showdown and a formal invasive species dinner.

Many of the species can even be enjoyed—and partially eradicated—without leaving home. For home chefs, websites Eat the Invaders and Invasivore offer guides to harvesting invasive species and cooking them.

“When people ask me for something easy they can start with, I suggest going out in your own yard and getting some dandelions,” Matt Barnes, editor of Invasivore, tells “I like to call dandelions a gateway invasive because people tend to be pretty comfortable eating them. We start them off there before we get them eating earthworms or something like that.”

Dandelion Sage Cocktail, Dandelion Tonic, Fresh Sage, Barr Hill Gin. Served at Hotel Vermont in Burlington, Vermont. (Courtesy of Hotel Vermont)

But Barnes also cautions that eating invasive species might not have the desired effect. He mentions colonial India’s “Cobra Effect,” which occurred when people developed underground cobra breeding operations in response to a bounty for captured cobras. Officials collected the bounty on farmed cobras instead and the main issue went unchecked.

It all comes down to awareness, says Barnes, who admits that even people with a healthy appetite may not be able to match the reproductive power of invasive species. “The real value of harvesting and eating invasive species is as a public education and awareness tool,” he says. “If people are aware of what invasive species are and what kind of impacts they have on the environment, that might prevent them from introducing the next invasive species.”

That awareness could help in Chicago, which has an Asian carp problem of its own. The species arrived in the downtown river in early 2015, only one block from Lake Michigan. Though the city installed three electrical barriers downstream in the Chicago River to stop the Asian carp before they get into the lake, some fish have already broken through. The carp could soon wriggle into the Great Lakes, but Chicago residents have a game plan. It involves Asian carp burgers and a big appetite for protecting the lake they love.

Ships Struggle To Battle Invasive Species As Global Trade Surges

Smithsonian Environmental Research Center
Strategy To Flush Invaders From Ballast Water Coming Up Short by Kristen Minogue In the battle against invasive species, giant commercial ships are fighting on the front lines. But even when they follow the rules, one of their best weapons is coming up short, marine biologists from the Smithsonian Environmental Research Center (SERC) discovered in […]

Do invasive species perform better in their new ranges?

Smithsonian Libraries
A fundamental assumption in invasion biology is that most invasive species exhibit enhanced performance in their introduced range relative to their home ranges. This idea has given rise to numerous hypotheses explaining “invasion success” by virtue of altered ecological and evolutionary pressures. There are surprisingly few data, however, testing the underlying assumption that the performance of introduced populations, including organism size, reproductive output, and abundance, is enhanced in their introduced compared to their native range. Here, we combined data from published studies to test this hypothesis for 26 plant and 27 animal species that are considered to be invasive. On average, individuals of these 53 species were indeed larger, more fecund, and more abundant in their introduced ranges. The overall mean, however, belied significant variability among species, as roughly half of the investigated species (N = 27) performed similarly when compared to conspecific populations in their native range. Thus, although some invasive species are performing better in their new ranges, the pattern is not universal, and just as many are performing largely the same across ranges.

In San Francisco, one wet winter can switch up Bay’s invasive species

Smithsonian Insider

For many Californians, last year’s wet winter triggered a case of whiplash. After five years of drought, rain from October 2016 to February 2017 broke […]

The post In San Francisco, one wet winter can switch up Bay’s invasive species appeared first on Smithsonian Insider.

Smithsonian scientists to help identify and eradicate invasive species in Alaskan waters

Smithsonian Insider

The Smithsonian Environmental Research Center in Edgewater, Md., and the Alaska Sea Grant Program of the University of Alaska, Fairbanks, were recently identified as the […]

The post Smithsonian scientists to help identify and eradicate invasive species in Alaskan waters appeared first on Smithsonian Insider.

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