Invasive Species Aids Salt Marshes

Invasive Species Aids Salt Marshes

Ailing Cape Cod marshes are recovering with the arrival of European green crabs.

By Kate Yandell | April 8, 2013

A European green crab / CATHERINE MATASSA/NORTHEASTERN UNIVERSITY

The green crab, an invasive species from Europe, threatens many native species in the United States, consuming shellfish, algae, and crustaceans. But its aggression has an unexpected silver lining. The hated species is indirectly preventing erosion in Cape Cod salt marshes by driving down the population of a native crab species that has multiplied out of control, according to a paper published in the journal Ecologylast month (March 29).

The native species, the purple marsh crab, feeds on cordgrass. In recent years, over fishing has depleted the crab’s predators. As purple marsh crab populations have soared, they’ve eaten increasing amounts of marsh grasses, which hold the marsh soil together, preventing erosion.

Green crabs do not ordinarily live in marshes, preferring rocky shorelines. But invasive green crabs have begun to colonize unhealthy marshes, where they can take advantage of the extensive network of burrows dug by purple marsh crabs.

The researchers showed that green crabs evict purple marsh crabs from burrows, either killing them or scaring them away. When they put the two species in cages, only 15 percent of the purple marsh crabs survived, while all of the green crabs did. When the scientists put the crabs together in a larger enclosure, the purple marsh crabs hid and ate less grass than usual.

A survey of 10 Cape Cod marshes and found that the density of green crabs was associated with recovery in damaged marshes.

Mark Bertness, an ecologist at BrownUniversity and one of the study’s authors, told ScienceNOW that he hoped the study would make people think harder before making blanket statements about needing to eradicate nonnative species. But Edwin Grosholz, an ecologist at University of California, Davis, who did not participate in the study, said that the green crab’s rehabilitation is far from complete. “It may have a positive effect in New England,” he told ScienceNOW. “It’s track record elsewhere is quite different.”

The cult origins of one of Florida’s most dangerous invasive species.

By Craig Pittman

Even as new residents come flooding into Florida every day, so do other things, and by that I mean invasive species. Florida has more invasives than any other state. We're talking walking catfish, Asian swamp eels, Cuban tree frogs, Argentine tegus—it's quite a motley menagerie. Sometimes I wonder if we’ve got a little Statue of Liberty at the state line that says, “Give me your slimy, your slippery, your sticky masses, yearning to breed free … ”

Some of Florida’s invasives have been here a long time—for instance, the monkeys that live in SilverRiverState Park, near the Silver Springs tourist attraction. The captain of Silver Springs' Jungle Cruise put them on a small island in the river in the 1930s to spice up the ride for tourists. He thought the monkeys would stay on the island. He didn't realize they could swim. One of them wandered over to the TampaBay area a few years ago to become the celebrated “Mystery Monkey of Tampa Bay.”

The island community of Boca Grande has been so plagued by iguanas—voracious little Godzillas that can grow to be 6 feet long from snout to tail—that county commissioners levied a special “iguana tax” to pay for trapping them.*

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The big name in Florida invasives is, of course, the Burmese python, which has done such a fine job of taking over the Everglades that it has wiped out all the rabbits, raccoons, foxes, and other small mammals that used to live there. You may have heard we had a big state-sponsored python hunt recently. It didn’t put much of a dent in the population.

Not even the alligators can do more than stall the pythons’ takeover. So far, the most effective killer of pythons in the Everglades is a 61-year-old great-grandfather with a shotgun. He says he can smell the snakes when they're nearby.

Nearly all of these invasives have a similar origin story—bought by a collector then escaped or turned loose because it got too big or too nasty. But there’s one invasive species in Florida with an origin story that blows the others away.

I’m talking about the giant African land snail, sometimes known as the GALS for short. Yes, that’s right, a snail. Not just any snail, though. GALS grow to 8 inches long, and their reproductive potential is stunning. Each snail contains both female and male reproductive organs, and every mated adult lays about 1,200 eggs each year. As of June 22, state officials say they have captured and killed more than 124,000 of the GALS from around Miami. And the snails are about as destructive as a Looney Tunes Tasmanian devil set on super slow-mo.

How big a pest are they? They will gobble up at least 500 different types of plants, but that’s not all. They also can cause structural damage to plaster and stucco by chewing on houses. Oh yeah, and they can carry a parasitic nematode that can lead to meningitis in humans.

So you wouldn’t want to mess with them, would you? But somebody did, and that’s where the story takes a particularly Floridian turn.

Florida authorities believe they were smuggled into Miami by followers of a religious cult based on the traditional African religion Ifa Orisha. One follower flew from Africa to Miami with the snails hidden under her dress, according to police.

Authorities said the cult leader, Charles Stewart, persuaded his followers to drink the snails' mucus as part of a “healing ritual.” As a result, one newspaper noted dryly, “several practitioners became violently ill.”

Stewart blamed the uproar over the snails on jealousy from Miami’s many occult Santeria practitioners.

"What I practice is somewhat different,” he said, “and that's what caused the backlash against me."

EPA Approves Use of Invasive Species for Biofuel

By Aviva Glaser

The U.S. Environmental Protection Agency (EPA) has approved a final rule which would allow for biofuels made from two well known invasive species to qualify for credits under the Federal Renewable Fuels Standard. The rule, which was finalized late Friday afternoon, allows two invasive grasses, Arundo donax (also known as giant reed)—assessed by the U.S. Department of Agriculture as being a high-risk species—and Pennisetum purpureum (commonly called napier grass), to qualify as cellulosic biofuel feedstocks under the Renewable Fuel Standard.

“By allowing producers to grow these two invasive plants for biofuel production, the EPA is recklessly opening a Pandora’s box,” said Aviva Glaser, legislative representative for agriculture policy at the National Wildlife Federation. “We want to move forward with homegrown sources of renewable energy, but by doing so, we don’t want to fuel the next invasive species catastrophe.”

The EPA rule, which was first proposed in January 2012, has been publicly opposed by more than 100 state, local, and national groups, including the National Wildlife Federation. Arundo donax is a non-native species that is a well-known and well-documented invader of natural areas. Currently listed as one of the world’s 100 worst invasive species, the plant is particularly destructive to riparian areas where it quickly becomes established. It has been shown to crowd out native-plant species, contribute to greater and more intense wild fires, and destroy habitat for threatened and endangered species such as the Least Bell’s Vireo. The U.S. Department of Agriculture, in their June 2012 weed risk assessment, concluded with very high certainty that Arundo donax is a high-risk species, noting that it is a “highly invasive grass” and a “serious environmental weed.”

The rule does require certain producers to put risk mitigation plans in place, but it has significant loopholes. Even with best management practices, wide-spread cultivation of these two highly invasive grasses is incredibly risky.

“Assuming that best management practices will prevent the escape of highly invasive weeds grown on a large scale is naïve, risky and dangerous,”Glaser said. “We’ve seen time and time again with invasive species that good intentions can result in expensive unintended consequences.”

Green Invaders

Catherine Clarke Fox

Green invaders are taking over America. Nope, not invaders from space. Plants. You might not think of plants as dangerous, but in this case they are threatening nature's delicate food web.
The invaders are plants from other countries brought here to make gardens and yards look pretty. Ever since people started to arrive on America's shores, they've carried along trees, flowers, and vegetables from other places.
Now there are so many of those plants, they are crowding out the native plants that have lived here since before human settlers arrived.
And that's a problem, says Dr. Doug Tallamy. He's an entomologist (an insect expert) at the University of Delaware. He explains that almost all the plant-eating insects in the United States—90% of them—are specialized. That means they eat only certain plants.
Monarch butterfly caterpillars, for example, dine on milkweed. If people cut down milkweed and replace it with another plant, the butterflies will not have the food source that they need to survive.
But the trouble doesn't stop there, it goes right across the food web. When insects can't get the right plants to eat and they die off, then the birds don't have enough bugs for their meals. Tallamy points out that almost all migrating birds depend on insects to feed their young.

"We cannot let the plants and animals around us disappear," says Tallamy. "The way to preserve them is to give them food to eat. But when we plant non-native plants, we are clobbering the food web, because then we don't have the insects the birds need to live."
Fewer of the right plants mean fewer bugs, and fewer bugs mean fewer birds. And that's bad for the Earth, because we need a variety of living things to keep the planet healthy and beautiful.
The good news is, gardeners everywhere are working hard to protect native plants and get rid of the invaders. Many local garden centers sell native plants. "Just Google 'native plants' and your location, and you can find out which plants really belong where you live," says Tallamy.
Planting the right things makes a real difference, and fast. He describes planting milkweed in a tiny city courtyard about the size of a living room one spring. By summertime, that milkweed patch had produced 50 new monarch butterflies!
Tallamy encourages kids to go out and plant native plants. "Adopt a bird species in trouble and see if you can't plant some things that will attract the insects they need," he suggests. "It will happen—insects move around a lot, and they will find the plants you put out there for them!"

Invasive Species: When Small Creatures Do Big Damage

by Rachel Cernansky, Planet Green

If you're an invasive species, you've got it good. You can often take advantage of resources that native species are unable to use, like the way that barbed goatgrass has been able to tap the low water and nutrient levels in the serpentine soils of the west coast more efficiently than native species. It has not only crowded out local plants, but resembles wheat enough that it has produced sterile seed and unmarketable crop.

Invasive species often have traits that predispose them to greater survival, such as fast growth rates, the ability to survive in a wide range of conditions and on a wide variety of foods, asexual as well as sexual reproduction, and phenotypic plasticity, or the ability to change phenotype to fit conditions of the new environment.

The adorable little water vole is one of the latest victims of invasive species in the UK, for example, where populations are succumbing to the predatory non-native American mink, which escaped from fur farms years ago. As if there weren't enough reason to avoid fur. (And really, there were enough reasons already.) Groups are working to save the water vole, but it's an uphill battle, so if you're in the UK—find out what you can do to help.

Economic damage

Invasive species, according to some estimates, cost the global economy $1.4 trillion a year—$138billion in the U.S. alone—through losses in agriculture and forestry as well as management costs of invasive species. Those estimates would increase dramatically if we had monetary values for all aspects of nature that are affected, including losses in biodiversity, species extinction, and ecosystem services.

Some invasive species are intentional introductions gone wrong, such as the cane toad, most famously and perhaps most destructively in Australia. Introduced in the 1930s in an effort to control pests mainly in sugarcane fields, the cane toad has since destroyed local biodiversity levels, causing a decline in populations of several native predatory reptiles and an increase in some species of prey of those reptiles, and spreading ever westward to the more fragile ecosystems of Australia's national parks. Almost without exception, the cane toad has become a pest wherever it's been introduced, including many Caribbean and Pacific islands, threatening native species as it achieves greater population density than it ever sees in its native region of Central and South America. Efforts in Australia alone to deal with cane toads may cost up to $7 million over 15 years.

Other species introductions have been accidental, like the zebra mussel, which was first detected in North America in the Great Lakes in 1988. Native to Russia, the zebra mussel is thought to have been carried over in the ballast water of transoceanic vessels, and is now estimated to cost $5 billion a year in economic losses and control efforts, now that it's spread throughout the U.S. and Canada, killed the native unionid mussel, and damaged harbors, boats, and power plants.

Governments are on the lookout for new invasive species—the Red-eared Slider turtle, for example, is banned in Australia and some U.S. states because of its potential to become an invasive species in non-native areas. But given the huge costs to both the economy and global biodiversity, many say not enough is being done.

Fighting back

Learn more about what organizations and legislators are doing to stem the invasive species problem. Efforts are underway from the Nonnative Wildlife Invasion Prevention Actcurrently pending in Congress to coalitions like the Global Invasive Species Programme that have banned together around the world to prevent further damage from non-native species.

Help stop the invasion

You can pitch in, too. Ever wonder why you're not supposed to travel with fruit, vegetables, or other dirt or pest-carrying items? They can carry pests or even become invasive species themselves.

Other steps you can take to help prevent the spread of invasive species:

- Before you buy plants for your home, make sure they are not invasive, and research plants already in your garden, and if any are invasive, replace them with non-invasive, ideally local alternatives.

- Don't buy exotic animals—they are often raised or transported in unsustainable, inhumane and often illegal conditions—and if you already have them or find yourself with them anyway, do not release them into the wild.

- Don't transport firewood—it can carry insects and diseases that harm both forest areas, clean water supplies, and entire ecosystems.

- If you have a boat, be sure to clean your boat thoroughly before changing bodies of water.

- Similarly, clean off your boots before hiking in a new area.

- Pitch in at a local park or wildlife area, or even just around the neighborhood if appropriate, to help remove invasive species. And talk to people while you're doing it--maybe you'll have a helper for next time.

- Volunteer. Download The Nature Conservancy's handy card and be on the lookout for native species wherever you go. Do it on your own, or volunteer to help the U.S. Fish and Wildlife Service fight these species around the country, starting in your own backyard.

Invasion of the Asian Carp

Public hearing outlines battle against alien species

By Matthew Zdun Living in a Rain Forest
Grade 2 $4.17

Asian carp have already left a trail of destruction and devastation through the Mississippi River system. Now, the invasive species of fish is making its way through the Illinois water system and heading toward the Great Lakes.