Screening out legal invaders
Importing live animals and plants into the U.S. introduces harmful nonnative species that can cause significant economic and ecological losses.
For 26 years, Rusty Kimble has fished on the Red and Atchafalaya rivers in central Louisiana. Every morning, he sets out on his small aluminum boat and returns with his catch—mostly a mix of buffalo fish, gou (freshwater drum), and several species of catfish. "I'm not a biologist. I'm not a scientist. I'm a commercial fisherman, but I know a lot about the fish in the river," he says. In the early 1990s, Kimble began catching something he did not recognize—a fish so strong that "when you have one in the net, you know something unusual is in [it]," he adds. It took nearly 10 years before Kimble learned that the newcomer was the exotic Asian black carp, an emerging threat to the rivers' ecosystems.
The black carp (Mylopharyngodon piceus) was first imported into the U.S. in the 1980s by aquaculturists to control pesky snails and their parasites. Then, aided by natural flooding of aquaculture ponds, the fish found its way into the Mississippi River Basin, which was already full of the invasive grass carp, as well as bighead and silver carp.
Unlike its vegetarian cousins, the black carp eats mollusks (snails and mussels) and is very efficient at wiping them out, says Leo Nico, a biologist and black carp expert at the U.S. Geological Survey. Mollusks are the most endangered group of animals in North America. And scientists are fretting over the fates of these imperiled native mollusks because 90% of those that are threatened and endangered live in the waters of the southeastern U.S. with free-swimming black carp.
Like the black carp, millions of individual organisms are imported into the U.S. every year for aquaculture, the food industry, biomedical research, the pet industry, live bait, and ornamental plant industry. Many of these plants and animals—either by accidental escape or deliberate release—end up in places where they can wreak havoc on the environment, agriculture, and human health.
Every year the U.S. spends billions of dollars managing invasive species, but the attempts are often futile. Scientists know that deliberate introduction through trade is currently the major source of injurious nonnative species in the U.S. As the largest importer of live animals and plants in the world, the U.S. is especially susceptible to the onslaught of legally imported invaders.
It's no wonder that environmentalists, economists, and ecologists are promoting the economic and environmental benefits of preventing such invasions from happening in the first place. The current situation in the U.S., they say, can be blamed on lack of resources, patchy regulations, and an overall reactionary approach to the problem, rather than a precautionary one. They are urging the federal government to put more resources into developing a much-needed risk-based screening system for these imports. The idea is to identify the potentially problematic species before they enter the country and bar them from importation. Australia and New Zealand adopted this approach more than a decade ago, note scientists and environmentalists, and it is time for the U.S. to catch up, they say.
Tangled up in the Lacey Act
In the U.S., three agencies have jurisdiction over animal and plant imports. The U.S. Department of Agriculture (USDA) is in charge of monitoring and restricting plant and animal imports that can pose a risk to the agriculture and livestock industries and relies heavily on the Plant Protection Act. The agency's Animal and Plant Health Inspection Service (APHIS) issues permits to import nursery plants, seeds, plant products, protected plants, weeds, and organisms used as means of biological control. Similarly, the U.S. Department of Health and Human Services (DHHS) uses the Public Health Service Act to protect the public from animal imports that are likely to spread diseases to humans.
The U.S. Fish and Wildlife Service (FWS) regulates imports that can potentially affect ecosystems and wildlife. The agency tracks live-animal and plant imports at the ports of entry, identifies the organisms imported, and also records other information such as how many individuals are being brought in. It can also ban organisms that are known to pose risks from being imported or traded across state lines, and to do this, the agency uses the Lacey Act's provisions on "injurious wildlife".
Of the three agencies, FWS is the least equipped to regulate imports, says ecologist David Lodge of the University of Notre Dame. Both DHHS and USDA have strong regulatory authority as well as the power to respond promptly to cases of unexpected escape and subsequent invasion or disease spread, he says. For example, in 2003, when more than 50 people in the Midwest became infected with the monkeypox virus—a virus that had made its way to the U.S. with tropical African rodents imported as exotic pets—DHHS was able to react relatively quickly and ban the import and sale of any African mammal that could potentially carry the virus.
But FWS cannot respond as promptly and as strongly as DHHS did in the case of the monkeypox, says Lodge. As a result, much of the discussion on regulating live-animal and plant imports currently revolves around FWS and its sole legal tool, the Lacey Act, he says.
Under the Lacey Act, FWS regulates the import and interstate transport of live salmonids (salmon and trout), wild mammals, birds and their eggs, mollusks, live or dead fish, and shellfish and their eggs.
In a September 2007 paper (Front. Ecol. Environ. 5 [7], 353–359), Lodge and his colleagues showed that the Lacey Act, in its current form, does not adequately protect the U.S. from injurious animals. Of the 24 different kinds of animals (species, genera, or families) listed as injurious under the act, only 7, including the brown tree snake, the fruit bat, the Indian wild dog, and the pink starling, were listed before they were brought into the country. In each of the seven cases, the listing prevented the animals from becoming established in the U.S. However, 56% of the animals were already in the U.S. when they were banned. Forty-four percent of those animals were already established in the wild, and of those, 71% have spread since being listed.
FWS currently takes an average of 3.6 years to decide on a new listing, estimates Lodge. Each one requires a series of proposed rulemakings and a public comment period, says Kari Duncan, chief of FWS's branch of invasive species. "We put all information for the public to see and comment on, and we also ask for additional information, things like, 'Did we get everything right? What did we get wrong?'"
These seemingly endless cycles of proposed rulemakings, comments, and responses are "simply a disaster when it comes to an organism, a living organism, which, while you're going through iterative rulemaking processes, is growing and spreading," says Lodge.
Case in point—the black carp. On October 18, 2007, FWS added the black carp to the list of injurious animals under the Lacey Act. It took the agency 7 years to come to this decision. The listing is supposed to "head off the establishment of the black carp in the U.S.," says Joshua Winchell, a spokesperson for the agency. But Kimble is convinced (and biologist Nico agrees) that a breeding population already exists in the Mississippi River.
The threat of legal invaders
In the past 50 years, an increasing number of species have been imported intentionally and legally because of booming trade in live animals and plants. Most of these trades are economically valuable. According to a 2004 study published in Frontiers of Ecology and the Environment (2 [3], 131–138), 11 million hobbyists in the U.S. support a $25 billion industry. Similarly, shellfish farming brings in more than $100 million annually. Yet every species that is imported is shadowed by potential costs from harm to either the environment (which is often hard to put a dollar value on), agriculture, or human health. Some prominent examples are:
Many species sneak in with imports of other animals or plants because of a lack of screening at the borders. One such example is the European (green) shore crab, which reached the San Francisco Bay area hitchhiking on seaweed used for packing live bait worms imported from Europe. The crab is now devouring pretty much everything on the coast, including commercially valuable species (described as a "mean, green, eating machine" by USDA).- It is very unusual for an American to contract the monkeypox virus, which usually infects tropical African small mammals. And yet, the U.S. experienced a monkeypox outbreak in 2003, affecting more than 50 people in the Midwest. The culprits—prairie dogs that became infected while sitting next to infected Gambian pouch rats in a pet store. The Centers for Disease Control and Prevention responded by immediately banning the import of all animals that could potentially carry the virus. However, some rats escaped and set up colonies on Grassy Key, one of the islands in the Florida Keys, where they could pose a serious health hazard to native wildlife.
- Aquarium releases are the biggest source of nonnative fish in Florida and the second largest source in the U.S. Because of one such aquarium release, the vollitan lionfish, a ferocious predator, is spreading along the Atlantic Coast and causing the decline of many other species.
Broken Screens
Even the relatively simple process of tracking live animal imports into the U.S. is flawed, according to an investigative report titled Broken Screens, released in August 2007, by the environmental advocacy group Defenders of Wildlife. The authors of the report used the Freedom of Information Act to procure and analyze FWS's documentation of imported wildlife species.
FWS regulations require animal traders to declare their imports at the port of entry and make them available for inspection. From 2000 to 2004, FWS recorded a little more than 1 billion individual animal imports, but only 6% of them were identified with their genus names. Additionally, more than 5 million kilograms of animal imports were recorded, 77% of which were identified. Altogether, FWS identified 2241 species that were imported during the 5-year period. The rest were either of ambiguous or unknown identity.
The Defenders of Wildlife researchers compared these 2241 imported species with existing accounts of injurious animals in the literature and in various databases, including IUCN—The World Conservation Union's global master list of injurious nonnative species. They identified 302 risky aliens. FWS could do a similar "coarse screen" of the live-animal imports and weed out the obviously injurious ones at the outset, says Peter Jenkins, one of the report's authors.
The report proposes the development of three lists—a black list for species that are sure to cause trouble, a white list for benign species, and a gray list for ambiguous animals that would be allowed into the country but monitored closely.
The challenge of risk analysis
"When you let a species in, you can have benefits and costs," says Reuben Keller, a postdoctoral fellow who works with Lodge. In the case of ornamental plant trading, "you get more benefits by keeping more species in trade because it generates economic activity." But that comes with the potential cost that some of those species are invasive, he says.
Is it possible to predict which species are likely to be harmful? "If you had asked that question 30 years ago or 40 years ago, I would have said, well, we really can't do it, we don't know how," says Lodge. However, "there's been a tremendous increase in the scientific capacity on this topic in the last couple of decades," which has improved the accuracy of risk analysis on nonnative species, he adds.
Past risk analyses were inaccurate for many reasons. Scientists did not know enough about the species—their life histories and ecology—to correctly predict which ones were likely to be harmful. In addition, in the past, invasions were not as well documented as they are today. Knowledge of the climates of species' native and new habitats was also minimal a few decades ago, and experts did not agree on what percentage of transported species can become established and invasive.
Even now, the task is colossal. "The big problem with this kind of thing is that literally hundreds and thousands of species could come knocking on your door," says Keith Hayes, a marine invasive species expert at the Australian Commonwealth Scientific and Industrial Research Organisation (CSIRO) Marine and Atmospheric Research. Many of these species are from remote parts of the world and poorly studied. "You're not going to be able to screen all these species, because you just don't have the data on them."
So, the trick, says Hayes, is to "narrow the game down." As he and his colleague, Simon Barry of CSIRO Mathematical and Information Sciences showed in a recent paper (DOI 10.1007/s10530-007-9146-5) in Biological Invasions, scientists can now rely on as few as three or four characteristics to determine the potential risk of an imported species.
After analyzing 49 published studies on risk analyses, Hayes and Barry determined that of all the factors pertaining to a species' native and new environments, climate is the most important. "Climate match is demonstrably a really important part of a species' likelihood to get in somewhere and establish," says Hayes. Recent advancements in climate data have given scientists the ability to predict whether a species from one part of the world is likely to become established in a different region. Two other key determinants of invasiveness for most types of organisms are the "history of invasion success" and the number of individuals of a species that are introduced or released in the new environment.
Additional diagnostic characteristics that are more specific to the kind of animal or plant can also be used. For example, Lodge has found that for alien mollusks, the larger the number of eggs that a species can lay, the higher its chances of spreading in a new environment.
Still, 100% accuracy is impossible "because we are dealing with ecological systems, which are really complex," says Keller. However 80–90% accuracy is a no-brainer these days, he adds.
Hurdles to jump
The National Invasive Species Council (NISC), an interagency body that coordinates all federal activities about invasive species in the U.S., has long recognized the importance of prevention when it comes to the threat of legally imported organisms. But little has come of that recognition. In its latest management plan, Meeting the Invasive Species Challenge, from 2001, NISC proposed the two-phase development of a "risk-based comprehensive screening system" to prevent introductions of alien species for any purpose. According to the plan, this screening system would have "different agencies taking the lead as appropriate for the different types of species."
In the first phase, which is already 4 years behind schedule, NISC hopes to develop a screening system for first-time introductions. During the second phase, it plans to focus on "species already moving into the U.S." NISC has yet to complete either of the screening systems.
Another problem with the U.S. approach is that jurisdiction (over nonnative species) is broken up among different agencies. This becomes confusing when discussing policy or executing regulations because "many organisms cause problems or potentially cause problems in all three of those areas," says Lodge. Jamie Reaser, chief scientist at the pet industry's organization, Pet Industry Joint Advisory Council (PIJAC), agrees. She would like to see a "biosecurity approach"—one that would unify the different agencies involved to develop a comprehensive action plan that would be both cost- and time-effective.
Jenkins, Reaser, Lodge, and others also point to the severe lack of resources that prevents new regulations on live-animal and plant imports. The U.S. is "way understaffed and underresourced" to even implement regulations that are "already on the books," says Reaser. "That's . . . a result of long-term erosion of wildlife protection and natural protection."
The lack of political will to tackle environmental problems, scant resources, and the patchy regulatory system aren't the only speed bumps on the road to developing a more efficient regulatory approach to the invasive species problem. "In general, Americans are very reluctant to interfere with commerce," says Dianna Padilla, a marine ecologist at the State University of New York Stony Brook. Many scientists point to the pet industry's reluctance to be regulated, although Lodge points out that some of the early opposition in the 1970s and 1980s was justified, because of inaccuracies in risk analysis back then. However, Reaser points to PIJAC's contribution to the development of the NISC management plan and insists that "there is probably more common ground (between industries, scientists, and environmentalists) here than is being currently recognized."
Ultimately, the financial incentives for risk-based screening of live animal and plant imports are huge. Jenkins estimates that in 2004, the U.S. spent $400 million to tackle diseases resulting from animal imports. According to one estimate by ecologist David Pimentel of Cornell University, the U.S. spends about $120 billion per year in damage control from invasive species. That number is probably conservative, according to the Ecological Society of America.
Countries like Australia and New Zealand that have taken strong preventative measures on imports are already profiting from their efforts. In January 2007, Lodge, Keller, and economist David Finnoff of the University of Wyoming published a paper in Proceedings of the National Academy of Sciences U.S.A. (104 [1], 203–207), in which they showed that Australia's plant quarantine program, in place for more than 10 years, has already paid for itself and continues to reap bountiful economic harvests. "It saves Australia money simply on the basis of avoided damages from agricultural weeds and avoided costs in herbicides and labor," says Lodge.
"We can run around trying to get rid of things once they invade, cleaning up messes once they're a problem," says Padilla. But ultimately, "we must be more risk-averse."
