By ROWAN SHARP/ecoRI News contributor
In his bestselling book, “The World Without Us,” Alan Weisman painted a vivid picture of Manhattan without people. He described how the physical infrastructure would degrade, and which plants would take over. One of the most ubiquitous plants, Weisman asserted, would be a Chinese shrub in the acanthus family. This hardy invader, brought to New York for landscaping, would thrive and even dominate in a post-human ecosystem — a more lasting human mark on Manhattan than the subway or the Empire State Building.
Not every non-native species is invasive. Invasives are those that, reproducing outside their native range, actively cause ecological or economic harm, according to the Invasives Species Act of 1996.
Lately, much attention has come to aquatic invasives in Rhode Island for their impact on human well-being. The Ocean State has some of the most invaded watersheds in the country — more than a quarter of the plants and animals in our watersheds are non-native, according to an analysis by the University of Rhode Island and Stanford University professors. Freshwater invasives have created nuisance conditions to the point of public outcry, and marine invasives pose a serious economic threat.
Dale Leavitt, Ph.D., an associate professor and regional aquaculture extension specialist at Roger Williams University, has worked in the aquaculture field for the past 30 years. Leavitt estimated that 75 percent of a Rhode Island oyster farmer’s workload consists of controlling “fouling organisms,” creatures that cover bags and structures where oysters are grown. They limit water and nutrient flow, and can stunt oysters’ growth or even kill them. Most fouling organisms are invasive.
Oyster farmers here may never have experienced their industry without such woes. Some of these critters — particularly a family of small invertebrates called tunicates — have colonized Rhode Island for about 40 years, and the oyster industry here is fairly young.
Still, Perry Raso, an oyster farmer in Matunuck, said he sees more invasives every year. “It’s hard to measure, but it’s certainly increased labor,” he said.
With larger species, like the crabs that nibble away at his oysters, Raso uses traps, but he said these aren’t very efficient. The Coastal Resources Management Council (CRMC), the state agency that monitors marine invasives, has left “test bricks” in his oyster farm, which are quickly encrusted with troublesome species.
These “test bricks” are just one facet of the CRMC’s marine monitoring project, now in its fourth year. This project keeps tabs on marine invasives at five floating dock sites. The CRMC’s marine invasives program is federally funded under the Invasive Species Act, and the CRMC, in turn, funds other survey, education and outreach programs, such as the Narragansett Bay National Estuarine Research Reserve and the Rhode Island Natural History Survey.
Marine invasive species are challenging to control. Most have a free-floating, planktonic life-cycle stage, where they’re invisible to the naked eye and could be swept just about anywhere on the tide. And it’s hard to stop new ones from coming in. It’s probably just a matter of time, Leavitt said, before the Japanese mitten crab, a significant shellfish predator, makes it to Rhode Island.
However, the CRMC’s Kevin Cute said the agency plans to expand its work from monitoring to “early detection and rapid response,” because the best way to combat invasives — and, in many case, the only way to eradicate them — is to catch them early. Surveys, and upcoming detection and response programs, are part of Rhode Island’s Aquatic Invasive Species Management plan, which was written by Cute.
The CRMC also is organizing Rhode Island’s first conference on marine invasives, tentatively planned for Aug. 17. “While we’re doing a lot of work in monitoring right now, we clearly recognize that there’s more work to be done,” Cute said.
Globalization of invasives
Some species exchange is natural. There’s always been drift — plankton moving in the tide, seeds scattered by storm winds or birds. Ecosystems change over time. Earlier human cultures brought hitchhikers with them as they migrated. But comparatively, today’s invasive species levels are massive. Off the charts. The reason? Human globalization.
Rhode Island’s struggle with marine invasives is “a direct result of us becoming that much more global,” According to Leavitt. “I’m not sure how to deal with it,” he said. “You can’t stop the mobility. You can’t stop global shipping, for instance.”
Shipping, by air and sea, is the primary cause of marine invasives, according to a 2006 study. The United States and China exchange species at a particularly high rate — a result of global trade and our ecosystem similarities. Chinese species tend to thrive in the United States, and vice versa. And foreign species established here are prime for secondary transfer to another region.
Leavitt, who sits on the Rhode Island Biosecurity Board, said that tougher regulations recently were proposed in China for ballast water in cargo vessels, a key carrier of marine invasives. But species encrusting the hulls of vessels remain unregulated.
The aquarium and water garden industry also is a significant contributor. Lionfish, an Indo-Pacific species popular among aquarium hobbyists for their dramatic — though venomous — spiny fins, have been released from captivity on the East Coast and have established here. They’ve even been caught at Beavertail State Park, Leavitt said. While the fish hail from warmer waters and decline significantly in winter, climate change could alter that equation.
Many freshwater invasives also stem from the aquarium and water garden industry. Or, more accurately, the hobbyists who romantically think they can “liberate” unwanted fish or plants by dumping them in waterways. Sue Kiernan, deputy chief of water resources at the state Department of Environmental Management (DEM), said her staff has found colored gravel from aquariums at the shores of local lakes and ponds. Kiernan said a law is in place permitting DEM to ban certain invasive aquatic species from the state, but the list of species has yet to be decided.
The bounded nature of freshwater bodies makes mitigating invasives possible, though not easy. But flow between water bodies is still an issue because most lakes in Rhode Island are manmade impoundments, still connected to the rivers they once were. Seeds and plant fragments can and do flow between them.
A growing outcry against freshwater weeds in Rhode Island originates mainly from lakefront property owners and focuses on “nuisance species” that impede recreational boating or fishing, or lower the value of lakefront real estate. Many non-native species, like fanwort and variable milfoil, clog water surfaces and can make boating and fishing difficult or impossible.
The large statewide group Save The Lakes was founded in 2007 and now includes more than 25 local lake organizations. Linda Green, director of the URI Watershed Watch, which also has begun to monitor invasives, sits on the group’s board. Save The Lakes has successfully agitated for more attention to freshwater weeds from DEM, and last year launched a pilot volunteer program that placed educators at freshwater boat launches around the state. Other states, such as Maine, have stringent boat launch inspection programs to keep unwanted species from spreading.
Most of the concern over freshwater plants has focused on human nuisance, not overall ecological harm, but Kiernan suspects that the two overlap. She explained that certain pondweeds, at a level upsetting to people, have probably also “reached a tipping point … that negatively affects the ecology.”
Little research has so far been done on this, however. And David Gregg, director of the Rhode Island Natural History Survey, said the fight against freshwater weeds poses an interesting question: “Do people have a funny understanding of what a healthy lake looks like? Do we need to adjust our expectations?”
Freshwater weeds are mitigated by type. Some, such as the water chestnut, can be effectively hand-pulled. But fanwort and milfoil can sprout whole new plants from fragments of their stems, so hand- or machine-removal can make the problem worse. For these, some use aquatic herbicides; DEM issues 50 to 55 permits a year for application of EPA-approved herbicides in public and private waters around Rhode Island. The department has not yet responded to requests for more data on the herbicides used.
There are a range of other methods for containing or eradicating freshwater invaders — floating nets, mechanical harvesters, dredging and water drawdown. Many methods require DEM approval and can be costly.
Currently, there is limited funding available for state-run mitigation projects, according to Kiernan. Though “it’s the department’s intent to get a program started” to handle freshwater invasives, Kiernan said funding is pending in the governor’s budget and still subject to a vote.
The statewide response to invasives is fragmented, because the problem is a sprawling one. Different agencies and groups address certain species, but neither Rhode Island nor the United States has an overall program to contain existing invasive species or guard against new ones.
“It’s so diverse, and its impacts are so diverse that it’s really hard to say that it’s a single subject,” Gregg said of the invasive species issue as a whole. “It’s a problem that we know how to do something about, but for a variety of reasons, we haven’t really wrapped our arms around an effective way of dealing with it.”
One reason may be that the problem, at a macro-scale, is as big as globalization itself.
Most invasives are likely here to stay — even, if, as author Weisman imagines, we aren’t. “The World Without Us” reminds us that if humans disappeared tomorrow, our redistribution of species would be a legacy to outlast our skyscrapers and highways.