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More action needed to stop invasive species

david strayer
Freshwater Ecologist

Humans have carelessly moved thousands of species outside their native ranges through activities such as transfer of ballast water, release of pets and bait, movement of untreated wood, escapes from agriculture and aquaculture, and deliberate release of species that we thought to be beneficial. Many of these species have had large, unwanted impacts on ecosystems, economies, and human health.

We don’t have a good comprehensive accounting of the total effects of invasive species in New York, the United States, or the world.

However, we do know invasive species are one of the most important ways that humans are changing ecosystems all around the world, that they cause enormous economic damages (estimated to be more than $100 billion per year in the United States alone), and that they harm and kill Americans every year.

We also know that New York is one of the most heavily invaded parts of the world, and suffers disproportionately from the impacts of invasive species.

Invasive species can cause large changes to our ecosystems

Even a single invasive species can turn an ecosystem upside-down. Let me illustrate this point by describing how the zebra mussel changed the Hudson River. Our research group has been studying the Hudson continuously since before zebra mussels arrived, so we have good measurements of zebra mussel impacts.

Zebra mussels are small mollusks native to Europe that came into North America in the mid-1980s, probably in untreated ballast water. They first appeared in the Hudson in 1991, and by the end of 1992 had reached a population of 550 billion animals.

Zebra mussels are filter-feeders, and the huge population in the river filtered a volume of water equal to all of the water in the Hudson every 1-4 days. As a result, the amount of plankton in the river dropped by 80 percent. Because plankton is one of the important foundations of the food web, many other species were affected. For example, 1,000 tons of fish food disappeared (this amounts to half of all the fish food in the river).

One result of this was that the number and growth rate of Atlantic shad dropped substantially. This fish is doing so poorly that the historically important commercial and recreational fisheries for this species were closed for the first time ever in 2010, and the zebra mussel has just added to its problems. Zebra mussels changed nearly everything that our group measures about the Hudson — water chemistry, water clarity, and the populations of many other plants and animals in the river.

The zebra mussel is not the only species humans have brought into the Hudson. A study led by Professor Edward Mills of Cornell University found that the fresh waters of the Hudson River basin contain more than 120 non-native species. Six or seven new species arrive each decade. In the past few years alone, we’ve seen snakehead fish, hydrilla plants, Chinese mitten crabs, and Asian clams appear in the Hudson basin, all species capable of ecological and economic harm.

And it’s not just the Hudson that’s being invaded — every part of the state now suffers economic and ecological damage from established invaders and is endangered by new invaders waiting at the doorstep.

New Yorkers living in cities and suburbs will likely pay billions to remove and replace ash trees killed by the emerald ash borer, communities along the Great Lakes and Finger Lakes are seeing valuable fish killed by viral hemorrhagic septicemia. The autumn tourist and maple sugaring industries are imperiled by the spread of the Asian long-horned beetle. Our farmers have to deal with stink bugs and plum pox and now wild boars. Hundreds of New Yorkers have been sickened and dozens killed by the West Nile virus — and so on.

We have many good tools to reduce the movement and effects of invasive species, but we need to use them. We can treat ballast water, keep potentially harmful species out of the pet, horticulture and aquaculture trades. We can stop moving untreated wood, better inspect our ports of entry and educate the public.

Here in New York, we have made a good start with the Invasive Species Council, the Office of Invasive Species Coordination and the programs they oversee, but these programs have too few people and too little money to take advantage of all of the good opportunities we have today to better manage invasive species.

I worry our children and grandchildren will someday look out onto a world filled with undesirable and unmanageable invasive species as they pay bills for problems we created and wonder why we did so little when we knew invasive species were a problem and had the tools to stop them.

Why are we doing so little?

david strayer
Freshwater Ecologist

Dave Strayer is a freshwater ecologist whose work focuses on measuring the long-term effects of zebra mussels on the Hudson River ecosystem, and understanding the roles of suspension-feeding animals in ecosystems. Strayer also works on broader issues in freshwater conservation ecology and invasion biology.

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