Know Your Neighbours: Paddling With Coastal Invaders

February-March 2006

This is an article from WaveLength Magazine, available in print in North America and globally on the web.
To download a pdf copy of the magazine click here: > DOWNLOAD

by Bryan Nichols

All over the world, millions of invasions are underway right now. Many islands and lakes are being hard hit, and both coasts of North America are being irrevocably changed. Who are these invaders? They’re foreign species, and they’re taking over.

On a basic level, the concept is simple: an invasive species is one your parents or grandparents never saw, a plant or animal from somewhere else that is now successfully reproducing in your neighborhood. The more successful its spread, the more invasive it becomes.

When Charles Elton wrote The Ecology of Invasions by Animals and Plants in 1958, it was largely ignored. Nearly 50 years later, his descriptions of ecological ‘explosions’ are being taken very seriously by scientists, environmentalists, public health experts and legislators. The book was republished in 2000. Why?

CHANGE IS BAD (ISN’T IT?)

It has become clear that invasive species can cause all kinds of changes, from a new critter appearing at your local beach to continent-wide ecological upheavals. These changes usually seem bad, for the locals anyway. For instance, for birds on the island of Guam, the invasion of the brown tree snake (Boiga irregularis) was an unmitigated disaster—nine of the island’s eleven species were completely gobbled up (see book review).

Many people believe invasive species are one of the primary causes of the mass extinction now occurring in the world. Aside from simply eating the locals, new species can out-compete them for food, pass along diseases to which they have no resistance, and even alter the ecosystems in which they live.

FOLLOW THE MONEY

Not surprisingly, the recent surge of interest in invasive species was probably influenced more by economic concerns than extinctions, notably the expensive and visible invasion of the Great Lakes by zebra mussels (see checklist). Much of the worry (and research funding) is related to critters that threaten established industries. Conservative estimates put the global cost of dealing with invasive plants and animals in the hundreds of billions of dollars annually. That kind of impact registers on even the most ecologically ignorant politicians and economists.

Why have invasive species become such a big deal? After all, species have a natural tendency to spread and have been crawling all over the planet for hundreds of millions of years. Why the sudden concern? If you guess that we might have something to do with it, you’re right.

ARCHITECTS OF INVASION

There’s a couple reasons why people are so important to the ecology of invasive species. First of all, we get around a lot. Thousands of ships and airplanes crisscross the world every day, and they carry much more than we intend. You’ve heard of rats abandoning a sinking sailing ship; a modern counterpart might be zebra mussels being flushed out of a supertanker’s ballast water. Or how about brown tree snakes hiding in the wheel wells of jetliners? Our planes, trains, boats and automobiles all carry a wide range of accidental tourists.

The second reason is human nature: we just can’t seem to resist tinkering with Mother Nature. Whether inspired by nostalgia, profit, curiosity or arrogance, we continue to try and ‘improve’ places by deliberately introducing animals and plants. Some of the more notorious examples include mosquitofish, mongoose, starlings and those rabbits that overran Australia. Thanks to our globetrotting, thousands of species are being deliberately or accidentally spread, wave after wave of potential invaders landing on new continents or swimming in new lakes and seas.

MUDDYING THE WATER

We often discover that ecology is more complex and subtle than we might prefer. On the coasts of North America, there is now considerable doubt as to which species are truly ‘native’. After all, ships have been sailing the world for centuries, but biologists haven’t been looking too closely at the birds and the bees all that time. When Vikings began visiting Canada, blonde guys with braids weren’t the only living things aboard their boats. When Columbus crossed the Atlantic nearly five centuries later, his ships undoubtedly had all kinds of critters attached to their bottoms. All those hitchhikers had centuries to become established before we began to examine which were newcomers and which were natives.

Many modern invasions are well documented though, so hop into your kayak for a trip around North America. For this checklist, we’ll look at some of the species that are invading our coasts right now.

Invasion Watching

Be sure to check out information specific to your locale, especially through regional government agencies or conservation NGOs. Reporting on the spread of invasive species like green crabs and Atlantic salmon can be helpful to industries and environmental groups. These websites will also be helpful:

  • 100 of the World’s Worst Invasive Alien Species, Invasive Species Specialist Group: www.issg.org. Features ecological troublemakers like rats, feral pigs and mongooses. They also have a species database.

  • Global Invasive Species Program: www.gisp.org. Up to date workshops, news and information.

  • Aquatic Nuisance Species Task Force: www.anstaskforce.gov. Information on watery invaders.

© Like numerous other species, biologist Bryan Nichols has been introduced to the state of Florida. Since it’s not clear whether he’ll be able to successfully reproduce there, he remains ornamental, not invasive