Cover

UNWELCOME IMMIGRANTS

They’re called invasive exotic species, and they’re doing a lot of damage

June 2 2003
Cover

UNWELCOME IMMIGRANTS

They’re called invasive exotic species, and they’re doing a lot of damage

June 2 2003

UNWELCOME IMMIGRANTS

Cover

They’re called invasive exotic species, and they’re doing a lot of damage

READY OR NOT, here they come. In its newly published Nature Audit, World Wildlife Fund Canada sounds the alarm about eight particularly threatening species—from fungus to fish—poised to infiltrate the Canadian environment. What the scientific community calls invasive exotic species are already well established among us—at least 1,500, and likely many more, plants, animals and other organisms that weren’t here before the Europeans turned up. Some were brought in intentionally, for decoration, food or other purposes. Others were unexpected guests, including hitchhikers in ballast water and packing material or on migratory birds. Once they gain a foothold, they’ve proven extremely hard to dislodge, as Lake Erie’s tragic experience with two invasives in particular dramatically illustrates (page 36). Now these newcomers are set to cause trouble right across Canada:

Emerald ash borer: Great efforts are being made to confine this Asian beetle to the Windsor/Detroit area where it has been killing the ash, a tree that’s abundant from Manitoba to the Atlantic provinces. It likely arrived in the wood used in packing cases for sea-going freighters.

Asian longhorned beetle: Another Asian inhabitant of shipping containers, it goes after maples as well as other forest and ornamental trees. Found in several states, it has been intercepted in Vancouver and southern Ontario.

Sudden oak death: This fungus that kills oaks, maples, Douglas fir and other trees turned up in California in 1995 and has made its way as far north as Oregon.

Asian tiger mosquito: A southeast Asian in-

sect capable of transmitting yellow fever, dengue fever, encephalitis and possibly the West Nile virus, it has been spotted in 26 states and southern Ontario.

Waterthyme (hydrilla): Expected shortly in the Great Lakes and B.C., this Asian water plant grows in thick mats that overwhelm waterways and seriously disrupt swimming, boating and fishing.

Whirling disease: This Eurasian parasite, in 22 states and spotted within 100 km of Alberta, attacks trout and salmon.

Bighead carp: An electric shock barrier may not stop this large Chinese carp, now thriving and displacing native species in the Mississippi system, from reaching Lake Michigan through a canal at Chicago.

Asian shore crab: A highly reproductive native of the western Pacific, it is crowding out native crab species on the U.S. east coast and heading toward Atlantic Canada. 171