Lax enforcement of the rules on importing wildlife risks harming both ecosystems and people
ALMOST every country has at least one environmental scare story involving exotic species. One of America’s recent tales of woe involves the zebra mussel, which arrived in 1988, probably in ballast water from ships. Over the past two decades this Russian native has disrupted ecosystems, competing successfully for food with local species of mussels, whose numbers are much diminished. The bivalve damages boats and harbours. Its larvae get sucked up into power plants and water-treatment systems, where they grow and wreck the mechanisms. The cost of the effort to remove the molluscs and repair the damage they cause has been estimated at $5 billion a year.
Such environmental catastrophes can at least be described as accidents. Not so, however, the disastrous introduction of Nile perch to Lake Victoria 50 years ago. The fish were placed in the lake as a catch for local fishermen. However these large predators ate up all the other fish that the locals used to eat.
Not all introduced species become a problem. Only a tiny share of alien species actually manage to establish themselves in their new home.
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