Nieuws - 13 oktober 2011

Invasive species

In the classic horror film The Day of the Triffids, exotic plants threaten to take over the world. Is this pure science fiction?

Terms such as invasive or alien suggest that the influx of new species is anything but innocuous. Take the American Waterweed, an underwater aquatic plant. When some authority (who and why?) put a few specimens into an Utrecht canal in the middle of the 19th century, he could not have guessed that this aquatic pest would quickly become a hindrance to shipping and fisheries: the plants had to be combatted. Then by the latter years of the 20th century, the plant was having a hard time and was put on the red list. And so it went from exotic species to pest to threatened species.
Alien species come in all sorts and sizes, each with their own story. Sometimes they were deliberately imported, as the English cordgrass was to absorb sludge, and the American black cherry tree was to improve the quality of forest litter.
A few years ago it was calculated that the damage done by exotic species in the Netherlands costs 1.3 billion euros. So what should we do? This is a question that managers, policymakers and researchers are scratching their heads over.
Muskrats undermine dikes, so that requires action, but is this also the case for the giant hogweed, the Japanese knotweed or the aforementioned black cherry? The open places that you are left with if you root out this intruder from America are soon occupied by even more black cherries. Perhaps in many cases, patience is a virtue after all. This must be music to the ears of ministry of ELI&I officials, as patience doesn't cost money.