Instead of Mulder and Scully, the President has named three of his most senior ministers to head a new Invasive Species Council. "There is no question that we are being invaded by alien species," said Under-Secretary James Baker. "We could call this order the X-Files order." Another member, Bruce Babbitt, the Interior Secretary, added: "The costs to the economy are racing out of control."
Nearly half of the country's endangered species are being threatened with extinction by the invaders, introduced to the US either directly by gardeners and pet owners or accidentally through trade and international travel. The leafy splurge, a weed from Europe and Asia, now plagues more than three million acres of rangeland in the western prairies. A Chinese ant is chomping its way through buildings in California. And the zebra mussel, again from Asia, has done more than $5bn (pounds 3.1m) of damage by clogging pipes in 19 states after arriving in the Great Lakes region aboard freighters.
There is nothing new about invading species. In 1980 an eccentric American introduced 60 starlings to New York Central Park on the strength of their being mentioned once in the works of Shakespeare - in a single line in Henry IV Part I. Now more than 200 million of them plague the country.
But what has alarmed the government is the range and rapid spread of the invaders. There are thousands of alien species in the US and the number is rapidly growing, according to leading Harvard biologist Edward Wilson.
The Asian gypsy moth, a threat to US forests, has been turning up in the Pacific north-west after arriving on grain carriers from East Asia. The moths are particularly drawn to the wavelength emitted by the ships lamps, and fly, dazzled in their beams, all the way across the Pacific. The Asian walking catfish and 20 species of lizards, all brought in by the pet trade, are spreading through Florida, while hydrilla, a popular aquarium plant, is now clogging up nearly half of the nation's rivers and lakes. And the European green crab, brought in in ships' ballast water, is devastating native shellfish in San Francisco Bay.
David Wilcove, senior ecologist at the US Environmental Defense Fund, calls the invasions the least recognised threat to wildlife today. But it is not all one way. North American crayfish are wiping out their European cousins; a jellyfish from the US has devastated the Black Sea, and the ruddy dove, brought to Britain by the great naturalist Sir Peter Scott, is killing off a native relative.