Real science sometimes seems ominously similar to science fiction. When NASA warns that “invasive species may pose the single most formidable threat of natural disaster of the 21st century,” it is all too easy to picture the aliens from Independence Day dropping in on our planet to strip it bare. Even if the invaders themselves don’t seem all that scary—gray squirrels, zebra mussels, and purple loosestrife are a far cry from gun-toting extraterrestrials—the threat they pose certainly does. Intruders crowd out native flora and fauna, spread new diseases, and cause costly environmental destruction.
Then again, things are probably not as bad as they seem. Science differs from science fiction in a crucial, marvelous way. Fiction withers in the face of disbelief—the audience has to put its skepticism aside for the story to work. Science, on the other hand, thrives on disbelief. Researchers spend their lives kicking against the conventional wisdom, searching for the precious piece of evidence that confounds current theories. Often they find that the world is more subtle and complicated than anyone expected.
So it is with invasive species. As Alan Burdick reports on page 34, the latest studies dispel the headline-grabbing stereotype of invasive species as rapacious destroyers. Humans are spreading plants and animals around the globe, but many of the transplants never gain a foothold in their new environment. Of those that do, 90 percent have no significant effect on the surrounding ecosystem. They slip in quietly, like their predecessors that were transported by winds, ocean currents, or migratory animals. When native species die out, it is rarely due to direct competition from the newcomers.
Nature is quite accommodating; humans are the ones who rebel at a loss of control. We decry the effects of “invasive” fungal diseases on our farms, forgetting that the crops we grow and the livestock we raise are invaders. We ache to preserve native ecosystems as they were, but the world changes anyway, both with and without our help. What appears to be a simplistic disaster story is finally overpowered by scientific research and a better understanding of how our planet works. Science is constantly skeptical, and the result is often surprising—even to scientists.