Another Kind of Genocide

Review of

Invasion Biology: Critique of a Pseudoscience

By David Theodoropoulos

Avvar Books, Blythe CA. 2003.

237+xiv pp. Paper. $14.50

One of my favorite ways of setting off small explosions is to tell a group of gardeners that I have no dislike of invasive plants. Since the polarization over the natives-versus-exotics issue is fierce, the discussion quickly heats up. But lately I've noticed some thinning of the ranks of the natives-only army, and the debate has grown much more nuanced and sophisticated. Many people still cling to the simplistic battle cry of "natives good, exotics bad" that was once almost the only view to be heard—or to get funding. But the murmurs of a few questioning voices have now grown to a full-scale argument, with a growing body of data on the "don't blame exotics" side.

David Theodoropoulos, a conservationist and founder of an excellent resource for seeds of multi-functional plants, J.L. Hudson Seedsman, has waded into the battle with an arsenal of scholarship. His book, Invasion Biology: Critique of a Pseudoscience, ranges beyond an examination of invasive-plant science (more properly, the lack it) and also explores the psychological, political, and cultural reasons behind our eagerness to hate certain species.

Theodoropoulos opens by reviewing the underpinnings of the anti-exotics movement, or invasion biology—the idea that certain organisms belong in certain places, and others don't. Quickly we see that unlike most scientific reports, papers in even academic journals such as Conservation Biology and Restoration and Management Notes bristle with xenophobic rhetoric: "all [species] should be treated as threats . . . unless proven otherwise." Species are labeled "nefarious," "stealing," "stormtrooper plants," and "intruders" that should be "weeded out" to "prevent their escape." Hardly the language of objective science.

Good science also requires that definitions and operating terms be rigorous and uniformly applied. Yet invasion biologists have not defined their terms and use them in varying, idiosyncratic senses. The usage of the words native, exotic, diversity, natural community, and other terms slip and slide in Humpty Dumpty fashion: The words mean whatever they want them to mean. What is a native? In the most recent one percent of the Earth's history, figs and breadfruit have grown in Wyoming, and neotropicals in Alaska. Elms and chestnuts thrived in California in the early Pleistocene—just yesterday. But no one calls them native to those places. And many species labeled as native turn out to have arrived a few years before, or a century ago, or 500 years. Native seems to mean simply, "It was here when I got here."

What defines a native's range? Monterey cypress, osage orange, and black locust are being exterminated as exotics only 100 miles from their accepted native habitat. Yet species can naturally extend their range that far in a few years.

And what is diversity? A patch of exotics and one of native plants can both offer equally high diversity, in all of the term's accepted meanings, whether number of species, species turnover, or relative abundance of each species.