Since 9/11 (three years ago tomorrow), national security has necessarily jumped to the top of all political agendas. Borders have tightened, government installations have gone on alert, and heaven help you if you leave your fingernail scissors in your carry-on bag!
But in the midst of the furor over keeping terrorists from crossing North American borders, another set of invaders crosses them daily. They go by names many cannot pronounce, spread across the countryside under our noses, and inflict billions of dollars worth of damages every year.
I am speaking, of course, of invasive species. Weedy species of plants and animals such as Scotch broom (shown in the picture), purple loosestrife, leafy spurge, lake trout and hogweed. 
Nationwide in the United States, roughly 400 invasive species cost the country about $138 billion in economic damages and associated cleanup costs per year (For comparison, in two installments so far the US Congress has appropriated $135-150 billion dollars to fight the war in Iraq). The wallet isn’t the only place it hurts: invasive species often out-compete native species that themselves provide food and habitat for other species and support entire ecosystems.
This problem reaches a similar scale here in Cascadia. In Washington and Oregon, aggressive, non-native weeds have overrun more than 400,000 acres of federal forestland, close to 2 percent of these states’ total. Idaho has more than 8 million acres infested with nonnative weeds, at a cost to the state of about $300 million per year (pdf) .
These weeds know no borders. They are not simply confined to remote forests and wilderness areas, but affect farms and ranches as well. In Oregon, ranches infested with leafy spurge, a particularly noxious invader, have been selling for about 10 percent of their pre-spurge value. Nationwide, the annual losses in crop productivity alone due to noxious weeds are estimated to be $7.4 billion.
(Find your state’s worst weed here. And see lists of noxious invaders here for Washington, Oregon, and Idaho.)
Forests and farms aren’t the only things hit hard by the plague, however; area wildlife is as well. Invasive weeds are, by definition, out of place in their new ecosystems and often out-compete native plants that provide food or shelter to native fauna. In coastal Washington, the spread of Spartina grass (pdf) has reduced critical habitat for shorebirds, juvenile fish (including salmon) and oysters (a multi-million dollar a year industry), and increased the threat of floods. (Similar wildlife impacts are evident in Idaho (pdf)). In fact, more than 40 percent of the species listed as threatened or endangered under the Endangered Species Act are imperiled primarily by bio-invasions.
And the ranks of the invaders are not filled solely by plants. Recently, for the fourth time, authorities stopped a pleasure boat with tiny, juvenile zebra mussels (see photo at right) stuck to its hull as it was heading into the Northwest on a trailer. This boat was intercepted in Spokane, en route to Puget Sound.
The diminutive mollusk represents everything distressing about invasives. 
It is hard to detect (it’s microscopic at birth and never more than about an inch long), highly destructive, and almost impossible to eradicate. It could wreck havoc on Cascadia’s watersheds, hydropower infrastructure, and irrigation and navigation systems, as it has begun to do in 22 states and two provinces (see this animation). Most smaller boats entering the Northwest are never inspected, so the zebra mussel may be establishing itself in the land of salmon even now. So far we appear to have been lucky, but in practice Cascadia has few defenses in place. In the case of the mussel, experts believe it’s only a matter of time.
Invasive species are organisms out of place. (Though most local invaders hail from Eurasia, the Northwest has done some exporting as well. Douglas fir has dramatically altered forest composition in Europe, and the rainbow trout has been nominated as one off the 100 worst invasives in the world.)
Adaptable and prolific, they thrive in ecosystems that have been cleared, disrupted, or otherwise “disturbed,” in biologists’ lingo. Disturbances were relatively rare and sporadic in the prehistory of Earth: fires, floods, windstorms, and landslides kept things from growing stagnant. But disturbances-and species transport-are commonplace now, in the era of 6 billion humans and globalization of commerce and travel. Ironically, instead of promoting ecosystem diversity, wide scale disturbance is now slowly reducing it.
Thus, Scotch broom festoons the roadsides of Washington and spotted knapweed follows horse trails through national forests in Oregon. Even one garden can be enough to start an invasion, as this Seattle Times article details.
Worst of all, the number of these species moving into the Northwest has been increasing since the middle of the twentieth century, after declining from its all-time peak a century ago.
Homeland security, it seems, means not only protecting ourselves from terrorists but also securing our land from the unwitting spread of noxious plants and aggressive animals. This latter threat, while it lacks a villainous mastermind holed up in some mountain fastness, does not lack for victims. Nor does it lack for heroes.
Many organizations and individuals have taken up the fight against bio-invasions. Most recently, for example, the Fraser Basin Council pulled together a provincial Invasive Species Strategy. (Check out the following links to see what’s being done in Washington, Oregon, and Idaho.)
Despite the fine efforts of many, the fight against invasive species still suffers from a lack of funding and
public awarene
ss. It cannot be successful until we begin to close the gap between the effort we put into stopping biological invaders and that we put into stopping the human ones.
