Alien invasives don’t fly into your backyard from Neptune, nor do they have three eyes or beam hostages up into their UFOs. But sometimes they do strike fear into the hearts of those who recognize them. Or they should.

Alien invasives, those in our backyards, woods and waterways, are nonnative plants, animals and insects that get a root–, claw– or foothold on our land. They may appear innocuous, but in reality they prove harmful to human health, the environment and our economy. By some estimates, invasives cost the United States more than $100 billion a year.

Yet every spring, the annual crop of gardening catalogs arrives full of photographs inviting us to buy these plants. You can purchase Russian olive shrubs, mimosa trees or even bittersweet, a vine that scales trees and smothers them. One catalog boasts that it “produces sunny yellow seed pods that give way to bright red, decorative berries.” The songbirds and floral industry “love” this “attractive plant, and so will you!” All yours, two for $7.99.

Every time I see bittersweet, I remember a friend who labored for years to eradicate it from his farm. He cut trees, burned vines and sweated to restore his land.

Ironically, my friend’s work was funded by government grants. The paradox here is that prevention—stopping these species from entering our country—is cheaper and easier than eradication. A recent study published by the National Academy of Sciences verifies this. Researchers analyzed Australia’s policies regarding invasive plants. They found that a screening program that prevents the entry of unwanted invasives paid for itself in 10 years while protecting that country’s environment and saving its economy millions of dollars. As David Lodge, a co-author, commented, “Screening is the next step in improving U.S. policy.”

The savings often come from avoiding the expensive measures to eliminate pests. In 2003, for example, federal and state agencies spent more than $14 million to slow the spread of the gypsy moths in a 10-state area that included much of the Chesapeake Bay watershed. Yet, the United States has no invasive plant screening program. Hence, I can buy that bittersweet if I want to, regardless of the consequences.

Why all the worry? Because they can spread quickly and have few predators, these invaders can wreck an ecosystem.

Take garlic mustard, a biennial herb now found throughout the mid-Atlantic. Garlic mustard tolerates shade and kills soil fungi. This translates into an ability to spread into mature forests and create profound changes. Scientists discovered that the fungi that garlic mustard kills are essential to dominant hardwoods like maple and ash. Seedlings from these trees did not grow where garlic mustard established itself.

So what will these forests look like in 50 years when no seedlings exist to replace canopy trees as they die?

Or take the nutria, a muskrat-like mammal imported from South America around 1900 for its fur, which never became popular. The nutria escaped, produced as prolifically as rabbits, and are now found along the Gulf Coast, the Atlantic seaboard and in the Pacific Northwest. They have decimated thousands of acres of mid-Atlantic marshland. In a single Maryland county, experts estimate nutria destroyed more than 7,000 acres of salt marsh in the last 40 years.

Or consider the hemlock woolly adelgid, a tiny aphid-like insect from Japan that has already killed thousands of hemlock trees in the mid-Atlantic. These miniscule creatures suck the life out of 80-foot trees. Once struck, the hemlock usually dies within five years. We already lost the chestnut tree to a foreign blight; what will happen to our cool mountain streams once the evergreen hemlock also disappears?

While invasives have forever altered many ecosystems, we humans can save what’s left. For starters, Congress must create an effective screening program, like Australia’s, that outlaws the sale of invasive plants and animals.

Until Congress does this, people can educate themselves and others, eradicate these invaders from their property and stop buying these plants. Likewise, citizens can urge their state legislators to enact restrictions. For example, Massachusetts has outlawed barberry and burning bush.

One last solution: Eat a few of these foreigners. Joe Franke, author of “The Invasive Species Cookbook,” claims that “it’s time to put all of those grumbling stomachs…to work in a way that benefits biodiversity conservation.” Franke provides recipes for hundreds of ways to do your ecological duty while filling your bellies for free. As Franke claims, “If you can’t beat ’em, eat ’em.” Maybe it’s time.

Distributed by the Bay Journal News Service