This ash tree has been attacked by the emerald ash borer. The larvae create long serpentine tracks under the bark. The bark is pock-marked with D-shaped holes where the adults chewed their way out. A few leaves are a hopeless effort to survive. Photo courtesy of Steve Sorensen

People talk a lot about aliens these days, whether they’re super-intelligent beings from some faraway planet, or human beings entering the United States from other parts of this planet. There’s another alien invasion, and it doesn’t get much press.

When a non-native species enters an area, it’s an invasion. And it has been happening for a long time. In 1966 George Laycock, a leading wildlife expert of his day, published a book called “The Alien Animals” for the American Museum of Natural History.

The book details many alien species. Like human immigrants (and maybe even space aliens if they’re here), not all pose a threat.

Take the brown trout. Those hook-jawed lunkers fishermen dream about are an alien species brought from Europe. And the ringneck pheasant, from China in 1882 (150 years after an earlier failed attempt). These provide treasured fishing and hunting opportunities, no one wants them to go away, and they do no harm to stream or land ecology.

Others are harmful. Today, it’s spongy moths (formerly called gypsy moths). And it’s kudzu, the insatiably aggressive vine that is smothering the American South. These are two of more than 300 other plant and animal species in North America that are not native.

Wherever humans go, creatures of one stripe or another will hitchhike along. One historian says coyotes found their way to Alaska by following the trail of dead horses left by prospectors seeking Klondike gold.

Man has been importing non-native wildlife to North America for centuries. Some devastate the environment. Wild pigs, sometimes called Russian Boars, came originally from Europe more than 100 years ago. Too bad we can’t send them back.

The original plan was for the porkers to populate a fenced enclosure to create a “hunting” opportunity for wealthy businessmen. They escaped (the pigs, not the businessmen), and their relentlessly growing numbers eat birds, small mammals, reptiles, the eggs of ground nesting birds (turkeys and grouse), acorns, the roots of endangered plants, and more.

Yes, that was a mistake, but hunters are not the guilty ones today. People other than hunters, however, play a large role in disasters caused by invasive alien species.

Did you know pet owners populated the Florida Everglades with Burmese pythons? They simply released them when they grew too large. Out of kindness, I suppose. Too bad the kindness didn’t extend to the countless victims of these enormous, ravenous snakes, now numbering more than a million (and growing) in South Florida. Soon pythons in Florida will be as populous as deer in Pennsylvania. (When you hit a python on the road, do you need to escape before it coils itself around your car?)

Pythons are not the only invasive species courtesy of pet owners. Domestic cats are often released in rural areas and left to fend for themselves. In Australia, domestic cats gone feral have driven 20 species to extinction, and threaten a hundred more. In North America, cats kill songbirds by the billions annually. It might seem kind to spare the life of a single unwanted cat by releasing it to fend for itself, but every cat directly causes the deaths of hundreds of other animals. Feral cats don’t pass the kindness on.

Invasive aliens are not limited to plants and animals. Zebra mussels originally came to the United States on ocean-going vessels from Russia and the Ukraine, and are spread from lake to lake by fishermen and recreational boaters.

The emerald ash borer is a beetle that is killing valuable ash trees, including a tree in my yard. Another tree-killing insect is the hemlock woolly adelgid, on pace to kill most eastern hemlocks in the U.S. within a decade. Imported from Japan and east Asia.

Who doesn’t like birds? A few fans of our feathered friends wanted the United States to be home to all bird species mentioned in Shakespeare’s works–an odd goal, but it’s why we have starlings. A wealthy immigrant to Cincinnati, lonesome for familiar, songful birds of Europe, imported some 4,000 of them. Years later, the Cincinnati Society of Natural History said, “the general principle” behind this effort was “zoologically speaking, a wrong one.”

Do modern hunters harm nature? Do their controlled harvests create problems? Nope, never. As highly visible as hunters are, unfair blame is often laid on them for doing what is legal, scientifically justified, and beneficial for wildlife. Meanwhile, people who cause an invasion of alien species are invisible to the public, but they introduce new warriors to the battles being waged in nature–warriors that have no business on our continent.

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When “The Everyday Hunter” isn’t hunting, he’s thinking about hunting, talking about hunting, dreaming about hunting, writing about hunting, or wishing he were hunting. If you want to tell Steve exactly where your favorite hunting spot is, contact him through his website, www.EverydayHunter.com. He writes for top outdoor magazines, and won the 2015, 2018, and 2023 national “Pinnacle Award” for outdoor writing.