Invasive plants and animals — they’re everywhere!

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The RoVing Naturalist

 By Dennis Prichard


Dennis Prichard

“Rolling along like a tumblin’ tumbleweed.” The Sons of the Pioneers sang this tune way back in the day about a plant that is synonymous with the Old West. It could just as easily describe our RV way of life. Nothing could be more American than tumbleweeds across the True West, right? Not so fast, pilgrim. Tumbleweeds are not native to the U.S. They came here from Russian steppes, found a habitat and a niche that were open for the taking, and settled into our folklore. 

Early in my career as a wildlife refuge manager people would ask, “Do you have any invasive species on your refuge?” By the time I retired 30+ years later the question was “How many invasives do you have on your refuge?” It was a given that the invaders were now part of the landscape. Plants and animals can travel farther and faster than ever before, and we oblige them with all our means of transportation: air, water, roads, even our own two feet. Some of this was intentional, some unknowingly so.

Plants are obvious invaders with a jillion examples: purple loosestrife in the north, kudzu in the south, Brazilian pepper in Florida Everglades, and Johnson grass almost everywhere. Saltcedar lines the waterways in the west, each plant sucking up to 200 gallons of water each day and transpiring it to the atmosphere. The salt that remains in the leaves accumulates in the soil when the leaves drop in the fall effectively limiting all other native plants from germinating. Tamarisk, as it’s known by scientists, soon has the playing field all to its own. Game over.

Animals too are finding new haunts via our help. Chuck Woodbury just wintered in Texas and probably saw more Axis deer than the native whitetail. Oryx and Barbary sheep from Africa out-compete pronghorns and mule deer for precious forage, while nutria and feral hogs rip up fragile habitats all along the Atlantic and Gulf coasts. A certain person thought it would be grand to have every bird species that Shakespeare ever wrote about brought to New York City, so after transplanting them here, we now have European starlings and English sparrows all across North America. Thanks a bunch! Eurasian collared doves have spread continent-wide in just a few decades, pushing aside the native mourning doves. Cattle egrets, those white birds standing in fields next to grazing cows, are native to Portugal and Africa. They first bred in America around 1953. By 1962 they were common in Canada. They now inhabit the entire western hemisphere.

A weed, by definition, is a plant out-of-place. Water hyacinth is beautiful in bloom, but so chokes waterways and drinking water intakes that it now costs us billions of dollars to control. Field bindweed covers pastures with pretty little flowers, but sends a root down 15 feet and secures all the nutrients for itself, eliminating native grasses and flowers. Dandelions are now established on Isle Royale National Park way out in Lake Superior, 22 miles from the nearest mainland. They took root around the boat docks from the seeds attached to boaters’ shoes. California’s eucalyptus trees didn’t grace the boulevards before the 1850s.

Nature sets the rules of who-eats-what in a habitat. If there are no predators to control a species, and there’s plenty of food, water, shelter and space for the newcomer, the niche is soon filled, and the race is on for the most adaptable species to survive. Arguably, humans can be considered one of the best invaders of all life forms as we have infiltrated every continent bringing our habitat components with us wherever we go. We are the best invaders of all time. So as we keep tumblin’ along in our tumbling RVs, realize we too are invaders just looking for a new place to inhabit. It’s in our nature!

Dennis Prichard is a retired park ranger. He’s worked and studied wildlife at many National Parks and Wildlife Refuges including Carlsbad Caverns, Mammoth Caves, the Everglades, Sequoyah NWR in Oklahoma, Sevilleta NWR in New Mexico, and Isle Royale National Park, to name a few. He travels in a fifth wheel with his wife and dog, a Labrador named Cricket.

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