Humans transport some non-native species on purpose. Others arrive by accident. The vast majority don’t hijack landscapes. But those that do come with high stakes.
SHAWNEE, Kansas — Rogue ornamental pear trees line the roadways of eastern and central Kansas. They’re inedible to caterpillars and, as a result, crowding out food for baby songbirds.
Brush and grasses from Asia and Europe muscle wildflowers and grasses out of prairies, costing ranchers money and remaking fields once full of variety into pollinator-hostile monocultures.
Managing disruptive species from faraway places has become an unending part of the job for many ranchers, park workers and homeowners across the Midwest. That won’t change, and more plants, insects and fungi will inevitably arrive.
So communities have begun looking for tools to curb the economic and ecological costs of some non-native species that hurt wildlife, wipe out street trees and reduce forage for livestock.
Those tools range from rules against the sale of specific plants to fish-offs that turn invasive white perch into fodder for delicious family cookouts. They range from cities getting savvier about street tree plans to public workers and volunteers pouring long hours into keeping their local parks as sanctuaries for native species.
“As our landscape changes, we have to learn to adapt,” said Amy Bousman, an educator at the Kansas Department of Wildlife and Parks who teaches people to identify and repurpose invasive species.
Better to use silver carp for fertilizer and food, she said, than to fall into a paralysis fueled by frustration.
“If we have a bit of a perspective shift in how we approach it,” Bousman said, “then we can save ourselves a lot of emotional damage through anger and resentment.”
The never-ending job
At the Johnson County Park and Recreation District, a worker can spend a morning killing the Callery pear trees that pop up all over Shawnee Mission Park, then head out for lunch and spot the same species for sale at a local store.
“It can be incredibly frustrating,” said Matt Garrett, the district’s biologist and natural resource manager. “Pretty daunting.”
Mainstream society pays little attention to invasive species and their impact on green spaces and wildlife. That’s why determined landowners and public agencies find themselves pouring large amounts of money, time and herbicide into controlling vegetation that their communities continue to plant.
Workers have killed hundreds of large Callery pears at Shawnee Mission Park, and many more saplings and seedlings. They’ve spent years clearing bush honeysuckle species from Asia that clog the forest, smother springtime wildflowers needed by bees, increase the spread of tick diseases, hinder vision on hiking paths and make joggers feel less safe.
“When you’re in a high-quality natural area, the human psyche just feels comfortable,” Garrett said while showing a reporter the ongoing work in 2022. After clearing hundreds of acres of bush honeysuckle plants, “we have multiple forest understories where you can look in all directions.”
But birds will continue to carry seeds from nearby neighborhoods into the park and the troublemaking plants can bounce back fast. In the past, park workers cleared some forest understory but failed to maintain it. Five years later, the honeysuckle had won yet again.
“So the goal of our natural resource plan now is to do the work long term,” Garrett said. Teams need to “follow up each year and make sure that we’re building healthy forests.”
That includes replanting the forest floor with plants that do a better job feeding and sheltering pollinators, mammals and other wildlife — things like pawpaws, woodland goldenrods, riveroats, sedges, ferns and redbuds.
Raising public awareness and seeking policy changes
Frustration with the situation forges allegiances among public agencies, landowners, nurseries, gardeners, scientists, birdwatchers and hikers sick of certain species dominating landscapes in ways that squeeze out other plants and wildlife.
Nonprofit and volunteer groups in the Kansas City area help remove bush honeysuckle from green spaces and parkland to restore some balance.
They amplify outreach efforts to turn public opinion against purchasing the invasive Callery species sold under names such as Cleveland Select, Aristocrat, Chanticleer and Bradford pear.
Each spring, local governments team up with private businesses and conservation groups in northeast Kansas and Missouri to dole out free oaks, serviceberries and other native alternatives to anyone willing to kill a Callery pear on their property.
Those springtime campaigns may not remove significant numbers of the trees, but they generate news stories and social media conversations about invasive plants. And they raise awareness that gardening with native plants is a surefire way to feed wildlife instead of harming it.
In February, the Kansas agriculture secretary signed a rule that effectively bans the sale of Callery pears in the state, or even driving across Kansas City to purchase one in Missouri and bring it home.
The rule takes effect in 2027.
After the Kansas Department of Agriculture announced it was considering restrictions on the species, more than 300 people wrote to the agency. For a variety of reasons, more than 90% favored taking steps against the species.
Carol Baldwin, a rangeland management specialist with Kansas State Research and Extension, wanted to protect ranches and prairies.
“If you look across the state line into Oklahoma,” she said in public testimony, “you can see the absolute devastating damage that these trees have done to the native rangelands.”
Ranchers have a hard time stopping Callery pears from eating up grassland because prescribed fire usually doesn’t kill them. The Kansas Forest Service has found the species spreading wild in at least 50 counties.
In Missouri, where the tree can be found statewide, lawmakers held hearings this year on whether to ban the sale of this and four other other invasive plants.
Banning a species can hurt the sellers and distributors who invest time and money into the products. That generates opposition.
Even talking about the option irks some people who see a potential infringement on their personal freedoms.
The unpredictability of invasiveness
Humans transport some non-native species on purpose. Others arrive by accident.
The vast majority, like the peonies in your garden, don’t hijack landscapes. But those that do come with high stakes.
Last year, an intergovernmental body of scientists focused on biodiversity issues reported that invasive species are a key driver of most plant and animal extinctions, particularly on islands.
“The severe global threat,” the body said in a news release announcing the report, “is underappreciated, underestimated, and often unacknowledged.”
Humans have moved around about 37,000 species worldwide and scientists have documented negative impacts that resulted from moving about 3,500 of these.
Many species introductions seemed like a good idea just decades ago and then quickly backfired.
Purdue University Extension calls sericea lespedeza, a brushy plant from Asia, “one of the most problematic invasive species” for prairies and uncultivated cropland and pastures.
It drives Flint Hills ranchers “absolutely crazy,” Strong City cattleman Daniel Mushrush said.
“You can walk into any hardware store in Missouri right now and buy it,” he said. “It should be right up with heroin and cocaine. … You shouldn’t be allowed to have it.”
People brought the species from Asia to control erosion and feed livestock, but cattle dislike its tannins. Old world bluestems from Europe and Asia offer a similar story. They convert varied grasses and wildflowers into monocultural stands that look more like cropland.
“Native prairie is important to our system … from carbon storage to erosion control to pollinators,” Oklahoma State University environmental science program director Karen Hickman told the Kansas News Service. “When we start forgetting that … that gets to be a sad day.”
Humans also shape their surroundings unwisely, paving a highway for rapid takeovers by species that better co-existed with their competitors in other places or in bygone times.
Salt pollution helps cattails that can hack it to commandeer roadside marshes. Greenhouse gases and the elimination of browsing elk from most of their range aid sumac and rough-leaf dogwood to take over threatened tallgrass prairie.
Using biodiversity to hedge against tragedy
One-third of new species introductions globally over the past two centuries were recorded in the past few decades.
Over generations, this unprecedented, rapid shuffling of plants, fish, fungi, microbes and more sets the stage for new evolutionary winners and losers. Nature is nothing if not opportunistic and in constant flux. Food webs experiencing traumatic upsets remake themselves through evolution, and some species have shown an ability to adapt relatively quickly. Others, not so much.
So conservation scientists warn against believing that ecosystems can recover fast enough to shield humans from the negative effects of so thoroughly disrupting food webs. People depend on healthy ecosystems to feed them, to fuel their economy, to clean their water and more.
Sometimes they depend on ecosystems in not-so-obvious ways — until an invasive species brings a rude awakening.
Consider the emerald ash borer.
Like the accidentally introduced Dutch elm disease and Chestnut blight before them, the beetles have killed millions of North American trees and reshaped forests.
They’ve chomped their way across almost every Missouri county and are spreading westward across Kansas. They cost cities millions of dollars to replace street trees that not only beautify neighborhoods but also cool them in the summer, slow stormwater during downpours, absorb air pollution and boost property values.
But some Midwest communities take steps to protect against future devastation. They’re turning their backs on the tradition of lining entire neighborhoods and parks with hundreds of identical trees.
Kansas foresters, arborists and community planners have come to prize variety over visual monotony. After all, keeping a healthy city canopy raises property values, counteracts urban heat islands, absorbs air pollution and mitigates street flooding.
The Winterset neighborhoods of Lee’s Summit spent $475,000 removing and replacing more than 1,500 ash trees. To hedge against future pests, the community traded uniformity for a mix of nine native hardwood species.
Even in suburbia and cities, people live in ecosystems, not on movie sets. Humans can’t control how insects, plants and other species will interact.
Overland Park doesn’t intend to repeat past mistakes, either.
Before emerald ash borer showed up a decade ago, ash trees made up a quarter of the city’s street trees. More recently, officials realized that maples now make up one-third.
They realized the popularity of the trees was teeing up another tragedy. The next pest that rolls into town could well feed on maples.
So for now, the city won’t allow developers and residents to add more street-side maples. They’ll learn to branch out.
Celia Llopis-Jepsen is the environment reporter for the Kansas News Service. You can follow her on Twitter @celia_LJ or email her at celia (at) kcur (dot) org.
The Kansas News Service is a collaboration of KCUR, Kansas Public Radio, KMUW and High Plains Public Radio focused on health, the social determinants of health and their connection to public policy.
Kansas News Service stories and photos may be republished by news media at no cost with proper attribution and a link to ksnewsservice.org.
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