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From noxious weeds to invading insects, species are considered invasive when they are introduced to an area and they have an adverse effect on native habitats. When it comes to invasive species and climate change, the combo can be unsettling. Climate change increases overall global temperatures, which in turn affects everything from extending the length of growing seasons to not getting cold enough to kill off invading insects.
More than ever, invasive species are creeping outside their comfort zone and migrating to climates previously too cold for their survival, competing with native plants and animals for resources, and leaving vulnerable populations at risk. Because they are introduced but not native, invasive species frequently have few or no known predators, giving them free reign to wreak havoc.
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1. Kudzu (Pueraria montana)
A standout among invasive landscaping plants, this member of the pea family and native of Asia was first introduced into the American South in the early 1900s as an ornamental plant, prized for its rapid growth and large, fragrant purple flowers. Later, it was widely used by farmers as a means of erosion control.
Kudzu thrives in warmer temperatures, and the increase in overall temperatures has allowed this plant to invade the Eastern Seaboard and to spread west and north from there. It also is a problem in the far Northeast and areas surrounding the Great Lakes, where climate change is helping the vine thrive. The Great Lakes Integrated Sciences and Assessments (GLISA) released a study citing an increase in average temperature by 2.3 degrees since 1951 and an additional 16 frost-free days, increasing the length of the growing season and making conditions more favorable for kudzu.
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2. Zebra Mussel (Dreissena polymorpha)
According to the New Hampshire Department of Environmental Services, zebra mussels were first spotted in the U.S. at Lake St. Clair, Michigan, in June 1988. The invasive shellfish have since spread to both freshwater and brackish waters throughout the Midwest and North Atlantic region, and the U.S. Department of Agriculture’s National Invasive Species Information Center reports they have now spread rapidly throughout the Southeast and Southwest.
With virtually no predators and a reproduction rate of 30,000 to 1 million a year, zebra mussels affect drinking water, clog pipes, damage docks and boat hulls, and compete with native species. Zebra mussels tolerate a wide range of temperatures, but most often thrive in water between 68 and 77 degrees Fahrenheit, and spawn in water temperatures in the mid-50 degree range. As water temperatures rise in more northern climates, the spawning ground for these animals is expanding north into Canadian waters and west toward the Rocky Mountains.
3. Cheatgrass (Bromus tectorum)
The seeds of this invasive grass from Europe were introduced in the 1800s. It grows rapidly and competes with native grasses. Of great concern is how cheatgrass disrupts the fire cycle in native sagebrush habitat, leading to an increase in both frequency and intensity of burns. Sagebrush has a slow recovery after a major wildfire, but cheatgrass, along with other non-native grasses, thrives in these conditions.
Climate change has led to more widespread drought, especially in the 11 Western states where the sagebrush steppe ecosystem is found, and thereby increased fire risk. Most grasses grow faster than nearly every other plant, so before adding an ornamental variety to your garden, look for native plant alternatives for landscaping that are not only beautiful but better for native insect and animal populations.
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4. Japanese Beetle (Popillia japonica Newman)
The Japanese beetle is rapidly becoming one of the worst invasive insects in the U.S., where it has no known predators. These beetles quickly demolish fruit trees, vegetables, turfgrass, and flowering plants, with adults devouring foliage and fruits and larvae destroying roots. Though it has invaded U.S. soils for nearly 100 years, until 2015 it was found primarily in all states east of the Mississippi River, except Florida. Today, there are infestations in Western states, including Arkansas, Iowa, Kansas, Minnesota, Missouri, Nebraska, North Dakota, Oklahoma, Colorado, and South Dakota.
According to a study done by Midwest Climate Hub Fellow, Dr. Erica Kistner-Thomas, model projections show that an increase in temperature would push the beetle’s territory northward into Canada while simultaneously increasing the range of southern invasions to the north.
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5. Burmese Python (Python molurus bivittatus)
Originally imported into the U.S. as pets, Burmese python’s wild populations exist now in Florida due to escaped or intentionally released animals. Burmese pythons compete with native wildlife like the indigo snake for food, and they prey on native species, including the Key Largo woodrat.
The United States Geological Service reports an estimate of tens of thousands of pythons living in the Florida Everglades alone. The populations have begun to spread throughout the state of Florida, and recent evidence from the Department of Agriculture shows at least one sighting of a Burmese python in the wild in Georgia. Warming temperatures from climate change could increase the spread of these destructive animals.
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6. Spotted Lanternfly (Lycorma delicatula)
Native to parts of China, Vietnam, and Bangladesh, the spotted lanternfly has become an invasive insect throughout the United States since it was first documented in 2014. A danger to grapes, fruit, and hardwood, the insects pose a huge threat. Longer growing seasons brought on by climate change offer more food, fueling the population. Warmer winters fail to kill off the growing population. Currently, the spotted lanternfly is a problem in 14 U.S. states along the Northeast, but the spread is a concern throughout the country.
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7. Emerald Ash Borer (Agrilus planipennis)
As the name suggests, the emerald ash borer is a bright green beetle, but don’t let its pretty color fool you. Adults feed on the foliage of the ash tree, but the larvae feed on the inner bark of the tree. This completely cuts off the tree’s ability to transport water and nutrients throughout the tree, leading to its untimely death. Believed to have arrived via shipping container from Asia, the emerald ash borer was first seen in 2002 in Detroit, Michigan, and since then has spread to 35 states and counting.
The U.S. Forest Service released a study in 2013 reporting that between 1945 and 2012, few places in the United States experienced cold enough temperatures to kill off the emerald ash borer. With temperatures on the rise, this invasive insect poses a greater threat than previously thought.
