Invasive species on the rise in the US

Botanical survey reveals how non-native plants are taking over in the US

Researchers have revealed through a new study that botanical invasive species – plants that are not native – are taking over many forests in the US specifically the southwest Ohio.

Biologists from the University of Cincinnati looked at exhaustive surveys conducted 100 years apart and focused their attention on undeveloped parts of cemeteries, banks of the Mill Creek and public parks that have remained protected from development during the last 200 years. Researchers found that many species purposely introduced as landscaping plants are flourishing in the wild.

Researchers are of the opinion that these nonnative invasive species continue to threaten the survival of native flora and fauna.

Efforts by park managers and volunteers to control invasive plant species has become a major part of their duties. This effort will be required in perpetuity and will be at great expense both monetarily and timewise due to collateral damage to native plants, wildlife and humans caused by the extensive use of herbicides, chainsaws and other mechanical equipment, researchers concluded in the study.

Horticulturists introduced most of the nonnative plants from Europe and Asia as ornamentals. Their seeds eventually spread in the wild. The biggest culprit? Amur honeysuckle, a woody shrub that has taken over many eastern forests.

Not to be confused with native trumpet honeysuckle, which grows in southern states and is referenced in the works of American writers William Faulkner and Robert Frost, Amur honeysuckle is a shrub from Asia that has delicate white flowers in the spring and red berries in the fall.

A survey by Braun in 1961 found Amur honeysuckle starting to grow in some parts of Hamilton County but not yet spreading in the wild in other Ohio counties. Today, it is a dominant woody plant found ubiquitously throughout the state, crowding out virtually all other low-lying vegetation, the study found.

Some invasive plants are successful because they produce chemicals that hinder the growth or germination of nearby competitors, an insidious weapon called allelopathy, researchers said.

According to researchers, where these introduced plants are found, there is often far less biodiversity to support wildlife and the food chain. Once they take hold, eradicating plants like Amur honeysuckle is labor-intensive, expensive and time consuming.

Callery pear trees with their pretty spring flowers and quick growing times were a favorite tree to plant in front yards of new subdivisions. Today, they grow wild along highways and forests.

The UC survey found dozens of other examples of foreign species that have taken root in southwest Ohio’s woods, including porcelain berry, tree of heaven, winged euonymus, European buckthorn, Oriental bittersweet, common privet and lesser periwinkle. It also found Norway maple, Amur cork tree and white poplar along with herbaceous species such as lesser celandine, garlic mustard, Japanese knotweed and Japanese stilt grass.

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