The Economic and Ecological Impact of Invasive Species Across the U.S.

Friday - September 22 2023, 06:52 UTC - 1 year ago

Invasive species, including plants, animals and fish, cause heavy damage to crops, wildlife and human health worldwide resulting in estimated losses of more than US$423 billion each year. They are regularly moved from their home areas due to intentional or accidental human activities. These recent articles from The Conversation describe how several invasive species are causing economic and ecological harm across the U.S. and steps that can be taken to prevent their spread.

Invasive species – including plants, animals and fish – cause heavy damage to crops, wildlife and human health worldwide. Some prey on native species; other out-compete them for space and food or spread disease. A new United Nations report estimates the losses generated by invasives at more than US$423 billion yearly and shows that these damages have at least quadrupled in every decade since 1970.

Humans regularly move animals, plants and other living species from their home areas to new locations, either accidentally or on purpose. For example, they may import plants from faraway locations to raise as crops or bring in a nonnative animal to prey on a local pest. Other invasives hitch rides in cargo or ships’ ballast water.

When a species that is not native to a particular area becomes established there, reproducing quickly and causing harm, it has become invasive. These recent articles from The Conversation describe how several invasive species are causing economic and ecological harm across the U.S. They also explain steps that people can take to avoid contributing to this urgent global problem.

1. The best intentions: Callery pear trees .

Many invasive species were introduced to new locations because people thought they would be useful. One example that’s widely visible across the U.S. Northeast, Midwest and South is the Callery pear (Pyrus calleryana), a flowering tree that botanists brought to the U.S. from Asia more than 100 years ago.

Horticulturists loved the Callery pear for landscaping and wanted to produce trees that all grew and bloomed in the same way. As University of Dayton plant ecologist Ryan W. McEwan explained, they created identical clones from cuttings of trees with the desired characteristics – a process called grafting. Unlike some trees, a Callery pear can’t fertilize its flowers with its own pollen, so plant experts thought it wouldn’t spread.

However, "as horticulturalists tinkered with Callery pears to produce new versions, they made the individuals different enough to escape the fertilization barrier," McEwan wrote. As wind and birds spread the trees’ seeds, wild populations of the trees became established and started crowding out native species.

Today, Callery pear trees are such scourges that several states have banned them. Others are paying residents to cut them down and replace them with native plants.

2. Tiny organisms, big impacts: Zebra and quagga mussels .

Invasive species don’t have to be large to cause outsized damage. Zebra and quagga mussels – shellfish the size of a fingernail – invaded the Great Lakes in the 1980s, clogging water intake pipes and out-competing native mollusks for food. Now they’re spreading west via rivers, lakes and bays, threatening waters all the way to the Pacific coast and Alaska.

As Rochester Institute of Technology environmental historian Christine Keiner wrote, it took several decades for the U.S. and Canada to regulate ships’ management of their ballast water tanks, which was the route by which the mussels were introduced to North America.

"Now, however, other human activities are increasingly contributing to harmful freshwater introduc­tions," Keiner wrote. Damming rivers for hydropower has opened new pathways for invasives, while climate change is making survival easier for nonnative species.