Invasive species are non-native organisms that negatively affect their new ecosystems, causing environmental and economic harm. These organisms can be brought to new environments accidentally, like the Japanese beetle, or on purpose, like the popcorn tree. What invasive species all have in common is their adaptability and the harm they cause native plants and animals, property, and the economy (1). According to the National Wildlife Federation, approximately 42% of threatened or endangered species are at risk because of invasive species (2). With few or no natural predators, invasive species take over ecosystems with little resistance. The annual cost to the U.S. from invasive species is $120 billion (3).

Wild boar (Sus scrofa)

Other names: Feral swine, wild hog, razorback, piney woods rooter, and Russian or Eurasian boar

U.S. Origins: Brought by European settlers for a food source in the 1500s

Ecological threat: Wild boars have an estimated population of over 6 million across 35 states, a number that is emboldened by their ability to survive in both warm and cold climates. This adaptable species causes major damage to property, agriculture, and native species with their rooting habits. The U.S. Department of Agriculture estimates this damage to cost over $1.5 billion each year. Wild boars can carry at least 30 diseases and almost 40 parasites, with the ability to transmit these diseases to livestock, pets, and humans. (4, 5)

Popcorn tree (Triadica sebifera)

Other names: Chinese tallow tree, Florida aspen, chicken tree, and candleberry tree

U.S. Origins: Introduced to South Carolina in the 1700s for seed oil production for soap making

Ecological threat: Mature popcorn trees can produce up to 100,000 seeds, which are then spread by birds and flood waters. Although popcorn trees are popular ornamental trees because of their fast growth rate and colorful leaves in the fall, they displace native plant species by outcompeting them for resources. Popcorn trees have deep taproots that allow them to exploit minimal water sources, giving them the ability to withstand drought. In addition to displacing native vegetation, popcorn trees’ leaf litter can alter soil conditions because of the high amount of tannins present. Their leaves and fruit are toxic to cattle and humans. (6, 7)

Japanese beetle (Popillia japonica)

Origins: Found in New Jersey in 1916, possibly from imported plants from Japan

Ecological threat: Japanese beetles cost the U.S. over $460 million a year in damage. These insects feed on over 300 plant species, eating the leaves, flowers, and fruits. They skeletonize these leaves and flowers by feeding on the tissue between major veins, which can injure or kill young or unhealthy plants. Japanese beetle larvae live underground and feed on grass roots, which damages lawns and turf grasses. Crops also incur damages since Japanese beetles prefer certain plants and fruits, including apples, grapes, plums, corn silks, and soybeans. (8, 9)

Apple snail (Pomacea maculata) - picture

U.S. Origins: Introduced in the 1990s with the theory that they spread from irresponsible aquarium dumping

Ecological threat: Apple snails have an aggressive feeding style that affects the nutrient dynamics in aquatic ecosystems. Their diet includes a variety of aquatic plants, algae, remains of decaying organisms, and other snail eggs, which depletes resources from native species. Because of the devastation apple snails have caused to rice crops in Asia, their presence is a threat to rice-growing areas of the U.S. like Texas. Along with crop destruction, apple snails negatively affect wetland restoration efforts due to their eating habits. (10, 11)

What you can do to help

There are simple actions that you can take to help curb the spread of invasive species (1).

When gardening, remove invasive plants and plant native plants.
Regularly clean outdoor equipment, like hiking boots after each hike and boats before entering a new body of water.
Don’t bring home animals, plants, or shells from different ecosystems.
Instead of bringing firewood from home to a campsite, buy firewood near your campsite.
Don’t release pets into the wild.

Citations

(1) National Geographic Society. (2012, October 9). Invasive species. https://www.nationalgeographic.org/encyclopedia/invasive-species/

(2) The National Wildlife Federation. (n.d.). Invasive species. https://www.nwf.org/Educational-Resources/Wildlife-Guide/Threats-to-Wildlife/Invasive-Species

(3) National Invasive Species Awareness Week. (2021, February 25). Resources. https://www.nisaw.org/resources/

(4) U.S. Department of Agriculture. (2020, June 2). History of feral swine in the Americas. Animal and Plant Health Inspection Service. https://www.aphis.usda.gov/aphis/ourfocus/wildlifedamage/operational-activities/feral-swine/feral-swine-history

(5) Katz, B. (2019, December 18). Feral pigs are invasive, voracious and resilient. They're also spreading. Smithsonian Magazine. https://www.smithsonianmag.com/smart-news/feral-pigs-are-invasive-voracious-and-resilient-theyre-also-spreading-180973824/

(6) University of Georgia - Center for Invasive Species and Ecosystem Health. (n.d.). Chinese tallowtree, Triadica sebifera. EDDMapS.org.https://www.eddmaps.org/species/subject.cfm?sub=3079

(7) Texas Invasive Species Institute. (2014). Chinese Tallow. https://www.tsusinvasives.org/home/database/triadica-sebifera

(8) Brougham, R. (2021, March 26). How to: Get rid of Japanese beetles. Bob Vila. https://www.bobvila.com/articles/how-to-get-rid-of-japanese-beetles/

(9) Hahn, J., Weisenhorn, J., & Bugeja, S. (2020). Japanese beetles in yards and gardens. University of Minnesota Extension. https://extension.umn.edu/yard-and-garden-insects/japanese-beetles

(10) Texas Invasives. (2019, August 30). Pomacea Maculata. https://www.texasinvasives.org/animal_database/detail.php?symbol=15

(11) Karg, T. (2021, March 17). Invasive species highlight: Apple snails. SOLitude Lake Management: Full-Service Lake And Pond Management. https://www.solitudelakemanagement.com/blog/invasive-species-highlight-apple-snails/

Invasive Species Spotlight: Wild Boar, Popcorn Tree, Japanese Beetle, and Apple Snail

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