What Are Invasive Species?

There are many threats to biodiversity including invasive species. They are species of living things (plants, animals, and microorganisms) that are brought into an area, so they are not native to that ecosystem. Sometimes they can harm the ecosystem by quickly spreading and threatening the biodiversity of the ecosystem by destroying food and killing animals, plants, and microorganisms. These invasive species aren’t eaten by predators because they aren’t natural to that ecosystem. Therefore they have no predators, and they can multiply into millions (which makes an even worse problem). Humans usually cause invasive species - intentionally or unintentionally. Invasive species are found everywhere. There may be many more than you think. To learn about an example of an invasive specie, read about the Asian Carp.

What Are the Main Causes of Invasions of Non-native Species?

Usually humans cause invasions of foreign species. We cause it by bringing foreign species from other countries to new ecosystems by ships, planes or other forms of transportation. The foreign species may be brought to combat pests, to farm, for research purposes, or for ornamental purposes.

Here’s one example of an invasive species. Kudzu was imported to America for ornamental purposes and for erosion control. It took a few decades to become invasive and for the U.S. government to declare it a weed.

Another example is the gypsy moth. In the late 1860’s, they were imported from France to the United States for silk production by E. Leopold Trouvelot. They were kept in cages in Trouvelot's backyard, but they were accidentally released and no action was taken to eradicate them. Now they’re a major threat to the forests in the United States.

Where are Invasive Species Found?

Invasive species are found all over the planet. One invasive species from South America is the South American cane toad ( Bufo marinus) which is now found in Australia. They were imported in 1935 to fight the beetles that were destroying sugar crops. The toads were accidentally released and have been multiplying ever since. The cane toad has glands on its backs that dispense milk like poison when threatened. So any predator that sees the cane toad as food falls victim to its poison.

Another invasive species is the zebra mussel (Dreissena polymorpha). It’s native to lakes in Russia, but it’s been accidentally released into other parts of the world like the Caspian Sea, the British Isles, the United States, and other parts of Europe. Zebra mussels have a grabber type thing called a byssus. It is thought that zebra mussels used their byssus to grab onto boats. Then when the boats go to other countries, the zebra mussels hitchhike along and then spread rapidly. An adult female can produce 30,000 to 1 million eggs per year!

One other invasive species is the ice plant (Carpobrotus edulis). In 1900, it was brought from South Africa to California, USA to stabilize dirt near railroads. Unfortunately, they spread like fire and are now directly competing with several endangered plants. The ice plant can grow all year round and flowering can occur at any time. They also produce a lot of seeds which may be why it's so hard to control. The ice plant is also found in the Mediterranean and inhabits vast parts of the coastline. Another invasive species, the black rat, is helping the ice plant by spreading it through its fecal matter. The ice plant is a food source for the rat. This is an example of two invasive species helping each other to flourish.

How You Can Help?

Here are some simple steps to stop the invasions of non-native species.

• Clean off your boots before hiking in a new place to get rid of seeds, insects, and microbes.
• Don’t release exotic pets into the wild.
• When traveling or camping, don’t leave behind a fruit, vegetable or other plant that may become invasive.
• Clean off your boat frequently to not carry invasive fungi or microbes.
• Don’t bring your own firewood purchase or find within 50 miles of the campsite and use all of it and if you don’t, don’t take it home.
• Make sure the plants in your garden aren’t invasive. It's best to just use native plants. You should always dispose of unused seeds in the trash.
• Volunteer at your local park to help get rid of invasive species.