Invasive is such a harsh word. How can a natural creature be considered an invasive species? Nobody likes weeds, but everyone likes pretty fish and colorful birds—so, how can those be considered dangerous?
An invasive species is any living organism that is found outside of their native environment and has or will cause harm. The harm it can cause can be to the nonnative environment itself, the economy, or humans, or a combination of the three.
The zebra mussels that I’ve spoken about are an example of an invasive species in the United States. They are native to the freshwaters of Eurasia but somehow made it to the United States in the 1980s. Wherever the zebra mussels have been found, outside of Eurasia, they have outcompeted all native species and have changed the environments that they have invaded.
Another example is the lionfish. Its native habitat is the Indo-Pacific Ocean, however, it has made its way to the Atlantic Ocean. It reproduces rather successfully and has no natural predators in the Atlantic waters, so it has decimated many coral reef populations by devouring the herbivorous fish that help keep the reefs clean of algae. Without the algae eaters, the coral are smothered by the thick blankets of algae that naturally grow on them.
Not all invasive species are easy to comprehend at first. For instance, in many countries, domesticated cats and dogs are considered to be invasive species. How can Mittens or Spike be considered invasive? Humans absolutely love them and they (mostly) love us!
Dogs, and especially cats, are considered invasive species in many countries outside of Europe. They were brought over during the time of colonization, and their populations quickly grew unchecked. Dogs threaten native small animal populations, and cats wreak havoc on the native bird populations. For example, the Galapagos penguin population has been hit hard by the invasive house cat populations in South America.
Invasive species don’t have to look exotic. Sometimes they look normal, or they’re hard to notice at all. Invasive species can include plants, animals, fungi, insects, and microbes. And their effects on the local populations can be devastating, as when settlers first encountered native people, and the germs the settlers brought with them killed a lot of the native people of the land who did not have the same immunities built up as the settlers did.
Invasive species can also cause harm in other ways. New microbes introduced to an area can cause illness in people. Insects that have hitchhiked in shipping containers can run wild in new places and hurt the people there, like invasive species of hornets or spiders. Invasive jellyfish can fill the waters and harm beach goers.
Invasive species can even cause harm economically. Invasive hornets destroy beehives that produce honey to be sold. Zebra mussels clog pipes and encrust boats; it costs a lot of money to remove them, and it’s usually not a one-time expense. Lionfish have made coral reefs barren, reducing the populations of game and harvestable fish to low numbers, and impacting aquatic tourism.
Luckily, there are ways to handle invasive species. The best way is to prevent them from entering delicate ecosystems that they don’t belong to. For humans, that means being more careful when transporting food and supplies over long distances. It means finding new owners for exotic animals when you no longer want or can care for them—don’t just release them into the wild!
There are also ways to reduce invasive species numbers. For instance, many places around Florida and the Caribbean offer cash prizes for lionfish through spear-hunting competitions. Or you can encourage local chefs and restaurants to serve invasive species on the menu. The National Aquarium in Baltimore, Maryland frequently serves invasive fish in their diner.
I’ve eaten lionfish, and it’s pretty tasty! Mine was served Jamaican style, featuring a lot of spices that I wasn’t used to, but if prepared properly, it’s a great fish to eat. I’ve also had invasive catfish that was found in our local waters, and it didn’t taste that different from the native catfish, just maybe a little sweeter. So there are all kinds of ways to deal with invasive species, but it’s up to us to keep them in check!