Many science teachers talk with their students about invasive species. They may talk about cases when foreign species have killed off the native species. They may even talk about how dangerous this is, and warn their students against releasing that pet python. But do these teachers practice what they preach? Many don’t, a study finds.
Classroom laboratory animals and pets can be a source of invasive species — animals that could compete with, and potentially overtake, native species. And teachers could be to blame. A study presented at the Ecological Society of America meeting last year, found that one in four teachers who use live specimens in the classroom said they eventually released them into the wild. Fewer than three in 100 classroom animals were local, native species that had been intentionally raised as part of a program aimed at building wild populations of those species.
This study was headed by Sam Chan of Oregon State University and funded by the National Oceanic and Atmospheric Administration. Chan’s team asked almost 2,000 teachers across the United States and Canada what species they used in their classrooms. They also asked what happened to the animals and plants when the school year was over.
How can giving captive animals a chance to survive in the wild be a bad thing? In nature, species over time tend to evolve a balance. Some animals eat others to keep members of one prey species from growing out of control — like a weed. Too many predator species will compete with each other for food until some of the predators starve. This ends up keeping the species in balance. But when a new species enters the local environment, its predators may not be there — or know where to find them. And that can let the newly released species become the “weed.” They may be able to grow out of control without anything to keep the numbers down. Or the newly released species may have other advantages over native species. They may be more tolerant of cold, less picky about the soil in which they grow in or may overeat species on which native animals depend for their survival.
Whatever the reason, these so-called “foreign” species can sometimes find they like their new home very much. The big, leafy kudzu that now covers the southeastern United States started out in Japan. The carp that are now overrunning the Mississippi also come from Asia. They had escaped from fish-farming operations where they had been imported to keep ponds clean.
Other species may not need to take over. Instead, they may carry germs or parasites that could cause disease in native animals. That’s a problem with European black currant plants. They often host a fungal pest that can kill valuable pine forests. Called white pine blister rust, the blight doesn’t hurt currants, but can devastate forests.
The Oregon State survey found that teachers had been using more than 1,000 species of organisms. These included things like mosquito fish, crayfish, amphibians and turtles. Many of these species appear on lists of known invasive species. For example, teachers in Ontario may buy crayfish for their class that are native far to their south in the Ohio River basin. These crayfish are aggressive and push out the wimpy crayfish already there.
I know, some of you are probably thinking: How big a deal could the release of one animal — or even a handful — make? Well, potentially a very big deal. Some people investigating the python crisis in the Everglades suspect the problem may have started when a few pet owners released a snake they could no longer manage. And genetic testing suggests as few as eight to 12 pet fish could be responsible for the epidemic spread of invasive lionfish in the western Atlantic.
Animals are a great help in science classrooms. When I was in third grade, we had a class hamster. I remember going to the back of the room to watch it during school as it went about its little furry life. In high school, the ecology class had a whole terrarium, with a turtle, a crayfish and a bunch of frogs. We learned how to care for them as part of our program.
But while I remember all these creatures, I never remember what happened to them when their time in the classroom was over. I never even asked. And while I might have known that the beautiful frogs were not native to my home state, I never thought what might happen if someone set them loose.
So it’s a not a good idea to let your lab specimens run free. But what else can you do with them? Chan suggests discussing the issue with a local veterinarian. In some cases euthanasia may be the only option.
However, Chan doesn’t want to stop people using species in the lab. They are important for learning. They also can make a lesson more interesting and memorable. But school should recognize the importance of using native species when possible. This will mean teachers can release them local without a problem (as long as they aren’t sick). And thinking about what you use in the classroom — and why — could be a great lesson in itself for students. So the next time you use a species in the classroom, pause and think. Where is it from? And where, in the end, will it go?
invasive species (also known as aliens) A species that is found living, and often thriving, in an ecosystem other than the one in which it evolved. Some invasive species were deliberately introduced to an environment, such as a prized flower, tree or shrub. Some entered an environment unintentionally, such as a fungus whose spores traveled between continents on the winds. Still others may have escaped from a controlled environment, such as an aquarium or laboratory, and begun growing in the wild. What all of these so-called invasives have in common is that their populations are becoming established in a new environment, often in the absence of natural factors that would control their spread. Invasive species can be plants, animals or disease-causing pathogens. Many have the potential to cause harm to wildlife, people or to a region’s economy.
euthanasia Killing an individual — often a hopelessly sick animal — in a relatively painless way, usually as an “act of mercy.”
native Associated with a particular location; native plants and animals have been found in a particular location since recorded history began. These species also tend to have developed within a region, occurring there naturally (not because they were planted or moved there by people).
organism Any living thing, from elephants and plants to bacteria and other types of single-celled life.
species A group of similar organisms capable of producing offspring that can survive and reproduce.