In some circles, “applied” science is a bit of a dirty word. But fear not, basic scientists! There are plenty of reasons one might wish to study invasive species as a means to approach pure and beautiful knowledge alone.
Species invasions represent an opportunity for ecologists and evolutionary biologists. No matter how diligent, few biologists can escape the niggling feeling that their experiments fail to capture the true complexity of natural systems. (Perhaps theoreticians don’t have this fear.) For logistical reasons, the experiments can never be large enough, last long enough, have enough historical knowledge, or enough replication that you don’t think “Well maybe the results would come out differently, if I’d just had infinite resources and perfect knowledge.”
Enter invasive species as model systems. Say you want to study the process of local adaptation. With your typical species/system, you’re never quite sure what the starting material was, or how long the species has been in a particular environment, so it’s very difficult to tell how fast or how much a species has adapted. But with many invasions, there is historical evidence pinpointing the date of introduction, and even the source population(s). Say you want to know how fast evolution occurs in nature? This might typically require some guesses about events that happened hundreds of thousands of years ago. With invasions, because of the short time scales involved, such guesses are unnecessary (though the time scale can also work against you). Maybe you want to know if patterns of evolution are predictable. The “natural experiments” of species invasions have already been replicated, many, many times.
And oh yes, let’s not forget the applied side of this. Maybe the work you do with an invasive species will do some good for the world. Maybe it will make some difference to people, as well as to nature. That’s nothing to shake a stick at. Plus, at the end of an experiment, when it is necessary to destructively sample your organisms, you don’t feel that bad about it. Said the botanist.