Hey from Austin! You didn’t think my holiday was all traipsing through the mosquito fields and staring at the ocean, did you? Of course not. I also read a lot. Admittedly, I read a few magazines, but I got deeply into this book, which I got at the Texas Master Naturalist Conference a couple of weeks ago. It’s whole title is Unnatural Texas? The Invasive Species Dilemma, and it was written by Robin W. Doughty and Matt Warnock Turner.
The authors didn’t want to put “invasive” in the first part of the title, because, as they frequently point out, none of the plants and animals they talk about actually invaded in the first place; someone brought them to this continent. In fact, the only animal who’s actually “invaded” that they talked about is the nine-banded armadillo, who’s been going farther and farther northward, on its own, for the past couple of hundred years. (I would add to this list the caracara/Mexican eagle and a couple of other birds that are coming northward since it’s getting warmer).
I really enjoyed learning how some of the plants I’d known about my whole life showed up, and how hard people have worked to get rid of them. I feel sort of bad, as an aquarium keeper in the 1960s (with Mom), who may have contributed to the influx of hydrilla and water hyacinth to our lakes and waterways. I remember the invasion of the beautiful purple flowers, and witnessed first hand how quickly they grow. My dad had a goldfish pond in our back yard, and put the floating plants in it. Every month or so, he’d have to cull at least half of them. It’s taken years to get the under control, thanks to importing an insect that slows them down.
The book is organized into chapters about different birds (English sparrows and starlings), animals (feral hogs, feral cats, and imported exotics like fallow deer), and more aquatic life like zebra mussels and lion fish). The authors are always careful to point out the reasons why people brought these exotics to the US, which I appreciate.
An important point they make is that a plant or animal is not invasive just because it’s imported. For example, the Chinese tallow tree was a very popular tree in cities for providing shade and beauty. They only became a problem years after they were introduced, when they started to take over the coast around Houston.
Another thing I learned is that most introduced plants and animals do not become invasive, since the conditions where they are placed aren’t right. Invasives are introduced somewhere that’s right for them climate-wise and where there’s not something to control them. Interestingly, many of these, especially the plants, aren’t a problem where they are native, because there are also controls there. Plants usually have insects or diseases that keep them in check, but those don’t travel along with them when they invade.
But, then, why not import the controllers? Well, one thing the researchers have learned is not to randomly bring one thing in to control another (like the grass carp they brought in to control hydrilla in Lake Travis here in Austin, which they had make sure were sterile).
I guess it’s clear that invasive species are really hard to deal with and there are no clear answers. I can’t wait to see what happens next, and I’m glad current Texas biologists and researchers aren’t out trying to “improve” this state and the country by bringing in beloved items from other places. Darn those English sparrows.