The Nature of Nature: Invasion!

My neighbor, Lee, came to my front door one afternoon.  He was holding out his hand for me to see something. The something turned out to be a very well preserved Cuban tree frog skeleton. Take the time to do a little research on the Cuban tree frog and you will discover that it is one of Florida’s many invasive species. You will also discover that Florida’s wildlife experts recommend euthanizing these frogs when they have been properly identified. Why? Because the Cuban tree frog is classified as an invasive, exotic species that represents a danger to native fauna.   While I was photographing this cool little skeleton, I got to thinking about what we mean when we talk about invasive vs. native species.   Turns out it’s not exactly a crystal clear distinction.

According to Wikipedia (no, I don’t consider Wikipedia to always be a credible scientific resource but for the purpose of this essay, it works), one of the most used definitions of an invasive species is:

The first definition, the most used, applies to introduced species (also called “non-indigenous” or “non-native”) that adversely affect the habitats and bioregions they invade economically, environmentally, and/or ecologically. Such invasive species may be either plants or animals and may disrupt by dominating a region, wilderness areas, particular habitats, or wildland-urban interface land from loss of natural controls (such as predators or herbivores). This includes non-native invasive plant species labeled as exotic pest plants and invasive exotics growing in native plant communities.[1]

Okay. That makes sense. A non-native species moves in and adapts so well that it upsets the ecological balance of the habitat. In the case of the Cuban tree frog, it is apparently a voracious eater capable of destroying native lizard populations among others. Another invasive exotic here in Florida, the Burmese python, is wreaking havoc in the Everglades despite attempts to bring its population there under control. And most of us are aware of the destruction caused by non-native insect species like the Japanese beetle.   So when we hear people talking about the need to control invasive species, we generally nod our heads in agreement.

But let’s take the time to think about this a bit. In truth, we are quite tolerant of some invasive species. One lizard here in Florida, the Cuban brown anole, has become ubiquitous.  It is literally everywhere you look. It is also a non-native, invasive species. The little brown lizards have certainly displaced a large segment of the native green anole population.  But the two species now coexist with the browns preferring habitat closer to ground level and the greens opting for a more arboreal lifestyle. I see both in my backyard. We’re very tolerant of this invader. Indeed we have become very fond of it. Has it had an adverse effect? To a degree. But no one is trying to exterminate it. As a professor of mine once remarked when talking about the problem of invasive species, “You have to be pragmatic about it.” Some battles are not worth fighting.

Thinking about this a little more, let’s take a look at our yards and gardens. If we were honest with ourselves, we might admit that grass is one of the most destructive of the invasive species introduced to this country. Yes, I know there is more than one type  but I will speak of them collectively.  Grass seed was primarily imported from Europe and its widespread popularity has led to a neighborhood monoculture that requires copious amounts of water and chemical pesticides for maintenance. Yet we love our lawns. In some ways, we revere our lawns. This despite the fact that they represent a habitat from which diversity has been stripped. We also love our non-native trees, shrubs, flowers and other garden plants. We nurture these exotics and exclaim over their beauty. And when they escape cultivation, we shrug. Has the non-native shell ginger growing wild in our local park interfered with the health and diversity of native flora and fauna to any significant extent? I don’t know. And I’m not sure that anyone does. These escapees from cultivation exist all across the country. We accept and welcome all these intruders. We don’t worry too much about the environmental changes they have brought about.

And then, well, there’s us. If we were really, really honest with ourselves, we would admit that we are perhaps the single most destructive, invasive exotic that the planet has ever known. We not only occupy our environment, we re-engineer it. We strip it of its resources. We change it constantly. In my view, one of our biggest challenges going forward will be to accept the fact that the world around us has already been changed in ways that cannot be mended and that we really don’t understand very well. If we truly wish to do the right thing and control those invasive exotics, we need to see ourselves as one of them. We need to see ourselves as part of the natural world rather than the masters of it.

So I’ll thank that little Cuban tree frog for making me think about all this. And I’ll leave you with a quote from Elizabeth Kolbert’s excellent book, The Sixth Extinction: An Unnatural History:

But extinction rates among many other groups are approaching amphibian levels. It is estimated that one-third of all reef-building corals, a third of all freshwater mollusks, a third of sharks and rays, a quarter of all mammals, a fifth of all reptiles, and a sixth of all birds are headed toward oblivion. The losses are occurring all over: in the South Pacific and in the North Atlantic, in the Arctic and the Sahel, in lakes and on islands, on mountaintops and in valleys. If you know how to look, you can probably find signs of the current extinction event in your own backyard.

There are all sorts of seemingly disparate reasons that species are disappearing. But trace the process far enough and inevitably you are led to the same culprit: ‘one weedy species.’

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© Karen Kleis –  All Rights Reserved

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