Invaders all around us

Many of us are horrified by stories of invasive species wreaking havoc on ecosystems, upsetting the natural balance, and even impacting humans directly.

The example of Chikungunya that I mentioned in my last post demonstrates two important aspects of the situation. First, humans actually very often transport the invaders to their new habitat, either unintentionally or on purpose. And second, humans are often affected directly by what the invasive species do. Chikungunya shows these two aspects perfectly. It is a tropical disease that has spread rapidly through the Caribbean Islands in the past few years. Many patients diagnosed in the US contracted the disease, which is transmitted by mosquitoes, during travels in that area. Even landlocked Oklahoma is affected. (Click for more information.)

Several examples of invasive species make it into the news, mainly because they involve spectacular species, like the Burmese Python, currently impacting Florida. This beautiful snake species from Southeast Asia, was brought to Florida as pet and made it from captivity into nature, where the snakes are doing so well that they are held responsible for severe declines in several species of mammals. One ironic wrinkle of this is, that Burmese Pythons are considered to be vulnerable to extinction in their natural range. Interestingly, South Florida is such a hotbed for invasive species from the tropics, that the Burmese Python shines a spotlight on the situation, even though it may not be the biggest problem for the ecosystems in South Florida.

In the bigger picture Biologists are trying to grapple with invasive species on a more than just practical level. On that level, all hope is lost already: invasive species are already part of a wildly unnatural situation surrounding us. But what do invasive species represent? In a way, we are making judgment calls based on our values: many people, and not just biologists, place a high premium on ecosystems that are as unperturbed as possible. These places are becoming increasingly rare and more and more difficult to protect. These ecosystems represent the outcome of eons of evolution and allow us to study both its outcome and process undisturbed by human activity. Often invasive species ruin the existing ecosystem, and our chance to study unique situations is lost forever. Under this view, for example, the introduction of placental mammals to Australia was an unmitigated disaster leading to the demise of the resident marsupials.

Another view is to see opportunity for studying both the ecology and evolution of new, albeit unnatural assemblages that are essentially created by humans and attach value to those. Why can’t a new, invasive plant have the same value as the indigenous plant it replaces? This is a view partly proposed by Emma Marris in her publications. How do we treat our crop plants in this context? Almost all of them are invaders, right? Looking at the beautiful oak tree in my backyard makes me wonder: Does a non-native tree in the mixed grass prairie of Oklahoma not give me the same esthetic pleasure as the same tree in a natural forest?

These are questions both debated by biologists and the general public, often with deeply personal answers. And, as we inhabit the Anthropocene longer and longer, these questions will present themselves with increasing urgency and have important impacts on conservation policies.

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5 thoughts on “Invaders all around us

  1. I really enjoyed this post, Ingo! It gives us non-biologists a very clear and more nuanced sense of how biologists are currently grappling with the practical and philosophical implications of invasive species. Can I push you to expand on this a bit by explaining how you define nature or natural in the context of this discussion?

    • I am using natural here to say evolved over a long period of time. An ecosystem like a forest represents both current functionality and a long evolutionary history that shaped the current form and function of this ecosystem. To me this is different from an assemblage of trees.

  2. I, too, find this post fascinating. In particular, I see much resonance between the way biological species are moved from place to place by humans and the way that cultural habits, ideas, and beliefs are moved from place to place. In both cases, it one cannot know how the foreign entities are going to affect local culture/nature, but it is clear that they do…very often, a lot. The thing that Ingo wants us to pay attention to is how we adapt to those things.

    I see a lot of commonality between the way that nativists in a country or region desire to protect that region from the outside and the way that some environmentalists seek to prevent exotic species from invading. I posit that the same fundamental psychology governs both cases, a desire to protect and preserve what is known and what is valued and a fear of the unknown. We need to dig deeply into this psychology in order to understand better what to expect as we encounter more and more change in our world—both naturally and culturally.

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