definearth

Different species aren’t inherently bad. Studies have shown that the effects of some non-native species are neutral, or even positive. One example I recently learned of is garlic mustard, a species that people spend a lot of effort trying to eradicate, and how the flowering plant might fare in a changing climate.

Invasive species have been referred to as ‘exotic’, ‘noxious’, ‘foreign’ and other terms that paint them in a certain light without providing much detail. An article in Smithsonian Magazine proposed the idea that some ‘invasive’ species, such as the Tamarisk shrub in the American southwest, bring ecological value to their new habitat. The Tamarisk was seen as a cancer for many years, not unlike other non-native species. When conservationists realized the shrub’s ability to house endangered songbirds, that perspective was flipped. But what would have happened if we used a more positive descriptive terminology for invasive species in the first place?

The Giant Tortoise in the Galapagos prefers to eat introduced species of vegetation that provide more calories and nutrition than alternative native plant food. For the island nation of Mauritius, bringing in the Giant Tortoise as a non-native species served the purpose of replacing the extinct native tortoise. The tortoises also should aide in seed dispersal for native woody plants. A different type of turtle, the wattle-necked softshell turtle, was introduced to the island of Kauai in the 1850’s by Chinese farmers who ate them in soup. Now, the population in China is endangered, but the turtles in Kauai are doing well. There is some concern that the turtles might feed on native fish. Still, the island remains their only option aside from extinction. Other non-native species have similar stories that defy the ‘toxic’ ‘damaging’ and ‘harmful’ narrative, such as Hippos in Colombia, red-crowned Amazon parrots in Hawaii, and spartina grass in California.

Another scientific study in Frontiers in Environmental Science (an open access journal) highlighted the nutrient stocking capability of the non-native wetland reed Phragmites Australis, which has been overwhelmingly successful in the United States. The reed will absorb nutrients from the surrounding environment and hold it in biomass and soil, which is beneficial to ecosystems like the Great Lakes where nutrient buildup causes eutrophication, which then suffocates fish and spawns algal blooms. Although P. Australis-dominated wetlands will retain more nutrients than meadow marshes, there is not a noticeable change in biomass, carbon or nutrient standing stocks when the reed takes over cattail marshes. The authors suggest reviewing the original vegetation type, difference in nutrient retention as a result of non-native species takeover, and the harm done to biodiversity and habitat value when making a decision about invasive species control.

Now let’s talk about word choice. Rhetoric undoubtedly matters in ecology. Disagreements between scholars, as evidenced in the Bulletin of the Ecological Society of America and other journals, of the exact characteristics of invasive species have proven as much. A paper in Diversity and Distributions suggests considering whether or not a species is ‘invasive’ on a case-by-case basis. The following quote outlines how rhetoric can be beneficial in science.

“Current science communication training does the important work of helping scientists understand and practice diverse ways of delivering their messages through storytelling, message framing, on‐camera confidence, and mixed media. But rhetoric can expand the horizon of that training by focusing on how to connect with audiences to prompt identification and action, and inspire critical attention to science.” – Why Rhetoric Matters for Ecology

One might begin to wonder, are humans an invasive species? According to science writer Sarah Zielinski, we meet many of the criteria, except for one: We are native to every continent, thus we can’t be invasive when we have always been such a widespread species. It’s an interesting take, but I would say that even if humans once inhabited every continent, those exact populations and their origins have definitely changed over time. One voice in the ‘what is invasive’ debate suggests that a non-native species becomes native once its genetics diverge from the original species. Of course, genetics are different from person to person, so this theory also needs to be fleshed out more.

Thanks so much for reading. I had a fun time crafting this post and got to learn about non-native species that aren’t necessarily harming the environment! Let me know what you think about humans as invasive species in the comments, or anything you’d like to add to the discussion on scientific rhetoric. Have a great day, Jess 🙂