After reading five chapters of Marris’ Rambunctious Garden, it is easy to infer that traditional ecology spurns the idea of invasive species coexisting with native species; invasive species are bad, native species are good. Years of field study and research have formed orthodox views that support the idea that invasive species hinder ecosystems due to their harmful nature, severely impeding biodiversity and ecosystem health. As Marris’ book states, “A species invades, and the ecosystem collapses, species go extinct, and complexity and diversity are replaced with a monotonous and weedy landscape dominated by invaders” (97). Proof has been seen for centuries all around the world. Zebra mussels in the Great Lakes, the yellow crazy ant in Australia, or the aggressive species introduced to Stephens Island that killed off ten of twelve native birds, leading to a cascading effect on other species serve as only a few examples. With so much proof, it is difficult to view exotic species otherwise. Chapter six and seven of Marris’ book, however, shine a new light on invasive species and propose the contentious idea that perhaps exotic species are not so bad after all.
Throughout chapters six and seven, Marris provides readers with an alternative vantage point, presenting the claim that exotic species may, in fact, be beneficial to an ecosystem. Marris’ first example pertains to an instance in which an introduced species of trees actually saved three native species from going extinct: On Rodrigues Island, fast-growing exotic trees were chosen to reforest the land and “almost accidentally” saved the island’s two endangered songbirds and a fruit bat. Marris furthers her argument by introducing two modern ecologists, Mascaro and Lugo, who also support the notion of “novel ecosystems,” ecosystems defined by anthropogenic change that are not under active human management (114). The stories support examples of native and introduced species living together diversely, sans “monocultures and other such nightmares.” She also makes the argument that targeting invasive species is simply not economical. Ridding an ecosystem of all invasive species requires a large amount of time, effort and money, and the results are not always permanent. In short, Marris provides readers with the general idea that “…some exotic species are a huge problem, the vast majority are not.” (98).
But is this really so? When assessed objectively, this blanket claim seems to fall short. It is true that a number of invasive species are introduced and eventually mellow out, but the impacts of exotic species are far direr than made to seem. Invasive species have high competitive ability, fecundity and their extremely quick growth rate is supplemented by the lack of natural regulators such as parasites or competitors that have yet to adapt to the new species. In fact, introduced species rank amongst the top five causes of modern extinction. What about the “good” invasive species Marris talks of in her book? They have a very high failure rate.
All in all, we cannot merely say that invasive species are good. We must strike a balance between giving exotic species free reign and entirely ridding areas of introduced species. I agree strongly with Joe Mascaro’s quote, “This isn’t about conceding defeat; its about a new approach” (122).
