When a new species is introduced to an ecosystem a major concern on part of conservationists and environmentalists is whether the new species will become “invasive.” In Chapter 6 and 7of Marris’ “Rambunctious Gardens” she gives numerous examples of nonnative species that have caused the decline of native species. For instance, in Stephens Island, a nonnative cat caused the extinction of the flightless wren. The wren did not have any predators, so it did not develop the ability to fly overtime and as a result was an easy prey for the cat. Furthermore, in Guam the brown tree snake, originally from Australia, killed “ten of twelve native forest-dwelling birds” (Marris 99). Ultimately this decline affected other populations in the ecosystem, in Guam the fruit trees were less dispersed because there were few birds left to carry the seeds across the land.
When the term “invasive species” is used, it has a negative connotation; it almost implies that the species is destructive. However, Marris also shares examples of “invasive species” that have a positive effect on the new ecosystem. For example, in Rodrigues Island during the 1970’s its native species of two songbirds and a fruit bat were declining rapidly almost towards the point of extinction; however, following the introduction of an exotic species of timber, the land was reforested and ultimately increased the population of the declining species to healthy numbers.
In fact according to Marris “the vast majority (of exotic species) are not (a huge problem)” (98). The term of “invasive species” was revamped by some scientists to “novel ecosystem” to include species that have both a positive and negative effect on the ecosystem. Still, there are many scientists who believe in the restoration of the native species even if it means taking out an invasive species that could be helpful. For example, ecologist Shahid Naeem of Columbia University “‘would love to get rid of every invasive species on the planet and put all the native species back in their place” (100). Moreover, in 1999 Bill Clinton also signed an executive order “declaring war against invasive species.” From these two examples, it is clear that there is a lot of contention towards invasive species and they are rarely seen as having a positive influence on the ecosystem. In fact, after Bill Clinton’s executive order, it influenced many volunteer efforts to combat the threat of invasive species. For example, Marris’ states that she recalls volunteering at a Seattle park to pull out English Ivy and holly because the species was spreading too rapidly.
Now, however, Marris believes that exotic species have the potential to create more diversity in the future and will eventually “evolve by adapting to local challenges and by genetic drift” (109). Instead of “invasive species” a few scientists have coined the term “novel ecosystems” to describe ecosystems that have been drastically changed in its species composition within a recent time period. These scientists noticed that many introduced species eventually calm down over time; for example, the strawberry guava was a very pervasive plant that eventually won the hearts of many Hawaiians and caused no conflict. In my opinion certain harmful invasive species such as the zebra muscles and phragmites should be removed because they will destroy the ecosystem, whereas the strawberry guava actually benefits the people of Hawaii and should not be removed just because it is a nonnative plant.
