In chapters 6 and 7 of Rambunctious Garden, Emma Marris discusses the concepts of exotic species and novel ecosystems. Exotic species are species that are not native to a particular area and have been introduced by humans. Many ecologists and conservationists consider these species to be invasive, and believe them to be detrimental to the habitats where they reside. Novel ecosystems are defined as ecosystems that contain many exotic species but function as well, if not better, than native ecosystems. These novel ecosystems provide humans with many ecosystem services such as water filtration, carbon sequestration, and a habitat for rare species. They are altered by humans, but not actively managed.
Many ecologists today argue that exotic species are detrimental to ecosystems and lead to decreased species diversity and extinction. Although this is true for some exotic species, Marris argues that for the majority, it is not. In fact, she argues that exotic species can be beneficial to habitats. The benefits of exotic species include supporting rare native species, controlling undesirable species, removing toxins from soil, and regulating erosion. Marris also points out that exotic species may create more species diversity in the future because they will evolve by adapting to local habitats.
Marris uses novel ecosystems to support her view that exotic species are not detrimental. She points out that many novel ecosystems, made up of exotic species that did not evolve together, function better than native ecosystems. In fact, many novel ecosystems are more diverse than their native counterparts. However, many ecologists shun these ecosystems because they are not pristine. Nevertheless, these novel ecosystems have the most potential for evolution, since exotic species need to find ways to survive. This can lead to new species and increased species diversity. In fact, many hybrid species, or combinations of native and exotic species, are being created in novel ecosystems.
Marris brings up some interesting points in these two chapters. After digesting all the evidence, I believe that exotic species should not be removed from ecosystems; they should be embraced. This is because exotic species benefit habitats in many ways. There is no need for ecologists to waste a tremendous amount of time and money on eliminating exotic species when most of them are beneficial. Exotic species rarely cause extinctions. In fact, exotic species are taking over the roles of extinct species and can help native species flourish, as demonstrated by Rodrigues Island in the Indian Ocean. This Island saw three endangered species saved by the introduction of exotic species.
I believe ecologists should invest money in studying novel ecosystems, including urban environments. Very little is known about novel ecosystems and why many of them are able to function so well. In addition, more money should be devoted to studying which exotic species will benefit an ecosystem and which will harm it. I believe the only exotic species that should be removed are the ones that are sure to be detrimental to the survival of the ecosystem. All the other exotic species should be allowed to stay. This is because, as the reckless invader hypothesis states, the dominance of an exotic species will decrease over time.
This chapter has left me with one question: Will there be a point where native species no longer exist and all species are exotic? I believe this will happen, but only time will tell.
