While the concept of human introduction is prehistoric, the understanding of an invasive species is much more recent. In chapter 6 of Rambunctious Garden: Saving Nature in a Post-Wild World, Marris describes it as a moved or non-native species that naturalizes and is able to reproduce in its new environment such that it “becomes a rowdy nuisance” (99). Some of these species include zebra mussels in the Great Lakes and pigeons in New York City.
Marris discusses whether or not invasive species are as bad and evil as the general society believes it to be. While it is generally argued that when a species invades, the “ecosystem collapses, species go extinct, and complexity and diversity are replaced with a monotonous and weedy landscape dominated by invaders,” an example within Rodrigues Island actually disproves this argument. With two types of songbirds and a fruit bat living on this island, almost all of these rare species became extinct because of deforestation. However, exotic species were used to reforest the island “for timber and erosion control” (98), and the rare native species began to regrow in numbers.
There are National Park Service teams that have “treated more than one thousand square miles” (100) and travel from park to park in the United States with a mission to destroy and remove any invasive species that is not native to the local area. While this may seem like a great idea to protect sensitive native species in danger of extinction, not every new species is harmful to their introduced environment. In fact, if new species show potential in helping diversify the environment in the future, they should not be removed. It seems to me that these strike teams are too focused on keeping ecosystems “prehistoric” or untouched.
Marris continues to negate the idea that invasive species are always a bad thing by explaining other factors that cause extinction of or harm to certain species. Many bird extinctions come from birds being killed, not via eating birds’ prey. Sometimes, introduced species may not automatically compete with native species or prey on unsuspecting natives. In fact, “invasive species” can contribute to an increase in diversity in ecosystems in the future. For example, Easter Island had around 50 native species before humans stepped on the island, but gained 68 new species thereafter.
Other than contributing to potential increase in diversity of species in an ecosystem, exotic species have positive benefits like removing toxins from the soil, regulating erosion, and controlling undesirable species.
In chapter 7, Marris discusses the idea of a novel ecosystem. A novel ecosystem is not necessarily an untouched piece of nature, but an environment that has been influenced by humans in the past, and then left on its own to go through changes without human interference. Marris briefly mentions that many ecologists consider novel ecosystems as not worth studying because they don’t find them as “pristine” as other ecosystems (112). Unlike some forgotten ecosystems, the High Line is a great example that has gotten a lot of restoring and revamping through Friends of the High Line. This public park stretches over one mile on the West side of Manhattan. Once a railroad for freight trains, this elevated structure was closed down and left to ‘run wild’ for a few decades, but has recently turned into a beautifully maintained and diverse environment.
Marris further supports the idea that exotic species are not detrimental to an environment by using novel ecosystems as an example. Many novel ecosystems, which are composed of many exotic/invasive species, actually function better than native ecosystems. Novel ecosystems have the most potential for supporting a diverse environment will continue to evolve and diversify many species—especially with the prospect of hybrid species.
After reading these two chapters, Marris has convinced me that exotic species can actually be beneficial to an ecosystem, and not as detrimental and harmful as the general society believes. Although humankind should be mindful of certain invasive species that may pose threat to specific native species, people must remember that not only is this pretty rare compared to initial beliefs, but also such a small possibility compared to many of its benefits. More ecologists should be interested in and focused on studying novel ecosystems.
