Prior to chapters six and seven, Marris talks about the dangers of introducing invasive species to an ecosystem. In these two chapters, Marris tries to dispel the negative stigma of invasive species by showing the various reasons why invasive species can be beneficial and why people still might not see invasive species as a positive.
Marris first talks about how invasive species can be beneficial to an ecosystem. One example Marris uses is how a foreign species of trees was able to help save two species of songbirds and a species of fruit bat that lived exclusively on Rodrigues Island (97). These three species were in danger of going extinct when the forest was cut down on the island, thus reducing their fruit source. A nonnative species of “fast-growing timber” were chosen to quickly replant the island, but in the end the rapidly growing plants served to save these three species since native species grew quite slowly and would not have been able to stop the endangered species from going extinct (98). Invasive species can play important roles in the ecosystem. In a similar example, invasive species can actually help nature flourish by taking of the roles of extinct species. In Hawaii, exotic birds are taking over the dwindling native bird species’ important duty of dispersing seeds (105). Sometimes the Without these exotic birds stepping in, seed dispersal might not be happening at all in Hawaii. In fact, some studies show that exotic species may even be considered to be functioning better than native species. One study compared a native only forest with former pine plantations of a similar age showed that the pine plantations were “richer in species, had greater aboveground biomass and used nutrients more efficiently” (113). If functionality is measured through species diversity, amount of biomass produced and the efficiency of using nutrients, then exotic species may function better than native species. In addition to this, exotic species may be able to help not only the ecosystem, but humans as well. One such species is the Chinese brake fern that can take arsenic, a harmful poison, out of the soil. Contrary to popular belief, the invasive species do not seem to be overly terrible and can be quite beneficial to the ecosystems.
Marris then offers an answer to why invasive species are held in such negative light. She suggests that this conception of invasive species partially comes from what people consider differences between species. For example, there are two cousin species of duck, the white-headed duck from Europe and the ruddy duck from the Americas (107). Though they look different and act different, the fact that they are able to successfully create a hybrid shows that they are compatible. The hybrid is becoming dominant, but many people are worried that each separate species will go extinct. Yet some scientists argue that the DNA from both species still carry on so it doesn’t matter if each species separately goes extinct.
In conclusion, Marris provide some great examples to show how invasive species and novel ecosystem can be beneficial to the biodiversity despite misconceptions.
