TOEFL Integrated Writing

📖 Reading Passage

The introduction of non-native species into new environments often has catastrophic effects on local ecosystems. However, some scientists argue that in certain cases, introducing exotic species can be beneficial and should be considered as a conservation tool. Three main arguments support this controversial practice. First, non-native species can fill ecological roles left vacant by extinct or endangered native species. For example, in the Hawaiian Islands, the introduction of the Chinese rose beetle (a decomposer) has helped break down leaf litter, a role once performed by native beetles that have largely disappeared. Second, exotic species can provide economic benefits, such as tourism revenue from charismatic animals like the introduced fallow deer in New Zealand, which attracts hunters and wildlife viewers. Third, some introduced species may help control invasive pests that damage native flora. In the American Southeast, the introduction of the Asian lady beetle has been credited with reducing populations of aphids that threaten crops and native plants, thereby decreasing the need for chemical pesticides.

🎧 Listening Lecture

The points in the reading may sound plausible, but they are flawed upon closer examination. First, the claim that non-native species fill vacant ecological roles is misleading. The Chinese rose beetle, for instance, does not break down leaf litter as efficiently as native beetles, and its activity alters soil nutrient cycles, harming native plant species that rely on specific decomposition rates. Thus, it does not truly replace the missing species; it disrupts the ecosystem further. Second, the economic benefits from charismatic exotics like fallow deer are short-term and often backfire. These deer overgraze native vegetation, leading to soil erosion and loss of habitat for endemic birds, which ultimately reduces long-term revenue from nature-based tourism that depends on pristine ecosystems. Third, the use of exotic predators like the Asian lady beetle to control pests is risky because these predators may also prey on native beneficial insects, including native ladybugs, leading to a decline in biodiversity. Moreover, they do not always target the intended pests, and their populations can explode, requiring costly management. Therefore, the supposed benefits of introducing exotic species are outweighed by their negative ecological consequences.