The introduction of non-native species into new environments is often viewed as a threat to biodiversity. However, a growing number of ecologists argue that, under certain conditions, introducing non-native species can be a beneficial conservation tool. This perspective is supported by three main arguments.
First, non-native species can fill ecological niches left vacant by extinct or endangered native species. For example, in the Hawaiian Islands, the extinction of native avian pollinators has left many plant species without a means of reproduction. The introduction of non-native birds, such as the Japanese white-eye, has been observed to pollinate these plants, thereby preventing their extinction.
Second, non-native species can enhance ecosystem resilience by providing functional redundancy. In ecosystems where a single native species performs a critical role, such as seed dispersal or predation control, the loss of that species can be catastrophic. Introducing a non-native species that performs a similar role can buffer the ecosystem against such collapses, as demonstrated in some island ecosystems where introduced rats have inadvertently taken over the seed-dispersal roles of extinct native birds.
Third, non-native species can provide economic and social benefits that indirectly support conservation. For instance, introduced game species, such as pheasants and trout, generate significant revenue through hunting and fishing tourism. This revenue is often used to fund habitat restoration and conservation programs, which benefit not only the introduced species but also native wildlife.
🎧 听力讲座
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The professor challenges the points made in the reading, arguing that the purported benefits of introducing non-native species are often overstated and can lead to unintended harm.
First, while the reading claims that non-native species can fill vacant niches, this is rarely the case. The Japanese white-eye, cited as an example, is a generalist feeder and does not pollinate as effectively as native birds. It also competes with remaining native birds for food and spreads invasive plants, undermining the very plants it is supposed to save. In reality, the loss of a native species is critical because its role is unique and cannot be easily replicated.
Second, the idea that non-native species provide functional redundancy is flawed. Introduced rats, as mentioned in the reading, are not seed dispersers; they are seed predators. They destroy seeds and prey on native birds and insects, causing further declines. The extinction of native species often leaves a complex web of interactions that a single introduced species cannot replace. Instead of buffering the ecosystem, these introductions often cause cascading negative effects.
Third, the economic benefits of introduced species are a double-edged sword. Revenue from hunting or fishing may fund conservation, but it also incentivizes the continued stocking of non-native species, which can lead to habitat degradation. For example, trout introduced for sport have depleted native aquatic insects and amphibians, harming the very ecosystems that conservation funds aim to protect. Thus, the short-term economic gains are often outweighed by long-term ecological costs.
📝 Hướng dẫn viết Summarize the points made in the lecture, being sure to explain how they cast doubt on the specific points made in the reading passage.
📊 TOEFL Integrated Writing Rubric
Content Accuracy: Accurately capture the relationship between lecture and reading
Information Completeness: Cover all key counter-arguments from the lecture
Structure & Coherence: Logical organization and progression
Language Use: Grammar, vocabulary, expression accuracy
Scored 0-30 based on holistic scoring (original 0-5, scaled to 30).
