The introduction of invasive species to new environments often leads to severe ecological disruption. One prominent example is the introduction of the cane toad (Rhinella marina) to Australia in 1935 to control agricultural pests. Three key arguments support the view that cane toads have caused irreversible damage to Australian ecosystems. First, cane toads are toxic at all life stages; their skin and parotoid glands contain bufotoxins, which are lethal to many native predators such as quolls, goannas, and snakes. Second, cane toads have a high reproductive rate and no natural predators in Australia, allowing their population to expand rapidly across the continent, outcompeting native amphibians for food and breeding sites. Third, the toads' range expansion has been facilitated by their ability to adapt to various habitats, from tropical rainforests to arid inland regions, leading to a continuous spread that is difficult to control. These factors together suggest that cane toads pose a persistent and growing threat to biodiversity, and eradication efforts have been largely unsuccessful.
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The professor challenges the reading's claims about cane toads. First, while it is true that cane toads are toxic, the reading overstates the impact. Recent studies show that many native predators have learned to avoid cane toads, and some species, like the Australian water rat, have developed strategies to safely consume them by flipping them over and eating only the non-toxic internal organs. Thus, the toxicity is not an insurmountable threat. Second, the reading claims that cane toads outcompete native amphibians, but this is not supported by evidence. Cane toads prefer disturbed habitats and open areas, whereas most native frogs inhabit pristine forests and waterways. Moreover, cane toads are less efficient at capturing certain prey, such as flying insects, so they do not directly compete with native species for the same food resources. Third, the reading suggests that cane toads are unstoppable, but recent research indicates that their range expansion has slowed. This is due to a combination of factors, including a disease called lungworm that has spread through toad populations, and the fact that toads in arid regions have lower survival rates. Some control methods, such as trapping and the use of pheromone lures, have shown promise in reducing local populations. Therefore, the situation is more nuanced and less catastrophic than the reading implies.
📝 写作提示 Summarize the points made in the lecture, being sure to explain how they cast doubt on the specific points made in the reading passage.
