The decline of the honeybee population, known as colony collapse disorder (CCD), has been widely attributed to a single primary cause: the widespread use of neonicotinoid pesticides. This view is supported by three main arguments. First, neonicotinoids are neurotoxins that directly impair bee foraging behavior and navigation, leading to disorientation and failure to return to the hive. Laboratory studies have shown that even sublethal doses reduce foraging efficiency and increase mortality. Second, these pesticides accumulate in pollen and nectar, which bees carry back to the colony, exposing larvae and the queen. This chronic exposure weakens the entire hive, making it more susceptible to diseases and parasites, such as Varroa mites. Third, the timing of CCD outbreaks correlates with the introduction and expansion of neonicotinoid use in agriculture during the late 1990s and 2000s. Regions with intensive neonicotinoid application, like the U.S. Midwest, have reported higher colony losses, suggesting a direct cause-and-effect relationship.
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The professor challenges the reading’s claim that neonicotinoids are the sole cause of CCD. While she acknowledges that these pesticides are harmful, she argues that the evidence is not conclusive. First, laboratory studies often use doses far higher than those found in real fields; field studies with realistic exposure show no significant effect on bee survival or colony health. Second, the accumulation of pesticides in hives is not unique to neonicotinoids; many other agricultural chemicals and even natural plant toxins are present, yet CCD is not linked to them. Moreover, the correlation between neonicotinoid use and CCD is weak: CCD has occurred in regions where neonicotinoids are rarely used, such as parts of Europe, and the U.S. Midwest, which uses many pesticides, has not consistently shown higher losses compared to other areas. Instead, the professor suggests that a combination of factors—including Varroa mites, viral pathogens, and poor nutrition due to monoculture farming—more plausibly explains CCD. These stressors often act synergistically, and when managed properly, hives can survive despite pesticide exposure. Therefore, focusing solely on neonicotinoids oversimplifies a complex problem and diverts attention from other critical threats.
📝 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.
