The urbanization of natural landscapes has been widely criticized for its negative environmental impacts. However, a growing number of urban planners argue that well-designed cities can actually enhance biodiversity. This perspective rests on three main arguments. First, cities create novel habitats, such as green roofs, vertical gardens, and abandoned industrial sites, which can support species that are rare in surrounding agricultural or monoculture landscapes. For example, certain native bee species have been found to thrive in urban gardens due to the diverse flowering plants and lack of pesticides. Second, urban heat islands can extend growing seasons and allow warmth-loving species, such as some butterflies and lizards, to expand their ranges toward the poles, thereby increasing regional species richness. Third, cities often act as refuges for endangered species because they harbor fewer natural predators and less intense competition than wild habitats. The peregrine falcon, once nearly extinct, now nests successfully on skyscrapers in many metropolises, benefiting from the absence of predators and an abundance of urban pigeons.
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The lecture challenges the reading's optimistic view that cities enhance biodiversity. While the reading highlights novel habitats, the professor points out that these habitats are often ecological traps. For instance, green roofs and vertical gardens attract insects and birds, but they lack sufficient soil depth and food resources to sustain breeding populations, leading to high mortality rates. Regarding the extended growing seasons from urban heat, the professor argues that this benefit is outweighed by the increased frequency of extreme heat events, which can be lethal to many species, especially those not adapted to high temperatures. Moreover, the expansion of warmth-loving species into cities often comes at the expense of native cold-adapted species, reducing overall biodiversity rather than increasing it. Finally, the professor disputes the refuge argument by noting that urban environments expose species to novel threats such as light pollution, vehicle strikes, and toxic runoff. The peregrine falcon example is misleading because its success is largely due to active human management, including nest boxes and captive breeding programs, not natural urban conditions. In summary, the lecture concludes that cities generally homogenize fauna and flora, favoring generalist species while driving out specialists, thereby undermining the reading's claims.
📝 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.
