The expansion of urban areas into surrounding natural habitats is often justified by economic growth, but this practice has severe ecological consequences. First, urban sprawl fragments habitats, isolating animal populations and reducing genetic diversity. When roads and buildings divide forests or grasslands, species such as large mammals cannot migrate freely, leading to inbreeding and increased vulnerability to disease. Second, urbanization increases surface runoff and pollution. Impervious surfaces like concrete prevent rainwater from soaking into the soil, causing flash floods and carrying oil, heavy metals, and lawn chemicals into rivers and streams, which degrades aquatic ecosystems. Third, city lights and noise disrupt wildlife behavior. Artificial lighting confuses nocturnal animals and migratory birds, while constant traffic noise masks the sounds used by many species for communication and predator detection, ultimately lowering reproductive success. These three factors demonstrate that urban expansion, if unregulated, poses a serious threat to biodiversity.
🎧 听力讲座
🎯 模拟考试环境：先点「播放讲座」听完内容，再作答。听力原文默认隐藏。
The reading presents a bleak picture of urban expansion, but its claims are overstated and ignore modern mitigation strategies. First, while habitat fragmentation is a concern, urban planners now design green corridors—strips of vegetation that connect isolated patches. These corridors allow animals to move safely between areas, maintaining gene flow. For example, in Banff National Park, wildlife overpasses have successfully reduced genetic isolation among bear populations. Second, the argument about runoff and pollution fails to acknowledge advances in green infrastructure. Cities are increasingly installing permeable pavements, rain gardens, and constructed wetlands that filter pollutants and allow water to infiltrate the ground. Studies show that these measures can reduce stormwater runoff by up to 80% and significantly lower pollutant loads in nearby waterways. Finally, the effects of light and noise can be mitigated through thoughtful design. Shielded streetlights that direct light downward, dark-sky policies, and noise barriers along highways have proven effective in reducing disruption. For instance, some cities have dimmed lights during bird migration seasons, resulting in fewer bird collisions. Thus, with careful planning, urban growth can coexist with ecological health.
📝 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.
