Nghe TOEFL

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Listen to part of a lecture in an environmental science class. The professor is discussing the effects of urbanization on local ecosystems. Professor: Today we're going to talk about urban heat islands, a phenomenon where cities are significantly warmer than surrounding rural areas. This happens because concrete, asphalt, and buildings absorb and re-radiate heat, while vegetation, which provides shade and releases moisture, is reduced. The temperature difference can be as much as five to ten degrees Celsius at night. This affects not only human comfort but also local weather patterns. For example, warmer cities can increase the formation of smog and alter precipitation patterns. One way to mitigate this is through green roofs, which are covered with plants. These roofs reduce heat absorption, improve insulation, and even capture rainwater. However, they require careful maintenance and are more expensive to install initially. Another approach is increasing the albedo, or reflectivity, of surfaces by using lighter-colored materials. This is cheaper but less effective in terms of additional benefits like biodiversity. So, as urban planners seek solutions, they must weigh costs, benefits, and long-term sustainability.