托福听力

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Listen to part of a lecture in an environmental science class. Professor: Today we're going to discuss urban heat islands, a phenomenon where cities are significantly warmer than surrounding rural areas. One major cause is the replacement of natural surfaces with materials like concrete and asphalt, which absorb and re-emit heat. Another factor is the lack of vegetation, as trees provide shade and release moisture through evapotranspiration. Interestingly, studies show that even small parks can create a cooling effect, lowering local temperatures by several degrees. However, the most effective mitigation strategy is the implementation of green roofs—rooftops covered with plants. These not only reduce heat absorption but also improve insulation, cutting energy costs for buildings. Some cities, like Toronto, have even passed bylaws requiring new developments to include green roofs. While the initial installation cost is high, the long-term benefits in energy savings and reduced air pollution are substantial. So, the challenge lies in balancing economic investment with environmental gains.