托福听力

🎧 听力原文

Narrator: Listen to part of a lecture in an environmental science class. Professor: Today we're going to talk about 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 retain heat. Another factor is the lack of vegetation, since trees and plants provide shade and release moisture through transpiration, cooling the air. However, cities can mitigate this effect through green roofs. A green roof is a rooftop covered with vegetation and a growing medium. These roofs not only insulate buildings, reducing energy costs, but they also lower the ambient temperature by reflecting sunlight and releasing moisture. Studies show that widespread adoption of green roofs can reduce a city's average temperature by several degrees. Additionally, they manage stormwater runoff, absorbing rainwater that would otherwise overwhelm drainage systems. So, while the initial installation cost is higher than traditional roofs, the long-term benefits are substantial. Now, let's consider some challenges...