托福听力

🎧 听力原文

Listen to part of a lecture in an environmental science class. Professor: Today we're discussing the concept of 'urban heat islands.' This phenomenon occurs when cities are significantly warmer than surrounding rural areas. The main cause is the replacement of natural land cover with materials like asphalt and concrete, which absorb and retain heat. Additionally, waste heat from vehicles and air conditioning systems contributes. One surprising factor is the lack of vegetation. Trees and green spaces cool the air through evapotranspiration, but in dense cities, these are often scarce. To combat this, some cities have implemented 'green roof' programs, where roofs are covered with plants. A study in Chicago showed that green roofs can reduce surface temperatures by up to 40 degrees Fahrenheit on hot days. However, the initial cost is high, and maintenance requires water and care. Still, the long-term energy savings for buildings can offset these expenses. Now, let's consider the social implications...