Narrator: Listen to part of a lecture in an environmental science class. Professor: Today we're going to talk about urban heat islands. As you know, cities tend to be warmer than surrounding rural areas. This is due to several factors. First, concrete and asphalt absorb and retain heat during the day, then release it slowly at night. Second, buildings and tall structures block wind, reducing natural cooling. Third, there's less vegetation, which means less shade and less evaporation from plants. One solution is to increase green spaces, like parks and green roofs. Green roofs are covered with plants, which can lower rooftop temperatures by as much as 30 degrees Celsius. They also reduce stormwater runoff and improve air quality. However, the initial cost of installing a green roof is higher than a traditional roof. But over time, the energy savings from reduced air conditioning use can offset that cost. Also, green roofs can extend the lifespan of the roof membrane. So, while the upfront investment is significant, the long-term benefits are substantial.