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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 concrete and asphalt, which absorb and retain heat. Another factor is the lack of vegetation, as trees provide shade and release moisture through transpiration. However, there are strategies to mitigate this effect. For instance, green roofs—rooftops covered with plants—can reduce building temperatures and lower energy consumption. White or reflective roofs are also effective because they reflect sunlight rather than absorbing it. Additionally, increasing urban tree canopy not only cools the air but also improves air quality. Some cities have implemented policies to require these features in new buildings. Yet, challenges remain, such as the initial cost and maintenance. Despite these barriers, the long-term benefits, including reduced energy bills and improved public health, make these investments worthwhile. Now, let's consider a specific example: the city of Melbourne, which has set ambitious targets for increasing green spaces.