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Listen to part of a lecture in an environmental science class. Professor: Today, let's discuss a fascinating phenomenon known as 'urban heat islands.' As cities grow, they replace natural surfaces like soil and vegetation with concrete, asphalt, and buildings. These materials absorb and retain heat from the sun much more effectively than natural landscapes. As a result, urban areas can be significantly warmer than surrounding rural areas, sometimes by as much as 5 to 10 degrees Fahrenheit. This temperature difference is most pronounced at night, when the stored heat is slowly released. Now, what can be done to mitigate this effect? One common solution is increasing tree canopy coverage. Trees provide shade and release moisture through transpiration, which cools the air. Another approach is using reflective roofing materials, often called 'cool roofs,' which reflect more sunlight and absorb less heat. Additionally, green roofs, covered with vegetation, can reduce heat absorption and improve insulation. However, these solutions require careful planning and investment. Some cities have adopted policies to encourage their implementation, but progress remains uneven. So, while the problem is well understood, the challenge lies in applying these solutions on a large scale.