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Listen to part of a lecture in an environmental science class. The professor is discussing urban heat islands. Professor: Today, let's talk about urban heat islands. This phenomenon occurs when cities are significantly warmer than surrounding rural areas. Why? Well, one major factor is the replacement of natural surfaces with materials like asphalt and concrete, which absorb and retain heat. Also, buildings and roads block wind, reducing natural cooling. Another contributor is the lack of vegetation. Trees and green spaces provide shade and release moisture through evapotranspiration, which helps cool the air. In contrast, cities often have limited green areas. To combat this, some cities have implemented green roofs, which are covered with plants. These roofs can lower rooftop temperatures by up to 30 degrees Celsius and reduce the need for air conditioning. Additionally, using lighter-colored materials for pavements and buildings can reflect more sunlight, further mitigating the effect. So, while urban heat islands pose challenges, innovative design can make a real difference.