Listen to part of a lecture in an environmental science class. Professor: Today, we're going to discuss 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 concrete and asphalt, which absorb and retain heat. Additionally, human activities, such as driving cars and running air conditioners, generate waste heat. But there are strategies to mitigate this effect. One effective approach is increasing urban vegetation, like planting trees on streets and creating green roofs. These plants provide shade and cool the air through evapotranspiration. Another strategy is using reflective materials for roofs and pavements, which bounce solar radiation back into the atmosphere. Some cities have also implemented 'cool pavement' programs, painting roads with lighter colors. However, these solutions require investment and planning. So, while the problem is serious, it's not unsolvable. What's important is that city planners and residents work together to adopt these measures.