Today in our environmental science lecture, we'll discuss urban heat islands. Professor Thompson explained that cities are often warmer than surrounding rural areas due to concrete and asphalt absorbing heat. However, a recent study in Melbourne found that planting more trees can reduce temperatures by up to 2 degrees Celsius. The study also showed that green roofs are less effective than street trees, but they still help with insulation. Interestingly, the cooling effect is strongest during the night, not during the day. This is because trees release moisture at night, which helps lower the air temperature. The professor concluded that city planners should prioritize tree planting in residential areas.