雅思听力

🎧 Listening Transcript

Good morning, everyone. Today we're going to look at how urban trees affect city temperatures. A recent study in Melbourne compared two streets: one with a dense canopy of mature elms, and another with only young, sparse plantings. Over a summer week, the shaded street had an average surface temperature that was 4.2 degrees Celsius lower than the exposed street. Interestingly, the air temperature difference was smaller, only about 1.1 degrees, because wind mixed the air. However, the researchers noted that the cooling effect increased significantly when tree canopies covered more than 30% of the street area. They also found that the type of tree mattered less than the overall leaf density.