การฟัง TOEFL

🎧 บทถอดเสียง

Narrator: Listen to part of a lecture in an environmental science class. Professor: Today we're discussing a phenomenon known as urban heat islands. Essentially, cities tend to be warmer than surrounding rural areas due to human activities and the concentration of heat-absorbing materials like concrete and asphalt. But there's a lesser-known factor: the lack of vegetation. Trees and green spaces not only provide shade but also release moisture through transpiration, which cools the air. A recent study in a mid-sized city found that neighborhoods with dense tree canopy were up to 5 degrees Celsius cooler on hot afternoons compared to nearby areas with few trees. Now, some city planners are proposing 'green roofs'—vegetated rooftops—as a solution. However, the initial cost is high, and maintenance requires ongoing care. So, the question becomes: should we prioritize planting more street trees, which are cheaper and provide immediate benefits, or invest in green roofs for long-term impact? The answer may vary depending on the city's climate and building density.