UPCAT Reading Comprehension practice question 18: The passage implies that the nighttime cooling effect of trees deserves attention because

Two neighborhoods in the same city can differ by as much as five degrees Celsius on the same afternoon. The mechanism is straightforward. Asphalt and concrete absorb solar radiation during the day and release it slowly after sunset, so a district with little vegetation stays hot long into the night. Trees interrupt the cycle twice: their canopies block radiation before it reaches the pavement, and the water they release through their leaves carries heat away as it evaporates.

Measurements across several tropical cities suggest that raising canopy cover from ten percent to thirty percent of a district's surface lowers peak afternoon temperature by roughly two to three degrees. The effect on nighttime temperature is smaller but more consequential for health, since sustained overnight heat is what drives hospital admissions during heat waves.

Canopy cover, however, tracks income closely. Wealthier districts were often planted decades earlier, and their trees have had time to mature; newer settlements built at higher density have narrow roads with no space reserved for planting. The result is that the residents most exposed to extreme heat, and least able to afford air conditioning, live where there is least shade.