長文読解（人文系・自然科学系の文章）- 問題22

The phenomenon of urban heat islands has become a significant environmental concern in cities worldwide. This effect occurs when urban areas experience significantly warmer temperatures than their rural surroundings due to human activities and infrastructure. The primary causes include the replacement of natural vegetation with concrete and asphalt, which absorb and retain heat more efficiently than plants.
Research conducted in major metropolitan areas shows that temperature differences between urban and rural zones can reach up to 5°C during summer months. Buildings, roads, and parking lots create surfaces that store solar energy during the day and release it slowly at night, preventing cities from cooling down effectively.
Scientists have identified several strategies to mitigate urban heat islands. Green roofs and vertical gardens can reduce surface temperatures by up to 3°C through evapotranspiration. Additionally, increasing tree coverage in urban areas provides natural cooling through shade and moisture release. Some cities have implemented "cool roof" programs, using reflective materials that bounce solar radiation back into the atmosphere.
The implications of urban heat islands extend beyond comfort levels. Higher temperatures increase energy consumption for air conditioning, contributing to greenhouse gas emissions. Moreover, extreme heat poses health risks, particularly for elderly residents and those with cardiovascular conditions, making urban heat island mitigation a critical public health priority.