Today in our environmental science lecture, we'll discuss urban green spaces. A recent study in Manchester found that adding rooftop gardens can reduce building energy consumption by up to 25%. However, the main challenge is the initial cost, which is often 30% higher than traditional roofs. Despite this, the long-term savings in heating and cooling, plus the benefit of reducing stormwater runoff, make them a worthwhile investment. The study also noted that community parks have a greater cooling effect than individual rooftop gardens, especially in densely built areas.