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Listen to part of a lecture in an environmental science class. Today we're going to discuss the concept of 'green roofs' and their benefits. A green roof is a building roof that is partially or completely covered with vegetation and a growing medium, planted over a waterproofing membrane. While this idea might seem modern, it actually has ancient roots, like the famous Hanging Gardens of Babylon. However, the modern green roof movement started in Germany in the 1960s. One major benefit is stormwater management. In cities, heavy rain often overwhelms sewage systems because water runs off impervious surfaces like concrete. Green roofs absorb rainwater, reducing runoff by up to 60% in some cases. They also provide insulation, which cuts heating and cooling costs. But perhaps the most exciting advantage is biodiversity: green roofs can create habitats for birds, insects, and plants that have lost their natural urban spaces. Of course, there are challenges. Green roofs are heavier and more expensive to install, and they require regular maintenance. However, as cities become denser, these roofs offer a way to combine urban development with environmental sustainability.