Today in our environmental science lecture, we're discussing urban farming. One key point is that rooftop gardens can reduce a building's energy consumption by up to 25% because they provide natural insulation. However, the initial cost of installing such a garden is high, often exceeding $50,000 for a medium-sized roof. Despite this, many cities offer tax incentives to offset these expenses. For example, in Chicago, building owners can receive a rebate of $5 per square foot of green roof. This has encouraged over 600 projects since 2005. But remember, maintenance requires regular watering and weeding, which adds ongoing costs.