Today in our environmental science lecture, we'll discuss urban green spaces. A recent study in Melbourne found that parks can reduce local temperatures by up to 4 degrees Celsius during heatwaves. However, the effect depends on the size and tree coverage. Small gardens with scattered trees have minimal impact, while large connected parks with dense canopy create a 'cool island' effect. Interestingly, the study also noted that water features, like ponds, contribute more to humidity than to temperature reduction. So, for city planners, prioritizing large, shaded areas is more effective than adding many small green pockets.