Today in our environmental science lecture, we'll discuss urban heat islands. Cities tend to be warmer than surrounding rural areas because buildings and roads absorb and re-emit heat. One surprising factor is the role of green spaces. Parks with trees can reduce local temperatures by up to 5 degrees Celsius. However, the effect is not uniform. The cooling impact depends on the size of the park and the density of tree cover. For instance, a small garden with scattered trees may only cool by 1 degree, while a large forested area can significantly lower surrounding temperatures. Planners should prioritize larger green corridors rather than many small patches.