A major contribution to the heat and drying out that many cities are experiencing is due to building structure and the paving over of the landscape. The re-radiation of sunlight as heat creates a "heat island" effect that contributes to planetary warming and prevents water from going into local aquifers. The strategies of UNpave, green roofs and urban reforestation are several ways of counteracting this problem. Another is the "living wall" incorporated into exterior multi-story building facades, such as the tallest living wall yet in Sydney, Australia.
Another living wall in Madrid (photo above) is also by Patric Blanc.
This is a creative approach that is used as an artistic statement, and an incremental one that can help mitigate the impact of construction in urban areas. It's a very visible application of plant material used as part of a dynamic urban environment, and puts in high profile the drip irrigation and grey water systems that recycle water and make it available to the environment again.