Planet Earth has been around for a long time. Chances are it is going to be around long after the spec of humanity is a forgotten scar on the face of the globe. There are basic elements that humans and other animals need to survive on this planet. The two most basic and most important are Breathable Air and Drinkable Water. The human body can only last about 3 days without drinking any water and only moments without breathing oxygen. Every day we neglect our responsibility to our environment is another day we threaten our survivability.
With the new technology, it's cheaper than ever to equip existing buildings with solar elements. Solar glass, solar roof shingles, industrial building panels. All public buildings should have them.