Plant Your Roof
It's a wonder that this concept attributed to the Hanging Gardens of Babylon, one of Seven Wonders of the World, didn't catch on sooner in the modern world. Legend has it that the roofs, balconies, and terraces of the royal palace of Babylon were turned into gardens by the king's order to cheer up one of his wives. Roof gardens help absorb heat, reduce the carbon dioxide impact by taking up CO2 and giving off oxygen, absorb storm water, and reduce summer air conditioning usage. Ultimately, the technique could lessen the "heat island" effect that occurs in urban centers. Butterflies and songbirds could also start frequenting urban garden roofs, and like the king's wife, could even cheer up the inhabitants of the building. Here, a green roof is tested at Chicago's City Hall.
Bioremediation uses microbes and plants to clean up contamination. Examples include the cleanup of nitrates in contaminated water with the help of microbes, and using plants to uptake arsenic from contaminated soil (like the Arabidopsis in the image above), in a process known as phytoremediation. The U.S. Environmental Protection Agency has used it to clean up several sites. Often, native plant species can be used for site cleanup, which are advantageous because in most cases they don't require pesticides or watering. In other cases scientists are trying to genetically modify the plants to take up contaminants in their roots and transport it all the way to the leaves for easy harvesting.