<http://schema.org/about>
"Trees in the city don't just provide visual relief and cooling shade in the midst of the hard-edged urban jungle: They remove greenhouse gases and pollutants from the air, lower power"^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.treehugger.com/natural-sciences/city-trees-photographers-explore-the-urban-forest-slideshow.html>