Green Energy

First of all, "merely decorative" has a big impact on our physiological and psychological well-being; urban greening appears to be able to improve things from respiratory difficulties to stress, anxiety and depression .

Second, "merely decorative" isn't even true. Trees lower both surface and air temperature in cities in a meaningful way (on the order of a couple of degrees on a well-treed street -- that can be the difference between "ah, it's a nice day for a walk" and "holy crap it's hot out".