That trees have a calming effect on populations and create a feeling of comfort and provision. Also, in hot places, if you remove the stressor of hot concrete and more heat from above, you might help people feel more relaxed.

Hm, yeah, trees to make me feel more placid and less oppressed than concrete, you're right. I wonder if, with less anger/feeling of being trapped, would-be criminals would rationally see other ways out of their crappy situations.