Both. People seek out trees, which drives up the prices of houses on tree-lined streets. But rich people also have more resources to spare to plant and protect trees.
Also, rich people tend to stay in the same place for longer, so they have more incentive to nurture small trees in the anticipation of enjoying big trees later in life -- pretty much the "owners make better neighbours than renters" issue.
Yes. I think owning versus renting/tenanting/being housed may have a lot to do with this. Why go the the effort of planting trees and spending your time on your landlords garden.
This is exactly why yard service is included with my rental home. I want to know my yard is being taken care of. However, in the 13 years I've been a home owner... I've never planted a tree. I actually had one removed during a backyard makeover.
In the US most of the trees you see in residential areas are actually species that are native to Europe, meaning that most of them were planted by a rich person at some point.
