On the other hand, trees cool down the area so having lot of them should lead to fewer heat-strokes. Last week we hit 95F in my area and I wouldn't be able to walk my dog if not for the trees.
An interesting question is: Have people trees because is rich, or they are richer because they had trees? (and this will save a lot of money each year on energy bills, food and even psychologists). Trees are a tool to fight poverty. The problem is how to made the poor people respect them.