People who were already poor would remain so. Most people who aren’t wealthy can’t afford to own acres of land that doesn’t produce crops. If leaves suddenly became money, that would not change the fundamental needs people have of food and shelter. So you’d have the wealthy with vast swathes of forest that would slowly die as they carted out a lot of compost for use in markets, and people who live in apartments or other rental situations would never see a leaf on the ground again. You might see suburban homeowners get really good about caring for their trees and planting more, so that’s one possible benefit but overall this would be a nightmare.