Wellesley is the longest running Tree City USA community of any city or town in Massachusetts. Wellesley's Tree Bylaw became effective July 1, 2011, requiring property owners to protect certain trees and critical root zones during construction projects, and replace trees that are cut down or donate money to a special tree fund. The Town's Natural Resource Protection (NRP) Development bylaw, approved by Town Meeting in 2013 applies to any subdivision generating 5 or more lots. This bylaw requires a minimum of 50% of the property be preserved as open space in exchange for reduced lot sizes without increasing density.