 Number one, take stock of what's around you. Number two is get involved with any neighbourhood groups that exist, and there's so many wonderful ones. Even just type in urban forestry and your city name, urban forestry and your neighbourhood name, urban trees and your neighbourhood name, and hopefully you'll come across an environmental group that is working on these issues, and that could either be advocating for more tree planting in your area, that could be maintaining the trees that are already there,