Put together a national collective through NPO's that plants trees. They improve land and appease the important goals of land/soil fertility, climate protection, species protection, population control, air quality assurance, and beautification. We should first target freeway areas which are the site of much CO2 emission, pollution, and visible land; next, target farm areas to prevent soil erosion and multiculture farming; then target environmentally damaged areas to ensure proper treatment of land. Last, target open landscapes that have no trees only because, well, we haven't planted any, and in 30 years they will be beautiful areas for us to enjoy.
This project is the most economically efficient way to accomplish all of these goals collectively even if you need to fund it a little bit.