Truth to tell, there is no magic cure for the world's ills. But you can help with sensible plantings. You will, for the most part, not see any change. However, in minute amounts, you will have worked for the better. You can plant to help the air, the water, and the ground.
To help the air, plant to create biomass and reduce CO2. Let's go back to elementary biology and the carbon cycle: Animals take in oxygen and give off CO2, a greenhouse gas. (So do vehicles and any sort of combustion.) Plants take in CO2 and give off oxygen. The more plant mass there is, the more CO2 it will consume. Now, look at your property. Any additional plant material will help reduce CO2. Look especially at your lawn. Do you use it? If you don't, consider putting anything else in that has more mass than grass. Grass is a thin layer spread over the earth; larger plants, especially trees, use up much more CO2 than the same area planted in grass. You can have both: Trees that create light shade will still allow for grass underneath (or grass and shrubs, even better.) Except when first planted, trees and shrubs use less water and fertilizer than immaculately kept lawns.