There are two things one can do when one finds oneself in a hole. One is to stop digging and the other is to start filling in the hole. Conservation really amounts only to digging more slowly. The solution to global warming is not just to put less CO2 into the air, but also to start taking some out. Trees do that.
The bigger and longer-lived the species the more CO2 it will take out of the atmosphere during its lifetime. Here is a link to the California Department of Forestry's seedling order form.
Vacant lots, roadsides, fields, hiking trails, private property, public property, anywhere is good. When Jews do this it is called Tikkun Olam. When non-Jews do it, it is called repairing the world.