Answer:
Growing new trees to replace old trees
Explanation:
Growing new trees in place of old ones sustains the environment, since trees help circulate oxygen and provide homes and nutrients for animals and other plants.
Any form of mining is bad for the environment and unsustainable in the long run, garbage is the same way, and putting it on land is only slightly better, and switching to other resources doesn't do anything but burn out more resources and does nothing to sustain anything.
Hope this helps :)
