I believe that gardens should be a more widespread thing. Roof gardens, backyard gardens, anywhere. Gardens are necessary because they provide many benefits–such as reducing carbon dioxide in the air, providing healthy, accessible food, and it lets you save money.
Wherever there is free space, we need gardens because the amount of carbon we humans put out is too much for the plants in the world to absorb alone. They need support from even more plants. These plants should be encourage by humans, who have cut down countless trees to make room for ourselves. To give back, even if the original actions were made long before we were born, we should plant things again. The place should be as green as it was when the humans were not there.
In the Permaculture Class at U-M, we learned that the forest used to cover the entirety of Michigan. When people came to settle in Michigan, many of these forests were cut, but now it is making its way back up to the original percentage of land coverage. However, just making it to the original is not sufficient because we have been burning many fossil fuels. This releases more carbon dioxide into the air than before, when the forests covered the entirety of Michigan. So we definitely need more greenery in the world to bring the carbon dioxide to a normal level.