Another left fairy tale. Grow food in the city, let the farms revert to wilderness, as one comment on the article suggested. The article itself suggests this is unlikely due to the biomass required.
Of course, it is now known that both North and South America's forests were under intensive management by natives for centuries. The wild state of the forests seen later existed only after native populations were devastated by disease. Thus reverting the countryside to a wild state would be something it has never been in five thousand years or more.