Debatable, a large issue is land use and for all the land we have here in the US alone large swathes of it are used for single family homes promoting horrible density. We dump carbon into the air, have less arable land, and destroy more natural habitats than necessary because of poor planning and regulation.

There is more issues to be solved, yes - but reversing wasteful land use is a HUGE component of preserving our planet and quality of life.