Following Korra's decision to keep the spirit portals open, Republic City has become overgrown with giant spirit vines. These vines are indestructible and disrupt daily life, causing Korra's public approval rating to plummet to 8%.
Facing banishment from Republic City by President Raiko due to the vine crisis, Korra and Tenzin decide to travel the world to find and recruit the new airbenders to rebuild the Air Nation . Key Themes [S3E1] A Breath of Fresh Air
The central theme of the season is established here, as the world adapts to the permanent presence of spirits and the rebirth of a long-extinct culture. Following Korra's decision to keep the spirit portals
The Legend of Korra S3E1 "A Breath of Fresh Air" - TV Tropes [S3E1] A Breath of Fresh Air