After a landslide in 2017 killed 1,141 people and left more than 3,000 homeless in Sierra Leone's capital Freetown, the recovery plan included training residents to plant 21,000 native trees to reduce the risk of future disasters on bare hillsides.
Amid erratic and unusually heavy rains, as well as urban expansion, the city's mayor has also run a "Freetown the Treetown" campaign to increase green cover 50% by the end of 2022, with locals tracking tree growth via a smartphone app.
In Seoul, meanwhile, the city government worked with residents to restore the Cheonggyecheon Stream, a river covered by a highway overpass for decades.