Arborescence by Rhett Davis

Bren and his partner Caelyn are feeling at a standstill in their lives. One day they come across a video of people in the forest who believe that if they stand still for long enough they will transform into trees. The idea is absurd. But it's spreading. Soon, people start to go missing and trees appear in unlikely places.

As cities decay and the world becomes greener, Caelyn becomes more and more convinced that arborescence is exactly what will save the planet from human destruction. Bren isn't so sure. Drifting apart, Bren and Caelyn are forced to question what it really means to be human - and if they are ready to stand still.