Originally Didn't Want to Get Involved [Natural Disasters]

A month of fine, drizzling rain had passed, and Wen Xian had stayed in this spring‑like southern town for the same duration. Finally, on a clear day, Wen Xian grabbed a basket to go pick some mushrooms in the mountains—only to be devoured by a suddenly appearing giant tree.

When Wen Xian returned to the town, he realized that the outside world had completely changed, as if humanity had been sent back to a primitive era, barely clinging to survival.

To make matters worse, humans were still killing each other.

Note: This is a mutated flora and fauna apocalypse story with natural disasters, but no zombies.