Here is the full list of all 10 The Forest Cathedral achievements.
Spray five swamps with DDT
Learn to use your tools and finish the Warehouse section
Finish the first scan of the swamp with the little man
Use the little man to restore power to Mr. Valve
Complete the Fish Ladder terminal
Complete the Gate Terminal
Come to a realization about DDT's interaction with the food chain
Complete the Eagle's nest terminal
Complete the final terminal with the little man
Tell the world about the dangers of DDT