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