The destruction is much to precise. This trumpet judgment will come directly from God. I believe that God will literally bring about a worldwide hailstorm. This hailstorm will be unlike any that man has encountered. These will be hailstones of fire and will bombard the earth unmercifully destroying one third of the trees and cover the ground like freshly fallen snow burning up all the grass.
Trees act as a giant air filter for the world, continuously cleaning and re-cleaning the air.
With one third less trees the air will barely be consumable.