If asked, before this study, I would have said the key feature in the Book of Joel is the locust; now I would say it is “the land” or “His land.” The reason for the locust came was to distress the people and clean the land. Sometimes our English translations don’t do the Hebrew text justice. Joel used specific words when he talked about valleys and mountains that change the mental pictures of his prophecy. He does the same thing when he is writing about land or ground; most of the time the word is erets, but twice the word adamah is used.
David states in Psalm 24:1 “the earth is the Lord’s and everything that is in it.” Joel is writing to the “elders” and “the all” that live in THE LAND. In 1:6 and 3:2 Yahweh refers to this piece of real estate as “My land” and Joel in 2:18 calls it “His land.” The word is erets and refers to earth or by extension all of the earth is His because He made it. But that little sliver of land we call Israel is very special to Him. It is no mistake that he led Abram there and promised it to his yet unborn children. New Jerusalem will be placed there and some Bible teachers will make the argument that is where the Garden of Eden (2:3) was. Those locusts were sent to strip the fields and pastures and so cover the mountains and valleys in order “to clean” it off. This, in turn, produced the anguish/repentance that was needed. The army of locust/army of people will be judged for what they do in Israel.
Adamah the word for ground/earth is used in 1:10 and 2:21, and it refers to red or productive ground and is the ground that Adam came from. This term is important because it is a promise for us; when we are obedient the ground is productive, but rebellion will hinder that productiveness. 1:10 is dealing with the rebellion/loss of production and 2:21 is when Judah is promised blessings again.
The razing of the land talked about in Joel sounds like the destruction that the Roman army brought when they destroyed Jerusalem in 70 A.D.
God is the Master Gardener; He is letting us use His earth we need to take care of it as best we can.