Joel was written during the locust plague, a time of great distress for the people. The prophet sees in the devastation of the locusts an indication of the coming of the day of the Lord. Therefore all must repent with fasting and mourning. With repentance, however, there is a promise of relief and God’s blessing for Israel.

Joel 1

1:20 The beasts of the field cry also unto thee: for the rivers of waters are dried up, and the fire hath devoured the pastures of the wilderness.