Jeremiah 12:4 - Matthew Poole's English Annotations on the Holy Bible

The prophet seems to give a reason of his former passion and prayer against those wicked men he before reflected on, because they were the cause of the nation's ruin, which is also asserted by the psalmist, Psalms 107:34. A land is said to mourn, metaphorically, when it is brought to an ill complexion, and looketh unpleasantly, the grass and green herbs in it being destroyed by enemies, or drought, or vermin. Nay, the effects of their wicked courses reached to the very beasts and birds, because they were so presumptuous as to conclude that they should do well enough, neither the prophet nor any other should see their last end.