This is a figurative description of what God will do to Israel’s enemies. They are like lush, fertile land, but God will make them like a desert (compare 41.18-19). He will reverse their present, comfortable situation. This contrasts with what he will do for Israel (see verse 16). Good News Translation inserts a stanza break between verses 15 and 16 to indicate this change in topic.

I will lay waste mountains and hills: The Hebrew verb rendered lay waste can mean “to cause to dry up,” as in 37.25, but here it probably means “to destroy” or “to make desolate,” as in 37.18 (see the comments there). Mountains and hills often occur together in Isaiah (see, for example, 2.2; 40.12; 41.15). Languages that do not distinguish between them may render this line as “I will destroy all [big and small] mountains.”

And dry up all their herbage indicates that God will dry up all the plants and trees on the mountains. These areas will become barren. This line may be rendered “I will make all their plants and trees dry up” (similarly Good News Translation).

I will turn the rivers into islands, and dry up the pools: These parallel lines speak of God turning well-watered places into desert-like areas. I will turn the rivers into islands means the rivers will dry up so much that islands will start to appear in them. The Hebrew noun translated islands is often rendered “coastlands” elsewhere (see the comments on 41.1). Some commentators emend the Hebrew word ʾiyyim rendered islands to read tsiyyim, which means “barren land.” In Hebrew the letters we transcribe as ʾ and ts look very much alike, so it is easy to confuse them. Translators may follow either reading here. Good News Translation follows the emended text with “deserts” (similarly Revised English Bible). The Hebrew word rendered pools can refer to small bodies of water and marshes (see the comments on 14.23 and 35.7).

Translation examples for this verse:

• I will cause mountains and hills to crumble,
and dry up all their plants and trees.
I will turn rivers into dry land,
and dry up marshlands.

• I will destroy mountains and hills,
and will cause all their plant life to wither.
I will change rivers into deserts,
and dry up pools of water.

Quoted with permission from Ogden, Graham S. and Sterk, Jan. A Handbook on Isaiah. (UBS Helps for Translators). New York: UBS, 2011. For this and other handbooks for translators see here .