Valuable farmland would revert to wilderness (cf. Isaiah 5:5-6), and it would only be good for hunting. Formerly cultivated land would be used for grazing because there would be so many briars and thorns and so few Israelites to take care of it. [source][source][source]
"This ends Isaiah"s address to king Ahaz. He does not expressly say when Immanuel is to be born, but only what will take place before he has reached the riper age of boyhood,-namely, first, the devastation of Israel and Syria, and then the devastation of Judah itself, by the Assyrians." [1][source]