Jeremiah 9:10

"For the mountains will I take up a weeping and wailing, and for the pastures of the wilderness a lamentation, because they are burned up, so that none passeth through; neither can men hear the voice of the cattle; both the birds of the heavens and the beasts are fled, they are gone. And I will make Jerusalem heaps, a dwelling place of jackals; and I will make the cities of Judah a desolation, without inhabitant."

The weeping and the wailing here are because of the forthcoming desolation upon Jerusalem and Judaea. The mountains, which once teemed with life, and the pasture lands (here called `wilderness') which once supported numerous herds of sheep and cattle, all of this is to be destroyed; even the Holy City itself shall be without inhabitant, deserted, a den of jackals! The answer as to why it is necessary for God to bring such destruction against the land of his people is in the following verses.