Source : Webster's Revised Unabridged Dictionary (1913)

Depopulation \De*pop`u*la"tion\, n. [L. depopulatio pillaging:
   cf. F. d['e]population depopulation.]
   The act of depopulating, or condition of being depopulated;
   destruction or explusion of inhabitants.

         The desolation and depopulation [of St.Quentin] were
         now complete.                            --Motley.

Source : WordNet®

depopulation
     n : the condition of having reduced numbers of inhabitants (or
         no inhabitants at all)