Complex sentence: The deer population reached unprecedented levels in the 1990s, leading to a city-sponsored program that airlifted deer to surrounding areas from 1999 to 2002; a deer control program of sterilization and sharpshooting was subsequently deemed more humane and effective and approved in 2008.
Split into simpler sentences: The deer population reached unprecedented levels in the 1990s, leading to a city-sponsored program from 1999-2002 that moved deer to rural areas. A deer control program of sterilization and sharpshooting was subsequently deemed more humane and effective and approved in 2008.