Complex sentence: In the 1990s, as the number of young plantations decreased, so did forestry damage from serows; concern instead turned to damage caused by sika deer, wild boars, and Japanese macaques.
Split into simpler sentences: In the 1990s, as the number of young plantations decreased, so did forestry damage from serows. Concern instead turned to damage caused by sika deer, wild boars, and Japanese macaques.