Biome Stick

Biome sticks can be used on your island to change its biome. This has a few mostly minor effects, with the exception of some specific biomes. Most changes are simply visual, although it can also affect mobs spawning on your island. You can limit the type of mobs that spawn with certain sticks, but you cannot stop spawning completely with it.

Uses

 * Warning: There's no biome stick for the default/plains biome, any changes made will prevent you from going back (although you can switch between biomes).

Biome sticks can be used in two ways:
 * Specific Area: This will convert a small area around where you use it to the new biome. Reload island (leave/come back) for the best effect. You can change the effect radius to between 1 and 5 (left click) or apply to biome to the targeted block (right-click).
 * Island: Talking to Jerry will let you change the biome for your entire Private Island. Note that you need to leave your private island to apply the biome.

List
All biome sticks change the color of foliage.