Biome Stick

Biome sticks can be used on your island to change its biome. Changing the biome of the island can cause a variety of changes which are mostly minor(ex: foilage color), but can also cause more major changes, like weather or mob spawning. Using the biome stick, you can limit what mobs can spawn by changing the biome, although it cannot completely stop mob spawning.

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).

Uses
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.