I was doing some bees, and i realize my biome was desert, so I go to change it and i switch it to jungle and i check F3 and nothing happens\ EDIT: It eventully changed
the biome is changed by a plugin which doesn't tell the client about the change, this means a reconnect is needed in order to update it on client side.
Well, Minecraft normally doesn't support changing biomes. the plugin edits the world save, but it can't send the update to your client. I'd also guess that forestry doesn't check each tick for the biome around the bees (which is good as it saves resources) so if you change the biome you need to reload the area. teleporting to a place far away (eg. nether) and not leaving a chunkloader would do as well as relogin.