As this game is still early in development, now is the perfect time to come up with a strong system to avoid the problem of griefers. While it is true that griefing is not as severe now as it may become, it is likely that an effective solution would require some kind of deep integration into the game, and would be impractical to add later. Consider a foundation; when you dig the foundation, you don't need it because there's no house on top of it; when you need the foundation, it's too late to add it, because there's a house in the way.
On to the matter at hand; we must first define what a anti-grief system should do. There are several options here; it could be that it identifies griefers, then warns, kicks, and bans them. It could be a purely democratic system that allows players to identify griefers and vote them out of the game. Or it could be a codeless solution, such as appointed moderators with god powers.
What needs to be considered at all times is: will this solution be worse than otherwise? Consider an automatic system; if it is wrong or poorly identifies griefers, then pretty quickly player will get fed up with getting warnings when all they did is cut down a tree in the wilderness. Even a democracy system could be exploited by a gang that goes around mob-accusing individuals before anyone else can vote.
So, let's work out a good way to do whatever a Anti-Griefer should do.