GB and opponent's Ancient Forest

I know that if I control both Ancient Forest (Field card) and GB, I can tag out the GB first before the Forest effect destroys. How about if the opponent controls Ancient Forest, does my GB still get to tag out first or are they destroyed by opponent's forest?

Ancient Forest: When this card is activated, if there are any Defense Position monster(s) on the field, that monster(s) is changed to face-up Attack Position. Flip Effects are not activated at this time. Also, if a monster attacks, it is destroyed at the end of the Battle Phase.

Erm.... its written very nicely on your own post....

Ancient Forest (Field card)

I'm not sure about field cards ruling, can you please be more specific?

If opponent controls a Ancient Forest, I can still tag out my GB after battle first before the ancient forest effect?

erm. obviously yes. field card gives both players the same effect, it is in this case, 'unbiased' to whichever side. therefore no matter who uses the field card, both gb players will be able to tag out.

ok, got it! Thanks.