Whenever a Forest enters the battlefield, green creatures you control get +1/+1 and gain trample until end of turn.
Grandeur — Discard another card named Baru, Fist of Krosa: Create an X/X green Wurm creature token, where X is the number of lands you control.
The first ability triggers when a Forest enters the battlefield under any player’s control, but only your creatures get the bonus.
The size of the Wurm token is determined when the activated ability resolves. It won’t change as the number of lands you control changes.