Scryb Ranger and Knights of Reliquary

[KobeBryan]

I have a scryb ranger and a knight in play.

I play knight to sac a forest. In response, I use my scryb ranger to bounce my forest to my hand.

Does my knight ability activate?

[Koby]

Both abilities require you to remove a Forest card from the battlefield to activate their abilities. You can only sacrifice or return one card to pay each of their costs. This requires 2 separate forests in play to achieve.

Once abilities are activated (costs are paid), their effect will happen even if the source is removed, provided it is not countered by spells or by the game (failed targets for instance).

[cdr]

As rukcus says, you have to distinguish between costs and effects. Costs are on the left side of the colon and are paid when you activate the effect, during which nothing else can happen.