Can you respond to a fetchland activation with a Stifle to counter it?

When you activate a fetchland (such as Flooded Strand), its activated ability is placed on the stack. Both players then receive priority and may respond before the ability resolves. Stifle specifically counters activated and triggered abilities, making it a legal and effective response to a fetchland activation.

Under CR 602.2, activating an ability follows these steps: announce the ability, pay costs (including the 1 life and sacrificing the land), and then the ability goes on the stack. Crucially, the land is sacrificed as a cost when the ability is activated — before anyone can respond — so the fetchland is already gone even if Stifle counters the ability.

Stifle (per its oracle text) counters target activated or triggered ability. CR 509.2 confirms that players receive priority after an ability is placed on the stack, allowing a response. When Stifle resolves and counters the fetchland ability, the ability is removed from the stack without effect — meaning you do not search your library or put a land onto the battlefield.

Concrete example: Your opponent activates Windswept Heath, sacrificing it and going to 19 life. In response, you cast Stifle targeting that ability. Stifle resolves; the fetch ability is countered. Your opponent has lost the Heath and 1 life but finds no land.

Note: Because the sacrifice is a cost (CR 602.2a), the fetchland cannot be 'saved' once activated — even if Stifle counters the ability, the land remains in the graveyard.