An ecologically critical gate is the gatekeeper scenario’s answer to the question of which automated decisions deserve the most scrutiny. Not every gate is equal — a film recommendation is not housing, employment, healthcare, banking, identity, education, public benefits, or justice. A gate becomes critical when a refusal significantly reduces a participant’s ability to continue functioning elsewhere in the ecology, which is a better test than the vaguer “high-risk AI” because it asks something measurable in principle: how much downstream traversability can this decision remove?
The classification is the point of the Gate Map: first locate every gate, then identify which ones can strand a participant. Those are the gates that most need contestability, alternative paths, propagation limits, and independent appeal — and the ones where letting a single model become the only route is least acceptable.