TheStockholm Resilience Centreidentifiesfreshwater useas one of theplanetary boundaries that has already been exceeded, threateningecosystems and biodiversity. Overuse of water resourcesdisrupts natural cyclesand leads todesertification and water scarcity.

Ocean acidification (B) is increasing but has not yetfully crossed the boundary, while ozone depletion (C) has beenpartially reversed due to global policy efforts (e.g., the Montreal Protocol).