Global seagrass decline is a serious concern. This study uses two long-term datasets from the western Gulf of Mexico (Laguna Madre) to investigate the rapid decline of seagrass meadows. A significant increase in water depth since 2014 (14–25 mm/year) coincided with the complete disappearance of *Halodule wrightii* and *Syringodium filiforme* at a deep-edge monitoring station within five years. A basin-wide assessment revealed seagrass loss at 23% of 144 sentinel stations. Models incorporating different sea level rise scenarios predict substantial global seagrass habitat loss (14,000 km²), with expansion into new shallow habitats limited by shoreline hardening.

Kyle A. Capistrant-Fossa, Kenneth H. Dunton