The tsunami disaster on December 26, 2004 affected our mangrove sites and many people we know; we feel that the antierosion function of mangroves has been paid too little attention. For years, we, together with many other scientists, have critically assessed and criticized the conversion of mangroves to tourist resorts or shrimp farms in light of the ecological, socioeconomic, and physical function of these forests. An early warning system to announce the arrival of tsunamis or other ocean surges (let us not forget that the much more frequent cyclones locally have the same effect) can save many lives, but an additional early warning system such as the one introduced in this paper to detect obvious or cryptic mangrove degradation may even save more in those areas where mangroves protect communities living behind and within the mangrove forest. We dedicate this paper to all those who were affected by the tsunami, particularly those who, were it not for inappropriate land management, could have been helped by mangroves.  [Dedication of Dahdouh-Guebas et al. 2005, Current Biology 15(6) cover paper]