By Sarah Lazarus and Jon Jensen, CNN
Kalpitiya, Sri Lanka (CNN)On December 26, 2004, a cataclysmic tsunami struck the coasts of countries in South and Southeast Asia.Sri Lanka was one of the worst affected nations -- the wall of water devastated the island's southern and eastern coasts.However, the tsunami's impact was uneven with some places suffering far more damage than others. Scientists assessing the landscape after the disaster discovered that some areas which emerged relatively unscathed were protected not by sophisticated warning systems or barriers -- but by their ancient mangrove forests.