AMS radiocarbon-dated palynological evidence from Embilikala Lagoon in Bundala National Park (one of the Ramsar wetland sites) on the southeast coast of Sri Lanka indicates the palaeoenvironmental changes during the last 2,700 years. The persistence of fewer mangroves (e.g. Rhizophoraceae taxa) suggests that sea level low stands occurred between 2,700-1750 cal yr BP. From the later age, the relative sea level rose, and it reached the present sea level at 950 cal yr BP as indicated by the mangrove maximum. At 2,250, 700-400 and 200-150 cal yr BP, the sudden increase in marine dinoflagellate cyst (e.g. Spiniferites mirabilis) and foraminifera (Globigerinoides ruber) suggests increased marine influences. This is consistent with remarkable decrease in mangrove habitats. Between 2,700-950 cal yr BP, severely degraded dry monsoon forests and the minimal level of the mangroves suggest human and marine influences were the critical drivers for changing the major vegetation types along the southeastern coast. Vegetation changes have been drastic over the last millennia.