Ancient Maya societies experienced a period of reorganisation and change in settlement patterns associated with social and climate instability at the end of the Classic period (750-1000 CE) and the subsequent Postclassic period (1200-1500 CE). Although it has been proposed that severe droughts and the breakdown of Classic political systems caused a migration of populations towards the coast, we have little evidence of the nature of land-use at coastal sites. Our understanding of subsistence on islands has been shaped by archaeological research indicating marine-based diets, with maize imported from the mainland. Here we provide, for the first time, palaeoecological proxy data that inform on ancient Maya land-use on an island site, located on Ambergris Caye, Belize. Using pollen and charcoal proxies, we present over 6000 years of environmental change and land-use history. Our reconstruction reveals evidence of cultivation, beginning at 2900 BCE and culminating during the Postclassic Period. We demonstrate that periods of higher land-use intensity correlate with climate instability, which corroborates archaeological evidence of migration to coastal locations. We hypothesize that the diverse marine and terrestrial environments of the island provided sustainable resources for the mainland Maya to use during times of both political and climatic stress.