Modeling Holocene coastal ecosystem availability and site distribution patterns for Borikén, Puerto Rico

Coasts are dynamic environments prone to the physical and social impacts of climate change. Examining the archaeological and environmental records of coastal areas can deepen our understanding of how humans respond to changing environmental conditions. In this article we consider how sea-level rise impacted coastal environments through time, and how these changes could pose opportunities or challenges to local indigenous populations. We present new findings of coastal zone transformations and past settlement patterns for Borikén, the largest island of the Puerto Rican archipelago, during the Holocene. We use paleogeographic modeling to reconstruct ecosystem availability for six discernible coastlines at 1000-year resolutions that accounts for past relative sea-level (RSL) heights and paleotidal ranges. We then compared ecosystem availability trends with the spatiotemporal distributions of available archaeological data to demonstrate the localized impacts of climate-related RSL rise across the island’s coastal ecosystems and suggest a consideration of habitat availability in past decision-making strategies. We observe a strong presence of Archaic Period sites in the island’s southwest coast where high coastal ecosystem availability and stability were present during this period. We also observe a significant expansion of intertidal ecosystems beginning at 3 kya for the north-central, north-eastern, south-central, and south-eastern coastlines that correspond to the appearance of materials associated with Early and Late Ceramic Periods cultures in these areas. This comparison of differential coastal transformations and site distributions conveys a deeper understanding of factors involved in past decision-making strategies and contributes to the emerging picture of human adaptations amidst changing environmental conditions.