Long-term vegetation dynamics, environmental changes, anthropogenic records, and carbon accumulation during 3,800 years in Krabi mangroves, Thailand

Abstract

A multi-proxy paleoenvironmental study of the Khlong Thom mangroves in Krabi, Thailand reconstructed long-term vegetation and fire dynamics, sea-level changes, human impacts, and carbon accumulation rates over the past ca. 4,000 years. A period of marine dominance between 3,780 and 3,480 cal bp, characterised by Rhizophora dominance with increased carbon accumulation, coincided with a gradual sea-level decline following a mid-Holocene sea-level highstand. Subsequent sea-level fall, lasting until approximately 1,920 cal bp, resulted in a vegetation shift to Bruguiera/Ceriops and terrestrial herbaceous plants becoming more dominant with lower carbon accumulation rates. Around 1,920 cal bp, seawater influence increased, followed by a transition to freshwater dominance at ~ 1,280 cal bp A dramatic rise in Rhizophora between 1,080 and 500 cal bp corresponded with a period of rapid sea-level rise. After 500 cal bp, mangrove composition fluctuated with sea-level changes and climatic instability. Human activity played a significant role in shaping the coastal landscape, between 1,920 and 1,080 cal bp, as indicated by increased charcoal and cereal pollen corresponding with known occupation phases at Khlong Thom, suggesting agricultural intensification. More recent human activities, from ~ 150 cal bp onwards, were marked by a resurgence of cereal pollen and the introduction of oil palms. Recent elevated fire activity reflects forest clearance for agriculture and shrimp farming in this region. This study revealed the intricate interplay between natural forces and human activities in shaping mangrove ecosystems over millennia offering insights for future changes and restoration efforts amid sea-level rise, climate shifts, and human impact.