Tropical islands of the Anthropocene: Deep histories of anthropogenic terrestrial-marine entanglement in the Pacific and Caribbean

Abstract

Islands are useful model systems for examining human-environmental interactions. While many anthropogenic effects visible in the archaeological and paleoecological records are terrestrial in nature (e.g., clearance of tropical forests for agriculture and settlement; introduction of nonnative flora and fauna), native peoples also relied heavily on marine environments for their subsistence and livelihood. Here we use two island case studies-Palau (Micronesia) and the Lesser Antilles (Caribbean)-and approach their long-term settlement history through a "ridge-to-reef" perspective to assess the role that human activity played in land- and seascape change over deep time. In particular, we examine the entanglement of terrestrial and marine ecosystems resulting from anthropogenic effects and cultural responses to socio-environmental feedback. We suggest that on the humanized tropical islands of the Anthropocene, mangroves, near shore and littoral areas, and coral reefs were major sites of terrestrial-marine interface chronicling and modulating anthropogenic effects.

Keywords: Lesser Antilles; Micronesia; archaeology; historical ecology; traditional ecological knowledge.

Fig. 1.

(Left) Map of the Palauan archipelago showing location of sites mentioned in text. (Right) Map of the Eastern Caribbean with insets of Lesser Antilles and the Grenadines showing marine and coral reef banks.

Fig. 2.

Schematic showing the interplay between land and sea for Indigenous peoples across major ecotones in (A) Palau and (B) the Caribbean Lesser Antilles. Note the prevalence of nutrient export into and through each respective habitat and the ecosystem services that each provides to humans (e.g., agricultural products, marine resources). Image credit: John Gordon Swogger (artist).

Fig. 3.

Synthesis of ridge-to-reef feedback loops. (A) In Palau (from left to right): land use activities that begin approximately 3000 BP, and intensify between approximately 2400 to 1200 BP through earthwork construction, lead to erosion and sedimentation infill of lagoons and coral reefs. Dependence on marine resources for protein is threatened and creates a positive feedback loop. Movement to the coast and construction of traditional (stonework) villages situated behind mangrove forests along with artificially built swamps for taro cultivation mitigate these effects, providing inland sediment traps and sustainable subsistence practices which are also more easily defendable. The implementation of bul conservation practices—perhaps in recognition of these issues—provide the cultural framework for ensuring responsible resource use over the long term. (B) In the Lesser Antilles (from left to right): burning and land clearance for agriculture that begins approximately 2500 BP leads to increased terrestrial runoff and sedimentation of mangrove and coral reef habitats, depressing recruitment of economically important fish and invertebrates. Positive feedback leads to intensification of terrestrial resources after approximately 1500 BP to offset loss of marine protein; land clearance for agriculture increases, accelerating sediment and nutrient runoff, contributing to further declines in reef and mangrove habitat and biota. This process is interrupted by negative feedback, where limited arable land and fresh water inhibit potential agricultural intensification and population growth. Sustainable marine resource extraction may be realized in these locations through a combination of fisheries management strategies, low population density, and the relative productivity of surrounding marine banks. Image credit: John Gordon Swogger (artist).