Ecological networks of French Polynesia: A new way to study sustainability during a millenium of human presence

Background/Question/Methods

Most studies of the relationships of humans and ecosystems are presented in terms of human impacts on ecosystems. However, our ability to understand and mitigate such impacts depends on research that identifies the roles humans play in ecosystems, including how they interact with other species.  Analysis and modeling of food web structure and dynamics provides a useful framework for quantifying the ecological roles and interactions of species including humans.  Here, we present a coupled natural-human systems research agenda focused on four French Polynesian islands, where humans arrived about one thousand years ago and lived sustainably on some islands but not others.  Our framework couples archaeological and ecological data with network analysis and dynamical modeling to develop better understanding of the integrated socio-ecological system and changes that have taken place since human arrival and establishment.  We are particularly interested in questions such as how humans and the species they brought with them fit into existing ecological networks; the interactions and feedbacks between environment, biodiversity, and human cultural development and demography; and how different types of human resource use impacted ecosystem function and the coexistence and persistence of species in different habitats.

Results/Conclusions

We present preliminary results on the composition and structure, including humans, of modern reef, lagoon and forest food webs of Moorea.  This is based on the Moorea Biocode Project, the first comprehensive inventory of non-microbial life in a tropical ecosystem.  We present additional results related to how human-centered interaction networks changed over the last millennium for Moorea and three other islands with strong archaeological records (Mangareva, Raiatea, Maupiti).  Our dynamical modeling framework builds upon a published model of Polynesian agriculture and population dynamics for Hawaii.  We are using the model to explore how humans interacted with natural and managed ecosystems on the islands.  For example, compared to classic fisheries management theory of maximum sustainable yield (MSY), a general version of the model demonstrates larger yield and profit at low exploitation rates, with fish extirpation and economic collapse at the higher ‘optimal’ exploitation rates predicted by MSY.  Our project aims to provide fundamental knowledge about how humans can interact more sustainably with a variety of ecosystems.  This and other coupled natural-human systems research is vital for addressing critical problems at the intersection of the social and natural sciences including resource overconsumption, climate disruption, and ecological and cultural degradation and collapse.