Ecosystem impacts of human arrival in the Azores: a comparative study of high-resolution multi-proxy lake sediment records

Abstract

Human settlement of uninhabited land masses can dramatically transform local ecosystems and its endemic biota around the world. These changes are particularly evident on islands, where human settlement usually marked a period of large-scale habitat destruction and extinctions of local flora and fauna. Historical records specify that the Azores archipelago in the North Atlantic Ocean was settled in the mid-15th century CE. The human footprint in the Azores was large and widespread: within six centuries of colonization more than 95% of the original native forests were destroyed. Paleoecological and geochemical reconstructions from the Azores have allowed us to compare ecosystem processes and dynamics before and after colonization.

To document the cultural evolution of human settlement in the Azores archipelago, we studied lake sediment records from four distant islands, located in the Western (Flores), Central (Pico and Terceira) and Eastern (São Miguel) group of islands. In particular, we investigated the role of the Medieval Warm Period and the Little Ice Age climatic periods as external driving forces for human displacement and potential triggers for cultural transformations. A suite of proxies – pollen, diatoms, chironomids, cladocerans, hydrogen isotopes, macroscopic charcoal, organic matter, inorganic composition (XRF scanning and X-ray diffractions), and lithofacies – were used to distinguish between different signals of climate change, landscape and ecosystem dynamics, and their local lacustrine responses. A comprehensive multi-disciplinary analysis of all the proxies provides strong indications that the Azores were colonized more than two centuries earlier than currently recognised. These early colonizers first reached the Central group of islands around 1100 yr CE and the Eastern group before the end of the 13th Century. The Western group was subsequently reached around 1300 yr CE. Early human activities included the introduction of domestic animals, land clearance and small-scale agriculture, and extractive forestry mostly for charcoal production. The origin of the early colonizers is further discussed during the presentation.