Small-scale harvest of big trees: impacts of land use changes over ~1300 years on SGang Gwaay, Haida Gwaii, B.C.

Haida Gwaii (British Columbia, Canada) is the ancestral home of Haida people. At its southwestern extremity lies SGang Gwaay, a small island of ~3 km<sup>2</sup>, and SGang Gwaay Llnagaay (UNESCO World Heritage Site), a village inhabited until the 1888 CE smallpox epidemic. We investigated vegetation and limnological changes on SGang Gwaay over ~1300 years with paleolimnological methods integrating sterols, stanols, stable carbon (C) isotopes, inferred lake-water total organic carbon (TOC), diatoms, and chlorophyll a. Changes were interpreted with respect to historical events and existing lake sediment palynological records aimed to understand long-term trends in C allocations to the pond. Stable C isotopes, C/N, sitosterol, and campesterol indicate that, historically, pond C was primarily from terrestrial plants. Trends in these proxies changed in the 13th century, after the expansion of the village and increased harvest of western red cedar (Thuja plicata). After ca. 1625 CE, sitosterol/campesterol and chlorophyll a indicate a transition to increased autochthonous C sources. Diatom assemblages after ca. 1388 CE suggest changes in light availability and increased water mixing, as a tychoplanktonic taxon dominates. Our results demonstrate that land -use changes on the island, including small-scale tree harvest, impacted C inputs to the pond and aquatic primary production.