High-resolution palynology, climate change and human impact on a late Holocene peat bog on Haida Gwaii, British Columbia, Canada

Haida Gwaii (formerly Queen Charlotte Islands) is an archipelago on the outer central coast of British Columbia. Drizzle Bog on Graham Island is a Sphagnum-dominated peatland selected for a multiproxy palaeoecological analysis using pollen, spores and other microfossils to see whether climatic changes such as the Mediaeval Climate Anomaly' (MCA), Little Ice Age' (LIA) and post-LIA warming could be detected in this hypermaritime region. A 90-cm-long Wardenaar peat core was sliced into 1-cm-thick subsamples and dated using Pb-210 back to ad 1892, and four accelerator mass spectrometry (AMS) radiocarbon dates back to 1800 cal. yr BP. Low pollen accumulation rates between similar to ad 1600 and 1875 support cool growing seasons during the LIA. At 34 cm (similar to 1875), total pollen and spore accumulation rates increased dramatically, coinciding with the end of the LIA based on evidence from glacier recession in the Coast Mountains of British Columbia. We suggest that the increased pollen production is likely a reflection of climatic warming and increased vegetation productivity following the LIA. Direct human impact is only apparent above 12 cm depth (similar to 1958) correlated with road building across the southwestern edge of the wetland.