Signals of human impacts in “pristine” environments: A case study from the South Island, New Zealand.

The extent to which human settlement has modified the New Zealand landscape is highly debated; leading to our perception of what is regarded as a “pristine” environment in comparison to what is considered an anthropogenic or naturally altered environment heavily uncertain (McWethy et al 2009). East Polynesia, largely consisting of island ecosystems including New Zealand was one of the last places where human arrival occurred (Wilmshurst et al 2008). As a result, many regions within New Zealand may have escaped the effect of anthropogenic influence. Research using paleolimnological techniques is sufficiently lagging in terms of understanding what impact catchment burning triggered by Māori and European arrival has had on inland aquatic ecosystems. Therefore, this study aimed to 1) Investigate whether human impact signals are apparent in an inland aquatic lake ecosystem within a remnant forested catchment and 2) Investigate the impact of the paleoclimate over the past 1000 years within the context of potential human disturbance. Lake Marion, a small sub-alpine mesotrophic lake located in a supposed forested catchment was examined. It has been assumed that this is a non-impact lowland site, suggesting it could be considered a “pristine” lake ecosystem. Core chronology down-core using 210Pb and 14C was provided to develop an accurate age model. Additionally, the sedimentation record and multiple paleo and environmental proxies including macro charcoal, chironomids and macrofossils were analysed to determine whether these signals of human impact have influenced the aquatic ecosystem. The results indicate a change in the sedimentation record and a statistically significant change in chironomid assemblage at around 1480 A.D., rejecting the notion that Lake Marion is considered a “pristine” ecosystem. The changes in the paleoclimate, in particular the Little Ice Age and enhanced westerlies are indicated to have caused the impact within this catchment. There is suggested evidence of Māori impact at around 1500 A.D. identified through the local charcoal and macrofossil record. This burning occurs after the changes identified at around 1480 A.D., implying that the paleoclimate influenced this local burning rather than Māori arrival. There is no evidence of large charcoal particles within the Lake Marion record during the time of European settlement, indicating there was no local burning from an anthropogenic influence. The beginning of European settlement coincides with the end of the Little Ice Age and a return to a climate similar to that of the Medieval Warm Period observed prior to 1400 A.D., indicating the paleoclimate to have contributed to the changes in the sediment record during this time. The results using the various paleolimnological techniques and multi-proxy analysis outlined in this study will allow for further forested catchments like Lake Marion to be investigated, allowing “pristine” environments to be distinguished from natural and anthropogenic induced changes