Localised human impacts on the Harataonga coastal landscape, Great Barrier Island, northern New Zealand

Abstract

Here we present results of analyses of sediment profiles and cores and coprolites from Harataonga Bay, Great Barrier Island. Using a range of analyses (sedimentological, plant microfossils, parasitological, microbial, and steroids and myoglobin) we concentrate on human impact and reconstruction of the geomorphology and vegetation of the near-shore environments.

Two different sub-environments are represented: dunes and alluvial plain. Dune instability coincides with a major increase in disturbance related plants (especially ground ferns) as a result of forest clearance for agriculture. The present form of much of the Harataonga dunes and the swamp at the eastern end of the bay is directly a result of human impact, no earlier than 737 ± 178 14C yr BP. In the record from the alluvial plain of the main Harataonga watercourse, at the western end of the bay, it is difficult to clearly resolve sedimentary inputs that directly relate to human presence in this former tidal inlet that was open to storm surge and stream floods. The only exception is the slopewash materials forming the terrace surface, sediments of which bear pollen consistent with vegetation disturbance. The landforms are natural but the rate at which the tidal inlet was infilled to form a terrace was accelerated by human activity. The nature and timing of the localised human impacts at Haratoanga are consistent with those observed elsewhere on Great Barrier Island and mainland New Zealand. Some of our techniques (e.g., bacteria, steroids) are newly applied to coprolites in New Zealand but none provided any useful information because of poor preservation.

Keywords

Sedimentology, plant microfossils, coprolites, Harataonga Bay.