JOURNAL OF QUATERNARY SCIENCE (2007) 22(3) 267–279 Copyright ß 2006 John Wiley & Sons, Ltd. Published online 30 August 2006 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/jqs.1027 Late Quaternary environments, vegetation and agriculture in northern New Zealand M. HORROCKS, 1,2 * S. L. NICHOL, 2 P. C. AUGUSTINUS 2,3 and I. G. BARBER 4 1 Microfossil Research Ltd, Auckland, New Zealand 2 School of Geography and Environmental Science, University of Auckland, Auckland, New Zealand 3 Department of Geology, University of Auckland, Auckland, New Zealand 4 Department of Anthropology, University of Otago, Dunedin, New Zealand Horrocks, M., Nichol, S. L., Augustinus, P. C. and Barber, I. G. 2006. Late Quaternary environments, vegetation and agriculture in northern New Zealand. J. Quaternary Sci., Vol. 22 pp. 267–279. ISSN 0267–8179. Received 7 September 2005; Revised 20 March 2006; Accepted 27 March 2006 ABSTRACT: A sedimentological and plant microfossil history of the Late Quaternary is preserved in two sediment cores from early Polynesian ditch systems on southern Aupouri Peninsula. The study places human activities into a geomorphological and ecological context and allows comparison of natural and anthropogenic effects on two different geological settings: a floodplain and a relatively closed peat swamp. The data fill part of the current gap in the environmental record from northern New Zealand, namely MIS 3 (57k–26k yr BP). There is evidence for an increase in fire frequency in the region after 40k 14 C yr BP, suggesting a shift to drier (and cooler) conditions. Pollen records show that conifer-hardwood forest dominated by podocarps (especially Dacrydium) prevailed prior to Polynesian arrival and deforestation within the last millennium, with Fuscopsora insignificant throughout. Both cores show sections with gaps in deposition or preservation, possible flood-strip- ping of peat during the pre-Holocene and mechanical disturbance by early Polynesians. The identi- fication of prehistoric starch grains and other microremains of introduced Colocasia esculenta (taro) in both cores supports indirect evidence that the ditch systems of far northern New Zealand were used for the extensive cultivation of this crop. Copyright ß 2006 John Wiley & Sons, Ltd. KEYWORDS: environmental change; plant microfossils; prehistoric agriculture; Colocasia esculenta; New Zealand. Introduction Relict wetland ditch systems constructed for water reticulation by early Polynesians have been recorded in far northern New Zealand (Barber, 2001). Although substantially destroyed dur- ing land development in historic times, remnants cover remark- ably extensive areas in excess of 100 ha. Earlier observers generally agreed that they pre-dated European settlement, but disagreed over their function (e.g. eel farming, duck trapping, various agricultural crops). Systematic archaeological research did not commence until the 1980s. Based on indirect evidence, the consensus was that the wetland ditch systems of far north- ern New Zealand were intended primarily for cultivation of introduced Colocasia esculenta (taro) (Barber, 2004). As part of a recent project investigating the purpose of these remnants (Horrocks and Barber, 2005), sediment cores were taken from the study areas to provide vegetational and environmental con- text, as well as possible microremains of cultivated crops. In the present study the former Motutangi Swamp on Aupouri Pensinsula and the floodplain of the Awanui River (Figs 1 and 2), both now drained and under pasture are examined. Several palaeoenvironmental studies have previously been car- ried out in far northern New Zealand, encompassing much of the last 80k yr, which we summarise here. A notable gap in the record is marine isotope stage (MIS) 3, spanning the period ca. 57–26k yr BP. In the southern part of the region, i.e. south of Aupouri Peninsula, a discontinuous pollen record from Lake Omapere (Fig. 1) shows that ca. 80–55k yr BP regional forest comprised mainly mixed Fuscospora (presumably Nothofagus truncata)-podocarp (mainly Dacrydium) forest (Newnham et al., 2004) (Fuscospora is a sub-genus of Nothofagus). A 25–2.5k yr BP record from Kaitaia (Fig. 1) shows that ca. 25k 14 C yr BP Dacrydium was more prominent than Fuscospora (Elliot, 1998). However, the latter increased during the Last Glacial Maximum (LGM) (ca. 22–14k 14 C yr BP) then progres- sively declined to negligible levels after ca. 7.6k 14 C yr BP as Dacrydium again became the dominant forest tree. Agathis also expanded after this time. Other pollen records from the southern part of the region, notably from the Bay of Islands and Whangape Harbour (Elliot et al., 1997, 1998; Horrocks et al., 2001, 2007) (Fig. 1), together cover much of the Holo- cene, showing Dacrydium-dominated conifer-hardwood forest undergoing large-scale destruction by Polynesian fires during * Correspondence to: M. Horrocks, Microfossil Research Ltd, 31 Mont Le Grand Rd, Mt Eden, Auckland 1003, New Zealand. E-mail: info@microfossilresearch.com