Paoay Lake, northern Luzon, the Philippines: a record of Holocene environmental change JANELLE STEVENSON *, FERNANDO SIRINGAN w , JAN FINN *, DOMINGO MADULID z and H E N K H E I J N I S § *Department of Archaeology and Natural History, ANU College of Asia and the Pacific, Australian National University, Canberra 0200, Australia, wMarine Science Institute, University of the Philippines, Diliman, Quezon City 1101, Philippines, zBotany Division, National Museum of the Philippines, Ermita, Manila 1000, Philippines, §Institute for Environmental Research, Australian Nuclear Science and Technology Organisation, Lucas Heights 2234, Australia Abstract The last 7000 years of environmental history for Paoay Lake and its surrounding landscape is examined through the analysis of pollen, diatoms, charcoal, mineral magnetics and AMS dating. Basal sediments contain shells of Cerithiidae and the saline-tolerant diatom Diploneis indicating that this was an estuarine environment before becoming a freshwater lake after 6000 BP . Pollen analysis shows that submontane forests, characterized by Pinus pollen, underwent a major disturbance around 5000 years ago, recovering to previous levels by 1000 years ago. Charcoal as an indicator of fire is abundant throughout record, although the highest levels occur in the earlier part of the record, between 6500 and 5000 years ago. An aspect of the project was to examine whether there is evidence of land clearance and agricultural development in the region during the late Holocene. While a clear signal of human impact in the record remains equivocal, there appears to be a correspondence between submontane forest decline and mid-Holocene ocean data that depict warmer and possibly drier conditions for the region. The study highlights the vulnerability of these montane forests to forecasts of a warmer and drier climate in the near future. Keywords: charcoal, Holocene, Philippines, Pinus, pollen Received 10 March 2009; revised version received 10 July 2009 and accepted 14 July 2009 Introduction The Philippine archipelago stretches from the wet tro- pics in the south to the monsoonal tropics in the north and although it has an important place within insular south-east Asia for understanding phenomena such as the evolution of the Asian Monsoon or the impact of ENSO, it has few palaeoenvironmental studies of any description and only one palynological study (Ward & Bulalacao, 1999). While the central aim of study is to document environmental change during the Holocene in the northern Philippines, one of the associated re- search questions is to assess if any of the changes are related to human activity. In particular land clearance and the development of rice agriculture during the Neolithic, as the timing and development of this is an unresolved question for the Philippines (Bellwood, 2005; Bellwood & Dizon, 2005). Our study therefore provides unique information on the landscape changes that have taken place since the mid-Holocene in north- western Luzon and makes a significant contribution to the study of climate change in the western Pacific. Environmental setting Paoay Lake is situated in north-western Luzon (18107 0 N, 120132 0 E) (Figs 1 and 2) along the western edge of the Ilocos lowland, a tectonic depression related to Late Pliocene to Quaternary activity of the Philippine Fault (Pinet & Stephan, 1990). Coastal progradation and the subsequent development of a sand dune barrier during the mid-Holocene are believed to have led to the formation of the lake (Siringan & Pataray, 1997) and it is now separated from the sea along its western edge by a sand dune complex approximately 2.3 km wide and with an average elevation of 40 m. The Upper Pleisto- cene Laoag formation bounds the lake in all other directions (N. P. Punzal et al., unpublished results). North-western Luzon has a monsoon climate, with a dry season in the lowlands from November to April and a wet season from May to October (Argete, 1998). Correspondence: Janelle Stevenson, fax 1 61 2 612 549 17, e-mail: janelle.stevenson@anu.edu.au Global Change Biology (2010) 16, 1672–1688, doi: 10.1111/j.1365-2486.2009.02039.x 1672 r 2009 Blackwell Publishing Ltd