Humans have influenced fire regimes for thousands of years through their impact on ignition rates, fuels, and land cover. Changes in fire-regimes have dramatically altered ecosystem dynamics by shifting plant communities, creating opportunities for recruitment of new species, and restructuring land-surface processes and nutrient cycles. Paleoecological and archeological data indicate widespread deforestation in New Zealand about 700 years ago associated with the first known Maori (Polynesian) presence. Abrupt deforestation through the use of fire was achieved by small transient Maori populations in the absence of climate change, a situation that is contrary to other temperate rainforest regions where deforestation was associated with sedentary populations and significant climate change. New Zealand offers one of the most dramatic examples of human-caused deforestation through the deliberate use of fire, and its vegetation and fire history provides an important case study for understanding the consequences of wholesale burning of rainforests. Earlier research used high-resolution charcoal and pollen data to document a distinct period of burning following Maori arrival on the South Island of New Zealand. This event now is termed the Initial Burning Period (IBP). This research project will address the following questions: What spatial and temporal patterns of fire are evident during the IBP, and do they suggest the motivation for burning? Were the environmental consequences of the IBP largely shaped by the nature of the burning, the introduction of a novel disturbance, or by site-specific physical characteristics? What limited the recovery of native New Zealand forests after the IBP? The investigators will use recently recovered records to closely compare fire regimes on the South Island, where agriculture was relatively unsuccessful and populations were transient, with those on the North Island, where settlements were well established and large. They will acquire new lake-sediment cores from the eastern coastal plain on the South Island and the fertile volcanic regions of the North Island. They will develop high-resolution macroscopic charcoal and pollen records that span the last 2,000 years and examine changes in fire regime and vegetation during the IBP. They will reconstruct detailed vegetation histories for each site and develop high-resolution chronologies to synchronize paleoenvironmental proxy from multiple watersheds. They will examine high-resolution geochemical, limnobiotic, and magnetic susceptibility data from multiple sites to document the sequence of watershed events during the IBP, and they will use a GIS database for multiple-site comparisons of patterns of fire with archeological, physical, and environmental characteristics. They will compare independent paleoclimate proxies with variations in fires during the past 2,000 years and use landscape simulation models to understand the sequence of events during and after the IBP. In coordination with the Science Education Resource Center at Carleton College, the investigators will develop and disseminate educational materials for broad outreach in the U.S. and New Zealand.
This project will contribute new information to debates about the extent to which pre-European landscapes were pristine or humanized. The application and refinement of new tools, such as molecular biomarkers (used to identify and characterize charcoal in sediments), and approaches to document and understand past fires have the potential to transform fire-history science into a truly interdisciplinary field. The project also will provide information about the historical range of variability of fire and post-fire consequences for natural resource managers and educational materials on the topics of human-environmental interactions, sustainability, and scientific discovery. The project's application of landscape simulation models to study fire behavior and spread will allow scenario testing of different combinations of fire, fuels, and landscape conditions to explain the past consequences of human action and its effects on ecosystems.
