Wilmshurst said archaeological evidence suggests that successful cultivation of introduced food crops, such as kumara and taro, was only possible in warmer northern coastal areas and the starch-rich rhizomes of bracken fern, which replaced the burnt forests, provided an essential part of Māori diets in colder regions.
"In their efforts to increase the productivity of lowland forests for food, Māori encouraged a more heterogeneous and economically useful fern-shrubland at the same time as making travel easier to search for food and stone resources for making tools," Wilmshurst said.
Newly derived records of past climate enabled the team to disprove the hypothesis that unusual climate conditions encouraged fire at around the time of Māori settlement.
"Our evidence suggests that human activity was the main cause of the fires, and that these fires were not related to any unusually dry or warm conditions at the time," McGlone said.
Before human arrival in New Zealand, fire was naturally rare in most forests, with lightning-started fires occurring perhaps only once every 1-2 thousand years.
"What is remarkable is that small mostly subsistence-based groups of people were able to burn large tracts of forests throughout the relatively large South Island (151,215 km2) in only a few decades," McWethy said.
Whitlock said "Changes in the fossils and chemistry of the lake sediments showed that soil erosion followed initial forest clearance. In some regions, this degradation was exacerbated by intensive clearance in the 19th Century by European pastoralists who developed the land for grazing sheep and farming."
|Contact: Melynda Harrison|
Montana State University