Two-step human–environmental impact history for northern New Zealand linked to late-Holocene climate change

Abstract

Following resolution of a long-standing debate over the timing of the initial settlement of New Zealand from Polynesia (late 13 th century), a prevailing paradigm has developed that invokes rapid transformation of the landscape, principally by fire, within a few decades of the first arrivals. This model has been constructed from evidence mostly from southern and eastern regions of New Zealand, but a more complicated pattern may apply in the more humid western and northern regions where forests are more resilient to burning. We present a new pollen record from Lake Pupuke, Auckland, northern New Zealand, that charts the changing vegetation cover over the last 1000 years, before and after the arrival of people. Previous results from this site concurred with the rapid transformation model, although sampling resolution, chronology and sediment disturbance make that interpretation equivocal. Our new record is dated principally by tephrochronology together with radiocarbon dating, and includes a cryptotephra deposit identified as Kaharoa tephra, a key marker for first settlement in northern New Zealand. Its discovery and stratigraphic position below two Rangitoto-derived tephras enables a clearer picture of environmental change to be drawn. The new pollen record shows an early phase (step 1) of minor, localised forest clearance around the time of Kaharoa tephra (c. 1314 AD) followed by a later, more extensive deforestation phase (step 2) commencing at around the time of deposition of the Rangitoto tephras (c. 1400-1450 AD). This pattern, which needs to be corroborated from other well-resolved records from northern New Zealand, concurs with an emerging hypothesis that the 'Little Ice Age' had a significant impact on pre-European Māori with the onset of harsher conditions causing a consolidation of populations and later environmental impact in northern New Zealand.

Māori settlement of New Zealand: The Anthropocene as a process

“…The vegetation succession on Ahuahu matches the pattern expected as a result of localised burning related to the creation of areas suitable for cultivation rather than the two‐step pattern of forest clearance suggested by Newnham et al . () for western and northern mainland New Zealand.…”

“…Newnham et al . () link these changes to the two‐step pattern of forest clearance evident in the Pupuke Lake pollen record.…”

“…Newnham et al . (), however, report that at Lake Pupuke, Auckland, the first 100 years of activity involved only minor forest clearance by fire. It was not until after the deposition of the Rangitoto 1/2 tephra, dated to 550–500 calBP, that a decline in nearly all tree taxa is shown.…”

“…At the time of colonisation, westerly winds were forced poleward, resulting in higher temperatures together with calm and stable conditions (Newnham et al . ). Anderson (), following Lorrey et al .…”

Historic development of heavy metal contamination into the Firth of Thames, New Zealand

“…The first major human impact on New Zealand resulted from the widespread forest clearance by the Polynesian settlers. Even though this vegetation change is well recorded in pollen-based paleoenvironmental reconstructions, the exact timing is still under debate and location dependent (McGlone 1983;Newnham et al 1998;Ogden et al 1998;McGlone and Wilmshurst 1999;Byrami et al 2002;Newnham et al 2018). South of the Coromandel peninsula (Waihi and Kopouatai), the onset of deforestation is dated to c. 1200-1300 CE (Newnham et al 1995a, b); in the following, 1300 CE is used to refer to this onset.…”