A radiocarbon investigation of Moriori forest use on Rēkohu (Chatham Island), southwestern Polynesia

The first colonists of temperate climate, southwestern Polynesia settled an archipelago unsuited generally to the cultivation of several tropical homeland crops, including fruiting trees. On the Chatham Islands, these colonists achieved settlement permanency after the thirteenth century AD to become the indigenous Moriori in the absence of all Polynesian domesticates. We test the thesis that edible and storable seeds of introduced New Zealand karaka or (in Moriori) kōpi trees (Corynocarpus laevigatus J.R. Forst. & G. Forst.) replaced tropical crops in the Moriori economy. Archaeological midden sites associated with kōpi are dated by radiocarbon (14C) from Rēkohu (Chatham Island), the largest island of the Chathams group. We examine new accelerator mass spectrometry ages for individual kōpi seeds and twigs < 10 years old and review extant standard ages. A local marine 14C value is determined to improve confidence in mollusc dates. Our results include the earliest reliable 14C age on a kōpi seed from Rēkohu (cal yr AD 1450-1620, 95% probability). Strategic tree plantings in sheltered locations and initial if not ongoing forest management are indicated. Archaeological evidence of comparable, later, leeward and windward island Corynocarpus use suggests that kōpi production supported the permanent Moriori settlement of Rēkohu.