The pre-contact past of Island Melanesia often remains perceived as being characterized by overall low population numbers, simple egalitarian political systems and scattered settlements, professing a deep difference with Polynesian chiefdoms and their dense settlement patterns. Archaeological data from the Southwest Pacific show that this supposed dichotomy has no real scientific basis and is merely related to ethnographic misconceptions. To illustrate the significant intensification process witnessed in this region, I will present a case study on the Grande Terre (Main Island) of New Caledonia. Over the millennium before first European contacts, the indigenous Kanak people developed complex agricultural practices on this large Island, raising extended taro poundfields on hillsides, high dryland mounds for yam planting in the floodplains, while managing their fragile landscapes as a global unity in a sustainable way. The paper will analyse how the natural constrains of living on an old fragment of Gondwanaland and at the limits of the tropical world were addressed by the Islanders, and how the impacts of the previous 1500 years of human settlement were used in a profitable way to ensure long-term viability of the traditional lifeways of the Kanaks. These archaeological results echo questions of future sustainability in New Caledonia’s political context of decolonization.