Past and future trajectories of forest loss in New Zealand

Historically, New Zealand was dominated by forest below the alpine treeline, but about 1000 years of Polynesian and European colonisation has resulted in the destruction of nearly three-quarters of the indigenous forest cover. In this study, the historical patterns of deforestation and forest fragmentation were assessed in relation to major topographical, climatic and anthropogenic variables that may drive forest loss. Deforestation has occurred almost equally on the two main islands, the North and South Islands, although the remaining indigenous forest is more fragmented in the North Island. Most deforestation has occurred in regions with a high-density of road networks, although gradients in climatic water availability and soil fertility also had weak effects. Deforestation rates over the period 1997–2002 were very low (nationwide deforestation rate of just −0.01% p.a.), but varied widely among political districts. Expansion of plantation forestry was the single most important driver of recent deforestation. Only 10 of 73 political districts are afforded long-term protection of native forest cover (having more than 30% forest cover that is managed by the Department of Conservation). Forest cover in the majority of New Zealand landscapes has been reduced below the level of an expected ‘extinction threshold’ (circa 30% native habitat cover) in 55 political districts, and long-term trajectories predict that ongoing deforestation threatens to force another five districts below the critical threshold within the next 45 years. Except for the most heavily deforested regions, relatively modest annual rates of habitat restoration could bring forest cover back above the extinction threshold by the year 2050.