deforestation

Canterbury’s gravelly outwash plains offer few of the natural deposits in which floral remains are typically preserved and hence represent a significant geographical gap in our knowledge about New Zealand’s pre-settlement terrestrial ecosystems and their response to anthropogenic activities. We contribute new insights into the poorly known Holocene vegetation history of this region by reporting two new mid-late Holocene pollen records from the western (Hallsbush) and eastern (Travis Swamp) margins of the Canterbury Plains.

New Zealand bracken (Pteridium esculentum) belongs to a group of closely related fern species of near global extent. Pteridium species worldwide are aggressive, highly productive, seral plants, functionally more akin to shrubs than ferns. Their deeply buried starch-rich rhizomes allow them to survive repeated fire and their efficient nutrient uptake permits exploitation of a wide range of soils. They are limited by cool annual temperatures, frost, wind, and shallow, poorly drained and acidic soils.

Pollen and charcoal analyses of sediments from northern coastal Taranaki, New Zealand, show that Maori settlement impacts on the vegetation began with the burning of tall coastal forest in the mid-17th century. Forest was replaced with a fern-shrubland, and small wetlands expanded with changing hydrological conditions. This forest clearance was much later than in most regions of the country, where major forest disturbance and clearance began between AD 1200 and AD 1400.

Pollen analysis of a high altitude bog (Winterton Bog) and an alluvial soil sequence in the upper Awatere catchment on the western flanks of the Inland Kaikoura Range, and radiocarbon dates on wood and charcoal from the Marlborough region, have established a Holocene, (post 10 000 years B.P.) vegetation history for this area.

Polynesian settlement of New Zealand (c. 1000 yr B.P.) led directly to the extinction or reduction of much of the vertebrate fauna, destruction of half of the lowland and montane forests, and widespread soil erosion. The climate and natural vegetation changed over the same time but had negligible effects on the fauna compared with the impact of settlement. The most severe modification occurred between 750 and 500 years ago, when a rapidly increasing human population, over-exploited animal populations and used fire to clear the land.