Climatic change effects on seasonal patterns of pasture production in New Zealand

Abstract

The performance of livestock industries in New Zealand is affected by a large spatial and seasonal variability in patterns of pasture production. A software package of a database and a predictive pasture production model has been used to make an initial evaluation of the impact of climate change expected around 2030, on the average seasonal pattern of pasture growth at four sites in New Zealand. Mean annual temperature is expected to be 1.2-1.8" C warmer and annual rainfall 510% less. On two cooler/ wetter sites in Southland and Canterbury (irrigated) the predicted pasture production, compared with present, was substantially better in winter (+80%, +50% respectively), better in spring and autumn (+20 to 40%), and unchanged in summer. On two warmer/ drier sites in East Coast (North Island) and Waikato, similar analyses showed improved autumn and winter growth (20-40%) with production unchanged in spring and slightly depressed in summer. Annual production was increased by 20% at South Island sites and about 5% at North Island sites. The onset of spring growth was 2-4 weeks earlier at all sites. Present technology would be expected to be able to formulate management strategies to cope with pasture changes of this magnitude. More reliable predictions of pasture growth will depend on improved climate models which can predict seasonal change in regional climate throughout New Zealand, especially rainfall variability. Keywords climate change, pasture production, mathematical modelling, regional climate