Feature article

Climate change – impacts on New Zealand agriculture

IPCC Fourth Assesssment Report

The Intergovernmental Panel on Climate Change (IPCC), in its Fourth Assessment Report, has released further information on climate change impacts, adaptation, and vulnerability.

Key findings for New Zealand agriculture, excerpted below, are taken from the final draft of the report, Chapter 11: Australia and New Zealand. This draft is subject to final editing changes, and is expected be published in full at www.ipcc.ch on 20 April 2007.

Cropping

For temperate crops, such as wheat and barley, higher temperatures could lead to decreased yields, but the fertilising effect of increased CO₂ is likely to more than compensate for this. The net impact in irrigated areas depends on the availability of water.

For maize (a crop that shows little or no yield response to higher levels of carbon dioxide), a reduction in time required to reach maturity may reduce crop water requirements, while locations further south than are presently cropped for maize may become more suitable for production.

Horticulture

Kiwifruit: Higher summer temperatures for Hayward kiwifruit are likely to increase vegetative growth at the expense of fruit growth and quality. Kiwifruit budbreak is likely to occur later, reducing flower numbers and yield in northern zones. Current kiwifruit varieties are likely to become uneconomic in Northland by 2050 because of lack of winter chilling. Production in the Bay of Plenty is likely to be dependent on dormancy-breaking agents and varieties bred for warmer winter temperatures. In contrast, more areas in the South Island are likely to be suitable.

Apples: Current varieties are very likely to flower and reach maturity earlier, with increased fruit size, especially after 2050.

Grapes: Red wine production is increasingly likely to be practised in the south, with higher yields. Higher CO₂ levels increase vine vegetative growth and subsequent shading is likely to reduce fruitfulness.

Pests: New Zealand is likely to be more susceptible to the establishment of new horticultural pests. For example, under the current climate, only small areas in the north are suitable for oriental fruit fly, but by the 2080s it is likely that much of the North Island will be suitable.

Pastoral farming

In cool areas of New Zealand, higher temperatures, higher CO₂ concentrations, and fewer frosts are very likely to increase annual pasture production by 10 to 20% by 2030, although gains may decline thereafter.

Subtropical pastoral species with lower feed quality such as paspalum are likely to spread southwards, reducing productivity, particularly in the Waikato. The range and incidence of many pests and diseases are likely to increase.

Water security problems are likely to make irrigated agriculture vulnerable, e.g., intensive dairying in Canterbury.

A leaflet summarising the impacts of climate change in New Zealand and the South Pacific, produced by NIWA and the Royal Society of New Zealand, accompanies postal copies of this newsletter.

Further copies are available from:

NIWA National Climate Centre
Tel: 0800 RING NIWA (0800 746 464)
Email: [email protected]
Also available online at: www.niwascience.co.nz/ncc