Climate change and agricultural production
Background to the climate study
Scientific research on global warming is well publicised and a consensus has emerged that the global climate is changing. In 2007, the Intergovernmental Panel on Climate Change (IPCC) published an impartial scientific assessment of climate change and concluded that warming of the climate system is unequivocal. It is virtually certain that warmer conditions will occur over most land areas as the century progresses, the frequency of heavy rainfall events is very likely to increase, and an increase in the area affected by droughts is likely. These findings are from the IPCC’s Fourth Assessment Report and strengthen conclusions from the IPCC’s previous Third Assessment Report in 2001.
Global models were run as part of the IPCC assessment processes to project how the climate could change by using a range of greenhouse gas emission scenarios. These models operate at a global scale and do not cover the effects of localised features well, like New Zealand’s hills and mountains. The New Zealand EcoClimate consortium took results from model runs used in the 2001 IPCC assessment as a starting point for more localised research.
This initial New Zealand study drew mainly on results from a single global climate model, the UK Hadley Centre climate model version 2 (HadCM2), although it considered a range of possible future greenhouse gas emission scenarios. This model was selected as being one which reflects an enhancement in the west to east rainfall patterns across the country.
The consortium downscaled the model projections to this country's regions by using known relationships between broad climate patterns over the southwest Pacific region and local rainfall and temperature patterns across New Zealand. The consortium then used data from agricultural and economic research to derive relationships between climatic variations and pastoral production in New Zealand. By applying these relationships to the projected regional changes in climate, they estimated how the production of dairy, beef and sheep products could change in future. Towards the end of the study, the consortium recalculated some of the work building on the 2007 IPCC assessment work and updated some conclusions. The resulting New Zealand maps illustrate projected changes to regional climate under various scenarios.
The report is a valuable first step in understanding what a changing climate means for agricultural production but the results in this study should not be treated as firm predictions. The results should be considered sensitivity studies indicating how agricultural production could change with changing patterns of temperature and rainfall.
The report provides a starting point for further analysis. There are a number of factors that have not been assessed, including:
• the effects on production of increased carbon dioxide concentrations in the atmosphere. Plausible estimates on the effects ranged from no effect to an increased projection of 15% in pastoral production by mid-century, in areas not constrained by soil fertility
• feed or livestock transport between regions, irrigation, land use change or changes in production or demand from other countries.
Contact for Enquiries
Sustainable Land Management and Climate Change
MAF
Pastoral House
25 The Terrace
PO Box 2526, Wellington
Tel: 0800 CLIMATE (254 628)
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