Climate variability and food security a New Zealand perspective

Content Partner: Lincoln University. The objective of this thesis was to develop a clearer understanding of inter-relationships between climate variability and food security in New Zealand. It was considered important to both clarify crop-climate relationships and possible response options available to regional planners and individuals. This is particularly relevant in the context of a probable global climate warming. An empirical-statistical analysis of crop-climate interactions was carried out. This was followed by a more detailed agroclimate analysis of the Canterbury region, and an evaluation of one possible response option in the face of present, and possible future, climate variability and change. This involved a field based study of shelterbelt effects. The final part of the Thesis gives a tentative assessment of the possible impacts on agriculture in New Zealand of regional greenhouse warming scenarios. Monthly rainfall and mean temperature data were used for the crop-climate analyses. Adjustments for site changes were made where necessary and missing values estimated. Trend removal was performed on temperate grain and pipfruit yield time series. Quadratic, and in the case of pears linear, trend lines were fitted to the yield data. Analyses were performed on the residuals. No trend removal was carried out on stonefruit data. Principal component analysis, followed by stepwise multiple regression, showed the barley crop to be the most spatially responsive to climate of the three temperate grain crops examined. Wheat was intermediate in its response and oats the least spatially responsive. Autumn sown wheat showed a negative relationship with winter rainfall and spring temperature. The dominant result with oats and barley was a negative effect on yield of late spring to early summer temperatures. Analyses of national stonefruit data met with mixed success. Peaches and nectarines, although of the same species, gave different significant predictors. This was attributed to differences in weighting on the climate data, related to geographic distribution. The susceptibility of apricots to late frosts appeared to show through with this crop. Cherries showed a strongly negative relationship with rainfall at blossom and harvest time. The most significant predictor with plums was a positive relationship with May temperature. This was treated with scepticism. These results highlight the need for further detailed analysis of these crops at the district level. Th