Effects of the global atmospheric carbon dioxide increase on climate and plant productivity: A new Zealand perspective : Presented in partial fulfilment of the requirements for the Degree of Master of Science in the University of Canterbury

Human activities are beginning to have global effects on the atmospheric envelope that surrounds the earth and is the heritage of all living things. While concern over the effect of atmospheric carbon dioxide on global climate has been expressed for over a century, the steadily increasing amount of carbon dioxide in the air has only been unequivocally observed over the past two decades. Anthropogenic emission of carbon dioxide results from the combustion of fossil fuels and the conversion of a carbon-rich landscape into farmland and cities. The atmospheric concentration of carbon dioxide has already increased by 27 percent over the pre-industrial value (based on recent estimates) and the potential exists for a many fold increase if abundant global reserves of coal are utilised. Since carbon dioxide absorbs and emits thermal radiation and is an essential nutrient for plants, changes in global climate and the productivity of biological systems are anticipated. Natural systems will also be affected and extinctions would result in those species which have isolated habitats and are unable to adapt. The consensus of the international climatological community is that continued emissions of carbon dioxide will result in a significant change in the global climatic state and a general warming unprecedented in human history. This study develops the global context of the carbon dioxide problem and then focusses on its implications for New Zealand. Historical changes are considered and scenarios of what New Zealand's climate might be like on a warmer earth are presented. New Zealand's dependence on renewable energy (hydroelectricity) and primary products increases our vulnerability to climatic change. Primary productivity will also be enhanced by elevated levels of atmospheric carbon dioxide. While the effects on these sectors is considered, the effects on our natural environment may be regarded as more important and are not subject to human adaptation. Overall, climatic change will have significant implications for New Zealand, and long-term planning should therefore be based on the most likely climatic outcome; a warmer earth. Possible responses include prevention, incremental adjustment and anticipatory planning. It is concluded that prevention (a global strategy) through the use of conservation and renewable sources of energy should be given much greater emphasis, and that anticipatory planning should be adopted where information is available, albeit uncertain