THE EFFECT OF CHANGING CLIMATE ON AUSTRALIAN BIOMASS PRODUCTION - A PRELIMINARY-STUDY

Increasing concentrations of carbon dioxide and other infrared absorbing gases are widely proposed as a mechanism for a global surface warming over the next several decades. Various methods have been used to anticipate the regional climatic changes which might result. In earlier papers Pittock has concluded that for Australia an increase in the extent of the summer rainfall regime is likely, with a decrease in winter rainfall. This is similar to a change which took place over much of Australia in the 1940''s. In this paper a climate scenario, roughly corresponding to the climate which might be expected to occur by about the middle of the twenty-first century, has been used as the input into the ''Miami Model'' of net primary productivity due to Lieth. Results show that about half of Australia might experience productivity increases in excess of 20%. A small area in the extreme south-west of Australia shows a small decrease in productivity. The direct response of plants to high ambient carbon dioxide concentrations, and many other possible effects such as changes in the incidence of plant diseases, pests, and soil erosion have not been assessed. Whether or not increasing carbon dioxide will lead to further climatic change in the next few decades, the results show that Australian primary productivity is quite sensitive to climatic variations within the range found in the historical records.