Effects of climate/weather on agriculture in WA
Marcus Harris and Dr Ian Foster after Dr Foster's presentation on the effects of climate/weather on agriculture
Dr Ian Foster from the Western Australian Department of Primary Industries and Regional Development (DPIRD) made an excellent presentation at our club meeting on 25 August, 2020. He spoke about the effects of climate and weather variations on agriculture in WA.
Dr Foster has considerable experience working on weather and climate. He graduated with an honours degree from the School of Environmental Science, Murdoch University at the end of 1979. He then completed his PhD studying the Development of Tropical Cyclones in Northwest Australia in 1987. Ian has been a climatologist at DPIRD since 1989 where his main responsibilities are reporting and forecasting season conditions. To do this, he works closely with the Bureau of Meteorology and WA water and fire management agencies.
Ian commenced his presentation with an overview of the systems influencing weather in WA. The Indian Ocean Dipole affects the climate in WA more than the El Nino and El Nina which tend to influence the East Coast more. The weather is affected by fronts rising mainly from the SW, tropical cyclones, cut-off lows, west coast trough, blocking highs, Southern Annular Mode and cloudbands. These all affect the amount of rain, heat waves and cloud cover which in turn affect agricultural production. Crops need a good amount of soil moisture, nutrients, sunlight, warmth, carbon dioxide and oxygen to grow well. Low or high temperatures and poor pasture growth also affect animal production.
Since the mid 1970’s the annual rainfall in the SW of WA has declined by up to 20%. This declining rainfall has resulted in a general shift in rainfall zones (isohyets) to the west effectively decreasing the potential for good rains in all areas, particularly the eastern wheatbelt. Despite this, grain yields have been steadily increasing in WA. This is due to improved agronomic practices and the release of better adapted crop varieties. Improved practices include the adoption of no-till agriculture (conserving available soil moisture) an expansion of field size (decreasing the percentage of non-cropped land) and improved weather predictions (allowing farmers to prepare for the season better).
The future of agricultural production in WA faces a number of dangers. It is predicted, that rainfall in the SW of WA will continue to drop, mean temperatures will increase and the frequency of extreme temperature events will increase. These will all adversely affect agricultural production.
Temperature projections are dependent on CO2 levels. Dr Foster showed how world CO2 concentrations were approximately 300ppm for the past 2,000 years but over the past 100 years have jumped to over 400ppm. There is a relationship of increasing earth temperatures with increasing CO2 (hence the term climate change).
No parts of Southern WA are predicted to receive more rainfall with climate change. Just as importantly, an increase in temperatures and extreme temperature events will dramatically decrease potential crop production. Yield decreases are expected in most locations in WA. Winter and spring are expected to be drier. Dry conditions during these cold season means there will be more frosts damaging both crops and animals. Dry conditions also lead to a greater fire risk. Some crop losses will be compensated by atmospheric increases in CO2 levels due to improved photosynthesis and improved water efficiency.