Projected decline in rainfall
Changes in average annual and seasonal rainfall can result in conditions that make a specific location unsuitable for that plant to grow or animal to thrive, i.e. the new rainfall range is outside of that species’ optimal range. The projected changes in rainfall for the South West are severe enough to result in large parts of the current ranges of many species becoming unsuitable for those species. Changes in rainfall are therefore a key indicator of ecosystem health in its current state.
Projections developed specifically for the South West NRM from 2015 onwards:
- Projected mean rainfall expected to further decline by 10-15% by 2030 and by 15-45% by 2090
- The region has a predominantly Mediterranean climate, with high winter rainfall and little summer rainfall. There has been a prolonged period of extensive drying from the 1970s to the present, particularly in autumn and early winter (Hope et al).
- Reduction in rainfall since 1910 best illustrated by reduction in amount of water entering water storage dams – “340 GL was the average amount of water collected annually from 1910 – 74, whereas it has averaged less than 200 GL since then and decreased further to around 100 GL since 2001’.
- Mean rainfall is expected to decline by 10-15% by 2030, as compared to the already decreased rainfall, and mean rainfall will decline by 15-45% by 2090
- Hope, P, D Abbs, J Bhend, F Chiew, J Church, M Ekström, D Kirono, A Lenton, C Lucas, K McInnes, A Moise, D Monselesan, F Mpelasoka, B Timbal, L Webb and P Whetton. 2015. Southern and South-Western Flatlands Cluster Report. Climate Change in Australia Projections for Australia’s Natural Resource Management Regions. Cluster Reports, eds. Ekström, M. et al., CSIRO and Bureau of Meteorology, Australia