Mal Washer (Moore, Liberal Party) Share this | Hansard source

It is a pleasure to follow the Chair of the Standing Committee on Climate Change, Environment and the Arts, the member for Makin, and speak on a few more specific aspects about the report titled Case studies on biodiversity conservation, volume 1. South-west Western Australia is one of Australia's 15 national biodiversity 'hot spots' and the only Australian biodiversity hot spot that is recognised by Conservation International. South-west WA has been identified as one of three areas worldwide containing 'very old, climatically buffered, infertile landscapes', known for their highly fragmented ecological communities with large numbers of endemic species. These species are particularly vulnerable to rapid climate change due to their evolution under climatically buffered conditions over the past tens of millions of years.

This area has undergone problems of changed rainfall patterns, tree decline, phytophthora dieback, reduced groundwater and connectivity between ecosystems. There was evidence of a drying trend in rainfall and stream flow patterns across south-west WA. Also, changes in rainfall seasonality and intensity have led to dramatically reduced amounts of run-off. Rainfall has reduced by nine per cent in the past 10 years and this has resulted in a 46 per cent reduction in stream flow compared with in previous decades.

Over the past decade, south-west WA has been experiencing widespread declines in a range of woodland tree species, including tuart, wandoo, WA peppermint, jarrah and marri. Exact mechanisms leading to these declines are uncertain, but they are at least partially due to the hotter and drier conditions attributed to climate change in the area. During the summer of 2010-11, the area experienced a mass collapse of around 18,000 hectares of northern jarrah forest, a key overstorey species, coinciding with a period of high temperatures, the driest year on record and the unprecedented ceasing of flow in both 'permanent' and ephemeral streams.

Marri trees are in decline and are a key species which a number of other threatened species, including the Carnaby's black cockatoo, depend on for food. While the precise causes for marri tree decline are unknown, researchers have suggested that the drying climate has increased the susceptibility of trees to such existing stresses, to the extent that pathogens are now more capable of killing the trees. Many forests have unnaturally high densities of young trees due to past timber harvesting, resulting in high water usage and higher susceptibility to tree decline under drought conditions. To regenerate tuart trees, Western Australian peppermint trees need to be burned to create a suitable ash bed. As peppermint trees provide important habitat for the threatened western ringtail possum, this creates a quandary.

Phytophthora dieback refers to the phytophthora cinnamomi pathogen, a waterborne mould which thrives in moist and warm soil environments within this Mediterranean climate. As many as 2,000 out of the estimated 9,000 plant species in south-west WA are susceptible to phytophthora dieback. Phytophthora dieback was described as a 'biological bulldozer' because of the severity and extent of its effect on native ecosystems. Low-nutrient, fragile soils favoured by phytophthora are also the sites of some of Australia's richest biodiversity, such as the heavily infected Stirling Range National Park. An increase in the proportion of rainfall falling during summer months in south-west WA due to climate change may exacerbate the threat of phytophthora.

There are similar problems emerging in the Tasmanian Midlands. The miena cider gum, endemic to the Central Plateau, is sensitive to the effects of drought, which has led to the death of mature trees in relatively large patches since the mid-1990s. With increased temperatures it is thought that most miena cider gums are now highly stressed by the end of each summer and need substantial rain in autumn in order to recover. These autumn rains are now delayed and diminished. So with urban clearing now exceeding agricultural tree clearing and climate change stressing trees, causing susceptibility to disease, the prognosis for tree species in many parts of Australia is dismal.

Professor Stephen Hopper, Director, Chief Executive Officer and Chief Scientist at Kew Royal Botanic Gardens, discussed with me on site the serious effects of climate change on biodiversity. Dr Hopper will take up a post at the University of Western Australia later this year as professor of biodiversity and will hopefully encourage better research and improved management of the serious tree decline in south-west Western Australia.

I also wish to thank the chair, the committee and the secretariat for their hard work on this inquiry.

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