Logging must stop in Melbourne’s biggest water supply catchment


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Clearfell logging in the Thomson Catchment with the Thomson Reservoir in the background.
Chris Taylor

David Lindenmayer, Australian National University and Chris Taylor, Australian National University

Continued logging in Melbourne’s water catchments could reduce the city’s water supply by the equivalent of 600,000 people’s annual water use every year by 2050, according to our analysis.

We calculated water lost due to logging in the Thomson Catchment, which is the city’s largest and most important water supply catchment. Around 60% of Melbourne’s water is stored here.

Since the 1940s, 45% of the catchment’s ash forests (including mountain and alpine ash forest) have been logged. There are plans to log up to a further 17% of these forests under the VicForest’s existing logging plan.

Past logging in the ash forests has reduced the Thomson Catchment’s water yield, which is the amount of water that flows through the catchment, by 15,000 megalitres (a megalitre is a million litres) each year. This equates to around 9% of water yield from ash forests across the catchment.

By 2050, continued logging in these forests at the current rates could increase this loss to 35,000 megalitres each year, or 20% of water yield. This will be equal to the water use of around 600,000 people every year, based on estimated water use of 161 litres per person each day.

Thomson Catchment showing the extent of ash forest, with historic and planned logging (left) and annual rainfall distribution (right).
DELWP, 2018; Xu and Hutchinson 2018; DSE 2007.



Read more:
Ashes to ashes: logging and fires have left Victoria’s magnificent forests in tatters


Why forests are important for water supply

The city of Melbourne has some of the best quality water in the world. A key reason for this is that the city’s first water infrastructure planners closed many of the key water catchments to intensive human disturbance, such as logging.

But there also can be competition for water between different land uses in catchments that are not closed and open to logging. Indeed, it has long been known that logging can significantly reduce the amount of water produced from forests, especially those close to Melbourne.

Research on forest hydrology shows that the amount of water yielded from ash forests is related to forest age. Catchments covered with old-growth ash forests yield almost twice the amount of water each year as those covered with young forests aged 25 years. This is because evapotranspiration, the process by which trees transpire water into the atmosphere as well as evaporation from the surrounding land surface, is higher in young forests compared with older forests.

Up to 200,000 trees per hectare germinate following logging or an intense fire which burns the whole stand. Intense competition between young trees results in rapid growth rates along with increased evapotranspiration. As the forest matures, the trees thin out, and after 200 years, an ash forest can have less than 50 trees per hectare. These older ash forests release more water back into the catchment.




Read more:
Mountain ash has a regal presence: the tallest flowering plant in the world


With logging occurring every 60-120 years, large areas of ash forest are kept in a high evapotranspiration stage of growth, therefore releasing less water back into the catchment.

Perhaps the losses in water yield could be justified if the value of the timber and pulpwood produced from logging exceeded the value of water. However, previous research has shown that the water in these areas is 25.5 times more valuable than the timber and pulpwood from ash forests.

What can the Victorian government do?

The ash forests in the Thomson Catchment are logged primarily for paper manufacturing. Under the Forest (Wood Pulp Agreement) Act 1996, the Victorian government is bound to supply Australia’s largest pulp and paper mills at Maryvale, owned by the Nippon Paper Group, with at least 350,000 cubic metres of native forest logs each year. The Thomson Water Supply Catchment is allocated for logging under this Act.

If logging was stopped in the catchment, what is the alternative for these paper mills? The answer is to source wood from current plantations. In 2017, Victoria produced 3.9 million cubic metres of logs from plantations. This could supply the pulp and paper mills at Maryvale several times over.

A challenge facing Victoria’s forest industry is the loss of jobs. One major factor in this is out-of-state processing. Australia tends to import lower volumes
of more processed and higher value wood products, including printing and writing paper. By contrast, higher volumes of less processed and lower value wood products, such as woodchips and unprocessed logs – largely from plantations, are exported.

Redirecting plantation sourced logs and woodchips from export markets to domestic processing can address some of these problems. In fact, detailed analysis suggests doing this would have an overall positive economic impact for Victoria.

Stopping logging in the Thomson Catchment and sourcing instead from well managed plantations could both boost water supply and create more jobs. Of course, some jobs would be lost for people who log from the catchment, but this would be more than compensated for by employment in the plantation processing sector.

The first Wood Pulp Agreement Act of 1936, which legislated supply of pulplogs from Victorian state forest to earlier paper manufacturers in Maryvale, featured a clause stating logging was to cease following the designation of the Thomson Catchment in 1967. This has clearly not occurred. In fact 63% of logging in the ash forests across the catchment has occurred since 1967.

The Thomson Catchment is the only one of Melbourne’s large water supply catchments open to logging. Given the critical importance of the Thomson Catchment, our work clearly indicates the Victorian government needs to cease logging and prioritise the supply of water to the people of Melbourne.The Conversation

David Lindenmayer, Professor, The Fenner School of Environment and Society, Australian National University and Chris Taylor, Research Fellow, Fenner School of Environment and Society, Australian National University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

BUSH HERITAGE AUSTRALIA – Update September 2008


One of the groups I have a lot of time for in Australia and one which I am planning to support in a more active way in the New Year (once I get back on my feet so to speak) is Bush Heritage Australia.

Bush Heritage Australia is actively seeking to protect 1% of Australia by 2025, ensuring the protection of our unique flora, fauna and wild places. This is done through purchasing land by money donated to it by those wanting to protect the Australian environment and natural heritage. Bush Heritage currently owns some 1 million hectares, meaning it needs to acquire a further 6 million hectares to obtain its 2025 goal.

In September 2008, Bush Heritage Australia purchased the 8 100 hectare Edgbaston Station, 140km north-east of Longreach in Queensland for 3.5 million dollars. In doing so, Bush Heritage has ensured the survival of Australia’s most endangered and smallest freshwater fish species, the Redfin Blue-Eye Fish. This region is the only location in which this fish species now lives.

But it is not only the Redfin Blue-Eye Fish that will be protected by the purchase of this property as this region and the springs found on the property is the only known habitat for several other species of fish, snails, plants and a crustacean.

The springs on Edgbaston Station are located in the upper catchment of Pelican Creek which flows into the Thompson River and Lake Eyre. There are some 50 artesian springs on the property, supporting a large diversity of life.

The 3.5 million dollars required for the purchase of Edgbaston Station included 1.324 Million dollars from the Australian government’s Maintaining Australia’s Biodiversity Hotspots program and donations from the Queensland Department of Natural Resources and Water and the Queensland Department for Sustainability, Climate Change and Innovation.

Bush Heritage will be working alongside of the Iningai people, who are the traditional owners of the land on which Edgbaston Station is located, to manage the property.

For information on what you can do to assist Bush heritage Australia or to get more information on any of the reserves managed by Bush heritage Australia visit the web site below.

http://www.bushheritage.org.au/