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Why prevent Clearfelling on West Wellington? PDF Print E-mail

Water Catchment...

Slow Forest Regeneration...

Endangered Wildlife...


Water Catchment Threat

Water catchment coupe map

Wellington Park was established to protect both the natural values of the area and the safety of water supplies to the greater Hobart region. West Wellington provides the headwaters for the water catchments of Judbury, Lucaston and Crabtree, but there is no reserve set aside to protect these catchments. Crabtree Rivulet flows through one of the coupes marked for logging on Forestry Tasmania's 3-year plan. Residents and graziers are reliant on creeks fed from this catchment for household supply, irrigation and livestock watering. However, Forestry Tasmania's code allows the logging of up to 5% of a water catchment annually - meaning a catchment area could be completely logged in a 20 year period.

Approximately twice as much rain falls on these mountains than in the surrounding valleys and the forest acts as storage for Graph showing high rainfall on WWthis water, which is then released gradually through a network of gullies and streams, keeping the rivers flowing through the warmer months.

Clear-felling in water catchments is a practice being abandoned on mainland Australia. Having suffered the devastating impacts of drought, many mainland communities are opposing clearfelling the forests in their water catchments. Independent hydrological studies have proven that clearfelling in catchments depletes water flow and damages downriver ecosystems.  The availability of water to local communities can be severely reduced, particularly in hot dry periods. Tasmania has been experiencing hot dry summers for at least a decade and increasingly the winters have been drier as well.

With clearfelling, there is increased likelihood of sediment coming into the system owing to erosion through run-off, particularly after heavy rain & burning. Forestry Tasmania believes it is good forest management to burn coupes after clearfelling, which is usually done in autumn, just prior to winter rainfall. This results in topsoil, debris and ash being washed into creeks. This is a particular problem in West Wellington owing to the steepness of many of the coupes.

In Forestry Tasmania's hydrology studies into the effect of logging and re-planting operations within water catchments, the only consideration is that of evapotranspiration, ie the loss of moisture into the air from evaporation and transpiration (from vegetation). So for instance a ‘middle-aged' forest might be expected to use and lose much more moisture than a recently re-planted one, such that Forestry claim that water flow in creeks could actually increase following clearfelling. What is not taken into account is the water retained in leaf litter, soil humus, rotting timber etc which helps to feed creeks throughout the year, even during hot summer conditions. This rich ground cover is completely lost by clearfelling and subsequent burning.

Forestry Tasmania's studies take no account of seasonality, or that heavy rainfall can be experienced in just a few hours. The Graph showing seasonal rainfallpresent forest moderates the flow of water, releasing it into the creeks & springs gradually. With clearfelling, creeks will be subject to high flows immediately following a big rain event, possibly leading to downstream flooding & siltation. During drier spells, creeks will dry up much more quickly than when there is full forest cover in the catchment.

If the winter and spring rains fail, as sometimes happens, then these water catchments and their eco systems will face a crisis similar to that experienced in many parts of south eastern Australia over the past few years.

 

Slow Forest Regeneration

West Wellington is home to many endemic species of flora and fauna, some threatened or endangered. Much of the area was burnt in the 1967 fires and so is considered re-growth forest. However, many old trees are still standing, their tops white and dead above the canopy, but very much alive underneath.

It is an elevated environment beginning at 600 metres above sea level and rising to 850 metres. The types of plants which thrive at these altitudes vary depending on exposure to the elements.  Temperatures on the plateau can regularly fall below zero from May to September. Overnight minimums can be as low as minus 4 to minus 5 degrees Celsius.  The canopy of a forest has a tempering effect on ground temperature and a thick forest understorey protects the soil from the hard frost that would form on open ground at these temperatures.  Hard frost damages the structure of soil and the micro-organisms that keep pathogens in balance.

The area is also subject to snowfalls and may receive over 20cm in a single blizzard, more in a prolonged snowfall period. When this snow melts there is a significant run-off swelling the creeks and rivers. A healthy mixed forest will moderate this effect. The plants and fallen debris in a mixed forest will slow the speed of the water as it makes its way into the watercourses.  Where the forest is clear felled and burned, the runoff from snowmelt and heavy rainfall can cause topsoil to be washed into the catchment systems.  The topsoil in the West Wellington Range is shallow, free draining and easily washed away and depleted of nutrients.

Pro-clear-felling science claims that burning the forest creates a seedbed rich in nutrients, therefore is it acceptable, even necessary to good regeneration. However the ash and topsoil, as well as seeds, are easily lost through water runoff. At higher altitudes the colder conditions mean that plants grow more slowly. Forestry Tasmania's assumption that the forest can be regenerated with the same mixed species underpins their clear-felling rationale and gives legitimacy to the industry. But at higher altitudes the environment is more fragile and there is no guarantee that all species will be able to re-establish. The result is a degraded environment. READ MORE ABOUT FLORA

Most of the species on West Wellington are high rainfall species, if the period of dry weather continuesDry 2010 such as is being experienced in 2010 (see graph), few species are going to regenerate successfully. Many of the minor and rainforest species will not have matured sufficiently to have set seed & hence will be unable to regenerate at all. In addition the generally wet sclerophyll and rainforest flora on West Wellington have a low tolerance to fire.

 

 

Endangered Wildlife

Whereas the presence of endangered species will be noted in Forestry Tasmania's FPPs, there is no requirement to halt logging operations where these are encountered. For instance if a grey goshawk or masked owl nest is discovered, the FPP states that forestry operations should keep100m away from the nest until young have fledged. This is despite forestry operations being highly audible for up to 3kms away. Application can also be made for a permit to remove nests. Grey goshawks have been seen on neighbouring properties.

Forestry's FPPs for roading operations state that efforts should be made not to disturb rotting logs which are the habitat of rare stag beetles. However, coupes will then be completed logged out & everything that remains will be burnt, such that the habitats are inevitably destroyed.

500m buffer zones are left around wedge-tailed eagle nests - for a creature that has territories of many kilometres. These iconic birds are often seen soaring high above the area under threat and neighbouring land. For the rare spotted quoll, the only effort will be to ensure that some potential habitat (eg wombat burrows and fallen logs) is left untouched at the edges of coupes. Where endangered flora is discovered, efforts may be made to re-route roads or change the boundaries of coupes, but if this is not straightforward, Forestry will continue regardless. Also if rare species of flora or fauna are not found in an initial survey it is left to the ground operatives to notify management of their suspected existence as they come across evidence. What incentive is there for an excavator driver to notify Forestry Tasmania of the existence of a nest for instance, that could stop them working? In the FPPs so far available for operations in West Wellington there is no mention of Tasmanian devils - which are believed to be in the area.

 

Slow Forest Regeneration

Endangered Wildlife



 

Last Updated ( Aug 19, 2010 at 11:05 PM )