Reports of a dying catchment 'greatly exaggerated'

The impact of logging in Melbourne's water catchments is topical, given the drought, but has been greatly exaggerated.

While it is true logging results in fast-growing regrowth that uses more water than mature forests, the fact that less than 0.2 per cent is harvested annually means the effect is small.

Overall, timber production for saw logs is only permitted within a 13 per cent portion of the total catchment area and this is planned for logging on an 80-year cycle.

The claim that stopping logging will save water is largely theoretical given it relies on the unlikely long-term absence of severe fire that has traditionally determined the extent to which regrowth reduces stream flows.

If dense forest regeneration is a concern, it can be thinned. This is the most efficient, cost-effective means of increasing run-off and is being practised in at least one Perth water catchment in response to reduced rainfall and low storage levels. A potentially warming and drying climate may make it an imperative here in the future.

Catchment thinning could substantially improve run-off into Melbourne's storages, and the capability to do it in the future relies on the continuation of a sustainable timber industry.

There are also claims that Victorian native-forest logging emits 10 million tonnes of carbon dioxide a year that contributes to global warming. However, as timber harvesting is sustainable and mostly occurs in regrowth stands, carbon uptake across the whole forest exceeds the carbon removed in harvesting.

Furthermore, much of the harvested carbon has a long storage in wood products both in-service and subsequently in landfills. The situation in Victoria is consistent with the conclusions of the National Greenhouse Gas Inventory that Australia's managed forests are a net carbon sink.

The harvesting of old-growth forest has long been used as an emotional hook for enlisting community support to shut down timber industries.

While old-growth forests are important repositories of biodiversity, they are nearing the end of their life and their management, either in parks and reserves or wood-production forests, raises important questions about forest renewal.

Ecologically sustainable forest management at the broad landscape level ideally requires a mixture of age classes to maximise biodiversity and ensure continuity.

Contrary to popular perception, old-growth forest is not endangered. About 94 per cent - or more than four million hectares - of Australia's old-growth forests are reserved. In East Gippsland, the current focus of the debate, there are 224,000 ha of old-growth forest, of which 191,000 ha (or 85 per cent) is in reserves. The balance is an important source of timber scheduled for harvesting over the next 30 years.