Document ID: chunk:federal_register_of_legislation:F2024L00270:body:0:p85
Version: federal_register_of_legislation:F2024L00270
Segment Type: other
Provision Reference: 
Character Range: 248701–251541

under half this catchment area, but yield 80% of the stream flow because they grow on the higher rainfall sites (Benyon et al. 1996). Approximately 20% of the mountain ash forest of this catchment area is in closed water catchments (Viggers et al. 2013).
The 'value' of water may be considered as a provisioning service (delivery and other functions such as filtering), some of which can be valued as the cost to replace this service with piping, pumping and filtering; as well as a product (quantity/runoff) (Keith et al. 2016). Keith et al. (2016) found that for their study area (of approximately 80 by 80 km2), 115,149 ha formed part of the water supply catchment for Melbourne and the surrounding regions. They estimated that for 2014 to 2015, water provisioning service for this area was valued at $75 million and water product at $876 million. The contribution to gross domestic product (industry value added) for water in the study area was estimated to be $267 million (or $2,319/ha) for 2014 to 2015.
Climatic conditions, natural disturbances (bushfires) and human activities in these forests all contribute to variation in water yields (Benyon et al. 1996; Creedy and Wurzbacher 2001; Lane et al. 2010). There is a well-documented empirical relationship between forest stand age and water yield for mountain ash catchments in the Central Highlands: catchments dominated by large old trees and old-growth forests yield significantly more water and improved water filtration than catchments comprising primarily young forest (Vertessey et al. 2001; Viggers et al. 2013). Furthermore, while an increased runoff occurs for some years after disturbance events such as high severity bushfire and clear-fell logging (Keith et al. 2016), regrowth ash forests use a greater amount of water than mature ash forests (Benyon et al. 1996). Changes to forest use will affect water yield into catchments, with cessation of timber harvesting likely to result in increased water yields over time.

Carbon storage
Forests are an important component of the global carbon cycle, and maintaining or increasing forest carbon stocks is a key indicator of sustainable forest management (Department of Environment and Primary Industries 2014e). Wet temperate evergreen forests such as those of the Central Highlands are very valuable for carbon storage, being the most "biomass carbon dense" in the world (holding the highest amount of carbon of any forests at 1,900 tonnes per hectare compared to an average of up to 500 tonnes per hectare for tropical forests) (Keith et al. 2009).
Because growth and retention provides carbon storage whereas harvesting and bushfires result in a net storage loss (Keith et al. 2016), management of native forests offers opportunities to change carbon storage capacity and contribute to global climate change mitigation