Plantation Sustainability – Environment
Water – Quality, Quantity & Salinity
When properly planned and managed, plantation development can contribute to more sustainable land use in rural areas by providing substantial environmental, social and economic benefits with little impact on water availability.
- Timber plantations, like all forms of agricultural crops, intercept and use water.
- Trees have a longer growing season, more foliage and deeper roots than pasture or crops.
- Timber plantations improve water quality, and assist in reversing salinity and erosion.
- The effect on stream flow of converting agricultural land to timber plantation is related to the catchment area affected.
- In smaller catchments, it is difficult to detect an impact when less than 20% of the catchment is planted.
- In major plantation regions, plantations occupy between 1% and 6% of large catchments.
Water balance
The establishment of timber plantations helps to restore the hydrological balance that existed prior to tree clearing. This has been documented in both the Denmark and Collie River catchments in Western Australia. Download Salinity Situations Statements for the Collie and Denmark River Catchments.
Read more: Salinity Situation Statement for the Collie River Catchment - a summary (pdf) & Denmark River— Salinity Situation Statement (pdf)
Timber plantations can be used as a tool to assist in the management of water, particularly by the planting of recharge areas to lower ground water and thereby reduce soil salinity. This is considered as a management option in the Murray Darling Basin Salinity Management Strategy. Access the MDBC Basin Salinity Management Strategy
Access some useful reports that further explain the complex interactions betweens planted and native forests and water quality and quantity:
Summary of Knowledge on Forests and Water
This brief paper, prepared by leading scientists from CSIRO and ensis, collates what is known about forests and water from a wide range of literature. The key points are that:
- Forests generally use more water than grass.
- Generalised relationships can be used to estimate the impacts of plantations on streamflow.
- Better capability is needed to assess the impacts of individual plantation proposals on streamflow because of the importance of site-specific conditions.
- All forms of woody vegetation may use more water than grass, not just plantations.
- It is important to differentiate between the impacts of plantations on streamflow and impacts on availability of water for allocation
- The role of existing native forests in controlling water yield and availability is as important at the national level as the impact of Afforestation.
- The impacts of climate variability and change on forests and water yield could be profound so more information is urgently needed.
- Management tools are available to manage water yield from forests and to mitigate the potential impacts of climate change.
Read more: Summary of Knowledge of Forests and Water (pdf)
Plantations and Water Use – A Review
The Bureau of Rural Sciences prepared a review of 'Plantations and Water Use' in 2004. The report reviews water use by agriculture and forests and the effects of land use conversion. It presents maps and statistics on the extent of plantations and other types of land cover in five major plantation regions.
Access the original review: Plantations and Water Use – A Review (pdf)
Plantation Impacts on Stream Flow – Science for Decision Makers
This BRS paper, updated in August 2007, presents results of recent analysis of plantation areas and other types of land cover in major plantation regions and a brief review of scientific literature relating to water use by forest plantations.
Access the BRS report: Plantations and Water Use – 2007 (pdf)
Forest Water Use and National Water Reform
This brief paper by Dr Ian Prosser, from CSIRO Land & Water, builds links between the National Water Initiative, plantation water use and actual impacts on available water, demonstrating in one example that plantation expansion has little impact on water available to irrigators and only small impacts on streamflows.
Access the paper: Forest Water Use and National Water Reform (pdf).
New: Lastest Research - Impacts of Plantations on Streamflows in the Murray-Darling Basin
Research published in Oct 2008, examining future threats to stream-flows in the MDB out to 2030. Estimates of plantation expansion in the catchment of up to 52,000 ha (an 18% increase) would reduce run-off in various regions of the catchment by less than 1% (compared to an 11% decrease due to climate change). However, localised impacts could be larger. The catchment wide impact of plantations may be up to 28 GL/year, which is small compared to other impacts including farm dams (170 GL/year), streamflow leakage from additional groundwater extraction (177 GL/year) and climate change (451 GL /year).
Access the paper: Water Availability in the MDB (pdf - large 15.5 MB).
