SHELTER BELTS ON FARMS

A recent scientific study by the CSIRO, the University of Tasmania, and Private Forests Tasmania indicates that shelter belts boost farm profitability and sustainability.

The study was conducted at four Tasmanian sites, with results published in August 2018.  A range of cropping and grazing operations were studied. 

Shelter belts are designed to provide shelter from wind and temperature extremes, but can also fulfil other functions, including protection of waterways, and enhancing biodiversity and ecosystem health. For both these aims an appropriate mix of native species is usually planted.  For agroforestry shelter belts, specific timber species are planted to create shelter, but at the end of the day are harvested for their timber value.

Financial returns from agroforestry were one focus of the research, with studies concluding that   ‘Internal rates of return of agroforestry systems are typically around 8%. Enterprises with agroforestry were more profitable than agriculture-only or forestry-only enterprises.’   While some may expect that it is the returns from the timber grown in agroforestry that is the greatest benefit, the studies suggest that ‘co-benefits’ are often more valuable. That is, the value of the shelter is often greater than the value of the timber. ‘Explicit recognition of co-benefits is important for understanding the full value of agroforestry. These co-benefits include:

Shade and shelter for stock for reducing mortality and stress in hot and cold weather

Shelter for crop and pasture production

Carbon that can be traded in carbon markets

Co-products such as biomass thinnings/prunings, oils, and honey can generate extra income

Improved amenity and land values, typically by 4 to 15%

Increased biodiversity and sustainability, managed water flows and reduced wind and water erosion.’

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To optimize financial returns from agroforestry, farmers should ‘Design the configuration of the trees to maximise shelter benefits, choose species with low market uncertainty, minimise harvest and logistics costs by ensuring sufficient scale of resource, and develop systems that generate returns earlier’.

As part of this research, Private Forests Tasmania, the CSIRO and the University of Tasmania have quantified the impacts of well planted tree shelter belts on pasture growth at four Tasmanian sites. At one of those sites in Cressy, ‘pasture productivity in Spring 2017 was on average 30% higher in the sheltered half of a paddock compared to the unsheltered half. A Pinus radiata shelter belt occupied approximately 1 ha of the paddock (4%), but induced a 15% increase in pasture growth over the remaining 24 ha, and effectively increased the pasture production to the equivalent of a 29 ha paddock’. A dramatic increase in productivity was also measured in a lucerne crop grown in the lee of a shelter belt.  ‘Lucerne hay yields were estimated to have increased by up to 300% due to reduced wind speeds in the lee of a pine shelter belt.  This equated to over $1,000 of additional benefit across the sheltered area of the paddock (about $147/ha)’.  

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Also published as part of the study was practical and detailed information about how to successfully establish shelter belts on a farm.  Key requirements were seen as good planning, good information, and commitment. 

A full report on the outcomes of the studies can be obtained from   www.publish.csiro.au/CP/CP17242  for  $25.

A field day was held at Cressy in conjunction with this project, and a summary of that day  – brief but useful – can obtained free from Private Forests Tasmania, or downloaded here.