Note Number: AG0989
Date Published: December, 2001
This Agriculture note describes the role and many benefits of farm forestry in rural property management.
Trees and farming
Figure 1. Integration of farm forestry into the rural landscape.
Farm forestry is the strategic integration of commercial trees into existing farming enterprises to provide direct and indirect economic, environmental and social benefits.
The concept of planting trees to yield products that may be sold for profit is readily accepted. However, further to being a stand alone commercial enterprise, farm forestry can provide a positive influence to other aspects of farming systems. Viewed as part of the overall farm business it may be regarded as a risk management tool in that it allows diversification of income streams while offering significant benefits to other parts of the farming system or other farm enterprises.
Plantations can make conditions more favourable for growth of crops, pasture and animals and can be instrumental in improving soil health problems such as water logging, salinity and acidification. Plantations can also improve the overall health of the farm ecosystem by enhancing biodiversity, recycling nutrients and controlling insect populations (by harbouring predators). Other benefits from trees include supplementary/emergency fodder, protection of soil from erosion, improvement of water quality, fire protection and scenic improvement and enhancement of living/working environments. In recent years there has been much discussion about carbon trading as a means to offset or control CO2 emissions. There is therefore potential for farm trees to either offset emissions from the farm (it possible that farmers may be charged for net emissions in the future) or generate carbon credits which may be sold to other carbon emitting industries.
Whilst trees may primarily be planted with commercial intent, through careful design the indirect benefits provided may in fact be of greater combined value than the products yielded directly by the trees.
This agnote will assist you to identify options to integrate farm forestry into rural property management (figure 1). When planning the establishment of a farm plantation it is prudent to consider its siting, orientation, spacing and composition in order to maximise the number of ancillary benefits and overall advantage to the farm.
Farm forestry offers an investment opportunity with the potential to diversify farm income and provide tax benefits. Unlike traditional agricultural commodities, trees can yield an array of products such as sawn timber, posts, poles, firewood, oils, seed, pollen (honey), gums and tannin. In addition, wood and timber products do not have to be harvested and sold in any given year or season. This allows the farmer to retain trees until market conditions are best and the work can be scheduled around other farming tasks. This will result in a more diverse and sustainable farm business in the longer term.
Shade and Shelter
The shade and shelter offered by farm plantations can affect productivity in several ways. Plantations can:
- Reduce physical damage
- Shelter from trees can reduce wind speed, which may otherwise have caused damage to fruit and cereal crops or pasture plants. If plants are flailed around, physical damage to leaves and stems can occur. This will reduce the amount of edible material available and result in the plant directing its resources into repairing damaged tissue and producing less digestible structural support tissue.
- Create a favourable microclimate
- Reduced wind speed can result in higher air and soil temperatures (sometimes by several degrees), increased humidity and reduced moisture loss. The microclimate produced will in most cases provide better growing conditions for plants and higher productivity.
- Protect livestock
- Stress from heat and cold extremes can have very significant impacts on stock productivity and infant mortality rates.
About one fifth of all newborn lambs in Australia die and half these deaths are from wind and cold. Lamb losses of up to 100,000 have been attributed to single extreme cold events in Victoria and 1 million sheep die in Australia each year from cold stress. Heat stress has been found to reduce fertility in sheep and depress wool growth. Ewes with access to shelter will produce lambs with higher birth weights and have more nutritious milk. Both these factors will affect lamb mortality.
High wool cuts are dependent on the density of secondary follicles that form on the lamb foetus during the last six weeks of pregnancy. The number of follicles formed is dependent on the ewe’s nutrition. Stressed ewes will produce lambs with fewer follicles and this trait will persist for the rest of the lamb’s life.
Shelter can increase wool production and the bodyweight of sheep. CSIRO studies at Armidale, NSW found wool production over five years increased by a mean of 31% at the highest stocking rate and sheep liveweights at the same stocking rate showed a 6kg advantage when shelter was provided.
Shelter has been found to increase production in dairy cattle. In a New Zealand example shelterbelts were removed from a farm. During the next season there was a district increase of 5% in butterfat averages, but the farm deprived of shelter produced 11% less.
Overseas studies show how shelter increases beef production. In the USA, two cattle herds wintered on the same rations, one herd sheltered, the other not. Each of the sheltered animals showed a greater weight gain by an average of 15.8 kg. This was for a mild winter. After a severe winter, each animal from the sheltered herd lost, on average, 4.5 – 7.5 kg less than the unsheltered beasts.
Reduce soil erosion
Large volumes of valuable topsoil are lost each year to wind erosion. The most obvious example of topsoil loss was visible to most Victorians during a major dust storm in 1983. Since the majority of soil nutrients are contained in the top 5 cm of soil, the loss of topsoil can have devastating effects on farm productivity. The ability of wind to transport soil increases exponentially with wind speed and so the reduction in velocity achieved by windbreaks will have very significant advantages in terms of reduced soil loss.
Act as a fire break
Tree belts can act as effective fire breaks particularly if the species planted have low combustibility. As well as providing a physical barrier, a windbreak will also reduce wind speed and so slow the spread of fire.
Reduce spray drift
Windbreaks will help reduce spray drift and so allow more targeted spray application and prevent damage to plants in non-target areas.
Competition for light, water and nutrients
Tree plantations will compete with other plants (crops or pasture) for light, water and nutrients and in many situations, crop and pasture growth will be suppressed immediately adjacent to the plantations.
However, the shelter provided by belts of trees can significantly increase the productivity of crops, pasture and animals. Studies have shown that the increased productivity resulting from the shelter provided would more than compensate for the decrease in productivity close to the trees.
Waterlogging and dryland salinity
Waterlogging occurs when the volume of water entering a catchment exceeds the volume leaving. This causes the water table to rise and saturate the surface soil. Extensive tree cover has in the past helped to maintain this water balance by continually transpiring groundwater to the atmosphere. With the removal of large areas of tree cover for agriculture, less water leaves a catchment and so waterlogging becomes more common. Farm forestry plantings can be established around water logged areas, and so enhance the productivity of the land around the plantation.
Figure 2. Sheep will soon benefit from the shelter provided by this young plantation
Dryland salinity is caused by the same process as waterlogging except that the water that rises to the soil surface is salt laden and so has dramatic effects on the soil structure, nutrient balance and soil biota. Commercial tree plantations for salt affected areas present special challenges and will inherently carry more risk. Species planted must be selected very carefully to tolerate the level of salinity and grow at an acceptable rate.
Farm forestry can have a significant impact on water quality. Vegetation cover reduces erosion by lessening the impact of raindrops on the soil and decreasing the volume and speed of runoff (through increased infiltration). This will decrease the turbidity and nutrient loading of the runoff and minimise siltation of dams and watercourses. A healthy plant community can act as a biological filter, especially if associated with a wetland. Such a system can remove pollutants, suspended solids and harmful microorganisms.
There are numerous species options for farm plantations that may be useful as supplementary or emergency fodder for stock. Examples such as Casuarina cunninghamiana or Acacia salicina have potential as high value timber species and are also readily eaten by stock. The leaves and pods of some species however are suspected to be toxic to stock if eaten in large volumes and so care should be taken when feeding out tree foliage. Sometimes plantations may be established specifically for the production of forage eg. Old Man Saltbush (Atriplex nummularia) and Tagasaste (Chamaecytisus palmensis)*. These plantations can also have multiple benefits in terms of reducing recharge, providing wildlife habitat and enriching soil.
* Tagasaste or Tree Lucerne has the potential to become an environmental weed and should not be planted near watercourses or where invasion of native forest areas is possible.
Biodiversity and Wildlife Habitat
Farm Forestry can provide direct and indirect contributions to biodiversity and habitat values. Usually, plantations that include many species and are modelled on natural forests make the greatest contribution to biodiversity. However, commercial timber plantations of only one or two species can still support a great diversity of life in and above the soil and will undoubtedly have a higher biodiversity value than cleared paddocks. Even one year old plantations have been shown to support a range of native rodents which have displaced the common house mouse often found in cleared paddocks (Law, 2000). The greatest benefit may be gained if the plantation is positioned next to a natural forest or conservation planting. The timber plantation can then provide extra habitat and food source for wildlife using the natural forest and provide a protective buffer by decreasing exposure to weather extremes, weed infestation and agricultural chemical drift. The plantation may serve as a link between remnants, enhancing the habitat value of the broader landscape. The forest area may also provide some benefit to the timber plantation by supporting wildlife that may help control pest populations or spread symbiotic fungi and bacteria (Law, 2000).
‘Studies suggest that in healthy eucalypt woodland birds may take about half of the insects produced (of the order of 30 kg per hectare per year). Small mammals, like sugar gliders, and predatory insects and spiders take a significant proportion of the rest. The average level of attack by insects and the frequency of outbreaks would be much higher without these natural predators.’ (Ford, undated).
Soil can become prone to erosion when vegetative cover is removed. It can take many forms including gully, rill, wind, sheet and water erosion. Trees can help reduce erosion by protecting the soil from the direct impact of water and wind, slowing wind and water flows, binding the soil together and increasing infiltration.
As crops are harvested and animal products are sold from a farm, nutrients are continually exported from the farm ecosystem. These nutrients need to be replaced if the farm is to remain viable in the long term. Whilst the bulk of these nutrients will be replaced by the application of inorganic fertilisers, trees can supplement this by transporting nutrients from the subsoil and leachate to their leaves and branches which are eventually added back to the soil as litter. Insects and birds feeding on the trees will also contribute nutrients through their droppings.
Loss of soil structure
Good soil structure encourages strong plant growth through good aeration and access to water and nutrients. Appropriate pore spaces will allow plant roots to penetrate and establish intimate contact with soil particles. Poor soil structure generally involves compacted soils that inhibit plant growth and allow more water runoff that leads to erosion. Trees can improve soil structure by increasing porosity, water infiltration and by encouraging soil microbes that help to bind soil particles together. Trees will also reduce the loss of organic matter by reducing erosion. Organic matter is crucial to good soil structure as it also acts as a soil-binding agent.
The ‘greenhouse effect’ refers to the warming of the earth’s surface caused by certain gases in the lower atmosphere including carbon dioxide (CO2) and methane. In nature, the concentration of these gases is kept in balance by processes that remove and release them from and to the atmosphere. Human activities have accelerated the release of these gases resulting in a higher atmospheric concentration and an ‘enhanced’ greenhouse effect.
Australia is a signatory to the Kyoto protocol which provides for countries to limit the amount of greenhouse gas they emit and for revegetation to remove CO2 from the atmosphere by sequestering or locking up carbon in their plant tissues and releasing oxygen (O2) into the atmosphere. They therefore provide what is known as a ‘carbon sink’.
It is possible that farmers in the near future will have to pay a levy for the greenhouse gases emitted by their enterprise (including gases emitted by ruminant animals) unless they have enough trees to balance this through carbon sequestration. Furthermore, if the number of trees more than balances the farm emissions, carbon credits may be generated which may be sold to other net emitting industries. The future value of carbon trading is still unclear and so it should not be the sole reason for planting trees. However it may eventually add to the overall value of commercial and environmental tree plantations on farms.
Pest plants and animals
Weeds can produce significant reductions in productivity by reducing the amount of feed available, fouling fleeces, poisoning stock and polluting crops. Tree belts can reduce the spread of weeds by acting as seed traps to wind-borne seeds and suppressing the growth of weeds within the plantation. Some weeds may persists within plantations but will be suppressed to the point that seed is not set.
A common perception is that plantations provide harbour for vermin such as rabbits. However trees can provide habitat for raptors and other predators like goannas that will help to reduce the number of rabbits over the whole farm, not just in the plantation itself.
Trees and other vegetation can provide important ‘environmental services’ to the individual landholder and the broader community. These services include such things as salinity mitigation, erosion control, biodiversity enhancement and carbon sequestration.
It is possible that in the future, significant income may be generated by environmental services provided by trees and other vegetation. It is prudent to hold an holistic view of plantations in terms of assessing both financial and other values. Salinity-control credits, carbon rights and payments for biodiversity enhancement may be sufficient incentive to establish new plantations.
Governments have begun to use stewardship payments in order to encourage a fundamental change in land use. Environmental and social benefits have been recognised as being part of the “triple bottom line” for any business, so annual payments are being considered for landholders willing to manage their land for values other than traditional farming. Such payments might be made for the environmental and social products arising from farm forestry such as providing improved water quality, abating dryland salinity, biodiversity enhancement and control of land degradation.
Aesthetic quality and land value
Strategically designed and located farm forestry plantations can greatly enhance the aesthetic value of a property which will make the farm a more pleasant place to live and work while increasing the capital value of the property (figure 3).
Multiplying the benefits
Figure 3. Plantations are a visual enhancement to the landscape
It is clear then, that the potential financial returns from farm forestry are considerable. However, indirect benefits to other farm enterprises, the environment and social values can sum to a much higher total. Careful planning and design is necessary to derive multiple benefits from farm forestry plantations. Your objectives for the plantation must be clear and priorities set since compromises may be necessary to achieve multiple benefits. Farm forestry has the potential to greatly increase the number of trees planted on rural land, which will have significant benefits for farmers, the environment and the community.
- Campbell, R. et al. (1988), Victoria Felix: Improving Rural Land with Trees, Department of Conservation, Forests and Lands & Graduate School of Environmental Science, Monash University.
- Ford, H. (undated). Farm Birds. Nature’s Pest Controllers (pamphlet), Canberra: Department of Arts, Heritage and Environment.
- Law, Brad. (2000), Biodiversity and Planted Forests. Bush Telegraph, Aug-Oct, 2000, State Forests NSW.
- Stewart, A. (undated), Farm Forestry as a Risk Management Tool. Non-Timber Values of Trees on Farms (pamphlet), VFF.
Shaun Quayle, Bendigo
- Bird, P.R., (2000) Farm Forestry in Southern Australia. A focus on clearwood production of speciality timbers, Department of Natural Resources and Environment.
- Abel, N. et al. (1997) Design Principles for Farm Forestry, Rural Industries Research and Development Corporation.
DPI's Private Forestry: http://www.dpi.vic.gov.au/privateforestry