Shelterbelts are usually linear strips of planted woody vegetation that have been planted for the purpose of providing a wind buffer and shade for livestock. Shelterbelts are often thought of as only newly planted vegetation, yet they can be very effectively built around existing features of the landscape, including existing remnant vegetation in riparian areas, old wooded crown roads and paddock trees. These existing features bring additional benefits, and relatively quickly. Well-designed shelterbelts provide a multitude of benefits to farm productivity and wildlife conservation.
Native species provide the best shelterbelts for biodiversity by providing habitat for wildlife. Native species are adapted to local conditions, are typically better able to withstand fire and prolonged drought, and are thus easier to establish and more likely to survive. Furthermore, native species make it more likely that ecosystem processes will be restored or maintained.
Shelterbelts are commonly established as windbreaks. By reducing wind speeds, they assist to reduce moisture lost from the soil (which improves pasture and crop yields) and protect livestock. Shelterbelts can provide effective protection from winds for a horizontal distance of approximately 12 times their height.
Reduced wind speeds reduce the amount of heat and cold stress experienced by livestock. This allows livestock to dedicate less energy to self-maintenance, and farm productivity can be improved. In one study, the presence of shelterbelts resulted in increased wool production by almost a third and a 21% increase of live-weight over a 5-year period. Furthermore, increased pasture yields and reduced energy demands for production will increase sustainable stocking rates.
Shelterbelts also provide shade and frost protection and, if planted along farm boundaries, can eliminate nose-to-nose contact with neighbouring livestock, thus providing biosecurity benefits.
Reductions in wind speed also lead to other, perhaps less obvious, benefits such as:
- the retention of topsoil, which is critical for maintaining farm productivity;
- moderating chemical spray drift by reducing the distance that airborne droplets travel; and
- filtering chemical particles from the air before they can reach unintended areas, such as neighbouring farms, paddocks and homestead
Biodiversity has dramatically declined across the agricultural landscape of south-eastern Australia, with much of the temperate woodlands and forests having been cleared. What remains is small in area and patchily distributed across the landscape. However, research by Sustainable Farms and others shows that farmers can do a lot to recover biodiversity on their farms and, if done well, shelterbelts can make a huge contribution to this.
Planting native vegetation or enhancing existing native vegetation for shelterbelts can provide essential habitat for native wildlife, including species that are threatened with extinction, such as Superb Parrots, Flame Robins, Speckled Warblers and Squirrel Gliders. Refuges, or areas that avoid the ongoing disturbances associated with agriculture (cultivation, livestock grazing and trampling, chemical applications etc.), and areas of dense shrubby and grassy vegetation, are ideal habitat for farm wildlife to nest, shelter, forage and burrow.
An increase in biodiversity will benefit the farm by contributing to healthy, functioning ecosystems and the ongoing provision of ecosystem services, such as natural pest control by native insectivorous species (including invertebrates, birds, bats and reptiles that eat crop pests) and crop pollination services. Over time, farmers’ expenses for pest control and the use of chemicals can be reduced.
With careful design, shelterbelts can also form corridors for wildlife to move around farms and the broader landscape, which is particularly important for tree dependent fauna such as squirrel gliders, which rely on habitat connectivity for their continued existence in the area.
The presence of wildlife also contributes to the aesthetics of the property: the sounds, colour and movement of wildlife create variety, pleasure and beauty, which can benefit mental health as well as adding value to a property.
Although shelterbelts take up land that might otherwise be used for cropping or livestock grazing, the benefits to productivity, coupled with the ecosystem services provided by increased biodiversity associated with native plantings outweigh and offset the loss of land.
Ultimately, farm health is improved and healthy farms are more resilient, which is particularly important with the onset of climate change. The establishment of native shelterbelts on farms will help ensure continuing agricultural productivity; safeguarding farmers’ livelihoods now and into the future.
Shelterbelts consisting of native plant species have a number of advantages over those using exotic plant species and for this reason we consider only native-based shelterbelts here.
Planning the location of a shelterbelt is influenced by many factors, including the location of existing property infrastructure, prevailing seasonal winds, soil type, problem areas of erosion and salinity, remnant vegetation, use of non-arable areas, the need for shade and other on-site specific features. The best way to decide on the location is by completing a whole-of-farm plan for your property.
Composition and Density
Shelterbelts should be semi-permeable to wind and of medium vegetation density to regulate – but not eliminate – wind speed without creating turbulence. Planting tree species that are dense from ground to canopy creates an impermeable barrier and tends to have increased turbulence on the windward side of shelterbelts. Thus dense species should be avoided.
Planting only trees can create problems because wind will flow, and increase in speed, as it moves below the canopy, thereby reducing the effectiveness of the shelterbelt as a wind barrier. Similarly, planting only shrubs limits the effectiveness of a shelterbelt.
Many early shelterbelts were planted with a high proportion of Eucalyptus species. When the trees were young, the shelterbelts performed well, but after 15-20 years the Eucalypts dominate the understorey species and the shrub layer thins out. When this happens, the effectiveness as a wind break is reduced, as the wind can flow beneath the trees. Planting taller growing trees in the middle and shrubs along the edges of a shelterbelt will create a more functional wind break and may enable shrubs to persist longer.
A combination of carefully selected native trees and shrubs will provide the most effective shelter from wind over a greater area and habitat for a greater diversity of native wildlife. Selecting shrubs and midstorey species that grow locally and or those that are known to persist will help ensure the long-term functionality of the shelterbelt.
Planting a diversity of species has benefits for wildlife by providing a variety of habitat and feeding resources. Include plant species that flower at different times of the year. The incorporation of large old trees into shelterbelts significantly increases their biodiversity value, as these trees provide additional wildlife resources, such as hollows and more reliable food supplies.
Integrating remnant vegetation into a shelterbelt can have substantial benefits for wildlife. Incorporate paddock trees, mistletoe, dead trees, paper roads (old or current crown road leases) or roadside remnant vegetation into the shelterbelt, or connect with remnant vegetation to improve the wildlife outcomes. Consider regrowth elements, as these support birds of conservation concern. Habitat for native animals and reptiles can be increase by incorporating timber (logs and trees) and rocky areas into a shelterbelt. Be careful not to overshadow the rocky areas, as reptiles need the warmth of the rocks to maintain their body temperature by basking.
Consider renovating old shelterbelts that are showing signs of degradation. Many shelterbelts have become less effective over time and are a good focal point for restoration. Old shelterbelts often have old growth trees that are so important to wildlife and these can be protected and reinvigorated with some supplementary planting.
The location of shelterbelts will determine how effective they are. Although establishing an effective windbreak may be the primary objective of a shelterbelt, other considerations such as the benefit of maximising shade for livestock and habitat for wildlife are also important. For example, shelterbelts can be used to enhance and connect remnant vegetation, control salinity and protect riparian areas. As they do not need to be strictly linear, shelterbelts can, for example, wind along creek banks or be made wider around remnant trees.
In general, establishing shelterbelts in higher parts of the property, such as ridgelines, will extend the area protected. Avoiding dense planting in or near rocky outcrops will reduce negative effects of shading on important native reptile habitat. Shelterbelts on gullies and riparian areas tend to support more bird species and are good focal zones for designing shelterbelts that maximise wildlife benefits.
Shelterbelts planted along boundaries can increase the biosecurity of a property.
In linear shelterbelts, turbulence can occur at the ends, leading to high wind speeds in the areas immediately surrounding the belt. It is important to ensure that the overall benefit of the shelterbelt is positive. For this reason, linear shelterbelts should be at least 10-12 times as long as they are tall (the expected height on maturity of the tallest layer). Where feasible, shelterbelts in high areas should end in low areas, which minimises the turbulence effect. Alternatively, the ends of a shelterbelt may be curved to minimise turbulence.
The best practice is to plant networks of shelterbelts. These will minimise or eliminate the effect of turbulence, provide shelter from wind in any direction and shade for stock at all times of day, and provide protective corridors for wildlife to traverse.
Determining how wide a shelterbelt should be is a trade-off between reduction in grazing or cropping area and the benefits of providing shelter to livestock, protection of cropping and pasture paddocks and habitat for native wildlife. The objectives of the shelterbelt and the area of available land will influence the width of a planting, and will also significantly influence the type and numbers of native fauna that will occupy it.
Wider shelterbelts (20-30m) provide more effective wind protection and superior habitat for native species, particularly those that have been severely affected by the loss and fragmentation of native vegetation (See Box 1). A typical best practice figure used for biodiversity plantings is around 5-7 rows of trees or more (or 20-30m depending on row spacing). A shelterbelt that takes in existing paddock trees, dead trees, roadside remnant vegetation, logs and rocky areas will improve wildlife outcomes by conserving and enhancing habitat, and providing wildlife with a greater variety of resources.
Narrow shelterbelts (2-3 rows of trees or less than 20 m wide) are less effective in slowing wind and have less space for the development of different layers of vegetation. Narrow plantings are also susceptible to wind tunnels caused by the loss of individual trees, and dieback can be a problem, particularly for widely spaced or isolated trees. However, many bird species will still use narrow or smaller remnants and plantings, so they should not be discounted if that is all that can be implemented as a shelterbelt. Wildlife benefits of narrow plantings can be maximised by intersecting connected narrow shelterbelts. This has been shown to have the same benefit for woodland birds as broader block plantings, with similar bird species richness being observed.
In summary, not all elements of shelterbelt design will be applicable or practical to everyone’s circumstances. The intended main purpose of a shelterbelt will ultimately drive its design, but with some thought around specification using current research and knowledge, shelterbelts can be designed to have additional benefits. A whole-of-farm plan will help inform overall shelterbelt design, and can help ensure you maximise additional benefits of a shelterbelt based on your specific circumstances.
Further advice on shelterbelt design is available from NRM groups such as Local Land Services, Landcare and Catchment Management Authorities, as well as staff from the Sustainable Farms project.
Three general principles for on-farm wildlife conservation should be applied to shelterbelt design to maximise the benefits to wildlife:
1. Protect remaining natural assets. Work with what you already have and utilise remnant landscape features for shelterbelts where possible. This can include old growth vegetation and individual trees, regrowth, existing plantings, mistletoe, dead trees, logs and rocks.
2. Restore what is missing. This can involve both managing to encourage regeneration and establishing new plantings.
3. Combine Protection and Restoration. Utilise the cumulative benefits of both protection and restoration by integrating revegetation and regeneration with remnant woodland elements. For example, plantings incorporating paddock trees have higher bird species diversity.
Many native species rely on large areas of suitable habitat to support their foraging and breeding requirements. Fragmentation of suitable habitat increases the area adjacent to unsuitable habitats and introduces edge effects—a phenomenon whereby the effect of degraded habitat extends into adjacent suitable habitat and alters species assemblages. Edge habitats typically support species that have adapted well to landscape disturbances and are already thriving in agricultural landscapes, such as the native but aggressive Noisy Miner. The wider a native shelterbelt is, the greater the ratio of core habitat to edge habitat and the more suitable it becomes for declining woodland fauna.
- Sources and Further Reading
Dorricott K & Roberts B. 1993. Wildlife Conservation on Planned Properties: A Guidebook for Queensland Landholders. Land Use Study Centre, University of Southern Queensland, Toowoomba, QLD.
Fisher J & Lindenmayer DB. 2002. Small patches can be valuable for biodiversity conservation: two case studies on birds in southeastern Australia. Biological Conservation, 106: 129-136.
Ikin K, Mortelliti A, Stein J, Michael D, Crane M, Okada S, Wood J & Lindenmayer DB. 2015. Woodland habitat structures are affected by both agricultural land management and abiotic conditions. Landscape Ecology, 30: 1387-1403.
Lynch J & Donnelly J. 1980. Changes in pasture and animal production resulting from the use of windbreaks. Australian Journal of Agricultural Research, 31(5): 967-979.
McKemey M. 2013. Managing Native Vegetation: how to look after your native vegetation and revegetate your land. Border Rivers-Gwydir Catchment Management Authority, NSW.
Lindenmayer DB. 2011. What Makes and Good Farm for Wildlife? Melbourne, CSIRO Publishing.
Lindenmayer DB, Claridge A, Hazel D, Michael D, Crane M, MacGregor C & Cunningham R. 2003. Wildlife On Farms: How To Conserve Native Animals. Melbourne, CSIRO Publishing.
Lindenmayer DB, Michael DR, Crane M, Okada S, Florance D, Barton PS & Ikin K. 2016. Wildlife Conservation in Farm Landscapes. CSIRO Publishing.
Lindenmayer DB, Blanchard W, Crane M, Michael D & Sato C. 2018. Biodiversity benefits of vegetation restoration are undermined by livestock grazing. Restoration Ecology, 1-8.
Lindenmayer DB, Knight EJ, Crane MJ, Montague-Drake R, Michael DR & MacGregor CI. 2010. What makes an effective restoration planting for woodland birds? Biological Conservation, 143: 289-301.
Lindenmayer DB, Northrop-Mackie AR, Montague-Drake R, Crane M, Michael D, Okada S & Gibbons P. 2012. Not all kinds of revegetation are created equal: Revegetation type influences bird assemblages in threatened Australian woodland ecosystems. Plos One, 7: 11.
Munro NT & Lindenmayer DB. 2012. Planting for Wildlife: A Practical Guide to Restoring Native Woodlands. Melbourne, CSIRO Publishing.
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