Wildlife corridors (biodiversity corridors) are corridors of land planted with appropriate vegetation, which allow flora and fauna to move across a wider territory. This allows the wildlife to:
- Repond to environmental variability, eg move from food/water scarce areas to food/water plentiful areas.
- Respond to population pressure - move from over-populated to under-populated areas.
- Access a wider range of breeding partners, thus preventing inbreeding and loss of genetic diversity in a local population.
In many parts of Australia, over-clearing of native vegetation has created a sea of agricultural land dotted with the occasional island of preserved native forest or scrub. To allow for wildlife movement, these fragments need to be reconnected, by establishing (replanting) vegetated corridors, using locally indigenous species, on previously cleared land.
The challenge facing the human species is to use some of the land for agriculture - growing food and materials for its own use - while minimising disruption to natural eco-systems, and protecting biodiversity. Thus, some land should be set aside for biodiversity conservation - as nature reserves.
To maximise biodiversity conservation per unit of dedicated land, these conservation areas should be connected together by wildlife corridors. Because species and ecosystems vary geographically, we need a network of corridors and conservation areas spread across all regions - a dense lattice within which human settlements and agricultural plots would nestle.
Where to Plant for Extra Benefits
Ridgelines and creeklines are good candidates for wildlife corridors, because (substantial) vegetation there prevents erosion (by wind and flowing water). Planting or retaining vegetation alongside roadways has the additional benefit of providing flexible impact barriers (frangible plants), and screening out distractions.
Creating wildlife corridors alongside croplands helps insect control by providing habitat for insect eating birds. Here, the distance between habitats, and hence the width of the cropland, should be small enough to allow local birds to fly out to the middle of the field and back again in one go, over and over.
EPA, Queensland, November 2003
Wildlife need to move across large areas of bush searching for food, nesting sites and mates. Corridors of vegetation linking areas of bushland are valuable as they allow movement of wildlife and also provide useful habitat in themselves. Corridors are often used by young animals moving out seeking new territories. This avoids overcrowding of existing habitats and allows recolonising of areas from which animals have disappeared.
Community members are volunteering to assist on working days with fencing, planting and mulching to assist the creation of wildlife corridors across private and public land.
What are biodiversity corridors?
Biodiversity corridors are areas of vegetation that allow animals to travel from one patch of native forest to another. A corridor provides shelter, food and protection from predators by imitating the structure and diversity of native vegetation. Birds, reptiles, amphibians, mammals and insects that would otherwise be isolated in one native forest patch, can utilise corridors to move between patches with relative ease and safety.
Why do we need corridors?
Our landscape was once covered by a mosaic of different vegetation types such as swamps, grasslands, forests and heath. This mosaic supported many species of animal that moved, mated and dispersed throughout their territories and beyond.
Disturbance such as clearing has left only isolated fragments of vegetation. Species unable to move across this changed landscape are vulnerable to local extinction. Local incidents of fire or disease can devastate populations existing in tiny native fragments, with species unable to recolonise the area as they once had. Corridors can help species to repopulate an area following local disturbances, assisting the long-term survival of the species.
How do we create a corridor?
Ideally, areas of vegetation are retained between larger blocks of native forest to allow for animal movement. On a farm property, this could be along a creek line or boundary fence. Around 40m is a reasonable guide for corridor width, however wider corridors are more likely to be utilised by shyer species.
Direct seeding can be used to quickly establish large areas of vegetation. Using local species of plants will ensure the seeding is successful in your local conditions, and will also help provide the food and other resources that wildlife need. Hand planting trees allows you to space them as they would be in native forest, so that trees grow quickly without competing against each other.
ABC - Earthbeat, 22 January 2000
Wildlife corridors are used to link bits of bush that have been broken up by agricultural or urban developments. If left alone, these fragments are like islands. Cut off from their neighbours their genetic diversity declines and the population can become unviable. It's a growing problem the world over. Ecologists and communities are now having to find innovative ways to manage these remnants. Not only to conserve them for their biodiversity, but to get them functioning again as part of the whole landscape.
Wildlife corridors maintain biodiversity, allow populations to interbreed, and provide access to larger habitats.
Wildlife Corridors connecting Core Reserves increase the effective amount of habitat that is available for species and effectively reverse habitat fragmentation. This is especially important for migratory animals and those with large home ranges. Larger habitats support greater Biodiversity, larger populations, and a wider range of food sources and shelter. They also allow populations to interbreed, improving long-term genetic viability. However, Wildlife Corridors cannot substitute for large areas of protected habitat like those in core reserve systems.
ABC - Gardening Australia, 2 April 1999
Wildlife corridors link areas of bush, providing a safe route for native birds and animals to travel through farmland or developed areas. An added benefit to farmers is the value of these strips as windbreaks and shelterbelts. Also, pest problems are significantly reduced by the increased number of predatory birds and insects which thrive in these native habitats.
Alan Reid recommends that 20% of farmland and gardens be set aside as habitat. He believes that this is the minimum required to support populations of local fauna. Corridors need to be 10m wide and must be fenced off from stock. A mixture of locally occurring trees and shrubs should be planted. It is important that local species are used, rather than simply 'native' plants. Many insects and birds are adapted to feeding and breeding on very specific plants. Larger wildlife can also be fussy. The best-known example is probably the koala, which only feeds on certain Eucalypt species.
Ridgelines and gullies should always be left forested to minimise erosion and as wildlife refuges. Catchment protection must also be considered, so revegetation of drainage lines is another priority. Once these areas have been protected, sites requiring windbreaks should be identified and planted. All plantings should be linked, creating a network of fenced corridors in which wildlife can live and move through safely.
In suburban situations it is also possible to create wildlife refuges. Choose a part of the garden which is little used and plant it densely to create a thicket. Birds feel safe in thorny, dense shrubberies. Berry and nectar producing plants will also attract birds and insects.
It is possible to place a covenant on areas of bush which protects them for all time. This is a legal status which means that when land changes hands, the bush is still protected.
ABC Science, January 2002
David Freudenberger is working with Greening Australia on an ambitious new program to bring the small woodlands birds back into the Australian landscape, while there is still time.
The 'rebirding' program is expected to lift the national revegetation debate to a new level because research has shown that many so-called wildlife 'corridors' and the scattered patches of natural bush restored by farmers are generally far too small to have much effect.
"Unfortunately we can no longer afford willy-nilly 'feel good' plantings. We've got to get specific in terms of minimum area, maximum protection from grazing, and correct plant composition," says Freudenberger.
"The main problem is that many replanted areas tend to be narrow corridors or small patches of a few hectares. But we're discovering these birds need a minimum of 10 or 20 hectares for them to reoccupy an area, and perhaps up to 100 hectares to settle and breed there."
Sandra Kanck, Australian Democrats, 30 August 2005
We need to plant north/south corridors of native vegetation to allow our native animals to move south to [adjust to climate change]. Global warming and the associated increasing temperature and decreasing rainfall has the capacity to decimate native wildlife trapped in isolated bushland in the north of the state.
The project has had a large-scale, positive impact on local roadsides by:
- Increasing greenery and providing visually-pleasing road corridors.
- Improving the roadside environment by reducing traffic noise and air pollution.
- Increasing safety by providing natural, flexible barriers along roadsides, and reducing headlight glare.
- Engaging the local community in tree planting events.
Planting Frangibles and Anti-Gawks (PDF)
Leon Beyleveld, Greening Australia
Frangible plants provide a flexible barrier for motorists, which will snap if hit by a car travelling at high speeds. This reduces damage to both the car and the motorist, while also reducing the speed of the out-of-control vehicle. Frangible trees have a trunk diameter of 150 mm or less.
Anti-gawk vegetation is used to obscure sightlines between lanes travelling in opposite directions, which discourages motorists travelling in one direction from being distracted by traffic or breakdowns on the opposite carriageways.
18 February 2006