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Restoring Habitat through Revegetation

Rohan Cuming

Introduction

What we know today as the Australian continent has an ancient biological history characterised by a continuous evolution dating back over 80 million years when the former great southern continent of Gondwana separated into what is now South Africa, India, South America, Antarctica, New Zealand, New Caledonia and, of course, Australia. Whilst 15,000 years ago large parts of Europe and the British Isles were locked under ice and devoid of life, our particular land had progressed relatively uninterrupted by cataclysmic events. Volcanic activity and glaciations both contributed to arrested evolution in Europe, leaving a legacy of fertile soils, whilst in Australia soils remained relatively poor, yet with only gradual climatic changes and relative isolation life evolved relentlessly to the modern day. What have been widely regarded as the new lands are in fact the oldest.

The Australian aboriginal people are thought to have arrived from south east Asia between 50,000 and 170,000 years ago, and as Tim Flannery speculates in The Future Eaters, brought a dynamic new influence on our environment. Predation on the larger mammals and the use of fire as a tool apparently has modified the nature of our ecosystems which we encounter today. Something like 2000 to 5000 generations of aboriginal people later, white Europeans entered the landscape and in the last 200 years have radically altered the ecology and landscape. Initially, forest clearance for timber and pasture, large scale fertilisation programs and mining, industrialisation and urbanisation have all depleted the indigenous environment to the present day where rural areas of south-east Australia host remnant vegetation and fragmented faunal habitats only. An area such as the Mornington Peninsula in Victoria, despite being well regarded for its natural beauty and character, supports only 6% of its original vegetation. With the isolation of these remnants comes a greater rate of decline as the pressures from weeds, feral animals, fungal pathogens and general exposure are heightened, greatly undermining inherently interdependent ecosystems.

Rural Land

Rural land in south-eastern Australia is made up of National Parks, which are reserved, crown lands with or without logging, smaller tracts of public land including roadside verges, and private land. Funding and general resources are very low for all public lands, and management issues are vast and potentially very expensive; likewise, private landholders can afford limited resources for landcare.

Land with soils which are poor for agriculture such as sandy soils, steep rocky country, salty land or exceptionally wet land, will most commonly be the least disturbed, and has often escaped clearance, while fertile soil such as river flats and what were previously open woodlands or grasslands for the most part have been developed for agricultural purposes. Land which has been extensively cultivated, fertilised or otherwise treated with pesticides will be relatively devoid of indigenous flora and fauna. Likewise most urbanised areas will exhibit few indigenous remnants. The nature of the land use and the extent of it will impact greatly on the ability of the indigenous flora and fauna to survive. In general, total land use farming and the creation of monocultures will be less favourable for the retention of indigenous ecologies than farming which uses the land selectively and produces a range of products.

Flora and Fauna

Flora

Australia has some of the most diverse flora and unique fauna in the world. Something in the order of 18,000 plant species have been recorded, and it has been estimated that some 7,000 species have yet to be identified.

Vegetation is described in terms of communities and sub-communities. Like environmental factors such as hydrology, rainfall, aspect, soil type and topography will determine whether the arrangement of plant species is described as a heathland, a rainforest, a woodland, a grassland, a wetland or swamp, a coastal community, a saltmarsh or a riparian or streamline community. Where subtle variations exist within an area, subcommunities may be described.

Whether managing an existing bush remnant or revegetating highly disturbed environments, it is important to establish which community naturally belongs on a given site. Where relatively intact vegetation occurs this process is not too difficult, but when much of the vegetation has been cleared an extensive survey of surrounding areas, including geology, soils and vegetation will need to be undertaken. Ultimately, an exact demarcation may not be possible, but such a study will provide much valuable insight into that particular environment, and importantly, the nature and extent of the ecosystem beyond the immediate area.

Fauna

The Australian fauna has clearly been devastated over the last 200 years. Wholesale vegetation clearance and the disruption of fire regimes within the bush have undermined many habitats, leading to extinction of many of the larger species and endangering many more. In general fauna, whether it be mammals, birds, reptiles, amphibia, invertebrates or microbes, requires intact, interconnecting habitats that are species rich and have a continual cycle of renewal.

Some Key Issues

• Small remnants are often not substantial enough for populations of animals - the provision of connecting vegetation corridors can allow passage from one habitat to another. Isolation of populations causes genetic bottlenecking (inbreeding).
• Remnant habitats are often vulnerable to factors such as weed infestation, run-off, nutrification and altered fire regimes, thus degrading the quality of that habitat.
• Nesting hollows for birds, possums and bats in many cases need to be provided as old natural hollows often don't exist. Also debris needs to be present on the ground as refuge for many insects, invertebrates, small mammals and reptiles.
• All strata of vegetation - ground storey, shrub layer and canopy need to be present to maintain diverse populations of fauna. Fire is a key element in regeneration of plant species, but it needs to be achieved in a mosaic manner. Hot burns are usually required but need to be carefully planned and supervised.
• Predation from feral animals is a major threat to many animal species.
• Chemical residues can undermine invertebrate and microbial life in the soil. Organisms at this level recycle nutrients, provide food for larger species and form symbiotic relationships with many plants and are consequently a fundamental basis for all ecosystems.
• Native birds consume vast amounts of insects and invertebrates from the bush and agricultural land, and are significant pest controllers. Introduced birds such as starlings may proliferate, using seed sources available from agriculture, and evict native populations from preferred habitats.

Getting Started

Hands on experience, especially in a local context, is an invaluable way to learn about bush regeneration. Friends groups and committees of management working days provide opportunities to meet naturalists and budding bush regenerators, whilst helping out with the management of a local remnant. Organisations such as Greening Australia, and the National Trust's Save the Bush offer training courses and newsletters whilst volunteer groups such as the Field Naturalists, Bird Observers Club Australia, Victorian Wetlands Trust, Society for Growing Australian Plants and various walking clubs offer activities and newsletters. The Indigenous Flora and Fauna Association (IFFA) provides a focus for research and commentary on current bush regeneration issues and a newsletter which includes a calendar of weekly activities occurring throughout Victoria. DCNE's Land for Wildlife also provides a network for private landholders and produces an excellent newsletter. If there is an indigenous nursery in your area this may well provide an important resource, but if there is not one that covers your area then either start one yourself or encourage somebody else to.

Funding: Most funding available is for public lands and is provided by Melbourne Parks and Waterways and DCNE grants. Local Councils may also provide funds for projects as do various private trusts. When looking for funding or resources for private land, the Federal Landcare program will assist with a priority for projects which cover large areas, for instance local landholders collaborating to work on the greater catchment region in which they reside.

Pre-European Vegetation

A substantial task needing to be carried out prior to major works will be a study into the pre-European environment, including maps and plant lists. Research will require assembling all available information relevant to your area including geology and soil maps, flora and fauna survey and historical records. At best this will give only an approximation to the prior indigenous environment, but the thought and groundwork required will become an invaluable process as any projects proceed.

The maps you create will indicate delineation between vegetation communities each of which will have at least a basic plant species list. When it comes time for planting, these lists can be referred to for each area. The research you do will also entail visiting as many local remnants as you can and comparing the relative environments with your own. Over time you should slowly acquire a feel for these places and progressively be able to visualise an outcome to which you are aiming.

Management Plan

The vegetation study referred to above will become the basis for a larger document, which will outline all management issues relevant to a revegetation project. Weed species will need to be identified and mapped along with control techniques, a priority rating and a seasonal timetable for their elimination. There will often be obvious and widespread weed species which will be dealt with over a protracted period, but there may well be species which are not abundant yet are known to be highly invasive and so may warrant highest priority. Other weeds may be regarded as ubiquitous and difficult to control in the short term and are consequently given lowest priority.

Management also needs to consider local drainage issues such as excess water and/or nutrient run-off from agricultural land and other problems such as fencing of livestock, the presence or absence of fire, erosion control, salination and forest dieback.

Ultimately a strategy or plan of action will be produced which will stage various activities on a seasonal basis.

Bush revegetation - practical

Having completed or obtained flora and fauna lists and created multi-layered maps of as many environmental factors as is feasible, a strategy can be put together. The strategy may focus on various activities such as weed control, propagation of local plant species, collection of seed, fencing, burning practices, various erosion controls, creation of wetlands, etc. This will go into a greater document known as a management plan which is in itself unlimited in its scope. All theoretical, philosophical items can be included here, as well as detailed description of techniques, practical considerations, funding options, timetables, and anything relevant to achieving a successful management program.

Some Key Points

• The principle that each area is unique. Apart from more discernible differences between flora and fauna species, there exist genetic variations between individuals that have reproduced sexually. Gene pools are described in terms of provenances, which describes like populations of organisms evolved to a given set of conditions. Local forms or variations exist to suit local conditions. This has great relevance in propagation of plant species or the breeding or introduction of fauna.
• The use of chemicals. Their use must always be questioned. Initial results can be flattering when eliminating weeds, but impacts on the soil or water may not be recognised for many years.

• Maintain diversity of:

  • species, habitats and communities
  • techniques: will allow opportunities for comparison at a later date

• One step at a time. Start with what you know. Be patient until an approach may serve from all angles. Remember, especially in good quality habitats we have a responsibility not to create further damage problems to what is a fairly vulnerable system.

The practical aspects of bushland management will involve some or all of the following techniques:

• Weed control: Careful handweeding, especially around existing native vegetation. Techniques are described by the Bradley sisters, which entail starting in areas of best vegetation and gradually working outwards, never overclearing, creating minimal disturbance and always following up in successive seasons.
• Herbicides are commonly used, either as a contact spray or as a stem injection. Their use must always be carefully considered as there is a risk of general environmental contamination.
• Solarisation: Smaller areas can be covered by plastic for periods of time to kill existing plants. In very weedy areas this may be repeated after a time to allow for regermination of weeds prior to mulching and/or planting.
• Slashing: This is part of a regular management procedure particularly for grasses and depends on seasonality. The aim here is to reduce the volume of weed seed entering the environment.
• Planting: Usually tubestock is used, however, smaller plugs or even mats of plant material supplied from local sources can be used. The choice of species is important. In more degraded areas vigorous larger tree and shrub species are required, in unsettled areas fast colonisers are useful, such as herbs and grasses. In some areas, such as semi-intact grasslands, slashing may become a key regenerative technique, so planting may become a hindrance. Planting nitrogen fixing large wattles such as Black Wattle (Acacia mearnsii) may help this environment, whilst still allowing slashing management to be carried out. Planting recharge areas in salt affected areas can lower the water table.
• Fencing: The exclusion of stock, feral animals and people is often important. Fencing simply to delineate a regeneration site may be useful.
• Brushing: The placement of branches with or without seed over exposed areas can significantly minimise erosion processes, thereby allowing microclimates for seedlings to establish. This is particularly useful in coastal areas, but the concept of establishing smaller favorable sites for regenerating plants within a larger area is a good one.
• Mulching: The quality of the mulch is essential here, especially when being used in high quality areas. Material from compatible native vegetation and free of weeds is important. In good areas it should be used sparingly, but is very useful where large areas have become exposed and planting is being done. Mulch creates a dynamic relationship with the soil and even attracts fungi from the air. It should generally consist of a mixture of plant species and contain leaves, sticks and small limbs, creating good habitat for ground fauna.
• Scalping is a fairly extreme method which physically removes a thin layer of topsoil and weed material contained within it. This is stockpiled and the site is then planted or seeded and mulched.
• Direct seeding: This entails spreading or drilling seed at a favourable time to densely recolonise the site. In some ways this is the most natural method of re-establishing plants. Planting tubestock can be viewed as direct seeding in some circumstances when the plants are expected to seed in the first year and broadcast onto similarly receptive sites. Problems with direct seeding are the lack of availability of local seed as a low germination result is often achieved and combating weed competition, especially without the use of residual herbicides.
• Slashing can be timed so that seeding of introduced species is prevented, whilst seeding of indigenous species is encouraged. Slashing may be required for fire safety, otherwise it may be done less frequently. The height of slashing will also affect the ability of certain species to flower and set seed thus influencing the make up of the communities.

Bush Industries

Landholders throughout Australia are more and more taking to indigenous products. Emu farming, yabbies, kangaroos, fish and oysters, timber, bush foods, medicines, cutflowers and tourism. Where these initiatives can take pressure off wild populations, create greater habitats or provide educational opportunities, these need to be encouraged.

An interesting example of a flourishing indigenous industry at the moment is the Earth Sanctuaries projects run by Prof. Ian Walmsley. By undertaking large scale fauna protection and breeding programs throughout Australia, these projects have generated tourism, provided education, and most importantly, conserved large tracts of landscape. It appears that the revenue derived from these ventures is providing for more investment and proliferation of this particular model of landcare and habitat replenishment.

Summary

Overall I see the aboriginal land rights issues and respect for their culture as a fundamental starting point for our future of flora and fauna preservation and land regeneration in this country. We must develop not only more information but also a cultural basis for our work that recognises the intrinsic worth of our natural environment

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Australian Plants online - June 2000
Association of Societies for Growing Australian Plants