Australia is home to many thousands of plants and animals. Many species are found only in Australia; 85% of flowering plants; 82% of mammals; 89% of reptiles and about 93% of our frog species are unique to this country. (Lindenmayer, 2007, p.33)
Bushland areas are an integral part of the biodiversity of our urban and rural landscapes, providing habitat for many native animals – from kangaroos and koalas to butterflies and beetles. Bushland also plays an important role in reducing the effects of global warming and controlling subtle changes to the local climate, and reduces the greenhouse effect by absorbing carbon dioxide from the atmosphere.
Our bushland provides important areas for recreation, tourism and education. Its biological diversity is highly valued by the community and helps define our cultural identity and heritage.
Bushland areas are also important for the local, regional and national economy. The bush provides environmental services such as protecting water quality, stopping erosion, providing a windbreak, producing oxygen and trapping nutrients. The CSIRO has estimated that environmental problems caused by vegetation loss costs Australia $1.4 billion in lost revenue each year. (LMCC Biodiversity Fact Sheet, 2012)
Nature conservation/ habitat
By planting local native plants and conserving local bushland we directly contribute to the conservation of the flora of the local area. As many species of birds, mammals, reptiles and other fauna are dependant on local vegetation we can also contribute to habitat conservation.
Many birds are permanent residents of urban bushland reserves while others are either nomadic or migratory. Patches and strips of bushland, no matter how small, provide these birds with food, shelter and resting places. In our city suburbs with remnant bushland many larger animals such as kangaroos, wallabies and possums can still be present.
Heritage
Native bushland often contains Aboriginal artefacts. Paintings, rock engravings, axe grinding grooves, middens, tools and caves dwellings are all present in local bushland. They all act as reminders of Aboriginal history. Native bushland also contains many reminders of early European settlement.
Scenic/ recreational/ psychological
Native bushland has an irreplaceable scenic value by diluting the visual clutter of our cities. Furthermore, the character of our landscape is provided largely by the local native vegetation.
Recreational use of bushland is often overlooked as it usually does not involve large groups. Activities include orienteering, abseiling, rock climbing, photography, painting, plant identification, bird watching, bushwalking and outdoor family adventures such as picnics or barbecues. Children tend to be specialist users of the bush and should be treated as a unique group for whom the bush is a world of adventure and daring physical achievements.
Native bushland and natural settings provide a sense of ‘well-being’ and the feeling of ‘getting away from it all’.
Environmental
Native bushland contributes to ‘ecosystem services’ such as providing our food, and many industrial products and medicines. Also bushland contributes to generating clean air, water and fertile soils through the processes of millions of interacting organisms that live in the air, water and soil. Basically, bushland contributes to ensuring the ongoing evolution of life on Earth.
Economic
Natural areas are a main source of economic income. A healthy environment rich in biodiversity is more productive and ensures industries such as food, medicine, timber and tourism are maintained economically in the future.
Some specific industries related to native bushland in Australia include:
- Honey production $300 million annually
- Bushfood production $100 million annually
- Wildflower exports $30million annually
Tourism is one of the cornerstones of our economy. Our koalas attract so many international visitors to Australia that they’re worth over a billon dollars annually to the economy.
Scientific/ educational
Native bushland provides opportunities for learning about the local environment and natural ecosystems.
Legal/ moral
We have legal and moral obligation to provide intergenerational equity. Conserving natural bushland is an important part of this legal and moral obligation. (See Lindenmayer, 2007, pp.21-28; Ralph, 2003, pp.2-3; Buchanan, 1989, pp.1-4)
Threats to bushland
Some of the key reasons why native bushland and therefore biodiversity is under threat include:
- Size and shape of reserves
- Fragmentation
- Edge effects
- Weed invasion
- Rubbish dumping
- Altered fire regimes
- Soil erosion/ degradation/ salinity
- Climate change
Vegetation clearing, fragmentation and edge effects
Vegetation clearing – for agricultural, urban and industrial development – is perhaps the single most important cause of environmental degradation, loss of species, and depletion of ecological communities, both in Australia and worldwide.
Over the decade 1990-2000, Australia had the sixth highest annual rate of land clearing in the world. Notably, Australia is the only country in the top 20 landclearing nations with a developed first world economy. More than 550,000 hectares of native vegetation are cleared in Australia each year. (Lindenmayer & Burgman, 2005, p. 229-230)
Vegetation clearing leads to habitat loss, fragmentation, sub-division and isolation. This habitat loss and fragmentation typically results in a decrease in the average size of habitat patches, increase in the distance between them, a decrease in connectivity between patches, and in an increase in the edge to size ratio. (See Lindenmayer & Burgman, 2005, pp. 255-292)
Basically, this loss of vegetation decreases native fauna biodiversity through the loss of habitat for breeding, nesting and feeding and increased competition for existing habitat areas. (LMCC Biodiversity Fact Sheet, 2012)
In general the smaller the size of an area (or bushland patch) the fewer species, and the fewer of each species, it will maintain. Small patch size and long distances between patches are the cause of local extinctions, sometimes to such a degree that formally common species are now rare or threatened.
Natural areas that are square or round are comparatively easy to manage as they have a low edge to area ratio. Long thin natural areas have a high edge to area ratio and the ‘edge affect’ caused by surroundings will have a high impact. (Buchanan, 2009, p.17)
Weeds
“Weeds are plants that are unwanted in a particular situation as they may threaten agricultural productivity, have detrimental effects on the natural environment or impact on human health.” (www.dpi.nsw.gov.au/agriculture/farm/pest-weeds-management/weeds)
In general terms, weeds are plants that do not naturally belong in the area. They may be introduced from overseas or from another part of Australia. Weeds for most of us are conceived as foes rather than friends. Certainly, we all need to consider our concepts of weeds and therefore how we manage weeds, as suggested by writers such as Peter Andrews. However, weeds (or invasive plants, if you prefer) now form a considerable part of the existing vegetation of Australia as the CRC publication – The introduced flora of Australia and its weed status (2007) shows.
Over 25,000 introduced species are presently in cultivation in Australia. Some 2,500 are considered to be weeds or invasive and a further 5,000 are considered potential weeds. (CRC, 2007, pp.6-7)
CRC also makes the following comments: “Humans are by far the most effective and efficient vector of plants around the world, and the nursery industry is a key, though not the only, commercial arm of this enthusiastic vector base.” (CRC, 2007, p.5)
‘Environmental weeds’ are plants that represent a threat to the conservation values of natural ecosystems. They invade native plant communities and out-compete them causing a reduction in plant diversity and resulting in a loss of habitat for native animals. Some examples of environmental weeds are morning glory, bridal creeper, bitou bush, boneseed, blackberry, privet and lantana.
‘Noxious weeds’ are plants that have been declared under the Noxious Weeds Act 1993 (NSW). This includes plants that cause serious economic loss to agriculture or have a detrimental effect on humans or the environment. Any landowner, including Local Councils, that have a declared noxious weed occurring on their land are obliged by law to control that weed.
Some weeds are so potentially damaging and have such a capacity to spread that they have been listed as Weeds of National Significance (WoNS). Many common bushland weeds are garden escapees – spread over backyard fences by seed, birds or dumping of garden waste. Weeds are adept at exploiting the changed environmental conditions associated with urban development. Weeds are often found when the follow factors are also present:
- Soil disturbance
- Increased water flow
- Increased nutrient flow (particularly the addition of fertilisers)
- Changed fire regime
- Changes to microclimate associated with land clearing and weed invasion (Buchanan, 2009, p. 19)
Weeds can damage natural areas because they:
- Compete with native plants for space, light, nutrients and water
- Damage biodiversity (that is: reduce the native plants and animals on the site)
- Can aid erosion
- Can change water flow
- Harbour pest animals such as rabbits or Indian myna birds
- Alter fire regimes (Buchanan, 2009, p. 19)
Some common gardens escapee weeds include Japanese honeysuckle, Spider plant, Asparagus- Bridal creeper and Fishbone fern.
Illegal rubbish and garden waste dumping
‘Waste’ isn’t just rubbish. Your garden waste can include lawn clippings, branches and unwanted dead (or alive) plants.
Dumping destroys native bushland and animal habitats by introducing disease, weeds and pests. It also increases the risk of bush fires and detracts from the aesthetic value of natural areas. (Lake Macquarie Backyard Habitat Planting Guide, 2013)
Altered fire regimes, climate change and change to natural cycles
Fire affects soil and plants, as well as life and property. Hazard reduction burns designed to protect urban areas have changed the normal season, intensity, frequency and scale of fire.
For over two hundred years we have intervened dramatically in the natural patterns of fire, natural water flow and water quality. (Buchanan, 2009, p. 23)
“Have human beings permanently changed the planet? That seemingly simple question has sparked a new battle between geologists and environmental advocates over what to call the time period we live in.
According to the International Union of Geological Sciences (IUGS), the professional organization in charge of defining earth’s time scale, we are officially in the Holocene (“entirely recent”) epoch, which began 11,700 years ago after the last major ice age.
But that label is outdated, some experts say. They argue for “Anthropocene”—from anthropo, for “man,” and cene, for “new”—because human- kind has caused mass extinctions of plant and animal species, polluted the oceans and altered the atmosphere, among other lasting impacts.
Anthropocene has become an environmental buzzword ever since the atmospheric chemist and Nobel laureate Paul Crutzen popularized it in 2000. This year, the word has picked up velocity in elite science circles: It appeared in nearly 200 peer-reviewed articles, the publisher Elsevier has launched a new academic journal titled Anthropocene and the IUGS convened a group of scholars to decide by 2016 whether to officially declare that the Holocene is over and the Anthropocene has begun.”
Read more at http://www.smithsonianmag.com/science-nature/what-is-theanthropocene-and-are-we-in-it-164801414/
Redistributing scarce water resources, primarily for cropping and other agricultural enterprises, has had significant impacts on biodiversity. The most dramatic example is the massive diversion of water in the Murray–Darling Basin. Similar impacts on biodiversity occur in river basins throughout Australia. Urban settlements require significant sources of fresh water, necessitating the construction of dams, diversion of water bodies, extraction of groundwater for human consumption, watering of gardens and recreation. Dams and impoundments, by their very nature, redistribute water, with knock-on effects on local and downstream biodiversity. Some forms of agricultural practice have compromised the inherent ability of the underlying ecosystem to recover from change – its resilience – so that restoration is virtually impossible. Extensive long-term use of fertilisers has changed some soils to such an extent that the original naturally nutrient-poor ecosystem will most likely never return to its previous state. (Australia’s Biodiversity and Climate Change: A strategic assessment of the vulnerability of Australia’s biodiversity to climate change, 2009, p.40)
Climate change will:
- Increase temperatures in many areas
- Change rainfall, its distribution, amount, seasonal pattern, and reliability
- Change the season, intensity, frequency and extent of fires
- Raise sea levels, causing flooding of coastal ecosystems such as tidal flats and freshwater lagoons and erosion of coastal dunes and beaches
- Alter the abundance, breeding, migration, and geographical range of many animals
- Alter the abundance, flowering time, success rate of fruit set, dispersal and range of many plants
- Cause possible breakdown between predator and prey, host and parasite, pollinator and plant
- Possibly reduce the nutrient content of leaves, which would have a dramatic effect on leaf eaters, both insect and mammals
- Cause extinctions, both local and total
- Favour highly adaptive species such as weeds and pest animals
(Buchanan, 2009, p. 24; for a detailed account see Australia’s Biodiversity and Climate Change: A strategic assessment of the vulnerability of Australia’s biodiversity to climate change, 2009, Chap. 5, pp. 88-143)
Soil erosion/ degradation/ salinity
When vegetation is removed from soil surfaces they become susceptible to erosion either by wind or water and frequently both these agents of erosion combine to remove surface soil.
Water erosion occurs in different ways that vary according to vegetation cover, soil type and structure and slope. The severity of rainfall events is a major factor in determining how much soil is transported down a slope.
Sheet erosion occurs in some locations when the energy of rain drops and water flows moves thin, relatively uniform layers of soil particles down slopes depositing them at the base or carrying them to waterways, where these suspended particles (sediments) are carried to lakes or the sea.
Where the movement of soil is not uniform, small gullies or rills can form. On average, about 14 million tonnes of soil in Australia is moved by water down slopes each year.
Gullying occurs in some soil types when surface and sub-surface water flows are combined by topography into drainage lines. Usually a gully deepens over time and frequently headward erosion also occurs (the gully moves up the slope) together with later branching. Gullying is the major source of soil transportation into rivers and streams. When water flows beneath the soil surface, sub-surface tunnels may be formed which are often only obvious when the land surface collapses. This frequently leads to further collapse and the exposure of small gullys.
Streambank erosion is also seen along most waterways running through urban agricultural land. This is increased by clearing riparian (stream side) vegetation that, when intact, slows flows into waterways and captures sediments thereby reducing stream turbidity and the mass transfer of soil to dams, lakes and estuaries.
Mass movement of soils occur sometimes as landslides and slumps.
Wind Erosion. In many respects, wind erosion is similar to sheet erosion caused by heavy rain. Uniform layers of particles are stripped from the soil surface by wind and transported over long distances. Again, as with water erosion, nutrients adsorbed to soil particles are also transported.
Soil salinity in Australia is not a new phenomenon. Salt derived from the oceans has been deposited by rain, wind and marine ingressions (land previously submerged beneath the sea) over millions of years then leached through soils into underground aquifers and ground water until natural equilibria have been established.
Secondary salinity has been brought about by vegetation clearance and the way land has been used in the past 200 years. The National Land and Resources Audit in 2001 estimated that about 2.4 million ha of land across Australia is saline with a total of 5.4
million ha deemed to be at risk.
Dry Land Salinity. At various locations in the landscape, geology and hydrology combine to provide a point at which water enters and flows underground. When these recharge areas are cleared of deep rooted vegetation, the balance between evapotranspiration (the movement of water from soils, through plants, and then evaporation from the leaves into the air) and the quantity of water naturally flowing underground down the slope is disturbed. The volume of water moving through the soil profile increases and the water table containing dissolved salts rises. (Land degradation Fact Sheet, www.australiancollaboration.com.au, pp. 1-5)
Coastal acid sulfate soils are naturally occurring sediments that are deposited under estuarine conditions. They contain iron sulfides, most commonly as pyrite, and/or the products of iron sulfide oxidation. When exposed to oxygen through drainage or disturbance, these materials produce sulfuric acid, often releasing toxic quantities of iron, aluminium and other metals. Coastal acid sulfate soils are widespread along the NSW coast. They occur in mangrove flats, salt marshes and tea-tree swamps, and underlie coastal floodplains, including farmland and urban areas. Because of its estuarine origin, coastal acid sulfate soil material is only found at very low elevations, generally less than 1 metre above sea level. (‘Coastal acid sulphate soils’- www.environment.nsw.gov.au, 1/3/14)
Vegetation loss and disturbance due to soil degradation and salinity are a major problem in Australia. Sedimentation from increased soil erosion also disturbs native bushland and creates nutrient-rich and moist sites for weeds to rapidly colonise. (Buchanan, 1989, pp. 48-49)
Some basic concepts in urban bushland management ~ Resilience/ degradation
Ecosystem resilience theory (Westman, 1985; Cairns, 1987; McDonald, 1993) is based on an ecosystem’s natural resilience and capacity to recover after disturbance. Westman (1985) appears to be the first to formally pose the question “whether the degree, if any, of a system to recover after natural disturbance may assist in the process of restoration after man-made disturbance.”
Tein McDonald states it is relevant to restoration for at least three reasons:
“Firstly, the reinstatement of a system’s capacity to regenerate is a fundamental goal for the restorationist – but the very capacity of some systems to perpetuate themselves may be coupled to pre-adapted disturbance/recovery processes. Secondly, a system’s specific capacity to recover after disturbance may be of positive assistance to the restoration process in the provision of site-adapted genetic material, propagules and distribution matrices. Thirdly, natural recovery processes may contribute models for the reconstruction of ecosystems where insufficient resilience exists on-site, and we have to start the restoration process from scratch.” (McDonald, 1993, p.18)
Generally, a continuum exists from healthy intact bushland sites which have greater resilience to sites with low to nil resilience depending on the scale, intensity and duration of disturbance/ degradation. Therefore, the degree (scale, intensity, duration) of intervention required for the restoration of a site is inversely proportional to the site’s resilience.
Tein McDonald introduced definitions for a sub-set of ecosystem restoration approaches:
Assisted Natural Regeneration – the form of restoration applied where a resilient remnant exists and only removal of obstacles or minor amendment of abiotic conditions are needed to effect recovery by natural regeneration.
Reconstruction – a form of restoration where little or no remnant component exists and the whole sale reinstatement of the original system’s abiotic and biotic elements are required to effect restoration of a functioning system
Fabrication – a treatment applied to sites where conditions are permanently altered and better adopted local systems can be installed to restore integrity to the broader system (not strictly restoration but may be required within a restoration program). An artificial wetland installed into a modified urban creek or drainage line would be a fabrication. (McDonald, 1993, p. 23; Adams, 1993, p. 58)
Robin Buchanan has included further ecosystem restoration approaches into this ecosystem resilience continuum:
Natural regeneration/ Prescribed natural regeneration – the recovery of an ecosystem after a disturbance such as fire or storm. Resilience is very high to high and no active intervention is required. For prescribed natural regeneration, a conscious decision is made to rely on natural processes.
Revegetation or reintroduction – involves adding plants to the ecosystem by planting, seeding or translocating. Resilience is moderate to nil.
Reconstruction or reassemblage – involves the artificial construction of the original community, or parts of the community, from scratch. This may include revegetation and the addition of other habitat elements such as nest boxes, logs and rocks. Resilience is low to nil.
Rehabilitation and reclamation – on sites where resilience is nil, tree planting or pasture is applied to stabilise terrain, reduce erosion, provide public safety and improve aesthetics on highly disturbed sites such as mined land. (Buchanan, 2009, pp.30-31)
The Bradley method and three basic original principles Joan and Eileen Bradley are generally credited with pioneering the bush regeneration movement. They played a major role in convincing conservationist and park managers that conserving urban bushland was not enough; it also needed careful and skilled techniques and management if it was to survive.
The Bradley sisters laid down three basic principles that determined their work plan: “Our methods of bush regeneration works on three general principles and you must not deviate from any of them. We cannot stress this enough. Over the years I have found that if you adhere to them in all respects, regeneration will follow. Cutting corners will invariably lead to future problems…
Principle 1 ALWAYS WORK FROM AREAS WITH NATIVE PLANTS TOWARDS WEEDINFESTED AREAS…
Principle 2 MAKE MINIMAL DISTURBANCE…
Principle 3 LET NATIVE PLANT REGENERATION DICTATE RATE OF WEED REMOVAL…”
(Bradley, 1991, pp. 19-21; Buchanan, 1989, pp. 77-79)
A final word on the bushland regeneration and revegetation industry is required here. A major problem facing Australia (and the rest of the world) is our failure to make appropriate investments in the our environment. David Lindenmayer and Richard Eckersley have raised this point in recent years:
“Unfortunately, it is easier to write policy than it is to implement it, and as a result we have an environmental policy surplus and a implementation deficit…Rather than simply writing plans for what might be done if enough resources were available, investment needs to be prioritised so that resources are made available right now. Practical environmental actions are almost always substantial and they require major investment…Initiatives like Landcare have helped significantly, but we can’t and shouldn’t rely solely on volunteers to save our country.” (Lindenmayer, 2007, p. 72)
“A landscape management industry: There was considerable discussion – and agreement – on the need for a landscape regeneration ‘industry’ that would produce the necessary capacity to implement policy, increase professionalism, and provide technical services, education and extension. ‘Success in this whole exercise would be if the ‘revegetation industry’ achieves the same status in Australia as the mining industry. You can count this as a number of things but it’s a cultural shift in that revegetation and sustainable land management are seen as part of our identity, what we do, both for rural people and city people. It also needs to be seen as an economic activity based on sustained, long-term investment through public-private partnerships. In the same way that realising economic benefits from mining depends on public investment in infrastructure, training and skills and private capital in resource extraction, large-scale revegetation and land repair will require public investment in green infrastructure and private investment in a range of benefits.’ ‘If it’s the case that government is going to step up with large amounts of money for large-scale work, then there is a bunch of structural problems in the system. Indeed, the revegetation industry doesn’t really exist. It’s a bunch of sheltered workshops and cottage industries around the place.’ ‘We really need to develop a whole level of professionalism…. if you take the mining industry analogy, we need the revegetation services business to be there, with all that technical expertise, just like we would expect from other sectors, rather than it being seen as a job for volunteers.” (Australia 21- Shaping the Future, ‘Repairing and preparing Australia’s landscapes for global change: Why we must do much more’ – A report on an expert roundtable, held at the University of Melbourne 21 February 2013 – Richard Eckersley June 2013, p. 19)