Land clearing in Australia
Encyclopedia
Deforestation
Deforestation is the removal of a forest or stand of trees where the land is thereafter converted to a nonforest use. Examples of deforestation include conversion of forestland to farms, ranches, or urban use....
and in Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
. Land clearing involves the removal of native vegetation and habitats, including the bulldozing of native bushland
Bushland
Bushland is any area in Australia that is predominantly indigenous flora and fauna.Bushland is the term commonly used by conservation protection groups and other environmental groups as a blanket term for natural vegetation, which may cover any kind of habitat from open shrubby country with few...
s, forest
Forest
A forest, also referred to as a wood or the woods, is an area with a high density of trees. As with cities, depending where you are in the world, what is considered a forest may vary significantly in size and have various classification according to how and what of the forest is composed...
s, savannah
Savannah
Savannah or savanna is a type of grassland.It can also mean:-People:* Savannah King, a Canadian freestyle swimmer* Savannah Outen, a singer who gained popularity on You Tube...
, woodland
Woodland
Ecologically, a woodland is a low-density forest forming open habitats with plenty of sunlight and limited shade. Woodlands may support an understory of shrubs and herbaceous plants including grasses. Woodland may form a transition to shrubland under drier conditions or during early stages of...
s and native grassland
Grassland
Grasslands are areas where the vegetation is dominated by grasses and other herbaceous plants . However, sedge and rush families can also be found. Grasslands occur naturally on all continents except Antarctica...
s and the draining of natural wetlands for replacement with agriculture
Agriculture in Australia
Australia is a major agricultural producer and exporter. Agriculture and its closely related sectors earn $155 billion-a-year for a 12% share of GDP. Australian farmers and graziers own 135,996 farms, covering 61% of Australia’s landmass. There is a mix of irrigation and dry-land farming...
, urban and other land uses.
As much as 70% of Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
's native vegetation has been cleared or modified in the past 200 years, most of which has occurred in the last 50 years. Prior to European settlement native vegetation
Flora of Australia
The flora of Australia comprises a vast assemblage of plant species estimated to over 20,000 vascular and 14,000 non-vascular plants, 250,000 species of fungi and over 3,000 lichens...
covered most of Australia but now only 87% of the country is vegetated by native species. In total 13% of Australia's native vegetation has been lost due to land clearing, with the majority of this being native forests and woodlands.
Tasmania
TasmaniaTasmania
Tasmania is an Australian island and state. It is south of the continent, separated by Bass Strait. The state includes the island of Tasmania—the 26th largest island in the world—and the surrounding islands. The state has a population of 507,626 , of whom almost half reside in the greater Hobart...
n (in Australia) ancient and unique temperate rainforest
Rainforest
Rainforests are forests characterized by high rainfall, with definitions based on a minimum normal annual rainfall of 1750-2000 mm...
areas, were in the risk of being converted into wood plantation
Plantation
A plantation is a long artificially established forest, farm or estate, where crops are grown for sale, often in distant markets rather than for local on-site consumption...
s for Japanese paper factories In 2007. The swamp gum tree or Tasmanian Oak (Eucalyptus regnans
Eucalyptus regnans
Eucalyptus regnans, known variously by the common names Mountain Ash, Victorian Ash, Swamp Gum, Tasmanian Oak or Stringy Gum, is a species of Eucalyptus native to southeastern Australia, in Tasmania and Victoria...
) is the world’s largest flowering plant and the tallest hardwood tree in the world.
Agriculture
The primary motivator for land clearing in Australia is agricultural production. Where soil fertility and rainfall allow, the clearing of land allows for increased agricultural production and increase in land values. Land clearing was seen as progressive, and there was the general view that land was wasted unless it was developedLand improvement
Land improvement or land amelioration refers to investments making land more usable by humans. In terms of accounting, land improvements refer to any variety of projects that increase the value of the property...
.
Historically, land clearing has been supported by the Commonwealth and State Governments as an essential part of improved productivity essential for national economic prosperity.a range of institutional incentives for agriculture increased the economic gain from land clearing, with offerings of cheap land along with venture capital in the form of loans or tax concessions. Other incentives included the War Service Land Settlement Scheme
Soldier settlement (Australia)
Soldier settlement refers to the occupation and settlement of land throughout parts of Australia by returning discharged soldiers under schemes administered by the State Governments after World Wars I and II.- World War I :...
, low interest bank loans and financial support programs such as drought relief assistance.
The majority of cleared land in Australia has been developed for cattle, sheep and wheat production. 46.3% of the Australia is used for cattle grazing upon natural vegetation on marginal semi-desert. This land is too dry and infertile for any other agricultural use (apart from some kangaroo culling) Some of this grazing land has been cleared of "woody scrub". Nationally, 15% of Australia is currently in use for all other agriculture and forestry purposes on mostly cleared land. In New South Wales
New South Wales
New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
, much of the remaining forest and woodland has been cleared, due to the high productivity of some of the agricultural land. Urban development is also the cause of some land clearing, though not a major driver. In The Australian Capital Territory
Australian Capital Territory
The Australian Capital Territory, often abbreviated ACT, is the capital territory of the Commonwealth of Australia and is the smallest self-governing internal territory...
for example, much urban development has occurred on previously cleared agricultural land.
Bushfires in Australia
Bushfires in AustraliaBushfires in Australia
Bushfires in Australia are frequently occurring events during the hotter months of the year due to Australia's mostly hot, dry climate. Large areas of land are ravaged every year by bushfires, which also cause property damage and loss of life....
are frequently occurring events during the hotter months of the year.
Response
Since the 1980s, the rate of land clearing has declined due to changing attitudes and greater awareness of the damaging effects of clearing. Clearing is now controlled by legislation in Western Australia, South Australia, Victoria, New South Wales, and to a lesser degree in Queensland. Land clearing controls differ substantially between jurisdictions, and despite growing awareness of the effect of land degradation, controls on clearing have been generally opposed by farmers.Effects
Land clearing destroys plants and local ecosystems and removes the food and habitat on which other native species rely. Clearing allows weeds and invasive animalsInvasive species in Australia
Invasive species are a serious threat to the native biodiversity of Australia and are an ongoing cost to Australian agriculture.Management and the prevention of the introduction of new invasive species are key environmental and agricultural policy issues for the Australian federal and state...
to spread, affects greenhouse gas emissions and can lead to soil degradation, such as erosion
Erosion
Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...
and salinity
Salinity
Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...
, which in turn can affect water quality.
The following table shows the Native Vegetation Inventory Assessment (NVIS) of native vegetation by type prior to European settlement and as at 2001-2004.
| Vegetation Type | Pre Settlement Total | 2005 Total | Percentage remaining |
|---|---|---|---|
| Forest and Woodland | 4,101,868 | 3,184,260 | 22% |
| Shrublands | 1,470,614 | 1,411,539 | 4% |
| Heath | 9,256 | 8,071 | 13% |
| Grassland | 1,996,688 | 1,958,671 | 2% |
| Total Native Vegetation | 7,578,204 | 6,562,541 | 13% |
Effects
Land Condition
As land cover is crucial to land condition, land clearing exerts significant pressure on land condition. Removal of vegetation also leaves soil bare and vulnerable to erosion. Soil stability is essential to avoid land degradation
Land degradation
Land degradation is a process in which the value of the biophysical environment is affected by one or more combination of human-induced processes acting upon the land....
.
Soil erosion
Soil erosion is a very significant pressure on land condition because it undermines existing vegetation and habitats and inhibits vegetation and other biota that inhabit the vegetation from re-establishing. Terrestrial vegetation is a source of nutrient replenishment for soils. If vegetation is removed, there is less biological matter available to break down and replenish the nutrientNutrient
A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. They are used to build and repair tissues, regulate body processes and are converted to and used as energy...
s in the soil. Exposing soil to erosion leads to further nutrient depletion.
Salinity
Another consequence of land clearing is dryland salinityDryland salinity
Dryland salinity is salinity that occurs in a landscape that is not irrigated, as distinct from irrigation salinity and urban salinity.-Overview:...
. Dryland salinity is the movement of salt to the land surface via groundwater. In Australia there are vast amounts of salt stored beneath the land surface. Much of Australian native vegetation
Fauna of Australia
The fauna of Australia consists of a huge variety of animals; some 83% of mammals, 89% of reptiles, 90% of fish and insects and 93% of amphibians that inhabit the continent are endemic to Australia...
has adapted to low rainfall conditions, and use deep root system
Root system
In mathematics, a root system is a configuration of vectors in a Euclidean space satisfying certain geometrical properties. The concept is fundamental in the theory of Lie groups and Lie algebras...
s to take advantage of any available water beneath the surface. In this way, plant roots help to store salt in the earth, by keeping ground water levels low enough so that salt is not pushed to the surface. However, with the removal of plants due to land clearing, the amount of water leaking into the groundwater beneath the root system means that the water table
Water table
The water table is the level at which the submarine pressure is far from atmospheric pressure. It may be conveniently visualized as the 'surface' of the subsurface materials that are saturated with groundwater in a given vicinity. However, saturated conditions may extend above the water table as...
rises to the surface along with salt. Salinity reduces plant productivity and affects the health of rivers and streams.
Biodiversity
The extinction of 20 different mammal, 12 bird and 97 plant species have been partially attributed to land clearing. While land condition is one indicator of the pressure of vegetation removal, the health and resilience of the vegetation that remains is also largely dependent on the size of the fragments and their distance from each other. This is also true for species living within these habitat fragmentsHabitat fragmentation
Habitat fragmentation as the name implies, describes the emergence of discontinuities in an organism's preferred environment , causing population fragmentation...
.
The smaller and more isolated the remnants, the greater the threat from external pressures as their boundaries (or edges) are more exposed to disturbances Pressure also increases with the distance to be traversed between fragments.
Climate Change
Land clearing is a major source of Australia’s greenhouse gas emissions, and contributes to approximately 12 percent of Australia’s total emissions in 1998. It has also been found that past clearing of native vegetation contributed to higher temperatures, decreased rainfall and more intense droughts. The removal of vegetation damages the microclimateMicroclimate
A microclimate is a local atmospheric zone where the climate differs from the surrounding area. The term may refer to areas as small as a few square feet or as large as many square miles...
by removing shade and reducing humidity
Humidity
Humidity is a term for the amount of water vapor in the air, and can refer to any one of several measurements of humidity. Formally, humid air is not "moist air" but a mixture of water vapor and other constituents of air, and humidity is defined in terms of the water content of this mixture,...
. It also contributes to global climate change by diminishing the capacity of the world’s vegetation to absorb carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
.
Deforestation and climate extremes
Deo et al. (2009) checked the
impacts on climate extremes and droughts
by analysing daily rainfall and surface temperature
output from the CSIRO Mark 3 GCM.
This work, the first of its kind, demonstrated
an increase in the number of dry days
(<1mm rainfall) and hot days (maximum
temperature >35°C), a decrease in daily rainfall
intensity and cumulative rainfall on rain
days, and an increase in duration of droughts
under modified land-cover conditions. These
changes were statistically significant for all
years across eastern Australia, and especially
pronounced during strong El Niño events.
Clearly, these studies have demonstrated
that LCC has exacerbated the mean climate
anomaly and climate extremes in southwest
and eastern Australia, thus resulting in longer-
lasting and more severe droughts.