Differing ideas on land use.

Over the years peoples attitude to land use and development has changed.  In Australia, the events surrounding the proposed Franklin Dam brought the environmental movement to the consciousness of most Australians.

The issue dominated Tasmanian politics throughout the late 70s and early 80s and caused great rifts between those who supported the construction of the dam and those who sought the preservation of the wilderness values of the
region. The issue In 1979 the Hydro-Electric Commission (HEC) released a
proposal to construct a 180 megawatt power scheme which would result in the
inundation of 37 km of the middle reaches of the Gordon River and 33 km of the Franklin River valley. The scheme would add to the huge power output already provided by the State’s 23 hydro-electric power stations and generate a significant number of jobs for the west coast — an area with one of the highest unemployment rates in Tasmania at the time.

The Franklin River Blockade, organised by the Tasmanian Wilderness Society (TWS) under the leadership of Bob Brown, commenced on the 14 December 1982, the day the Western Tasmanian Wilderness National Parks World Heritage Area was listed. A total of 2613 people registered at the TWS headquarters in Strahan to participate in the campaign of nonviolent civil disobedience. Protesters chained themselves to gates at the HEC compound in Strahan and formed blockades in rubber duckies at Warners Landing.



As boat load after boat load were arrested, new waves of protesters came to take their place. The campaign continued throughout the summer of 1982-3 and resulted in the arrest of 1272 persons. Bob Brown was imprisoned for
three weeks, and many people, including internationally renowned botanist, David Bellamy, were remanded in custody.

During the height of the campaign, the Tasmanian Government rejected $500
million offered by Prime Minister Malcolm Fraser to construct an alternative
power scheme outside the boundaries of the World Heritage Area. Further offers by the newly-elected Labor Government under Bob Hawke were similarly turned down. Then, on 31 March 1983, the Hawke Government, which had recently been elected into office on an anti-dam platform, passed regulations forbidding HEC works within the World Heritage Area. Despite this, the HEC continued with the construction of works while the Tasmanian Government’s
challenge to the validity of the legislation was heard in the High Court. It was the decision of the High Court on the 1 July 1983 which, after a four to three majority ruling, prevented the damming of the Franklin River.

The whole affair altered the political and legal landscape, and provided impetus for conservationists to challenge other activities that they thought would cause irrevocable damage to the environment.


Why do people want to alter the landscape?  Generally the benefits are economic for a community or individual.  They may provide direct jobs such as mining, or support industries that service the activities of the developer (e.g. restaurants and cafes, other small businesses that may service and repair machinery of the developer, and so on).

Why do people wish to preserve the landscape? The reasons are often varied and may include:

1. Public access
2. Recreational use
3. Maintaining biodiversity
4. Keeping the area free from pollution and preserving the quality of life for existing users/residents of particular site
5. Spiritual/cultural links
6. Historical significance of the site.

In the local area, there have been a number of controversial issues centered around the development of the foreshore near the town centre

These have included the building of the Rydges Hotel and the demolition of the old Post Office and subsequent redevelopment of site into holiday units. The conversion of State Forest to National Parks has been of concern to those involved in the timber industry.

The relevant level of government will often try and balance the needs of stakeholders where it can. However, it is rare that all interested parties are satisfied when such decisions are handed down.

Acid sulphate soils

Acid sulphate soils are generally a problem where land that has been subjected to tidal influences in its recent history is drained for use in agriculture. In the local area, many floodplains were drained to try and farm on them.

The seawater has high amounts of sulphate in it.  When it seeps into the soil, bacteria reduce the sulphate to sulphide, which often reacts with iron of the soil.  This results in a grey somewhat smelly result.  However, its not a problem for the environment. This is because there is a layer of waterlogged soil that blocks oxygen from penetrating the soil layers and stopping any chemical reaction.

If drainage channels are dug out the water barrier is removed the oxygen can then enter the soil and then react with the sulphides.  These form sulphur oxides which in turn form acids.  Apart from stopping anything from growing in the soil the acid enters waterways which can dissolve concrete structures.

The increasing acid will cause fish to develop ulcers and shellfish shells can quite literally dissolve (bad news for the local oyster industry!) 

To rehabilitate the area, the local council backfilled drains or installed weirs to allow lands to be re-flooded. Acid discharges have been reduced and wildlife are returning to affected areas.  Below is a shot of the Rossglen rehabilitation before and after.  Note the bare soil where nothing would grow on the left photo.

Changes in local land use

The area was first settled by Europeans in 1821 when a penal settlement was established. Many convicts engaged in agriculture, with wheat, tobacco, cotton, vegetables, maize and sugar growing. Initially small areas of land were cleared to support this.

A painting of Port Macquarie soon after settlement

Some growth occurred in the 1860s and 1880s with the arrival of pastoralists, who used the land mainly for maize and sugar growing and vineyards. Timber has always been an important industry in the area, with many timber mills established in the late 1800s. By the start of the 1900s the main agricultural pursuit was dairying, although this changed to beef cattle farming by the late 1900s. 

On Transit Hill and surrounds, fruit and vegetables were extensively grown.  This began to wind back as residential developments began to encroach on the area.

Some residential expansion occurred after the opening of the railway line from Maitland to Wauchope in 1914. Significant growth did not occur until the post-war years, especially from the 1960s when the tourism industry boomed. It is from this point onwards that the local land use began to switch in some areas to being highly urbanised, with large numbers of housing being built along the coast.  To cope with the population increase, roads, water services and other structures have had to be constructed.  As a result there have been substantial changes to these parts of the local council area.  Some of these will be described in more detail later.

Having said this over 90% of the local area is zoned either as parkland or for agricultural use.

Changes in land use on waterways.

One of the problems that land clearing and development produced is the removal of surfaces that can readily absorb and deal with water that falls as rain, with impermeable surfaces.  These can include roads, roofs and footpaths.  Because the water cannot be absorbed it is diverted into stormwater drainage systems.

 

This means that they are subject to short sharp bursts of water flows during and just after rain events.  The water flows are very high but only for short periods of time.

Because they have high flow rates when running, they are often able to pick up sediments and pollute waterways when discharging.




If sediments are being transported in this manner, they can also begin to alter the course of waterways.  In the case below the left side of the creek will continue to erode while the right will have sediment depositing on it.

In addition, pollutants can accumulate on impermeable surfaces, which means that when they eventually are washed into stormwater with rain, they can lower water quality even further.

Land clearing

When land is cleared in Australian environments, native plants with deep and extensive root systems are usually removed.  Without roots to stabilize the soils, erosion is often the result. In addition the plants that would normally soak up the water are no longer there and so the buffering capacity of the soil is reduced if large amounts of rain fall quickly.  Erosion poses the greatest problems where urban developments are taking place in the local council area.  Not only does it affect the land but will adversely affect the waterways if nearby.  More on this in a later entry.

There are a number of types of erosion.  Those most likely to affect the local area are described below.

Sheet erosion is the uniform removal of soil in thin layers by the forces of raindrops and overland flow. It can be a very effective erosive process because it can cover large areas of sloping land and go unnoticed for quite some time. Sheet erosion can be recognized by either soil deposition at the bottom of a slope, or by the presence of light colored subsoil appearing on the surface. If left unattended, sheet erosion will gradually remove the nutrients and organic matter which are important to agriculture and eventually lead to unproductive soil.

Rill erosion is the removal of soil by concentrated water running through little streamlets, or headcuts. As soil removal continues or flow increases, rills will become wider and deeper

Classical gullies are an advanced stage of channel erosion. They are formed when channel development has progressed to the point where the gully is too wide and too deep to allow machinery or livestock to safely cross. These channels carry large amounts of water after rains and deposit eroded material at the foot of the gully. They disfigure landscape and make land unfit for growing crops.

Streambank erosion can occur in 2 ways.  It can be caused by recreational boats producing bow waves that reach the shore and cause damage. It can also be the result of altered water flows which occur when land is cleared and developed.  Look at the following entry for more information.

Soils

What is soil?

The material that we call soil is a complex mixture of eroded rock, mineral nutrients, decaying organic matter, water, air and living organisms, mostly micro organisms.  Although soil is considered a renewable resource, it is produced very slowly by the weathering of rock, deposits of sediments and the decomposition of organic matter in dead organisms.

While soil contains living organisms, it is considered part of the non-living environment (abiotic).  However, its composition will dramatically affect the types of organisms in an area.  Other abiotic factors that will affect the area’s flora and fauna include; temperature, rainfall, light availability and so on.

The best way to examine soil is from side on.  This is known as soil profiling and is usually done by digging a hole and examining the features of the walls.

These horizons collectively are known as a soil profile. The thickness varies with location, and under disturbed conditions: heavy agriculture, building sites or severe erosion for example, not all horizons will be present.

The uppermost is called the organic horizon or O horizon. It consists of detritus, leaf litter and other organic material lying on the surface of the soil. This layer is dark because of the decomposition that is occurring. This layer is not present in cultivated fields.

Below is the A horizon or topsoil. Usually it is darker than lower layers, loose and crumbly with varying amounts of organic matter.  The more fertile the soil, the thicker the topsoil layer.  The topsoil layer is where most of the complex organic matter is broken down into simpler substances.  Some of these will leach downwards into the B layer.  In cultivated fields the ploughed layer is topsoil. This is generally the most productive layer of the soil. This is the layer that soil conservation efforts are focused.

As water moves down through the topsoil, many soluble minerals and nutrients dissolve. The dissolved materials leach downward into lower horizons.

The next layer is the B horizon or subsoil. Subsoils are usually lighter in colour, dense and low in organic matter. Most of the materials leached from the A horizon stops in this zone.  As a result this layer contains a significant amount of dissolved ions. 

Still deeper is the C horizon. It is a transition area between soil and parent material. Partially disintegrated parent material and mineral particles may be found in this horizon.

At some point the C horizon will give up to the final horizon, bedrock.

Rocks and Minerals

A mineral can be defined as; a naturally occurring, inorganic, solid element or compound with a definite chemical composition and a regular internal crystal structure.

Rocks on the other hand can be made up of a single mineral but are generall made up of 2 or more minerals.  Have a look at this granite (made up of 3 minerals).

What are some of the characteristics that assist with identifying minerals include cleavage.  This refers to the way the crystals split.  Some examples are below.

Another characteristic is lustre.  This refers to how the mineral reflects light and its surface appearance.  Some of the categories are below.

Metallic: very high reflectance, opaque 
Sub-metallic: medium reflectance, opaque 
Adamantine: very high reflectance, transparent 
Glassy: high reflectance, transparent or translucent 
Resinous: medium reflectance, translucent 
Waxy: medium reflectance, translucent or opaque 
Pearly: low reflectance, translucent or opaque 
Dull: no reflectance, opaque


Mohs hardness scall is a useful classification tool.  The items listed below are reference materials,  If your material scratches the reference material, it is harder than that substance.  If the reverse happens then you material is softer than the reference substance.

Colour is unreliable for mineral identification in some circumstances.

Density of specific gravity of a mineral is also a useful tool.