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.

Proxy data

What is proxy climate data?

Proxy climate data is an indirect measure or estimate of what the climate was like by indirect measurements (not with a thermometer or other instrument).  Most proxy data substitutes for direct data that predates accurate temperature measurements either locally or globally.

Direct measurements date back to the invention of reliable thermometers.  Countries with strong naval histories tend to be the earliest recordings of weather and temperature.  Accurate thermometers became available in the 18th century.

There are 2 ways historical climate can be determined.  The first way is by accessing tree rings.  This type of proxy data is useful for looking at local climates in terms of either temperature or rainfall patterns.  The dark regions or rings are usually associated with winter growth with the light ones being summer growth.  A large gap between dark rings indicates good growing conditions while narrow gaps indicate poorer growing conditions.

Ice core sampling produces alternating light (summer snowfall) and dark (winter snowfall) bands.  The thickness of the layers is a good indicator of temperature.  In addition, gas bubbles trapped in the layers can be extracted and tested to see what the atmosphere was like at the time of deposition.


This has led to some alarm owing to the rapid rise of CO2, a result of burning fossil fuels for just over 200 years.  When CO2 levels and estimated temperatures are compared, there appears to be a strong link.  The spike in CO2 in recent times is unprecedented for the last 500,000 years.  This is causing considerable debate now as groups argue for and against the link of CO2 and global warming.

Carbon "Locked Away"

One of the things that stromatolites and other photosynthetic organisms have done over time has been to "lock away" carbon.  They remove carbon dioxide during photosynthesis:

These carbohydrates have been used to:

1. Make more biomass (plant mass or growth)
2. Enrich the soil with organic matter
3. Removed carbon long term and be stored as coal underground.

In addition, carbon dioxide is removed when it dissolves on sea water.  It is combined with calcium by many mollusks and corals to make calcium carbonate or limestone.  

When the reef is buried or compressed the process of limestone formation is complete.  This kind of removal is another long term storage way of storing carbon and keeping locked out of the atmosphere.

It is fortunate that we have this means of removing carbon (especially carbon dioxide) out of the atmosphere and storing long term (i.e. 10's or 100's of millions of years). It is this reason that the planet has had a stable climate for so long.  If this hadn't happened Earth may have shared the same fate as Venus with a runaway greenhouse effect and surface temperatures over  400 Celcius.

Earth's Atmosphere over time.

The Earth's early atmosphere would have consisted of light volatile (low boiling point) gases contained in the meteorites and other bodies that were colliding with Earth.  These would have escaped into space.  Gases such as hydrogen and helium, bromine and iodine would have been lost very early on. 

As the crust formed on the earth and began to stabilise (around 3.8 billion years ago), volcanoes would have been the major contributor of the atmosphere.  This process is called outgassing.  Analysis of volcanoes today give us a clue to what may have been in the Earths "2nd atmosphere".  One point to note is the absence of oxygen. 

With the rise of the stromatolites and removal of iron from the oceans, oxygen began to accumulate in the atmosphere.  Since they began photosynthesis, the amount of CO2 also fell from the atmosphere.

The combine efforts of stromatoloites and the other photosynthetic organisms that followed lead to the composition of the atmosphere that we have today.  These levels are pretty typical of the planet for the last 450 million years.

Stromatolites, Photosynthesis and Banded Iron

It is thought that for the time from 3.5 - 1 billion years ago that stromatolites dominated the shallow seas around continents.

Stromatolites are made up of photosynthetic bacteria that form a colony by sticking together with mucous.  Sediments from the water also stick to the mucous.  As the cells divide the new cells that form on top block the light out from those below.  While these die, they contribute to the upward growth of the stromatolite forming a column.

Stromatolites are by far the oldest non-microscopic fossil found on Earth.  The oldest are found in the Pilburra region of Western Australia and are thought to be around 3.4 billion years old.

The early Earth's oceans had a lot of dissolved iron in them.  From space, the oceans would have appeared green from all the iron, rather than the blue of many famous space images.  Iron can stay dissolved in water if no oxygen is present.  When dissolved iron comes into contact with water, it chemically combines to form solid iron oxide.  When that happens, the iron settles out of solution.  






This iron was thought to enter water from volcanic vents where water mixed with rising magma.  The water would dissolve some of the iron from the magma and would heated up.  As a result, jets of iron rich super-heated water would enter the oceans.  Some of these exist at mid-ocean ridges today.  The black plume is from iron compounds in the water.

So as the iron rich water circulated and came to the areas where stromatolites (and therefore oxygen) were present, it would react, form a solid and settle out forming an iron rich sediment layer (see image above).  When either the iron or the oxygen was exhausted from an area, it would mean that a layer of iron poor sediment would be placed on that.






The reasons for this layering of iron rich and iron poor sediments has been subject to a number of hypotheses.  These include:

1. Cycling of ocean currents replenishing the water with iron after its removal from the water by oxygen.

2. Seasonal variations of temperature which affects the rate of photosynthesis and therefore oxygen levels

3. Death and regrowth of stromatolite bacteria from oxygen poisoning.  The bacteria die as oxygen rises.  Any remaining oxygen is removed by the iron.  The bacteria regrow and oxygen levels rise.  The cycle starts again.


About 1.5 billion years ago (other estimates are earlier and vary), the formation of banded iron stopped.  This is because the iron levels in the oceans were near exhaustion and the new iron entering the oceans was reaction in oxygen rich waters which were deeper and well away from stromatolites.  As a result oxygen could now accumulate in the atmosphere and this again would lead to dramatic changes in the chemical makeup of the planet.

The start of life on Earth

The Urey Miller experiment showed that the chemicals of life on Earth could be produced on Earth under the conditions that were thought to be occurring between 3.5 and 4 billion years ago.  Geological evidence tells us that liquid water was around and that no oxygen was present at this time.  

Some of the mudstones that make up the Barbeton mountain range in South Africa are up to 3.5 billion years old.  Microscopic analysis of these suggests that there are fossilised bacteria in these rocks.  Not only do they look similar to modern bacteria, but some appear to be dividing, an indication of life.

Similar finds of bacteria have recently been announce in Western Australia.

The step from the chemicals of life to life itself is not well understood.  While scientists have been able to make cell components, they have been unable to asseble them into anything resembling a cell.  It is an area of some molecular biologists whose aim is to make a "synthetic cell".


How did the first bacteria obtain energy and nutrients?

It is possible that the earliest bacteria consumed the complex molecules that were formed before life arose. That would make them heterotrophic ("eats others").  As these molecules were exhausted, some bacteria were utilising the energy provided from minerals in volcanic springs.  These types of bacteria are autotropic (make their own food), more specifically chemoautotrophic (make their own food using simple chemicals).  However, some bacteria began using a far more available source of energy to make their own food, the sun.  

This was the start of photosynthesis for life on Earth, and would allow some organisms to produce their own food by sunlight.  This was the beginning of photoautotrophic life on Earth.  One of the by-products of this was oxygen.  It was this oxygen that would change everything for Earth and shape it's future.

The Urey Miller Experiment

In 1953, Stanley Miller, a PhD student, proposed to his supervisor Harold Urey, an experiment to test if the chemosynthetic origins of life were possible under the conditions of what early Earth was like.

This would in part answer the chicken and the egg question about whether it was possible for the early Earth to produce the chemicals needed to sustain life, before life itself actually got going on Earth.

Energy source and some of the gases that Miller proposed to use.           Note NO OXYGEN.

Miller then set up his experiment as follows:



Over a number of days the apparatus showed orange brown materials sticking to the glass and in solution.  Chemical analysis showed the following:


The final group of materials include amino acids (used to make proteins). Other substances include metabolites that certain types of cells can get energy out of.  


The findings were significant for a number of reasons:

1. The early Earth could not have had oxygen present (supported by other geological evidence)
2. The early Earth had conditions that could have allowed for the generation of molecules that would sustain life
3. Other variations of the experiment showed that molecules that could be used in DNA and RNA could be produced.

Differentiation of the Earth

As we covered previously, the Earth was likely formed from the collision of dust and rocks circling the sun.  The kinetic energy of these collisions was converted to heat.  Because of the heat and constant bombardment the very early Earth would have been a largely molten homogeneous mass (1).

As the bombardment slowed and essentially ceased, the materials that made up the Earth would begin to sink or float depending on their density.  Lighter less dense materials float, while the heavier denser materials sink.  As the surface of the Earth cooled, a solid crust formed with lighter water covering most of it and even lighter gases surrounding everything.

This process is differentiation.

Formation of the solar system

The solar system was formed only 4.5 billion years ago.  This compared with the 13-14 billion year history of the Universe.  So in overall terms, the solar system is a bit young.  The force that created our solar system was an explosion from another large star in our galaxy going supernova.  When it did so, it compressed a cloud of gas and resulted in ...... well everything in our world for starters.



What are the stages?

1. The blast wave compresses the gas and dust cloud.  It now begins to be attracted to other molecules by the force of gravity.
2. The debris begins to compress and spin.  Over time it forms a disk.
3. Larger particles begin to collide with other particles.  They fuse together forming even bigger ones.  As they grow, the gravitational attractive force that they exert begins to increase.
4. Eventually all the debris in a path is swept up leaving a single large body called a planet.

What evidence supports this theory?

1. The chemicals that make up the solar system are all the same age.
2. The planets of the solar system all rotate on the same orbital plane.