How sustainable are private forests?
We have learned to value sustainability in our land management practices. This has always been highly regarded by professional foresters dealing with long term crops and high value forests. Plantations are managed according to the Code of Practice for Timber Plantations in Western Australia which sets out principals for sustainable plantation management. The Blue Gum plantation programme was initiated to assist sustainable management of the agricultural systems which are under threat from salinity and water-logging from rising water tables and wind and soil erosion.
How are environmental practices in forestry managed?
Environmental practices are generally regulated by State agencies. In Western Australia forestry is affected by legislation, the most significant of which includes:
- Local Government planning schemes;
- Conservation and Land Management Act (1984);
- Forest Products Commission Act (2000);
- Bush Fires Act (1954);
- Country Areas Water Supply Act (1947);
- Environment Protection Act (1986);
- Health (Pesticides) Regulations 1956 and Aerial Spraying Control Act 1966;
- Soil and Land Conservation Act 1945.
- Tree Plantations Agreement Act 2003
- Carbon Rights Legislation 2003
What is the Code of Practice?
The plantation industry including the growers representative group, Australian Forest Growers, and the Forest Products Commission have consolidated the content of these regulations and interpreted them to develop the Code of Practice for Timber Plantations in Western Australia `(the Code of Practice). The Code of Practice expresses State-wide principles, goals and guidelines for environmental care, safety, planning, access, establishment and maintenance, harvesting, protection, monitoring and review. The Code of Practice is currently being reviewed by the industry and government to incorporate changes in community attitudes and forestry practices which have developed since the first Code of Practice. The Code of Practice is a voluntary industry code. However, most companies have committed to the Code and are obliged to maintain this commitment through the Corporations Laws.
How do forests affect catchments?
Catchments in the Great Southern are naturally covered by forests, woodlands and scrubby heaths. This native vegetation has been cleared from much of the agricultural land. The pastures and crops use less water than the original vegetation. As a result of clearing the native forests, run-off from the land increased and ground waters are recharged more than previously. Compaction of soils by cloven hoofed animals and movement of machinery causes less infiltration and accelerated run-off of rainfall. De-forested catchments are likely to yield increased flows of water moving rapidly down the catchment. This water is more likely to be destructive causing erosion and flooding. The water will carry soil and nutrients from the land polluting rivers and estuaries downstream. Trees can protect the soil from falling rain, reducing erosion. Forests modify the soil increasing the percolation of the rainfall into the soil, reducing overland flow. Plantations achieve this with ripping and mounding along contours. The roots of trees and under-storey species bind the soil together preventing it from washing away.
How do trees assist salinity?
In the natural environment the native vegetation has achieved a balance between rainfall and water use. This balance has been upset by sowing pastures and crops which use less water than the original vegetation. As a result, underground water stores rise to the surface in the absence of deep rooted trees. This water is likely to include naturally occurring dissolved salts which accumulate at the soil surface when the water evaporates. This results in dry-land salinity. In higher rainfall regions the surface salt is more likely to be leached back into the deeper soils. Establishing deep rooted vegetation such as trees aims to restore the balance of rainfall and vegetation water use so that ground water returns to balance. Some crops such as strategically located fast growing tree crops use more water than the original vegetation. This allows a proportion of the catchment to be planted and the remainder to be used for agriculture without increasing groundwater recharge. Forests provide a less disturbed environment for soil flora and fauna such as worms. These organisms recycle nutrients into the soil and reduce soil compaction.
Will the regional groundwater supplies be depleted by plantations?
Groundwater supplies are important to the City of Albany and towns around the Great Southern providing most of the drinking water. It would not be acceptable for plantations to use all the ground water. At present only a minor proportion of the landscape has been planted to trees and this is unlikely to have an impact on regional groundwater supplies. Studies by CSIRO at Mount Gambier found that the extensive pine plantations in that region were not affecting the regional ground water supplies.
What happens when the soils run out of water?
The largest threat to the long term sustainable growth of Blue Gum plantations in the Great Southern region of Western Australia is related to available moisture. Deep rooted, fast growing trees transpire large quantities of water. This characteristic can be used positively where rising water tables are a problem. Blue Gum is not particularly responsive to drought and can grow into stress and even death, because it fails to "shut down" during dry periods. These mechanisms are being actively researched by CSIRO and the industry. Accurate soil mapping and good management is essential for successful and sustainable plantations. Site assessment must identify where moisture is likely to be limiting during droughts. Experience has shown that Blue Gum plantations on shallow soils or over shallow saline water tables can result in failures. Building on the experience of plantations in the South West modern plantations are established on suitable soils and drought risks are reduced.
Will the soils be depleted?
All crops require nutrient management. Tree crops are able to use nutrients which have leached beyond the root zone of shallow rooted grasses and common agricultural crops. Eucalypts are remarkably efficient at recycling many nutrients within the canopy of the plant. However, to be sustainable, the nutrients lost when the trees are harvested will have to be replaced. Frequently harvested crops will export larger amounts of nutrient than long cycle crops. Fortunately, much of the nutrient value remains in the foliage and bark which does not have to be exported from the plantation at harvest. However, if the site is burned after harvesting there will be substantial losses of organic matter and nutrients. CSIRO and the industry are studying techniques to minimise the loss of nutrients at harvest and how to effectively replace them.
Don't the trees acidify the soils?
Addition of common fertilisers such as urea and super-phosphate can cause soil acidification. This is an important issue for conventional farming. Plantations use smaller quantities of fertiliser than agriculture and there is no evidence of trees causing soil acidification in this region. What are the benefits to farm production? The main benefits of trees of farms come from shelter for stock. Trees reduce exposure of the land to wind by forcing the wind higher and making the land surface rougher taking energy out of the wind. As a result of slower winds the micro-environment of the pasture is moderated. Maximum temperatures are lower and minimum temperatures are warmer. There is shelter for stock to avoid extremes. The trees do use more soil moisture and it is common to observe reduced pasture or crop production close to belts of trees because of this. However, numerous studies have repeatedly shown that the overall effect of trees is more beneficial than detrimental to agricultural production. It is normally recommended that shelter belts be semi-permeable, not be grazed to avoid a cleared browse line under the trees and that they be spaced approximately 10 times the height of the trees perpendicular to the damaging winds.
Will the trees be a fire hazard?
The experience in South Western WA has been that plantations of Blue Gums do not burn as fiercely as alternative land uses. Blue Gum plantations tend to have lower fuel accumulations on the ground than pine plantations and native vegetation. Forests exclude the winds driving wild fires. Plantations should have adequate fire breaks maintained annually around the perimeter and access breaks every 30 to 100 hectares. These facts combine to render fires more controllable when they enter plantations.
How do forests affect the atmosphere?
The photosynthetic processes of plants use solar energy, atmospheric Carbon dioxide and water to produce carbohydrates (plants material) and Oxygen. Because of the depth of the canopy and efficiency of their leaves fast growing forests are relatively efficient plant producers. A critical challenge for our Global community is the management of the atmosphere from which we draw our air. Critical problems have developed as the developed world burns massive amounts of fossil fuels releasing pollutants including nitrous oxides (NOX) and sulphuric oxides (SOX) and greenhouse gases. The fossil fuels come from ancient forests and organic matter compressed over eons to form coal and oil. Forests are recognised by the Kyoto Conference on Greenhouse Gases as potentially contributing to the sequestration of atmospheric Carbon. International positioning has prevented the extent to which this is counted towards national goals being resolved.
What is the Greenhouse effect?
The Greenhouse effect is essential to life on Earth. The Greenhouse effect is the name given to the effect of the atmosphere insulating the surface of the Earth from radiation. The atmosphere absorbs and reflects incoming radiation so that it does not reach the surface of Earth in harmful levels. The atmosphere also prevents the reflection and re-radiation from the surface so that energy is lost. The upper atmosphere moderates the environment at the Earth's surface allowing a suitable environment for life as we know it. Unfortunately, through industrialisation we have made significant changes to the composition of the atmosphere to the extent that it is affecting the role of the atmosphere as a moderator of the climate. There is evidence that increasing concentrations of Greenhouse gases including Carbon dioxide and methane are causing an increase in temperature at the surface of the Earth. Changes in the temperature are expected to have serious implications to life on Earth including rising sea levels and more extreme weather events such as storms, droughts and floods. There is much debate about the changes in temperatures because it is difficult to distinguish short term variations from long term trends. The cause of change may natural and inevitable or may have been accelerated by human activity. There is little doubt that human intervention efforts will be relatively small compared with events such as volcanoes and wildfires.
What is Greenhouse action about?
Action to address the Greenhouse effect aim to firstly reduce the contribution of Greenhouse gases to the atmosphere. Reduction in energy consumption for human activity is likely to be the most effective action in this regard. However, moves to source energy from non-fossil fuel resources will arrest the release of fossilsed Carbon back to the atmosphere. Solar energy, hydro-power, nuclear/atomic energy are energy sources with minimum Carbon dioxide emissions. Biomass can be burned releasing Carbon dioxide to the atmosphere but at least it is recycling carbon which was already in the human bio-sphere. Forests can be grown as additional sinks fixing Carbon dioxide from the atmosphere. However, this will be a temporary benefit only given that when the forests are burned or harvested, the carbon store will be released to atmosphere as the products are burned or decompose. However, if the total area of forest is increased on a sustained basis, the total inventory of carbon stored in forests will increase.
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