Humus
Glenn Morris, a local property manager, argues that landholders are at the mercy of drought caused by climate change but can minimise the effects of drought and reduce atmospheric carbon dioxide by raising the humus levels in their soils.
Australia now has the greatest level of green house gas emissions per person in the world, 35% higher than even America.
In 1990 at the conclusion of the world commission on environment and development an urgent message was sounded. Over twenty-one nations from the world stated, " we are unanimous in our conviction that the security, well-being and very survival of the planet depended on urgent changes." This warning has been largely ignored by governments as the desire for short term wealth continues to be more important than concern over living standards for future generations. The current generation fails to realise that money is a very poor alternative to preserving a safe environment with clean air, clean water and healthy soil.
On world environment day our leader John Howard stood up and said, "Australia can not afford to ratify the Kyoto agreement." We have recently been told we have one of the best performing countries in the world, this is due to the fact we use more energy and contribute more to global warming per person (28 tonnes) than any other nation on earth. The Kyoto protocol calls for a mere 5% reduction in CO2 emissions by 2008. Mr. Howard’s vision for Australia cannot extend past his own term of government which demonstrates a complete absence of long term leadership. Australia and the world need leadership with intelligent vision, leadership which enhances the social quality of life and cares for the vital support systems of the earth, particularly soil, water and air. The threat of terrorism will rate a poor second to global warming when millions of people worldwide are starving and dying of thirst.
Farmers and scientists will have a number of key responsibilities in repairing our environment:
Active carbon (humus) can hold four times its weight in water. Soils with a humus level of 1% will hold approximately 113,000 litres of water per hectare. A one-inch rainfall supplies 320,000 litres of water per hectare and will therefore saturate 1% humus soil causing runoff and erosion. Soils with 6 percent humus will hold in excess of two inches of rainfall.
High carbon soils are invaluable in dry periods, but as well as drought proofing farmland, the additional moisture increases the hydrological processes of an area through evapo-transpiration and gradual water system recharging. Soil is an impediment to water movement, and free (interstitial) water can take as long as 1-40 years to percolate through to streams. Greatly alleviating droughts, it also recharges the retention storages along the way. (Odum, 1974)
Additionally, the building of soil carbon levels may prove to be our greatest sink for returning atmospheric carbon to the soil, estimates of 25 ton/ha absorbed for every 1% increase in carbon have been made (Wilson 2002).
A 500 hectare property with a 5% increase in humus would therefore store an additional 282.5 million litres of water and absorb 62 500 tons of carbon from the atmosphere.
The figures above demonstrate the absolute importance which good soil management can not only play in producing healthy crops but also in addressing global warming and restoring hydrological cycles.
Where possible, fire should be excluded from farmland, whether for hazard reduction or "green pick" (burning grasses to promote fresh green shoots for cattle).
Burning leaf and grass litter means minerals, including carbon, are lost in smoke and by leaching next time it rains. There's nothing left to rot into new humus and the blackened soil absorbs heat from the sun. After a fire, water tends to run off rather than penetrating.
All this means lower soil moisture which in turn means the land will burn more readily next time.
Farmers must understand the preservation of trees and forests is essential for the cycling of moisture and assuring regular rainfall events continue.
Understanding hydrological processes and the natural forces which contribute to weather patterns should help us design natural landscapes which encourage rainfall. Realising that trees can be responsible for localised rain may help us to see agricultural design as a complete system. Observation of climate behaviour in other countries which have been cleared of forests for centuries may help us understand the need for well balanced landscapes. The search to find solutions to restore and maintain water supplies in Australia could be greatly assisted by examining successful drought proofing strategies in other continents. Countries such as India, where some regions have already been through the process of desertification and restoration, may act as a valuable case study. Suzuki and Dressel (2002), give a case study of one area in India where soils would no longer hold moisture and the rivers no longer flowed. Small check dams (traditionally known as a bund ) were built in the dry rivers to create small water storages. The theory was based on a traditional form of complex water harvesting and storage which had existed before the age of deep wells and river destroying large dams. The low cost dams are individually designed to suit each site. The first very simple check dam gave water for four months instead of just two in the first year. The next year, the villagers were delighted to get seven months of water. Now, only two years later, the river has become perennial again; it was a completely unexpected miracle. These small dams are now providing over thirty villages with water and have returned previously abandoned cropland back into full production. The explanation seems to be that impounding the seasonal water for even a few months recharges the local aquifers so much that trees and shrubs grow prodigiously, as one might expect in such a climate. The foliage and roots trap more moisture, more things grow in the revitalised soil, more rain percolates down into the groundwater, and the process mushrooms. Presumably swales on slopes would do the same thing without disturbing the river bed.
Dealing with something as complex as the hydrological process will require a solution with equivalent complexity, a combination of clever engineering with the harnessing of natural forces and good soil science. Good carbon management is the key to reliable water supplies and drought proofing soils.