Agriculture and climate change

Australian agriculture both contributes to climate change and is adversely affected by it. Any campaign in to force urgent government action on climate change has to include a demand for the radical transformation of rural land use and farming systems to be ecologically sustainable.

There are a number of ways agriculture contributes to climate change. Australian agriculture is fossil fuel intensive — both in terms of agricultural production, and in the transport used to take produce from the farm to the point of consumption in cities.

Even if 100% renewable energy was used to power farm production systems and land transport, agriculture would still make a significant contribution to global warming unless other actions are also taken.

Soil carbon

The loss of soil carbon is a historic, and continuing, contribution to atmospheric CO2 levels. For every tonne of soil carbon lost, 3.67 tons of CO2 is released into the atmosphere.

Soil carbon is destroyed through excessive cultivation or overgrazing, anaerobic (airless) conditions like compaction and water-logging, and the use of synthetic fertilisers and chemicals — particularly herbicides.

What is common to all these practices? They disrupt the carbon cycle in the soil so that carbon is consumed faster than it is replenished.

Methane is emitted by farm animals such as cows, sheep and goats as a by-product of their digestive system, which involves anaerobic fermentation. Methane is 23 times more potent than carbon dioxide as a greenhouse gas.

Worldwide, there has been a doubling of nitrogen in the "soil nitrogen cycle" over the last 100 years, leading to increased nitrous oxide emissions.

This is the result of using synthetic nitrogen fertilisers, the increased growing of legumes (which fix nitrogen from the air into the soil) and the burning of fossil fuels. Nitrous oxide captures 296 times more heat in the atmosphere than CO2.

Other particular problems include the burning of savannas, burning stubble (the remainder of grain stalks after harvest), nitrous oxide emissions from manure management and methane emissions from rice production.

Extreme weather events

Climate change also impacts on Australian agriculture by magnifying existing problems.

Increased incidences of extreme weather events, like cyclones in the far north and heatwaves in the south (leading to catastrophic bushfires), all disrupt farming operations and food supply, as well as leaving a legacy of land degradation.

Furthermore, water cycles are disrupted. Ground water resources are being used faster than they are recharging. Deforestation has disrupted rainfall patterns. Hotter conditions mean an increased need for water at a time when rainfall is decreasing and becoming erratic.

Biodiversity loss on farms, through mono-cropping and the decline of native habitats, further reduces resilience to extreme weather conditions.

Increased droughts can lead to a loss of ground cover and hence a further loss of soil carbon.

Salinity and erosion issues lead back to problems with soil hydrology being disturbed by the absence of deep rooted perennial plants and soil carbon loss.

As crop varieties and livestock breeds are lost, and farmers rely on growing a small number of market-leading varieties of crops, we hamper our ability to adapt to our new environment.

Are livestock the main problem?

In 2006 the UN Food and Agriculture Organisation released a report titled Livestock's Long Shadow — Environmental Issues and Options. The report linked the world's livestock to major problems including deforestation resulting from the pressure for grazing land, high greenhouse emissions, land degradation through overgrazing and the high burden on water and land resources among others.

Animals are a necessary component of all ecosystems, but if there are too many in a particular environment they will be highly destructive. What would be the appropriate number of livestock for sustainable agriculture?

The answer will always be found farm by farm or district by district. Also, what is appropriate one season may not be the same the next, given drought or good rain.

Totally eliminating livestock from farming, however, would make Australian agriculture less sustainable rather than more.

Composted manures are an invaluable source for biological enhancement and soil fertility. Along with properly processed human waste (bio-solids), its application can help break farming's dependence on synthetic nitrogen inputs.

Furthermore, well managed grazing land is one of the most effective ways to sequester carbon in the soil.

Livestock can add to the biodiversity of farms that predominately grow crops, as does diversifying crops, developing wildlife corridors and repairing creek areas.

Livestock operations fit very well with agro-forestry (as opposed to monoculture tree plantations). Sustainable pastures can contain a plethora of species without the need for input-intensive cultivation.

Growing topsoil

To reduce atmospheric carbon dioxide levels, it will be necessary to reverse the loss of soil carbon caused by capitalist farming methods.

Building up soil carbon levels involves increasing soil biological activity, increasing the return to the soil of organic residues and maintaining ground cover with actively growing plants.

Plants sequester carbon from the atmosphere through photosynthesis. Plant residues that are digested by the soil are eventually transformed into more stable carbon compounds such as humic acids.

An interesting technology that can play a part in drawing carbon back into the soil is biochar, a type of charcoal created by heating organic matter in an oxygen-poor environment.

Biochar is a far more stable form of carbon than the organic matter from which it is made. It can last in the soil for hundreds of years.

For farms with degraded soils, biochar can increase water holding capacity, nutrient retention, increase biological activity, and improve soil structure.

Rebuilding carbon levels in the soil does not depend on undeveloped, speculative technologies — it is a current practice used by most organic and bio-dynamic farmers.

One exciting development for Australian agriculture is the Natural Sequence Farming system developed by agriculturalist Peter Andrews. Andrews' system seeks to restore the soil hydrology by returning carbon to the soil and reversing the damage to creek and river systems so that water is stored in the landscape rather than drained away.

For example, leaky weirs are constructed in deeply incised creeks and planted out with reeds, slowing the water down and allowing the creek to support a higher water table in the landscape.

There are many other aspects to Andrews' system. He has written two books, Back from the Brink and Beyond the Brink that are essential reading for those interested in sustainable agriculture.

Pasture cropping

Another important farming system, pasture cropping, was developed in NSW in 1992 by Colin Seis.

With this technique, winter cereal crops are sown directly into native pasture and harvested before the pastures growth phase starts.

The crop yield is slightly less than crops sown in worked-up ground but there is no tillage, no bare ground and the grazing value of the pasture is maintained.

Pasture re-sown into stubble often takes a season to establish, so in a mixed-farming system pasture cropping is more productive over all. Unlike traditional agriculture, it is a system that can increase soil carbon levels.

There have been farms growing food sustainably in Australia for decades. The challenge is to introduce sustainable farming, not just on a farm-by-farm basis, but across the whole sector.

Financial pressures on many working farmers are such that there isn't enough capital available without going further into debt to undertake new infrastructure programs, or to retool equipment for minimum tillage.

Furthermore, there is often a financial imperative to crop fence-post to fence-post, or carry extra stock, to squeeze out an few extra dollars per acre.

Market barriers

Can market forces encourage farmers to undertake sustainable farming practices? The evidence for this is highly dubious.

The introduction of water trading, for example, has resulted in the cost of water rising through local government buying water for urban users, and companies and individual farmers speculating on the water price.

The real efficiency gains in water-use, however, come through direct investment in infrastructure such as the conversion from open channels to pipes, switching from flood irrigation to overhead spray, or better still, underground drip irrigation.

Offering a regular income stream for environmental management services would allow some financial certainty for farmers.

Increased funding for research into new techniques and technologies that will improve ecological sustainability are also essential.

In particular, the federal government has to fund the rapid development of biochar production facilities around the country rather than leave it to the private sector to implement it only where it is profitable.

Governments need to massively expand their budgets for farm reforestation and not just link that funding to native tree planting. State investment in redeveloping urban waste systems is needed so that organic matter, including bio-solids, is returned to farm land.