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The organic solution to climate change


(CB)As a leader in the organic movement, where does climate change fit in your hierarchy of priorities?

(TM) When it comes to choosing the food I buy, organic is actually my fourth choice. I would choose local and seasonal products, particularly from farmer’s markets, ahead of organically-certified products, particularly if those products have travelled long distances.

I feel that our diet needs a diversity of foods, all of which I would consider ahead of organically-grown food. Climate change is the issue and organics is an integral part of the solution, but it is a means to an end, not the end itself.


(CB)What is your solution to the issue of climate change?

(TM) Most of the responses to climate change being considered will not stop the global mean temperature rising to critical levels. If we stopped emitting greenhouse gases today, there is already enough CO2 in the atmosphere to cause climate chaos. It is the ‘legacy load’ of 200 years of industrial emissions.

The options of  ‘clean coal’ and nuclear power cannot capture existing CO2 in the atmosphere, they can only prevent future emissions.

Forests can absorb legacy load CO2, but there is not enough space on Earth to plant enough trees to absorb the world’s emissions. We would need seven planets!

Soil is the largest carbon sink over which we have control. It holds twice as much carbon as the atmosphere, and twice as much as all the vegetation on Earth, including forests (see diagram opposite). Sixty percent of Earth’s habitable surface is used for agriculture. This soil can remove CO2 from the atmosphere faster and more economically than trees or any other method.

Simple changes in land management can initiate the process of CO2 removal. These changes can be made immediately if farmers are paid carbon credits. A 1% increase of soil carbon in 10% of Australia’s agricultural soils would remove 10 years worth of legacy load from the nation’s emissions.


(CB)Why hasn’t the organic movement got government support like the tree plantation industry?

(TM) The organics movement lacks a figurehead and unity within the alternative approaches to organics. Without a concentrated focus there are no funds. The non-renewable energy lobby of coal, fertilisers, farm chemicals and genetically-modified seeds has the ear of government. Organics is a system that has to fight defined products that are vastly more powerful.


(CB)Can you explain why soils are a better carbon sink than trees?

(TM) Soil carbon is more stable. Trees can be burnt and trees drop leaves so they shed carbon during winter or droughts. There is more carbon below ground than above it, particularly in the roots of trees. The most efficient method of accumulating carbon in soils must be by direct decomposition of plant material. Soil carbon is created by bugs and microbes living and dying as a consequence of the vigorous root action in the soil. The rotting remnants of organic matter feeds the microbes that produce soil carbon.

Plantations, particularly monocultures that replace natural forest, destroy diversity. Yet the forest lobby has influence and tax deductibility, not offered to organic growers.


(CB)What organic soil carbon levels should we be striving for?

(TM) Soil carbon levels are highest where optimum growing conditions exist. Except in the tropics, where biomass is concentrated in the vegetation, there is actually more carbon under the ground than above.In temperate regions, a 5% level is normal, whilst dry grassland is approximately 3%. Australia’s soils have fallen to about 1.5%, as a consequence of poor management.

Ploughing disturbs microbes, dries out the soil, and releases CO2 into the atmosphere. During a wheat cropping cycle, land is exposed, heated and dried, suppressing biological activity. If farmers went back to a grazing/cereal crop rotation, as organic wheat farmers do, organic levels would rise, as manure and grass provide good conditions for microbes below the ground maintaining more carbon in the soil.

Gardeners who compost and mulch their plants usually have organic levels of 5–10%, which is as much as is needed to maintain sustainable, fertile oils. Organic soils are not just the solution to climate change, they also hold more water, assisting with our water shortages too.

The Carbon Cycle

The Carbon Cycle by Tim Marshall

The Carbon Cycle

Almost all the carbon on earth is locked into rocks, mainly in the carbonate form, including limestone, dolomite, gypsum and marble. Also in the earth are deposits of coal, petroleum and natural gas (carbon and hydrogen), which are actually the decomposed remains of once-living plants and animals.

The atmosphere contains some carbon (0.03%) and oceans also contain vast amounts. Carbon is slowly extracted from the rocks into the soil, by weathering, which is largely the action of plants and microbes. Living organisms cycle carbon through their bodies and release it again in the process of respiration, when sugars (carbon compounds) are oxidised to make carbon dioxide and water. Respiration is a process common to all.

Organic matter, made from the remains of once-living things in and on the soil in various states of decay, contains a larger store of carbon than living plants. When the huge numbers of microorganisms (which are also at least 50% carbon) are added, the soil store becomes much larger than that of the vegetation alone.

We cannot control all carbon, but we can control the annual increase in CO2 into the atmosphere.

We need to contribute to carbon storage by learning to deepen and enrich soils with humus, plant more trees and plants, and convert as much of our land as possible to organic growing methods.

Tim Marshall is an organic consultant who advises and writes articles for Diggers magazines. Carbon Cycle diagram © The Diggers Club.

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