Why climate change threatens our biological system

Our fossil fuel reserves are 5 times as great as the 600 billion tonnes that is the limit that must not be burned if we are to keep our temperature increase to just 2°C . In short we can only mine 20% of our known reserves (imagine a mining industry that wouldn't accept a mining tax being forced to agree to that!). Our current CO2 levels are the highest they have been for a million years and they are increasing faster than at any other period in history.

To reach this target, considering that we are already at a 0.9°C increase, means that by the year 2050 we need to have reduced our emissions to zero, effectively de-carbonising our economy and using renewable energy sources that exclude burning coal, gas or petroleum or other sources of carbon from decomposed fossil fuels.

If we fail to de-carbonise our economy, temperature rises of 6°C are forecast by 2100 and those temperature increases will affect S-E and S-W Australia to an even greater level. Drier conditions that have afflicted Perth will follow to S.A., Victoria and Tasmania.

In general, drier regions get drier and our northern tropics get wetter. So let's ask the question of what life would be like if we continue to ignore the warnings?

The 48°C day that started the Black Saturday bushfires reached temperature increases not expected until 2030. So a 6°C increase would put maximum temperatures well over 50°C, which are the sort of temperatures that cause plant collapse and inevitably give rise to desert conditions like the Middle East to reach close to our costal populations. Temperatures rise higher over land than the sea, hence the extreme impact of hot northerlies on our southern states with accompanying drying of the climate. The commentators, who some would call catastrophists, are alarmed by the sudden unpredictable tipping points that can be triggered as temperatures rise.

For example, in the arctic there are 1600 billion tonnes of carbon under ice which could be released by rapidly melting ice caps. If this were to occur our 600 million tonne budget would be blown and extremely rapid and potentially uncontrollable changes would occur, similar to the time 55 million years ago when CO₂ levels reached 1000ppm compared with today's 400 ppm.

As spring temperatures rise flowering is earlier altering fruit set and yield potential. Some crops such as tomatoes which originated in the cooler mountains of South America drop flowers during 30°C plus nights and yields drop. Reproduction of animals, insects and butterflies is triggered earlier and plants and animals migrate to cooler habitats. Australia producers 93% of its food and exports 76% of its agricultural production so the impact of climate change is expected to reduce cropping yields and milk and meat production partially because of increased pest and disease problems. Vineyards will be forced to migrate and forestry yields will be affected. Gardeners can help by bringing CO₂ down to earth at home by planting trees and burying organic matter.

A summary of Generating a Renewable Australia by Tim Flannery and Veena Sahajwalla (Climate Commission) © 2012

Gardeners are at the forefront of understanding the impacts of climate change. We probably are far closer to understanding its impacts than most farmers because we work with the soil, rather than plough it (in the comfort of air-conditioned tractors).

We till the soil, recycle our waste materials, feel the worms and understand the interaction of birds, bees and butterflies. We hand water our gardens, are in tune with the seasonal changes of trees and shrubs and can enjoy the sunrises and sunsets in our own created beauty.

We understand how we can reverse the carbon cycle by growing plants so that in our backyards we can bring carbon down to earth.

If God is concerned about the impacts of climate change then surely we are the chosen tribe! But we all have a weak point we need to address to feel that we are doing our utmost to do solve the problem.and Valerian, so all you have to do to make a compost batch is chop down the nearby foliage.

My particular passion is planting trees. I have the advantage of inheriting a farm that is an ideal place for planting trees and farming organically. Over the years with lots of help we have established tree lucerne for windbreaks and stock fodder, an avenue of stone pines and carobs for erosion control, apples for root stocks, poplars for drainage, and hazelnuts and paulownias for experiments. Now none of this has made any commercial sense but it has beautified our property and of course pulled carbon from the atmosphere and sequestered it in our soil.

When talking about putting carbon back into the soil it is important to understand that there are three different categories of carbon that have vastly different impacts.

The biomass of roots, worms, bacteria, fungi and microscopic living animals is a carbon store called green carbon which is three times as large as the carbon in the atmosphere (grey carbon – caused by burning fossil carbon) which is why it has such potential to increase. In fact it is estimated that 35% of the C0₂ in the atmosphere has come from us disturbing the ecological balance by cutting down our best reservoirs of carbon from our old growth forests.

This is a hugely contentious issue because the IPCC says continuing deforestation is accounting for a massive 18% of our annual global emissions; which is just behind that of the combined impact of growing and transporting food from farms to supermarkets rather than growing it at home. So here is a ‘win win’ for gardeners in the sense that by growing our own food at home and growing trees we are actively reducing our emissions by nearly 50%.

However when we grow trees in mono cultured industrial forests (brown carbon) as we do for pulp and for building etc., the carbon levels defined are only about ⅓ that of old growth forests. The difference is described by the term bio-diversity.

Old growth forests support decaying woody debris and the protection from a shady canopy cover from natural undisturbed systems of natural eucalypt forests yields 2-5 times as much carbon as from plantations (source – Green Carbon, Brendan Mackey). In a garden situation where we plant a mixture of trees that can produce a canopy, we create an ecology on the ground by starting a soil base that protects and supports living biota which recycle dead material and build up stores of carbon.

Last year we planted about 180 deciduous English oaks as well as evergreen Holm oaks and I'm delighted to find that we have a survival rate of over 90% despite having a heat wave of four days over 40°C and no remedial watering.

The real benefit in having high carbon levels is the hugely improved water holding capacity, particularly during the continued growth in dry weather when soils dry out and growth stops.