Saturday, March 06, 2004
Forests that ‘gobble’ CO₂?

After reading this a number of thoughts struck me. (Sadly, I missed the TV programme.)

I would have thought it was obvious to any ecologist……

Matter can neither be created or destroyed – this is the first Law of Thermodynamics. It is also, according to Garrett Hardin, a fair assumption to make in relation to ecological systems.

Mature forests neither net generate or absorb CO₂. All things being equal biomass is being created in photosynthesis (and held in trees and plants) and destroyed in respiration (by microbes and fungi) in equal measures at any one time. It is when further factors (some natural, some man-made) such as cyclones, reduced rainfall, soil erosion and introduced bio-pests are added into the mix that any natural balance is throw out of kilter.

The El Niòo Southern Oscillation has been particularly high in most of the last 12 years, causing drier than average conditions for Australia. The last three years rainfall figures have been particularly bad for NE Queensland (see charts) which would presume a lessening (all other things being equal) of biomass in the Daintree/Atherton Tablelands area.

However, in addition, all other things are not equal. Native vegetation clearing continues in NE Queensland (albeit, much slower than in the past), which would have the effect of increasing soil erosion and reducing fauna concentrations that have the beneficial impact on improving flora pollination and seed dispersal and further improving the genetic stock.

It is doubtful (as the programme implies) that the Daintree Rainforest is generating its own dynamic in global warming by being a carbon producer rather than retainer. The rate of carbon release from the burning of fossil fuels, reduced CO₂ concentrations in the world’s seas from the warming oceans and global climate change driving such things as the melting of permafrost are probably far more important in increasing rates of global warming and drying the forests of NE Queensland.

It is known (from studies in Amazonia) that higher concentrations of CO₂ in the atmosphere have driven forests into becoming more efficient carbon sinks - presumably by becoming denser and tying up more biomass than the conditions of normal rainfall/temperature/soil type would otherwise allow.

However, these studies did not imply that if we continued to release carbon into the atmosphere at the (increasing) rates we currently are doing, existing forests would simply absorb it. We are simultaneously releasing CO₂ at an unsustainable rate and reducing forest cover on the globe.

The TV programme’s narrator suggests that the carbon release of the forest was a localised problem for Daintree and the forest itself is not helping Australia’s efforts to reduce its increasing production of CO₂. (Australia’s non-signatory status with the Kyoto Protocol is a whole new story.) What should we do ? Cut it down ?

The forest is now producing CO₂ due to the impact of mankind. Don’t blame it for this.

The work of the Canopy Crane Project (not withstanding the ABC journalist’s interpretation of it) is very interesting. It is a shame that most of its most interesting publications are not for open source. Still, science doesn’t come for free – ask Timberlands West Coast Ltd of New Zealand.

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