Unpicking the climate forest furphy
Is Tasmania really a world leader in climate action? Not so fast, explains John Hunter
PREMIER Peter Gutwein said in a media release on June 25 that Tasmania was “a world leader in mitigating climate change” because “we have hit our target of net zero emissions by 2050 for the fourth year in a row”. What does this actually mean?
It is helpful to divide greenhouse gas emissions into two types — those predominantly related to energy production (burning coal, oil and gas), industrial processes and agriculture; and those related to land use and forestry (technically called “Land Use, Land Use Change and Forestry” or LULUCF, pronounced “lulu-see-eff”).
The first type is commonly called gross emissions and the sum of both types is called net emissions. Let’s look at how these have changed since 1990.
Firstly, if we look at gross emissions (predominantly energy production, industrial processes and agriculture), it is hard to see any differences between averages taken over five-year periods 1990-1994 and 2014-2018. In fact gross emissions have actually increased about 6 per cent over that time.
Although our gross emissions have been dwarfed in the past by LULUCF, they are still large on a per-capita basis. If Tasmania were one of the 37 OECD countries, our per-capita gross emissions would only be exceeded by six countries. Australia (heading the pack), US, Canada, Luxembourg, New Zealand and Estonia. We are certainly world leaders in this regard.
Secondly, let’s look at forestry. Over many decades, Tasmania had significant forestry activity which mainly converted native forest timber into pulp which, in turn, was converted into paper. Now, paper has a lifetime of only a year or so before it breaks down, returning carbon dioxide to the atmosphere.
Over those decades, Tasmania’s emissions were dominated by LULUCF, about 11 million tonnes of carbon dioxide per year being released into the atmosphere. Added to this were gross emissions of about 8 million tonnes per year, resulting in net emissions of about 19 million tonnes a year, which were among the highest percapita emissions in the world.
Around 2010, logging in native forests was more than halved due to changes in global prices and an increased demand for plantation timber (driven partly by environmental advocacy).
Recovering and regrowing forests began to draw carbon dioxide out of the atmosphere such that LULUCF “emissions” became negative at around -9 million tonnes per year. As noted, gross emissions have changed little and are still about 8 million tonnes a year, resulting in present net emissions of about -1 million tonnes a year (ie we are removing carbon dioxide from the atmosphere) — which is why the Premier can claim “we have hit our target of net zero emissions’’. But is this fair?
The validity of including LULUCF emissions in any assessment of our climate aspirations, targets and performance is controversial, for several reasons: ESTIMATING LULUCF is very uncertain, the science being poorly understood and required observations being sparse. Historical estimates are therefore often recalculated as fresh data comes in, and as understanding improves. For example, as a result of recalculation, this year’s assessment of Tasmania’s LULUCF for 2017 differs from last year’s assessment by 1.8 million tonnes — more than the annual emissions from our entire transport sector.
OUR VERY DEFINITION of LULUCF is somewhat arbitrary. How do we apportion these emissions between natural and human causes?
CARBON DIOXIDE can move from forests to the atmosphere relatively easily. Although a tree may take decades to grow, it can be destroyed in hours, as was evident from disastrous bushfires. This is in contrast to coal, oil and gas which, until the arrival of humans, had been safely locked up for many millions of years.
THE PRESENT DRAWDOWN of carbon dioxide is not permanent and will reduce over decades as the regrowing forests mature.
THE PRESENT DRAWDOWN of carbon dioxide is a direct result of the recovery of forests from decades of logging and paper production, during which Tasmania had among the highest per-capita emissions in the world.
Is it fair we use this recovery from past bad behaviour to
offset our gross emissions now?
If our Premier really believes we are “a world leader in mitigating climate change’’ what advice could he give to other countries? Perhaps it is this. Firstly, do nothing to reduce your gross emissions over a quarter of a century. Secondly, heavily log your forests for a few decades (resulting in world-leading per-capita emissions), then substantially reduce logging and take credit for the drawdown of carbon dioxide from the atmosphere that will inevitably follow.
It’s a perverse logic, isn’t it?
Dr John Hunter is a semi-retired climate scientist and oceanographer working in an emeritus position at the Institute for Marine and Antarctic Studies, University of Tasmania. His interests are sea-level rise induced by climate change and the response of Antarctic ice shelf cavities to global warming. He developed the Canute sealevel rise tool and a method of deriving sea-level planning allowances used in Australia, New Zealand and Canada.