This question troubles some people, and on this website, and on many others, you’ll find contradictory answers: it’s a net SINK! No, it’s a net SOURCE! My past position was that by and large Australia was a net sink, though since we export a lot of coal, we’ve passed on some of our GGE to other countries. In short, I don’t think it’s a question of enormous significance. But others are sure that it is, so I thought I should do some more work on the subject and provide interested readers with a little background.
Let’s start with the notion of sinks and sources. Carbon sinks are natural systems of some kind — plants, soils and oceans — that take carbon dioxide from the atmosphere and store it. A carbon source is what you might expect it to be: a volcano is one example, human activity in burning fossil fuels is another, while cement-making, deforestation, crop-growing and farming animals are four other examples. We ourselves pump out carbon dioxide (and some methane, too) every time we breathe out or pass wind. In a model world, sinks and sources finally balance each other in net terms. So plants use C02 for photosynthesis and release it through respiration, oceans take up and release carbon dioxide, as do soils.
The bit that is different is the human addition, only about half of which seems to be taken up. The other half is added to what there is already in the atmosphere, about 400+ parts per million. Most land, most people and most industry are in the northern hemisphere, so the northern hemisphere is a bigger source of human GGE than the southern. Because carbon dioxide is a well-mixed gas, it is not long before the proportions are much the same in each hemisphere. Oh, there is a jagged edge to the growing carbon dioxide line, as in the growing season of the northern hemisphere the carbon dioxide in the atmosphere is consumed at a rapid rate, slowing down in the northern winter.
That’s the background. I haven’t filled the page with tables, graphs or numbers, because all this is reasonably well known, and I think uncontroversial. Once Australia signed up to the Kyoto Protocol it became necessary for us to measure where carbon dioxide was being generated by human activity, otherwise the whole business of carbon- offset trading couldn’t operate for us. So we set to with a will, and Australians are good at this type of task — we did the world’s first modern census. The IPCC had already set out what it wanted, so we followed that pattern.
After a few years those entrusted with the work thought it would be a good idea to include the whole Australian land mass as the foundation for their database, and did so. If I’d been part of the team I would have agreed. The IPCC was not interested in whether Australia was a net sink or a net source, and our people didn’t explore that question either.
The blogosphere controversy, nonetheless, is about whether or not Australia as a whole is a source or a sink. If it is a source, then for alarmists it is imperative that we reduce our GGE; if it is a sink, then it doesn’t really matter, unless you think that Australia should be leading the world — and some do. The Australian National Greenhouse Accounts for the first quarter of this year show a tiny increase from the first quarter of 2018. I can’t copy things from the pdf, but Figure 4 at page 7 shows that electricity generation produced a third of our GGE, transport nearly a fifth and agriculture a seventh. The puzzle lies in a category called LULUCF, meaning ‘Land Use, Land Use Change and Forestry’. LULUCF is the only area where the outcome is negative, that is, a decrease in GGE. The decrease was only 19.4 million tonnes of CO2 equivalent, while human-induced emissions were more than 550 million tonnes of CO2 equivalent. Does that mean Australia is a net gigantic source? I shook my head at the ratio. It just didn’t seem to make good sense.
Yet the truth is that I don’t know. If you look up LULUCF you will find that it refers to ‘direct human-induced changes in carbon stocks’. I’m quoting here from the IPPCC Good Practice Guidance for LULUCF. At once there is a quandary. I take it that a state forest, of which Australia has a large number, is a forest in LULUCF terms, even if no logging takes place (and only a tiny proportion of our forests is logged). But what about a national park? You can’t log them, and if you could the only area that was ‘forest’ would be the area set aside for logging. The same would apply if some part of a national park were open to mining, for uranium, for example. We have a lot of national parks and other like areas, nature conservancies, wild-life reserves, special habitats and the rest. They do not seem to me to be examples of ‘human-induced changes in carbon stocks’.
What about public land not elsewhere defined? My memory is that in England, to take that example, there is no public land, as we understand it. In England it is Crown land, and it is not available to you. But Australia has a hell of a lot of land that is just land (technically it is Crown land too, but not in the English sense). Public land is owned by the Commonwealth, a state government or a local council. There may be things you aren’t supposed or allowed to do there, like collect timber, or light fires or dig for oil without a licence. But it’s not farmland, there are no fences, it isn’t being ‘used’ in any productive way; in my view it would be drawing a long bow to say that it is being ‘managed’. So is it part of LULUCF or not? What about roadsides and railway edges? What about mangroves (11,500 square km)? What about IPAs (indigenous protected areas)? There are 48 million hectares of them. And so on. Most of the arid inland Australia is public land, and much of it is a mixture of scrub and grassland. Australia, unlike the countries of the EU, is a big place, and a lot of that land is neither freehold or leasehold. Is public land included, and what would all that mean?
You can get a sense of all this by going to The Australian National Greenhouse Accounts paper Australian Land Use, Land Use Change and Forestry Projections to 2030 of September 2013. There doesn’t seem to be a more recent such publication The first thing to be aware of is that just about every number is an estimate of some kind, inferred from something else, or modelled. Satellite data are the basis ofthe Full Carbon Accounting Model (FullCAM), which estimates the biomass of vegetation on lands across Australia, the carbon stored in above and below ground vegetation and soil, and emissions resulting from land management activities.
Second, while there’s a sense of ‘human-induced’ in the reference to land management in that quote, there’s no division between natural and managed. It is as though the whole Australian land mass is the field of this paper. You would think that, for example, the great Australian soil mass, of 7.7 million square kilometres, is either gaining or losing carbon dioxide in net terms, but I can’t find an estimate about whatever is happening to it. There is nothing about mangroves, 18 per cent of the Australian coastline. While there is legislation to protect them, does anyone ‘manage’ mangroves? I don’t think so, from what I have read.
So I rang up, and talked to a helpful guy from the Department of Environment and Energy who agreed that I was asking difficult but interesting questions. He directed me to the 350 pages of Volume Two of the National Inventory Report 2017, published earlier this year. This is a splendid account of what is known and modelled, with wonderful maps, comprehensive tables and easy-to-understand text. Unfortunately, it does not anywhere answer my question, and indeed it hardly refers to ‘human-induced changes to carbon stocks’ at all.
To repeat, asking whether or not Australia is a net sink was not the job of our clever people. Having said that, it also seems that those concerned forgot about the need to distinguish between what naturally occurs and what human activity has done. I’m not blaming them, it wasn’t quite their job, but it is an awkward lacuna from my point of view. It’s reminiscent of the IPCC’s failure to distinguish the natural from the human-induced in global warming.
So, is Australia a sink or a source? My tentative answer is that no-one knows. But this is a progress report, and I’ll keep on working at it. In the meantime, someone else might come up with some answers, and I might have missed something blindingly obvious. It happens to us all.