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Dry period in semi-arid central Australia James Cleverly

Back in 2010-11 Australia “greened”, as record-breaking rains triggered a boom in plant growth that removed huge amounts of carbon dioxide from the atmosphere and stored it as carbon in the landscape.

But what happened after that? Our latest research, published in Scientific Reports, shows that this greening was short-lived and was rapidly dissipated through drought and fire.

Our study also shows that as extreme wet years are getting wetter and more common, Australia’s terrestrial ecosystems will play a larger role in the global carbon cycle.

Carbon, water and climate change

Each year, land plants absorb the equivalent of more than a quarter of the carbon emissions generated by burning fossil fuels and deforestation. This helps to partly offset global increases in atmospheric CO₂ concentration. In 2011, this “land carbon sink” was unusually large, thanks largely to the greening of Australia’s vegetation, which accounted for 60% of the global carbon uptake anomaly that year.

Flux towers for measuring carbon and water fluxes between ecosystem and the atmosphere: (left) Calperum near Adelaide; (right) Alice Springs Mulga woodland in central Australia. Both sites are part of Australia’s Terrestrial Ecosystem Research Network, or TERN. from www.ozflux.org.au

Satellite imaging and ground observations from CO₂ “flux” towers showed that much of the 2011 greening happened in savannas and grasslands, largely in central Australia. New data shows that the return of drought conditions in many of these areas has quickly un-greened them.

Mulga dry tropical forest in central Australia was extraordinarily green and took large amounts of carbon dioxide from the atmosphere. James Cleverly Be resilient, be prepared

To an extent this is no surprise. Australia’s dryland plant species live in the most variable climates in the world. As such these ecosystems can swing rapidly between being highly productive in wet years and becoming nearly dormant to withstand drought during dry ones.

Given that the 2010-11 extreme greening followed on rapidly from the protracted Millennium Drought, it should hardly be surprising that we find the ecosystem has now swung back the other way so promptly.

Australia’s climate is the most variable in the world. (a) shows the variability of rainfall (coefficient of variance or CV) compared with other continents; (b) shows the same in Australia for four periods. Ma et al. (2016) Australia’s unique native hummock grassland (Spinifex) in dry season (left) and wet season (right). James Cleverly Drought and fire count

On a biological level, the reason that plants take up less carbon dioxide during dry periods is because this process costs water. Plants exchange gases with the atmosphere via tiny pores on their leaves called stomata, through which CO₂ diffuses in during the day but through which water also escapes.

When water is scarce it is more important to conserve it. This is why during drought conditions plants tend to reduce their carbon dioxide uptake by closing stomata or even shedding leaves entirely.

Sometimes the combination of heat and drought can be so stressful that plants die, ultimately decomposing or burning and releasing all of their stored carbon back to the atmosphere.

Australia’s ungreening

Our research shows that these processes began to take hold across Australia during the second half of 2012 and into 2013. As the chart below shows, this diminishes Australia’s large net carbon uptake as boosted by the 2010-11 wet year.

Drought rapidly eliminates Australia’s large land carbon uptake. (left) SPEI drought index; (right) satellite measures of ecosystem productivity and water storage across Australia. Ma et al. (2016)

We also found that carbon dioxide emissions from fires increased during this period. This makes sense too, given that the productive wet period spurred more plant growth, which then became fuel for fire during the subsequent drought.

As a result, Australia’s semi-arid landscapes are mostly dry once again, although the speed with which they greened and then ungreened suggests that they will be quickly refreshed when the next big deluge arrives.

Not alone

Australia’s giant green carbon sink was remarkable, but was it unique? There are two ways we can answer this question: we can wait and see if there’s another one, or we can go back and look at the historical record.

Fortunately, with long-term satellite observations, we have measurements of the entire continent back to 2000, and even earlier for some data sets. Our new research shows that the 2010–11 event was not unique. Rather, it was something that tends to happen whenever Australia has a strong wet phase, such as the one in 2000-01.

This means we can expect more large greening events to happen again in the future. One important question is whether these will be as strong as in 2010-11 – or perhaps even stronger?

Wilder, not milder

Interestingly, by looking at continent-wide rainfall records for each significant wet period dating back to 1900, we found that Australia’s wet episodes have become significantly wetter over the past century. Given this trend, we expect that in the near future Australia’s terrestrial ecosystems will come to play a larger role in the global carbon cycle. The intensification of these wet pulses is mostly seen in central and northwestern Australia.

A wilder future with more rain during wet years will have important implications, not only for carbon uptake by plants, but also for many other important issues such as flood risk management, water rights and increased bushfire danger once the landscape dries out again. We had better keep an eye on that.

Intensification of Australia’s wet extremes since 1900s. Most of the intensification is seen in central and northwestern Australia. Ma et al. (2016)

Australian ecosystems are important locally and globally: they absorb carbon, produce food and contain huge species diversity. But these “ecosystem services” are vulnerable to climate change and the increasing frequency of extreme wet and dry events.

Knowing in detail how the landscape is likely to respond to these ever more erratic swings between wet and dry will be a crucial help in learning how we can best respond to drought and deluge in future.

So long, farewell, (for now) Australia’s “great green boom”.

Xuanlong Ma receives an Early Career Research Grant (PRO16-1358) from the University of Technology Sydney.

Alfredo Huete receives funding from The Australian Research Council, NSW-RAAP, NHMRC, TERN, and UTS.

Ben Poulter receives funding from the United States National Science Foundation, the United State Geological Society, and the National Aeronautics and Space Administration.

Derek Eamus receives funding from The Australian Research Council, Google, Hunter Water Corporation, Mid-Coast Water and UTS.

James Cleverly does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond the academic appointment above.

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Originally published in the Manchester Guardian on 9 December 1916

Surrey, December 7
Cattle coming back slowly to the homestead in the mist of early afternoon pause to browse among the clumps of furze which stud the heath all over the top of the down. These furze bushes are well out in yellow bloom; it makes almost the only charm of colour left us here. The younger cows, nosing about, tear off the budding shoots, taking little account of the prickly stems, which are not very stiff as yet. Cattle feeding in this way can, as it were, lick up whole mouthfuls at a time or select only the smaller dainties with that wonderful instrument their tongue. Reaching the stable they are more disdainful, tossing out the sour hay from the manger, sniffing over the mangold, and trampling couch grass bedding underfoot. But, dark as it may be, they recognise you when you approach with a handful of new bran.

The frost has been hard enough to make the higher land fit for carting manure over, and not too hard to stop the plough where hands have been available to drive a furrow on our stiff marl clays. These cut now almost like a cheese, hard at the outer rind and mellow where the point of the share drives in. Withal, there is more company in the birds. They are tame while the frost pinches, and are busy in their separate, small parties about the barns. A pair of blackbirds run, flirting their tails and pecking almost everywhere, seemingly regardless of whether there is anything to pick up or not. But it is very difficult to tell what is in the mind – or the eye – of a bird.

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Germany gets 12% of its electricity from wind power. Renewable energy Germany photo from www.shutterstock.com

The Australian government is reviewing our electricity market to make sure it can provide secure and reliable power in a rapidly changing world. Faced with the rise of renewable energy and limits on carbon pollution, The Conversation has asked experts what kind of future awaits the grid.

The Finkel review of the National Electricity Market is an opportunity to consider how Australia can transition its electricity system to be less carbon-intensive.

Germany’s energy transition is often held up as an incredible success story. Starting from a sector relying predominantly on fossil fuels and nuclear energy in the 1990s, renewable energy now provides about 30% of Germany’s electricity.

Germany is on track to achieve its 80% renewable target by 2050. This transformation has been the result of a range of policy measures.

The depth and breadth of these legal and regulatory reforms can provide valuable lessons for Australia.

Strong policy

Energy policy and climate policy have been expressly integrated in Germany since 2007. The government’s Energy Concept sets out Germany’s energy policy until 2050 with a strong focus on transforming the energy system.

It contains short, medium, and long-term targets for reducing greenhouse gases, increasing renewable energy, and improving energy efficiency in consumption, the building and transport sectors. While target-setting in a policy document may seem no more than a political gesture, it shows ambition and leads to political pressure for action. The policy targets for renewable energy are also binding as objectives in the German Renewable Energy Sources Act.

Notably, German legislation for the electricity industry, the Electricity Industry Act 2005, picks up on the ambition of transforming the energy system. It provides that electricity supply should not only be “cost-effective, consumer friendly and efficient”, but also “environmentally compatible” and “increasingly generated from renewable sources”. While the reference to environmental compatibility was already contained in the 1998 law, the express reference to renewables was added in 2011.

Australia, in contrast, continues to keep climate and energy policy separate. The National Electricity Objective remains narrowly-confined to achieving the reliable supply in an efficient way. Overall, Australia lacks long-term target setting, which stymies the necessary planning.

Supporting generators

Germany’s generous feed-in-tariffs (FITs) for renewable energy have been a major driver of transformation since they were first introduced in 1990. The FITs were set separately for each generation source. As a result they have funded a diverse range of renewable sources.

They also enabled the emergence of small and medium-sized renewable generators, which greatly reduced the political power of the big “gentailers” (generators and electricity retailers owned by the same companies).

Twenty-year payback periods and guaranteed dispatch for renewable energy made the FIT a major driver in Germany’s electricity transformation. They have also been a very costly way of supporting renewables.

With renewable energy now maturing, Germany is moving to increased market exposure for renewable energy through reverse auctions similar to mechanisms employed in the Australian Capital Territory.

The Australian Renewable Energy Target (RET) and state-based FITs have predominantly supported wind and rooftop solar. However, both are hampered by the lack of ambitious and long-term targets and considerable policy insecurity. Reverse auction schemes may provide a way forward to efficient support for a diverse range of renewables.

Transforming networks

A crucial part of Germany’s energy reforms is the focus on making networks more renewable-energy friendly. Germany’s renewable energy act requires network businesses (the owners of the poles and wires) to prioritise connecting renewable energy, and upgrade infrastructure where needed. This investment is overseen by the regulator.

No such mechanism for network investment to enable renewable energy exists in Australian network regulation.

German regulation now considers the whole system to strategically update electricity networks. This includes a nationwide and binding planning regime and investment into north-south interconnection. This is to help absorb the massive investment in wind generation in the north.

Network constraints are a major barrier to a 100% renewables future in Australia. Different modelling exercises for large amounts of renewable energy have been done by Beyond Zero Emissions or the Australian Energy Market Operator. Achieving these scenarios would require strategic and binding network planning across the whole of the NEM.

The Australian Energy Market Operator provides information to support efficient network planning, but actual investment decisions are in the hand of the network businesses. The network businesses continue to operate within each of the states. They invest in networks if necessary to guarantee reliable electricity supply.

There are no incentives for “greening” the network and strategically planning beyond state borders in the current regulatory framework.

Lessons for Australia

The German example is by no means a blueprint for Australia. Australia has different natural resources, existing network and generation infrastructure and the lack of neighbouring countries to connect to.

We can see though that a single instrument, be it a RET, Direct Action or a carbon price, will not be enough to enable a transformation.

Energy transitions need reform across the sector. This starts with a high level setting of ambitious, binding and long-term targets for emissions reductions and renewable energy.

It requires not only mechanisms to support generators financially, but also targeted regulation to adapt electricity networks to enable more renewables.

Reform in Germany is ongoing. There is now an impressive amount of legislation and amending legislation that deals with different aspects of the transition.

Crucially, the German government has shown willingness to go back and adapt policy instruments to changing circumstances or to address unintended consequences. Yet the overall commitment to the energy transition remains steady.

The terms of reference for the Finkel review recognise the need to integrate energy and climate policy in Australia. Hopefully it can take a more holistic view of the reforms necessary for decarbonisation of the industry.

A more detailed comparison of German and Australian reforms can be found here A Barrier for Australia’s Climate Commitments? Law, the Electricity Market and Transitioning the Stationary Electricity Sector.

Anne Kallies does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond the academic appointment above.