Feed aggregator

Climate policy review presents clear opportunity to join host of other countries choosing a credible pathway to net zero emissions by mid-century.

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.

Proposal for 2000km sub-sea cable to export solar power from Pilbara and Kimberley to Indonesia described as financially viable, possible within decade.

The Minister has approved the retention of three species in the same category of threat in the list of threatened species.

The Minister has approved the inclusion of 14 species in various categories.

Spot prices in NSW and QLD are up 70% over a year ago, and gas prices have doubled. The idea that more gas fired generation is going to solve energy security needs in the medium term seems fairly untenable.

The Minister has approved the inclusion of 14 species in various categories.

Malcolm Turnbull joins right wing bloggers in blaming wind energy for last week's blackout. It seems renewable energy will be sacrificed as Coalition admits Direct Action is a farce, prepares the ground for a baseline and credit scheme. And more gas and more coal.

Australia is progressing towards a USstyle of policy development, with states implementing ambitious policy as they seek to reduce emissions and capitalise on investment

Independent investigation into failure of subsea electricity cable linking Tasmania to mainland Australia has returned a verdict of “cause unknown.”

Herbert Smith Freehills has advised the CEFC on its A$110 million equity investment in the Investa Commercial Property Fund.

As prime minister Malcolm Turnbull plans to meet the boss of Indian company Adani in Melbourne, anti-fossil fuel campaigners rally against the federal government proposal to lend $1bn to the company to build a rail line from the planned Carmichael coalmine to the sea

Continue reading...

The construction of a solar road in France is turning numerous heads due to the novelty value of the project. Solar experts have a different view.

Paris, Madrid, Athens, and Mexico City will ban diesel engines by 2025, mayors of the four major world cities announced this week.

Abandoned working dogs and puppies find new homes; solar power runs composting machines; and Matt Wilson is living the dream, opening his own micro brewery in Albany in WA.

Redflow Limited today announces seven more approved installers for its new ZCell energy storage solution.

Environmental water releases from Menindee Lakes to the Lower Darling river will increase over the coming week.

Away from the sound and fury around Adani’s proposed coal mine in the Galilee Basin, a tectonic shift is happening in the global energy industry.

The Government released today terms of reference for its review of climate change policies in 2017.

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.

Continue reading...