https://www.crikey.com.au/2025/03/12/carbon-credits-australia-human-induced-regeneration-accus/

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With the corporate sector increasingly sceptical of Australia’s carbon credit system and rumours that the government’s Climate Active voluntary credits scheme will be shut down, in February the Clean Energy Regulator (CER) — the body charged with overseeing Australia’s carbon credit system, issued a remarkable paper.

Designed to provide assurance that carbon credits based on “human-induced regeneration” (HIR) carbon sequestration projects — which are crucial to Labor’s underwhelming climate action policies — were credible, it purported to show how “projects registered under the HIR method earn carbon credits based on the sequestration of carbon in native vegetation. It provides an overview of the robust framework for large-scale sequestration throughout Australia”.

As we know from a wide range of scientists and experts in the administration of HIR schemes, the framework is anything but robust. In fact, it is almost entirely at odds with the basic science of vegetation regeneration.

The arguments made in the paper, which have been scrutinised by Andrew Macintosh, Megan Evans, Don Butler, Marie Waschka and Dean Ansell of ANU and UNSW, raise concerns that the Clean Energy Regulator — which has a history of attacking scientists who question its claims — continues to ignore science in favour of propping up a scheme crucial to Labor’s efforts to pretend it is serious about climate action.

In particular, the CER continues to push the claim that forms the illusory basis of around 95% of HIR projects — that stopping animals grazing on land allows plants to regenerate into woody vegetation, thereby storing carbon. The scientific consensus is that this is simply not true — it is the amount of rainfall that determines regrowth, not ceasing grazing. That means that the great majority of HIR projects are simply never going to do what their owners are being paid for, and the resulting Australian carbon credit units (ACCUs) are worthless in terms of stored carbon.

As Crikey detailed in 2023, the CER has fought a bitter battle against the science — including misrepresenting experts as backing the CER’s view. In documents released under freedom of information laws, we know that the CSIRO told Labor’s Chubb review of the integrity of ACCUs that “there is at present no clear evidence that changes in management of total grazing pressure will consistently result in an increase in carbon stocks in woody biomass across all regions of Australia’s rangelands”, before the CER demanded the document be edited.

As Macintosh and his colleagues note, the CER has since modified its position slightly but still defies science. In its February tract, it says “although many factors affect regeneration, the most important factor in sustaining the growth of vegetation following rainfall events is the nature, extent, intensity and duration of activities that suppress the growth of native vegetation”.

This is demonstrably false. As the Wentworth Group of Scientists told Chubb:

Most HIR projects have, however, been directed to arid and semi-arid regions where vegetation has never been cleared. In these boom or bust systems, rainfall is the key driver of vegetation change, and drives both increases and decreases in biomass. While reducing grazing pressure can result in increased tree and shrub cover in these landscapes, from a carbon sequestration perspective this effect is small relative to cyclical climatic drivers.

But the CER continues to reject the science. In its February paper, it claims “a 2021 analysis by Beare and Chambers found strong evidence that established HIR projects have resulted in significant increases in vegetation when compared with a business-as-usual scenario in a study of projects in New South Wales and Queensland.”

But what did the Beare and Chambers analysis, which examined 72 HIR projects in NSW and 51 in Queensland, actually show? It revealed a statistically significant increase in cover compared to control areas, but the actual increase itself was small, well below the levels for which the projects have been credited — and in nearly a quarter of projects there was no change, or vegetation actually reduced.

Moreover, the analysis relied on a dataset that the CER had itself previously dismissed as too inaccurate to assess projects, when Macintosh and co used the same dataset to show minimal increase in tree cover. There’s a similar inconsistency in the CER’s citation in the paper of a report by Dr Chris Brack as evidence that HIR works, when it too relies on satellite imagery-based data which the CER dismisses when it is used by critics.

The CER tries to resolve this contradiction in the latest paper by claiming “national-scale data sets may be useful to monitor the performance of the whole portfolio of projects once it matures to forest”. Presumably only if the CER likes the results.

Further evidence has emerged about the failure of HIR over the last year. A review by the ANU/UNSW experts assessed 116 HIR projects that had been established before 2017, which should have had substantial regeneration of woody vegetation by now. The study revealed the great majority of projects were not even compliant with the baseline requirements for generating carbon credits, such as having previously been comprehensively cleared, or with progressive requirements relating to revegetation.

And given the length of time after project registration, well over half of the projects should have had near-100% forest cover, but in reality only a small number had anything like the cover suggested by the amount of sequestration for which the projects had been credited. And changes in vegetation were heavily responsive to climatic events such as El Ninos and La Ninas.

The study concludes:

While some projects appear to have had a positive additional effect on canopy cover, even for these projects, the effects are small relative to the levels of credited sequestration and there is limited evidence of material regeneration. At the aggregate level, across all projects in the sample, the data suggest the projects have had only a small effect on canopy cover, with most of the change being attributable to seasonal variability in rainfall.

That is, the observed results are consistent with what the science has told us to expect: HIR works only at the margins. ACCUs based on HIR projects remain an expensive con.

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