Forest regeneration projects used to offset carbon emissions are having "negative or negligible" effects in Australia, new research from the Australian National University has found.
The projects can be assigned carbon credits under the federal government's offset scheme, now known as the Safeguard Mechanism.
Companies which emit more than 100,000 tonnes of carbon dioxide a year can then purchase carbon credits to offset their emissions. Each credit represents one tonne of carbon dioxide.
Forest regeneration projects are the most popular type of project covered under Australia's offset scheme, receiving 37 million credits as of June 2023.
The regeneration projects can include reducing pressure from livestock and feral animals, managing non-native plants and cessation of clearing native plant regrowth.
The ANU research studied 182 such projects between 2013 and 2022, mostly located in dry outback areas in Queensland, New South Wales and Western Australia.
The research was conducted in partnership with Haizea Analytics, University of New South Wales and the University of Queensland.
Researchers analysed the extent of increase in forest cover and woody cover, but found expected changes had not occurred.
'Over-credited and largely failing'
One of the report's authors, ANU Professor Andrew Macintosh, said the results indicated these projects have been "substantially over-credited and are largely failing".
"The projects in the study received more than 27 million credits over the period of analysis and most of them claim regeneration started around 2010 to 2014," Professor Macintosh said.
"Due to this, their effects on woody vegetation cover should be very clear.
"But the data suggest tree cover has barely increased at all and, in many cases, it has gone backwards"
Almost 80 per cent of the analysed projects showed negative or negligible change in tree cover over the period.
Across the entire credited area - 3.4 million hectares - areas with so-called woody cover (either forest or sparse cover) increased by 0.8 per cent.
ANU Professor Don Butler, who led the statistical analysis in the study, said the results suggested changes in vegetation cover were not necessarily linked to regeneration efforts.
"The results suggest the observed changes in woody vegetation cover are predominantly attributable to factors other than the project activities, most likely rainfall," he said.
The researchers say one of the key issues with the regeneration projects is that carbon sequestration is modelled, rather than directly measured.
Carbon sequestration is the process of capturing and removing carbon dioxide from the Earth's atmosphere.
UNSW Canberra's Dr Megan Evans said relying on these projects for carbon offsets could exacerbate climate change.
"Where carbon credits are issued to projects that do not sequester as much carbon as they are supposed to, it makes climate change worse - credits from low integrity projects facilitate increases in emissions but the increases are not offset by reductions elsewhere."
