Bushfires and carbon

Wednesday 22 Jan 2020

Australia bushfires spew 2/3 of national carbon in one season - Australia's bushfires are believed to have spewed as much as two-thirds of the nation's annual carbon dioxide emissions in just the past three months, with experts warning forests may take more than 100 years to absorb what's been released so far this season.

Until recently, Australia's forests were thought to reabsorb all the carbon released in bushfires, meaning they achieved net zero emissions, but scientists say climate change is making bushfires burn more intensely and frequently.

Dr Pep Canadell, a senior research scientist for CSIRO and the executive director of the Global Carbon Project, said that meant slower regrowth rates in Australian forests between bushfires.

"We used to see hundreds of thousands of hectares burned in bushfires, but now we are seeing millions on fire," he said. "It is drying in south-east Australia, that prompts the question if these trees will be able to bring all that carbon back [into regrowth].

"We may need more than 100 years to get back to where we were, after those mature forests with beautiful tall gum trees have burned."

A 2015 landmark study lead by Murdoch University, Interval Squeeze, shows how climate change, drought and escalating fires combine to reduce forests' ability to reabsorb carbon.

One author of the study, University of Tasmania professor of pyrogeography and fire science, David Bowman, said "normally bushfires are thought of as carbon neutral" but "in very simple terms, we're seeing climate extremes carry a double punch, with more frequent fire and drought."

"Normally the forest would bounce back, but because it's been under huge drought stress, the capacity of forests to regrow is limited."

Emissions from natural causes such as bushfires are excluded from Australia's target under the Paris climate agreement to cut human-induced emissions on 2005 levels by 26 to 28 per cent by 2030.

"Climate change doesn't care where the carbon emissions come from. It's the total amount of carbon that accumulates in the atmosphere that counts," Canadell said.

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