The fires have doubled Australia’s carbon emissions – ecosystems may never absorb them

The bushfire season is once again underway in Australia, where summer has just started. Yet the country is still recovering from the record-breaking wildfires of two years ago that killed at least 33 people, destroyed thousands of homes and burned more than 65,000 square miles of land.

How quickly the natural landscape recovers depends on the climate for years to come. It may take a few decades under average conditions. But if the weather remains hot and dry, and more extreme forest fires occur in the meantime, the ecosystem may never return to normal.

This is what should be remembered from a to study published last month in AGU advances who examined the impact of record-breaking fires on Australia’s carbon cycle.

These fires likely released around 186 million tonnes of carbon into the atmosphere, research shows. That’s a staggering amount, more than the entire country emits in a typical year by burning fossil fuels.

Normally, it would probably take about 20 years for the landscape to absorb all of this carbon again, as trees and other plants gradually begin to regrow. But climate change poses a problem: The weather in Australia is getting hotter and hotter and the risk of drought is increasing.

It could slow things down, potentially indefinitely.

“It’s getting hotter and drier, so it may take longer to recover from the fires. Plus, you have more fires, ”said Brendan Byrne, postdoctoral researcher at NASA’s Jet Propulsion Laboratory and lead author of the new study. “It is a concern that we are causing permanent carbon losses in these areas. “

Under typical conditions, Australia’s forests and grasslands act as a carbon sink: they absorb carbon dioxide from the atmosphere and store it. This makes it a valuable climate resource. On the other hand, when these landscapes are stressed or damaged, they can release carbon into the air.

Byrne and the other researchers, from institutions in the United States, Australia and New Zealand, examined the impact of drought and wildfires on the Australian ecosystem during the 2019-2020 bushfire season. . They conducted the study using satellite observations, which monitor the concentrations of carbon dioxide and other greenhouse gases in the atmosphere.

The study found that bushfires more than doubled Australia’s annual carbon footprint.

In a typical year, Australia emits around 104 million metric tonnes of carbon by burning fossil fuels. The 2019 and 2020 fires, along with the additional effects of the drought, added an additional 186 million tonnes.

This matches estimates from other research.

Since the peak season, several other studies have attempted to quantify the amount of carbon produced by bushfires. Some of them used different methods: they looked at the total amount of land burned by the fires, and then estimated the emissions based on that area burned. Yet they came to similar conclusions.

The fact that these bottom-up estimates largely agree with top-down estimates produced by satellite observations means scientists now have “quite a bit of confidence in what those emissions really were,” Byrne said.

Byrne and his colleagues also examined how the Australian landscape is recovering under different conditions.

When forest areas are hit by drought, they tend to lose carbon. But when the weather turns cooler and wetter again, they tend to rebound quickly. Areas that have been burnt by forest fires, on the other hand, recover much more slowly from drought.

This means that drought and fire can compromise the earth’s ability to absorb carbon from the atmosphere. And global warming increases the chances of both.

Based on their observations, the researchers estimate that it would take around 21 years for the Australian ecosystem to absorb all the carbon it lost in the 2019-2020 bushfires. It is in average conditions. In a cooler, wetter climate this could be done in about a decade.

On the other hand, if the climate becomes hotter and drier, some of that carbon may never be recovered. This is especially likely if more and more forest fires interrupt the recovery process.

The study highlights several growing concerns among scientists regarding climate change and natural ecosystems. As parts of the Earth heat up, dry out and burn more easily, they can emit more and more carbon into the atmosphere. This could further accelerate the rate of global warming.

Satellite studies are one way to keep tabs on these kinds of events, Byrne noted.

At the same time, as the Earth continues to warm, some landscapes can be drastically and irreversibly changed.

“It’s something that people really worry about – you end up in kind of a transition to a different kind of ecosystem,” Byrne said. “That’s the kind of real concern in this area.”

Reprinted from E&E News with permission from POLITICO, LLC. Copyright 2022. E&E News provides essential information for energy and environmental professionals.