A new study analysing the carbon budget of global forests over the past 30 years has revealed critical insights into carbon storage and sinks, with Australian levels emerging as a significant negative outlier.
The findings, published in Nature, were led by Dr Yude Pan, from USDA Forest Service, Northern Research Station in the United States.
Dr Heather Keith, from Griffith University's Climate Action Beacon, was the only Australian author on the global study of forest carbon levels and contributed national data for Australia and interpretation in the global context.
"While our findings highlighted that the total global forest sink is being maintained over decades and removing from the atmosphere nearly half of fossil fuel emissions, we found a troubling trend of deforestation and forest degradation that are causing emissions. The sink is vulnerable if these activities continue, combined with climate-induced disturbances such as drought, insect outbreaks and wildfire," Dr Keith said.
" Australia is emerging as a significant negative outlier as forest areas and carbon stocks have declined. In the 1990s and 2000s, Australia's deforestation and forest degradation were major sources of carbon emissions. By 2010, legislative changes slightly mitigated this, but the damage continues."
Dr Heather Keith
Key findings from the study include:
- The world's forests declined in area by 5% from 1990 to 2020, equating to a loss of 210 million hectares.
- Global forest carbon stock decreased by 5% in the same period, primarily due to losses in tropical forests.
- The global forest carbon sink, crucial for absorbing some of the elevated carbon dioxide in the atmosphere, remains significant but varies across biomes, with notable decreases in boreal and tropical intact forests.
- The total global forest sink, which sequestered 107 petagrams of carbon from 1990 to 2019, was equal to nearly half of fossil fuel emissions. However, tropical deforestation caused the emission of 67 petagrams of carbon and thus negated two-thirds of the sink benefit.
In Australia, extensive deforestation for agriculture has been a major driver of carbon emissions. While legislative measures have slowed land clearing in recent years, deforestation and degradation remained substantial issues.
Additionally, the harvesting of native, high-carbon-density forests and their replacement with lower-carbon-density regrowth forests further exacerbated carbon loss. Intensified droughts and wildfires in the 2000s and 2010s also contributed to increased emissions.
Dr Keith said Australia had found itself in the unusual position as a developed country still engaged in significant deforestation and conversion of natural forests.
"It's devastating to see old native forests, home to trees hundreds of years old and a myriad of dependent flora and fauna, being logged in states like Tasmania and New South Wales."
Dr Heather Keith
The study authors also stressed the urgency of implementing effective land management policies for climate mitigation.
"Protecting carbon stocks in forests and all ecosystems and reducing emissions from fossil fuels are essential steps in combating the climate crisis," Dr Keith said.
"These findings underscore the vital role of forests in moderating climate change and the need for continued efforts to restore and protect these crucial ecosystems."
The study 'The enduring world forest carbon sink' has been published in Nature.
