The report from UNESCO found these sites can absorb approximately 190 million tons of carbon dioxide from the atmosphere each year — roughly half the amount of the United Kingdom’s annual fossil fuel emissions.
But in the past 20 years, many of these sites showed an increase in emissions, some even exceeded how much carbon they were removing from the atmosphere.
UNESCO researchers said two main factors are causing forests to flip from sinks to sources: climate change-fueled extreme weather events including wildfires, storm and drought; and human land-use pressures such as illegal logging, wood harvesting and agricultural practices such as livestock grazing.
Given the scale of these forests, Tales Carvalho Resende, project officer at UNESCO’s natural heritage unit and co-author of the report, says this is increasingly a global issue, meaning global action is needed.
“What the results revealed here is that it’s not necessarily an issue related to a specific country or region, but that it’s really a global issue,” Resende told CNN. “When we see where the 10 sites that have become carbon sources are, they are scattered all around the world, so the takeaway of the findings is that climate action is needed at a global level.”
From the Congo Basin to the Redwood National and State Parks, the planet’s 257 World Heritage Forests cover more than 170 million acres of land, nearly twice the size of Germany.
But the report shows that since 2000, the threats of extractive industries, environmental degradation and climate change have been reported in roughly 60% of the World Heritage sites, which have lost more than 8.6 million acres of forests, larger than the size of Belgium. Out of 10 sites they found to have flipped to carbon emitters, three are located in the United States.
The authors point out that it’s the first time researchers have quantified how the world’s forests are sequestering atmospheric carbon dioxide. Over the centuries, the World Heritage Forests have stored approximately 13 billion tons of carbon, which exceeds the total amount of carbon in Kuwait’s oil reserves.
“We can now see the important role World Heritage forests play in stabilizing the global climate,” Nancy Harris, research manager for the World Resources Institute’s Global Forest Watch and co-author of the report, told CNN. “And the truth is, we are completely undervaluing and underappreciating them.”
Most of the sites that sequester the most carbon dioxide were in tropical and temperate regions, such as South America and Australia. Although those sites are still sequestering carbon, researchers said there are signs that more of them could join the rest in becoming carbon sources.
Wildfires, in particular, have burned vast swaths of these forests in recent years. While fires are a critical part of the forest ecosystem, with many plant species relying on them to disperse their seeds, scientists say fires are intensifying which risks the potential of releasing the carbon long stored within the soil and trees.
In the last decade, warming temperatures and dry conditions have primed much of the environment for wildfires to ignite. The report pointed to several examples of significant fires that have occurred in the last decade at World Heritage sites, including in Russia’s Lake Baikal in 2016, and Australia’s Tasmanian Wilderness and Greater Blue Mountains Area in 2019 and 2020.
“We have seen some wildfires in some sites that have emitted more than 30 million megatons of CO2 — that’s more or less what Bolivia emits in from fossil fuels in one single year,” Resende said.
“One single event can actually be the emissions of a whole country,” he added. “And bear in mind, the fact that the emissions that have been accounted for in the study are only within the limitations of the sites, so this means that they represent only a small portion of fires in the broader landscape.”
The report builds on recently published maps that track the global exchange of carbon between forests and the atmosphere during the 2001 to 2020 period, using site-level monitoring to analyze the forests’ climate impacts as well as the consequences of human activities to these World Heritage sites.
“Our analysis illustrates how we can stop taking nature for granted and start putting a value on the climate benefits generated by these and other important forest sites around the world,” Harris said.
Forests play a vital role across societies. According to the International Union for Conservation of Nature, which also contributed to the report, nearly 25% of the world’s population — many in developing nations — depend on the forests for their livelihoods. Additionally, forests bring in up to $100 billion per year in goods and services. It’s also home to 80% of Earth’s land biodiversity.
The forests’ ability to prevent the climate crisis from spiraling out of control makes the threats they face all the more concerning, Resende said.
World leaders will gather in Glasgow, Scotland, next week for the UN-brokered international climate negotiations, where the focus will be on getting countries to commit to stronger fossil fuel cuts and putting an end date on coal. They will also discuss stronger commitments to protecting and restoring the planet’s forests as carbon sinks and to ultimately halt deforestation.
“We hope to really trigger climate action, to safeguard these jewels that are World Heritage sites,” said Resende. “These are laboratories for environmental changes as a whole, not only related to climate but also biodiversity. We want to facilitate dialogues with the key stakeholders to actually fund and provide some sustainable investments to these sites.”