Large numbers of trees have died in the Harz mountains, Germany, due to extreme weather and bark beetles
Rob Cousins/Alamy
A sudden and dramatic decline in the amount of carbon being soaked up by European forests is causing alarm among scientists, with fears that the sharp downturn could undermine efforts to curb global warming.
For decades, Europe’s forests – which cover around 40 per cent of the continent’s land area – have been relied on as a source of timber and as a sink for carbon emissions. But that picture is rapidly changing as extreme weather pushes forests to the limits of their endurance.
“Many [European Union] countries will miss their [land use climate] targets because of this drop in the sink,” says Glen Peters at the CICERO Center for International Climate Research in Norway.
In January, authorities in Finland announced that the country’s forest biome has flipped from being a net sink for carbon to become a net source. The news came just a few months after Germany admitted that its forests are now a net source of carbon emissions, for the first time in the country’s history. Meanwhile, in the Czech Republic, forests have been a net source of carbon emissions since 2018.
These are just the most extreme cases. In other countries, the annual carbon drawdown of forests is rapidly declining, even if, overall, they remain a net sink for emissions. In France, for example, the amount of carbon removed by forests has almost halved in just 14 years, from a 2008 peak of 74.1 million tonnes of carbon dioxide per year to 37.8 million tonnes in 2022, according to research published last month. In Norway, forest removal of CO2 dropped from 32 million tonnes in 2010 to 18 million tonnes in 2022.
“The general trend was quite stable until about 2013-2015-ish, where we see a clear start of the decline of the [forest] sink,” says Anu Korosuo at the European Commission’s Joint Research Centre in Belgium. “It is quite a general trend. It’s not just because of one or two countries – we can see a similar trend in basically all countries that have forests.”
Much of Europe’s forested land is privately owned and managed commercially. Some of the decline in the sink is attributed to an increase in harvesting, particularly in the aftermath of Russia’s invasion of Ukraine in 2022 and the subsequent sanctions applied to Russian timber imports into the EU. In Finland, for example, “the driver is demand for timber and a high level of harvest”, says Raisa Mäkipää from the Natural Resources Institute Finland.
But in other parts of the continent, scientists point to escalating climate impacts as the main reason for the sudden downturn in carbon storage.
Swathes of Europe have been struck by several droughts in recent years, including severe ones in 2018 and 2022, points out Wouter Peters at Wageningen University in the Netherlands. His research shows that the 2022 drought triggered a sharp decline in carbon uptake by European forests over the summer months. “We are seeing the instantaneous effects. The trees are stressed,” he says.
Even though researchers expected some decline in the European forest sink as the world warms, the scale of the recent downturn has still come as a surprise. Researchers didn’t think the sink would decline so sharply at this level of warming, says Wouter Peters. “The impact seems to be larger than we expected.”
That could be down to the compound effects of repeated droughts occurring in the space of just a few years, alongside other extreme events such as storms that can also wreak havoc in forests. “You don’t just have the 2018 drought, but then one in 2021 and another one in 2022,” says Wouter Peters. “Our models were not very good at doing the sum of all of them in such a short period.”
Rising temperatures are also driving more frequent and widespread bark beetle outbreaks across Europe, causing huge damage in spruce forests. In the Czech Republic, one of the hardest-hit countries, there have been seven major outbreaks of bark beetles between 2018 and 2021.
A waning forest carbon sink threatens the EU’s climate goals, which rely on trees to absorb a large portion of ongoing emissions from other sectors of the economy. The EU has even been planning to expand this carbon sink to help in the push towards its climate ambitions, aiming for land and forests to remove 310 million tonnes of CO2-equivalent per year in 2030, up from about 230 million tonnes of removals in 2021.
But according to analysis published in April, Europe’s forest carbon sink is expected to fall short of the 2030 goal by about 29 per cent, with the researchers warning that the capacity of Europe’s forests to remove carbon is “progressively deteriorating”.
There are actions that can be taken to stem the decline. Reducing harvest rates, for example, and banning the clear cutting of plantations, would help to preserve carbon stocks. Meanwhile, diversifying tree species and leaving some deadwood in forests can improve the health of woodlands, making them more resilient to pests and droughts.
But Wouter Peters says policy-makers are overestimating the amount of carbon that forests can absorb in a warming climate. “For greenhouse gas emissions specifically, our reliance on forests was probably overoptimistic,” he says. To deliver on Europe’s climate goals, other sectors of the economy will need to cut emissions more rapidly, he argues. “It means we will have to step up in other areas.”
Levels of carbon dioxide in the atmosphere are now rising at the fastest rate in history, despite an overall plateauing of greenhouse gas emissions. Scientists blame this acceleration on the weakening of the global land sink, with forests, wetlands and peatlands around the world absorbing carbon at a slower rate than expected, in part due to deforestation, increased emissions from wildfires, and drought.
The problem is most acute in the mid-latitudes. Alongside Europe, boreal forests in Alaska and Canada have also registered a significant decline in their carbon sink capacity. But tropical forests have seen a decline in their carbon-storing capacity too, largely due to deforestation and wildfires.
That is a worry for the world’s plans to reach net-zero emissions. “In the big global picture, the whole concept of net zero works around forests and ocean taking up a lot of carbon,” says Glen Peters at CICERO Center for International Climate Research in Norway. “If they start to stop taking up the carbon, then that means more of it stays in the atmosphere, and global warming would accelerate.”
Topics: