Just like many other countries and regions around the world, Germany has been affected seriously by wildfires in recent years.

2022 was particularly bad for the country. Authorities registered over 2,300 fires, which made it the year with the second-largest area of burned forest since officials began gathering statistics in the late 1970s.

A big question is why those areas burned in the first place. Were fires caused by nature or was a person involved?

Authorities often left empty handed

In Germany, only a tiny fraction of wildfires are caused by natural phenomena such as lightning.

Most fires where the origin is known are created by people. The cause can be identified as negligence if a person didn't take proper care, or as arson if he or she acted deliberately.

And in certain situations (categorized as "other causes" in the graph), authorities do not necessarily assume negligence: this can be the case when sparks are created while a person uses forestry machinery, or when there's ignition by ammunition on a military training area.

But differentiating between these causes is tricky. Finding potential culprits and substantial evidence to determine whether fires were started deliberately is a significant challenge.

Authorities are often left empty handed and the cause remains unclear.

As a recent investigation by German newspaper Die Zeit revealed, "police hardly ever find the perpetrators. The crime scenes are isolated, clear traces and witnesses are rare. By the time the fire is discovered, the perpetrators are often in a safe place."

Nevertheless, official statistics say around 20% of wildfires last year in Germany were caused by arson. And 36% of all burned land was set on fire on purpose.

So how exactly do officials compile these statistics, especially if it's so difficult to determine the cause? And how reliable are they in the end?

Searching for clues

One person who can help answer these questions is Knut Sierk. He works at the forestry in the German state of Lower Saxony and is involved in wildfire prevention.

He tells DW that a key part of the investigation is determining where the fire began. Finding a tree that was hit by lightning would point to a natural cause. Finding the origin near a street could hint towards a burning cigarette that was thrown out of a car window.

If, however, the beginning of the fire was in the middle of a forest, in a place not frequented by walkers, then investigators could look into possible arson.

"Every fire is looked at very meticulously to determine what happened and what triggered it," Sierk says.

Other clues that could be relevant, especially to determine possible deliberate action, include witnesses that may speak to authorities or any unusual objects that were left behind.

"It could be a half-burnt petrol container that is still lying in the fire area. It may be dry shrubbery that has been piled up, or the remains of a candle," he explains.

But Sierk, as well as other experts contacted by DW, agree that finding these objects is very uncommon.

"It's not the rule, these are exceptional cases," says Ulrich Cimolino, wildfire expert at Germany's Fire Protection Association.

Potential cases of arson

But despite these difficulties, some recent cases have given insights into how authorities deal with potential cases of arson.

In one notorious example, four people are being investigated for possibly causing a large fire last year in Germany's Saxon Switzerland National Park, in the eastern part of the country, which affected around 2,500 square meters (26,910 square feet).

The four people were apparently using shisha pipes in the park, and one of them has been charged with intentional arson for throwing three pieces of charcoal down a slope.

The other three have been charged with negligent arson by ommision because, for example, they left the national park without calling for help.

Another case, in the nearby state of Brandenburg, one of the most affected regions in Germany, has also garnered some attention. Two people are in court for allegedly having burned 20,000 square meters because they wanted to have "some action."

Authorities were able to link them to the wildfires only after they stopped one of the men during a drug control, realized he had soot in his hands and asked him about the wildfires. He confessed and incriminated the second person.

They could be sentenced to up to four years in prison.

Stats are not always reliable

Cases like these may end up in the statistics that are collated by Germany's Federal Office for Agriculture and Food . 

Stefan Stegemann is responsible for these statistics and explains his team receives the basic information from each German state.

"We collect and bundle the data in a way that you get a nationwide overview," he tells DW. "But we do not interpret the data."

The problem, according to experts, is that each German region can have different ways of categorizing causes and collecting information.

And this essentially means that statistics on wildfire causes are not always considered to be reliable.

Ulrich Cimolino, from the Fire Protection Association, says these regional differences contribute to fire-cause statistics being a "nationwide problem that has been going on for decades."

And he adds: "You can use them as an estimate, but no more."

Cimolino concludes that having more reliable information on what caused a wildfire is important.

"If we knew the causes more precisely, we could try to better inform the population in preparation and hazard prevention," he stresses.

Edited by: Ines Eisele

A previous version of this article confused square meters with square kilometers. This has been corrected on August 28, 2023. We apologize for the error.

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