At first glance, the conditions were ideal. It was warm, rain would not have disturbed the party guests. But that was exactly the problem: In many communities in Germany, the Easter bonfires were canceled last weekend. The reason for this was the high forest fire risk.
The situation in many parts of the country is already worrying, although the summer has not yet begun: The Ministry of the Environment in Brandenburg has declared the highest forest fire warning level 5 nationwide. In the north of Saxony, some forests may not be entered for the time being because of the sometimes very high forest fire danger. Up to and including Easter, the region fell on average just 2.1 liters of precipitation per square meter. The long-term average for April is 58.4 liters. Shortly after Easter, the first fires broke out.
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Stage 5 of 5: Threatening forest fires in German forestsIf you look at the website of the German Weather Service (DWD) currently has a look at the forest fire index, then it is especially in northeastern Germany on the highest warning level five: In addition to Brandenburg is the south of Mecklenburg-Western Pomerania, northern Saxony, the east of Saxony-Anhalt and the region around the Lower Saxon Celle very much at risk. The second highest warning level prevails, among others, in parts of Bavaria and Baden-Württemberg.
In Thuringia, the soil is already drier than in July 2018
The index is calculated among other things from the air temperature, the humidity, the wind speed and the precipitation amount. And he is just a snapshot, explains the meteorologist Andreas Brömser of the DWD. At most four days one could look so into the future. "From the currently low soil moisture values, one can not conclude which forest fire danger we will have in the summer," says expert Brömser.
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But already now it is clear: In many regions of Germany the soils are at least currently much drier than on average. According to DWD calculations, the soil moisture levels in April of this year were even lower than those of 2018. "If the dry weather continues in the coming months, the drought of 2018 could be repeated or even exceeded," warns the agricultural meteorologist Udo Busch ,
In this case, farmers would have to fear yield losses again. In addition, this year could also be affected forests and plants with roots that can actually tap the moisture in deeper soil layers. Because even there, the stores are much less well supplied than in the previous year. Due to the lush rainfall in the autumn and winter of 2017/2018, at least these reservoirs were still well filled a year ago. That's over now.
The DWD calculates that although in Germany in the months of December 2018 and January and March 2019 more precipitation than usual has fallen. The sometimes extreme precipitation deficit from last year is not yet balanced in many regions.
Forest fire hazard index of the German Weather Service for the 25.4.2019
Geobasisdaten Federal Agency for Cartography and Geodesy - DWD
In Thuringia, soil moisture under the grass is already as low as in the drought summer 2018 in mid-July, according to the meteorologists. Even assuming that there is a lot of rain from now on, the soil moisture in Thuringia and Saxony-Anhalt would still be well below the long-term average until the summer, according to the DWD.
"Increasing the risk of forest fires"
The forestry operation of the state of Lower Saxony warns that the risk of forest fires is still a little higher this year than in the previous year. "Cause are the dry plant remains of the past year," said spokesman Mathias Aßmann.
"The specific forest fire risk at a given location depends on a large number of factors that are also interdependent," says forestry scientist Christopher Reyer of the Potsdam Institute for Climate Impact Research (PIK). In 2017, together with other scientists, he published an overview of forest fire causes in the journal Nature Climate Change.
In it, the scientists are investigating how a combination of drought, fire, wind, insects and fungal infestation increasingly causes problems for many forests on earth. The correlations in the forest fire risk are not always easy to see. In some cases, a great drought can even reduce the risk of forest fires - because fewer plants can grow between the trees and the flames spread so poorly.
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However, the basic message of the researchers is unequivocal: "If climate change makes it drier and warmer, we expect an overall increase in the incidence and risk of forest fires," warns Reyer.
Fire Brigade Association calls for more fire-fighting helicopters
What the long-term, large-scale trend for a specific forest area means, that can not be said. If everything goes well and the people in the region act responsibly, a time of high forest fire risk may well pass by without a fire breaking out.
For safety's sake, the German Fire Brigade Association demands more fire-fighting helicopters for Germany. Helicopters with external load containers are useful for firefighting, said federation president Hartmut Ziebs the "new Osnabrücker newspaper". "This is a common practice, but sometimes fails due to the number of helicopters available." According to his statements, the largest water tanks hold 5,000 liters and can only be flown by helicopters of the Bundeswehr type CH-53. "But they are not always available - here the Bundeswehr would have to hold a few more helicopters," said Ziebs.
At least in the short term, the forest fire situation in parts of Germany should relax for the coming weekend, says the DWD. On Friday, the temperatures would drop in many places, until next Monday, then also be expected with rainfall - although so far no one could say, where exactly fell.
New sensor is intended to improve alarm
About 5 to 15 liters per square meter are to be expected on average. "This temporarily moistens the vegetation and reduces the risk of fire," says meteorologist Brömser. "But when it's sunny again, it evaporates after two or three days."
Soon a new type of forest fire sensor developed at the Humboldt University Berlin could also help. He should strike already if no smoke is visible. The system searches for hydrogen in the air after the gas, which is already formed in the early phase of a smoldering fire.
The sensor is not yet commercially available, according to the researchers, but he has already passed practical tests. Sometimes it may just be necessary to detect broken forest fires early. To then delete them as quickly as possible.