Beetle attacks on dead wood could boost the amount of carbon released during wildfires.
鈥淭he beetles do make a difference,鈥� says at Vrije Universiteit Amsterdam in the Netherlands.
Researchers already knew that, by killing trees, insect infestations in forests can alter the risk of wildfires. Many species of beetles and other insects also eat downed trees on the forest floor, leaving tracks and holes in the wood. This can make it decompose more quickly, releasing carbon into the atmosphere. But it wasn鈥檛 clear how these insect holes affected the way the dead wood burns.
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Cornelissen and his colleagues drilled holes into logs from two common European tree species, mimicking the number and size of cavities left by bark beetles in real logs in a forest. They then ignited the logs in a fire chamber.
Because the beetle holes ventilated the wood, the logs with this damage burned significantly longer and smouldered more than intact ones, the researchers found. This caused more of the wood to burn, releasing more carbon monoxide and carbon dioxide. The logs with holes were also easier to ignite.
The experiment provides evidence that insect outbreaks can affect wildfires not only by killing trees, but also by changing the flammable properties of wood in a forest, says Cornelissen. 鈥淐oarse wood doesn鈥檛 burn completely very often.鈥�
However, he says it is too early to quantify how this beetle-hole effect would change emissions in a real wildfire. For instance, beetle holes in standing trees could have different consequences to those in downed wood.
As well as beetles, the researchers are studying other ways biological variables 鈥� alongside factors like drought and temperature 鈥� can influence the flammability of forests.
For instance, they found that a can make dead trees more flammable by hollowing them out. Even woodpeckers could have an effect. 鈥淭hey make big holes,鈥� says Cornelissen.
Ecology
