Ore., USA — Forestry management techniques used after wildfires may actually lead to worse repeat fires, say researchers who studied one of largest forest fires in recent US history.
The 2002 Biscuit Fire in southwest Oregon engulfed more than 200,000 hectares, over 18,000 of which had been burned previously, in the 1987 Silver Fire. In the three years after the Silver Fire, more than 800 hectares were logged to salvage any wood that could be sold, and the land was replanted with conifers.
“For a long time there was a perception that by salvage-logging fire-killed trees, you would be removing a lot of potential fuel for future fires,” explains Jonathan Thompson of Oregon State University. Such logging also enables commercially interesting trees such as conifers to be planted.
Using before and after satellite images from both fires, Thompson and colleagues found that areas that these “managed” areas burned more severely during the second fire than areas that had been left to regrow naturally.
This type of forest management should, therefore, not be used in an attempt to limit risk of future fires, hesays.
Conifers to blame?
The satellite data available was not sufficient to allow the team to determine whether it was the logging or the replanting that made the second fire worse in certain areas.
Salvage-logging operations can leave a lot of the higher branches on the ground where they can fuel future fires, but it is difficult to say how much of an effect this would have had 15 years, Thompson says.
He believes it is more likely that the conifers that replaced the original forest provided a homogenous fuel to the 2002 fire, causing replanted areas to burn more. Thompson notes that this could create a positive feedback, where each forest fire makes the next one worse.