Marin County focusing fire prevention efforts on removal of troublesome eucalyptus trees
Marin County has taken an aggressive approach to fire prevention and much of that effort has been on reducing the fuels that can turn a fire into an inferno, with special focus on one particularly dangerous type of tree.
Pick any season and eucalyptus trees are causing problems. In wet weather, they are the trees most likely to fall and cause damage, as one did across 19th Ave. in Golden Gate Park in January. And when the hot dry winds begin whipping up wildfires, the oily leaves make them go up like a Roman candle.
"Some people believe that eucalyptus trees just explode on their own, and they don't," said Mark Brown.
He has a lot of experience with the trees as executive officer for the Marin Wildfire Authority. Brown said what is often the biggest danger is not what's high up in the tree.
"You'll notice, the higher you get up, there's less bark that's on it," said Brown.
It's the bark that sloughs off and lands on the ground that acts as both kindling and a ladder fuel to send flames up into the canopy, at the same time becoming embers that are picked up by the wind. An area on a ridge above San Rafael where the trees can be found is causing the most concern.
"Our biggest concern is, on a Diablo wind day, that we get a fire within that grove and eucalyptus trees can cause huge embers up in the air, and they can go miles downwind," said Brown. "And we literally have a fire that happens in San Rafael, have those embers get lofted into the air and get sent to San Anselmo. Or the far side of San Anselmo and start burning through the Mt. Tam watershed."
Marin County has approved an aggressive plan to reduce the danger. They will begin removing any eucalyptus trees that are 10 inches in diameter or less in a 150-acre area, as well as cleaning out the area underneath. That will leave only the larger trees with higher canopies, reducing the risk of ignition.
"It's a much more aggressive approach than a shaded fuel break," said Brown. "However, with the number of large diameter eucalyptus trees that we are going to leave, there will still be shade in that area. But we're also going to allow some of the native trees to regrow in that area."
But eucalyptus trees don't go quietly. Chop one down and new trees start growing from the stump. So, after each tree is removed, the remaining stump must be brushed with an herbicide to prevent re-growth.
"Eucalyptus trees are ground-sprouting trees, so when you start removing them, if you don't treat them with herbicides, you are just going to simply be having even more trees replacing trees that you removed," Brown said.
The project will begin in a few months but could take several years to complete. It's estimated that more than 16,000 trees will be removed in the operation. Eucalyptus were brought to the region because they grew fast and spread quickly. It seemed like a good idea at the time.
But Marin County is now dealing with a problem that took root more than a century ago.