The trees are lovely, but they’re tremendous fire hazards.

When the earthquake shattered the region, a wave of refugees tumbled across the bay, looking for steadier ground, higher ground. They spread up into the hills like goats, cropping the native forests down to the bare earth, asphalt, concrete, quickboard housing; the earth shuddered in its new nudity.

Recognizing this, the government offered funding to reforest the hills, to regrow the shade that is the earliest and most durable sign of wealth in a city, to stabilize the ground, to purify the air. An arboreal gold rush resulted. Rather than replanting the oaks and pines native to the region, speculators imported eucalyptus from the other side of the world — quick-growing, fragrant, easy to harvest — figuring on a quick, sustainable cash crop financed by state money.

Didn’t pan out; the wood was worthless, even for railroad ties. Harvested, it warped and rotted quickly, but left alone, the leaves and bark shed by the still-growing trees resisted decay, lingering and drying, choking out undergrowth, colonizing the hills. The trees themselves are an arsonist’s dream, exuding a volatile sap that explodes in a fire, throwing flaming shrapnel into the undecaying litter below.

Fire has swept through these hills, and will again; a living powder keg, a triumph of the entrepreneurial spirit.