In dealing with Sudden Oak Death, we’re trying to limit or cope with an enormous wide-ranging biological change, the sort of thing we can’t quite map let alone stop. Its outlines are almost fractal; one complication leads to more and those to more still, and that’s true at whatever scale we see it. But fractals can be calculated, and we don’t quite have the knowledge to calculate this stuff precisely.
Scale changes our maps in a perverse way right from the start: The smaller-scale the organism that’s been introduced to a naïve population, the larger the effects will be. That’s practically a law of history. Europeans inflicted breathtakingly evil slaughter on the humans they met in the Americas, but guns and steel were outdone in killing by the germs they brought with them, long before they had a clue about microorganisms.
Similarly, we can’t stop Phytophthera ramorum by sitting in treetops or in front of bulldozers or in courts of law. As UC Environmental Science researcher Brice McPherson put it, “There’s no way to eliminate the pathogen short of a neutron bomb—if even that worked.”
We can’t protect wild trees from it or from opportunistic insects like the ambrosia beetles that are apparently making individual infections invariably fatal. They’re also making individual sick trees more dangerous to humans and other animals; their galleries, bored into damaged tree limbs, can be so quickly numerous as to make the limb fall off spontaneously. Bad news compounds bad news when the trees we’re talking about are in the parks that do double duty as wildland preserves and recreational refuges for us breakable humans.
We’re doing one thing right, at least—or at least not doing one thing we did wrong against the chestnut blight that devastated Eastern North American forests less than a century ago. Yielding to our cultural imperative to Do Something and helpless to cure beloved chestnut trees, foresters tried clearcutting a cordon sanitaire around many of the identified loci of infection. This, along with strict quarantine zones, might have worked except that spores of what we currently call Cryphonectria parasitica—a true fungus, unlike P. ramorum—traveled faster than law or loggers.
In their thoroughness, foresters leveled every chestnut they could get to in these areas, healthy-looking or not. Now we find ourselves scouring the continent for isolated remnant chestnuts in hope that these individuals were exposed to the blight but managed to resist or survive it. Biologists have been collecting seed and crossbreeding some with resistant Asian chestnuts to renew the species.
There are chestnut orchards in America now, some local to us, but the eastern forests have been changed forever. Even the oaks that replaced the chestnuts in some ways are showing problems now, partly because they’re all about the same age, an unnatural situation, a sort of temporal monoculture.
Some oaks in the hardest-hit, best-studied places in Marin County are surviving the first tide of death. Their resistance might be inheritable.
Meanwhile, redwoods are said to be sweeping into some oak-deprived places. It would be good to see that devastated species make a comeback too.