The Good and the Bad About Alien Eucalyptus

By RON SULLIVAN Special to the Planet
Tuesday May 11, 2004

I never thought I’d find myself writing in defense of eucalyptus, but here I am. Go ahead, quote me: Eucalyptus is not the devil. 

I speak as a hardcore native-plant fanatic—no, actually more of a native-landscape fanatic. I love native California plants for themselves alone, and certain calochortuses make me whoop and swoon, but I love them also because they’re part of the splendid world we live in here, nested in the varied food webs that supply and are supplied by all of the creatures here, from mycorrhizal fungi to mountain lions, and including, for scores of millennia, us. They make the air I breathe and filter the water I drink and they feed and inspire me; after some 30 years here, I am composed mostly of California landscape, however much of that nice imported cider and ham and smoked paprika from The Spanish Table I consume. 

I myself am not alien here in any meaningful sense. My species has long been here and shaped this landscape, brutally at times, but sometimes with such finesse and elegance that latecomers have assumed that the land was “wild” and “untouched.” One of the most brutal things we’ve done, in recent eras anyway, was the introduction of alien plants to this landscape. Eucalypts? Yes, but only among others, as a sideshow. Some of us brought in annual grasses, by accident or deliberately, and changed the very color (and flammability) of our state. It’s possible that tamarisk, with its invasive thirst, will turn out to be our worst ecological terror, west of the kudzu belt. 

But eucalypts, some dozens of species of trees imported from Australia and its neighbors, are to some the very emblem of invasive species. They’re not amiss in this calculation, but some eucs are worse than others, and few are bad for the reasons usually mentioned. 

When people here talk about eucalyptus, they usually mean Eucalyptus globulus, blue gum. It’s a bother, all right, and a conspicuous one. For one thing, it’s been planted in wildlands, whereas most other eucs are town-dwelling ornamentals. In wildlands it, like most exotics, is essentially a non-taxpaying parasite. Eucs look “healthier” here than in their home ranges because until recently there wasn’t much here that ate them. They turn a place into a near-monoculture, allowing few species to live under them and supporting even fewer. You’ll get 12 species where there should be 120. 

And they seem to be a trap to some—the estimable Rich Stallcup of the Point Reyes Bird Observatory has pointed out an apparent tendency of warblers to smother on euc goop when they feed on the sweet flowers. Aussie birds that use eucs are built differently, with their nostrils set farther up their bills to avoid the sticky stuff; probably they’ve been shaped by the trees themselves, as we all shape each other. 

So yes, they gotta go. Not because they get big or have shallow roots or drop limbs or get blown over or lift sidewalks or invade waterlines—all this happens with big trees regardless of their species. Not even because they’re flammable—native pines and bay laurels are too, and a crown fire sends torches flying no matter what’s burning. 

But eucs in wildlands, including parks, aren’t pulling their biological weight, not supporting their neighbors, and as we have less wildland this becomes more dire. So we need to remove them and replace them with native trees, or with no trees where they don’t belong. But we have to do it slowly and thoughtfully, a few at a time, because wholesale clearcutting sets loose its own demons, like landslides and sunscorch. And some local species get some value out of eucs—monarch butterflies seem to favor them, for example, and some raptors have longstanding nests in certain eucs. In some situations, if you’re a desperate bird or salamander, any tree is better than no tree. We need to remove them slowly, carefully, thoughtfully—and first we need to find out why they’re useful to anyone like those monarchs, and figure out how to supply that use. Reflexive reaction and wholesale slaughter will only compound the problems we’ve made in our clumsiness.