Putting blue gums in their place


Your article on the invasive Tasmanian blue gum on the California coast was well-written and carefully researched ("Beauty or Beast?" HCN, 12/23/13). However, it fell into a common journalistic trap: "A says this; on the other hand, B says this." This journalistic "fairness" doesn't illuminate the subject.

I am smitten by the genus Eucalyptus. I traveled to Australia in 1977 specifically to see the trees in the wild. I am still deeply in love with the genus and with this particular species, and have urged the San Francisco Recreation and Parks Department to plant more of them in our developed parks, where they won't create problems.

What is missing from your article is the all-important question of the damage done to natural systems, and the reason why biologists and others are so troubled by invasive species. A source in your story says that blue gums "are now part of our ecosystem and causing us to redefine the word native." No, they aren't. The term native does have meaning. It means that the plant has been part of an intricate and complex web of animals, plants, pathogens, fungi, bacteria and microorganisms for a very long time – one in which the rules of coexistence have been thoroughly worked out. Such communities are stable, orderly and diverse.

Introduce a novel organism, and you may be asking for problems. The natural controls in its native ecosystem do not exist in this new place. The critters that depend on the indigenous plants are unable to handle the chemical defenses of the new plant and leave it alone. The plant has no predators, nothing sucking its energy and passing that energy up the food chain, as native organisms do. The energy the new plant captures from the sun goes instead into proliferation, overwhelming indigenous plants and destabilizing the system. It is not just a matter of aesthetic preference.

And then there's water, an important issue in the West. Mussolini used the Tasmanian blue gum to drain the Pontine Marshes south of Rome. It is used around the world for draining wetlands. As for the monarch butterfly, what did it do before the blue gum was introduced in the 1850s? Insects are opportunists and adapt themselves to whatever is available; eucalyptus are not essential to the monarch's survival. There are many reasons for the butterfly's decline.

Jake Sigg
San Francisco, California