California Wild Winter 2005 - Letters to the Editor

The Magazine of the CALIFORNIA ACADEMY OF SCIENCES

Letters to the Editor

Good Gum Trees

Thanks so much for Gordy Slack's spirited defense of the eucalyptus in his article "Monarchs Hail the Eucalyptus" (Summer 2004). This isn't the first time that he has reminded our community of amateur scientists that evolution marches on, as he did in "Evolution in the Park" last year.

The eucalyptus also serves many species of birds that would not otherwise be here in San Francisco. The raptors, herons, and cormorants nest in and hunt from them. The hummingbirds feed in them during winter months when they are one of few sources of nectar. The trees that are native to San Francisco do not provide either amenity. There were few trees native to San Francisco and those that survived our harsh conditions were more accurately described as shrubs.

The eucalyptus is also our greatest protection against the wind. Joe McBride, the certified arborist who did the wind study for the Presidio, reports in that study that the eucalyptus is the strongest of the "big three" in our windbreak (also Monterey cypress and pine). Many of our most valuable landscapes would not exist without the protection of that windbreak, including Golden Gate Park and the Presidio.

Your readers may be interested in an article by Arthur Shapiro, Professor of Ecology at UC Davis about butterflies native to California: "The California butterfly is dependent upon alien plants," (Diversity and Distribution, 2002, 8, 31-40). The monarch is only one of many examples of insects that have adapted to introduced plants. Shapiro reports that many of our native butterflies have adapted to introduced plants and some are now dependent upon them. Since many introduced plants are productive year around, we shouldn't be surprised that insects would find them more reliable hosts than the natives that are dormant during the dry season.

I also recommend the recently published Invasion Biology: Critique of a Pseudoscience by David Theodoropoulos (Avvar Books, 2003) as a resource on this topic. He confronts many claims that introduced species are invasive and carefully dismantles them. He makes a strong case for the positive contributions made by introduced plants to greater biodiversity.

Mary McAllister
San Francisco, California

Academy Connection

I am writing in regards to the article in California Wild (Fall 2004) entitled "Return of the Native Oyster." I am a former curatorial assistant at the Academy where I worked on the SFBay:2K survey headed by Dr. Rich Mooi. I think it is unfortunate that the aforementioned article made absolutely no mention of the work that has been done (and is still being done) by Academy researchers in regards to the native oyster. There are large amounts of historic and current data regarding its distribution in the San Francisco Estuary stored right in the Academy's own collections. In addition, we have shared this information directly with graduate students working for Mike McGowan, who was quoted several times throughout the article. Much of their data and information came directly from the SFBay:2K project.

I think a tremendous opportunity was missed to tout a very important bit of research being conducted in the magazine's own building.

Chris Brown
Marine Invasions Research Lab
Tiburon, California

Traces of Technetium

Jerold Lowenstein writes (Fall 2004, p. 48) that "After about ten half-lives... virtually nothing is left of the original material." In fact, after ten half-lifes, the quantity of an isotope has been reduced by a factor of 1024. Whether the resulting amount is "virtually nothing" or not depends entirely on the amount that was present to begin with. If there was a kilogram, there is only a gram left. If there was 1,000,000 kg to begin with, there is 1,000 kg, or half a tonne. Etc.

Regards to an otherwise fantastic magazine.

Steven S. Muchnick
San Francisco, California

Jerold Lowenstein responds: It's a rule of thumb in nuclear medicine that an isotope is gone for all practical purposes after ten half-lives, even though a tiny amount remains, as Muchnick reminds us. In the case of technetium, the longest half-life is 4.2 million years, which, divided into the 4.6 billion year age of the earth, means that it underwent 1,100 half-lives, which is one followed by several hundred zeroes. Even if we started off with the 1,000,000 kg posited by Muchnick, the amount left today would be about 10⁶/10³⁰⁰, a decimal followed by about 300 zeroes. That would mean the number of molecules left on earth today, if any, would not be detectable.