 The Yew Tree A Thousand Whispers by Hal Hartzell, Jr Hulogosi Books, 1991 reviewed
by Michael
Hofferber Members of the Cowlitz tribe of Native Americans used to crush yew needles into a paste to put on wounds. These are just a few of the dozens of historic uses recorded in The Yew Tree, an impressive biography of the species written by an Oregon treeplanter, Hal Hartzell, Jr. The seven species of yew trees spread across the earth are descended from a single ancestor 200 million years ago, Hartzell reports. Their populations were expanding until the end of the most recent Ice Age when the species Homo Sapiens found uses for them and began harvesting. "Unfortunately for the yew," he writes, "when we discovered its value as wood for weapons and a host of other articles, or as foliage and bark for poisons and medicines, we began a continuous deforestation project that left the crumbled dominions of Egypt, Greece and Rome bereft of natural yew groves." The remaining yew forests of Europe are not faring well and Hartzell fears for the future of the largest remaining population of the trees in the Pacific Northwest now that their bark is sought as a cancer cure. Much of modern medicine has its roots in the plant kingdom. Many pharmaceuticals have been derived from plants, bacteria, or fungi. A drug that staves off childhood leukemia, for example, is produced from a periwinkle. The National Cancer Institute, consequently, has been screening plant samples for anti-cancer properties since 1960. Twenty years into the project the search slowed down because nothing new had been discovered. Then, in 1985, a new screening technique was developed and the search began anew, this time discovering that the taxol derived from the Pacific yew inhibits cell growth in certain types of cancer. In clinical trials, taxol proved very promising in the treatment of ovarian cancer and is being studied for fighting other cancers as well. The National Cancer Institute immediately placed an order with the Forest Service for dried Pacific yew bark, which until 1987 had no commercial value and was commonly burned in slash piles after logging. The yew tree is thin-skinned, yielding only about five pounds of bark per tree, according to Hartzell. The 1991 harvest amounted to about 825,000 pounds of bark, or 165,000 trees. That's enough to treat a little more than 12,000 cancer patients. But nearly 1 million people die of cancer each year, Hartzell points out, and if taxol is as promising as some doctors believe the pressure on the Pacific yew forests could be tremendous. "A million treatments of taxol would require 2,000 kilograms of taxol or 60,000,000 pounds of Pacific yew or the equivalent of 12,000,000 yew trees ten inches or larger in diameter. There is no way bark can be the answer," he concludes. There are less than 4 million yew trees still standing, Hartzell estimates, enough to cure only one-third of the terminal cancer cases in a single year. "Chances for wild yew's survival are tenuous at best," Hartzell concludes. "The Pacific yew is the last sizeable population of native yews left on earth, and now we have discovered in it the gift of a powerful anti-cancer compound. It is a sad commentary on our times that the only feasible way we have yet devised to acquire this gift is to kill mature trees for their five pounds of bark." And yet, Hartzell's eulogy for the yew may be premature. Scientists meeting at an American Chemical Society gathering in San Francisco in 1991 announced rapid progress on making taxol synthetically from yew needles, stems and even cedar oil. The drug could be widely available as early as next year without increasing yew harvests. The taxol issue aside, The Yew Tree is a fascinating in-depth botanical study of a single tree, its natural history, and its interaction with humans down through the centuries. It even includes chapters on cultivating yews and poetic images associated with yews, and appendice listings of all the known yew species and associated cultivars. Until recently, Hartzell points out, the yew was considered a "trash tree" by Northwest foresters and treated accordingly. Now that taxol has reversed its reputation the lesson of the yew tree is clear. There are no unimportant species, only undiscovered potential.
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