AN UNUSUAL ROLE FOR TREES

A scientist advocates reforesting Canada with trees that have several chemical ecofunctions
Diana Beresford-Kroeger pointed to a towering wafer ash tree near her home. The tree is a chemical factory, she explained, and its products are part of a sophisticated survival strategy. The flowers contain terpene oils, which repel mammals that might feed on them. But the ash has a powerful lactone fragrance that appeals to large butterflies and honeybees. The chemicals in the wafer ash, in turn, she said, provide chemical protection for the butterflies from birds, making them taste bitter.
Beresford-Kroeger, 63, is a native of Ireland who has bachelor’s degrees in medical biochemistry and botany, and has worked as a Ph.D.-level researcher at the University of Ottawa school of medicine. She calls herself a renegade scientist, however, because she tries to bring together aboriginal healing, Western medicine and botany to advocate an unusual role for trees.
She favours what she terms a bioplan, reforesting cities and rural areas with trees according to the medicinal, environmental, nutritional, pesticidal and herbicidal properties she claims for them, which she calls ecofunctions. Wafer ash, for example, could be used in organic farming, she said, planted in hedgerows to attract butterflies away from crops. Black walnut and honey locusts could be planted along roads to absorb pollutants, she said. “Her ideas are a rare, if not entirely new approach to natural history,” said Edward O. Wilson, a Harvard biologist who wrote the foreword for her 2003 book Arboretum America. “The science of selecting trees for different uses around the world has not been well studied.”

Some of Beresford-Kroeger’s claims for the health effects of trees reach far outside the mainstream. Although some compounds found in trees do have medicinal properties and are the subject of research and treatment, she jumps beyond the evidence to say they also affect human health in their natural forms. The black walnut, for example, contains limonene, which is found in citrus fruit and elsewhere and has been shown to have anticancer effects in some studies of laboratory animals. Beresford-Kroeger has suggested, without evidence, that limonene inhaled in aerosol form by humans will help prevent cancer. David Lemkay, the general manager of the Canadian Forestry Association, a nonprofit group that promotes the sustainable use of Canada’s forests, said, “She holds fast to the notion that if you are in the aura of a black walnut tree there’s a healing effect,” Lemkay said. “It needs more science to be able to say that.”

“What trees do chemically in the environment is something we’re only beginning to understand,” said Beresford-Kroeger. A recent study by researchers at Columbia University found that children in neighbourhoods that are tree-lined have asthma rates a quarter less than in neighbourhoods without trees. The Center for Urban Forest Research estimates that each tree removes 1.5 pounds of pollutants from the air. Trees are also used to remove mercury and other pollutants from the ground. And they store carbon dioxide, which mitigates global warming. Canadian officials have announced plans to preserve 55 million acres of forestland.
Beresford-Kroeger has proposed using stock from old-growth forests for planting new forest in the hope of taking advantage of good genetics. She has 60,000 daffodils, more than 100 rare hellebores from Turkey and Iran and extremely rare peonies from China in her sprawling gardens, which are sometimes open to the public. And she grows more than 100 types of trees, including rare fir trees and Siberian cherry trees, and disease-resistant chestnuts, elms and butternut.
- JIM ROBBINS, New York Times