Image: Courtesy of S. MERKLE
To gain an appreciation for the promise--and perils--of genetically modified trees, consider the case of the American chestnut.
Few trees have had such a remarkable presence and impact on the American landscape and ecosystem as the chestnut. Mature trees grew to 100 feet tall and their trunks had diameters that spanned five feet. Each fall, their fruit--polished, nutritional, protein-packed chestnuts--rained down on forest denizens (including human gatherers) as manna from heaven. Then, in 1904, an accidentally imported fungus began to attack the trees. In less than 50 years, the trees that had once defined forests from Maine to Georgia were virtually wiped out. Today, stumps of once-mighty chestnut trees may sprout small clones. But even if these saplings avoid the relentless fungus, they can reach only half the height of the previous chestnuts. The young clones rarely attain reproductive maturity.
Breeding American chestnuts with their fungus-resistant Asian cousins could bestow protection--but only slowly, over many generations of the long-lived trees, and through several lifetimes of their human breeders.
Or, with genetic-modification techniques, the protective genes could be inserted into the trees in just a few years.
No solution, of course, is ever that easy: the downside is that transgenic trees, just as with any other genetically modified (GM) plant, could breed and swap lab-inserted genes with wild trees--with unpredictable, and perhaps ecosystem-threatening, results.
According to researchers and industrial groups, trees are the next big crop plant, and GM trees could provide a variety of advantages over natural forests and traditionally bred timber. GM trees could be designed so that they ease paper processing, for instance. They could grow faster, requiring less land to generate the same amount of lumber. They could be engineered to be pest-resistant--saving on chemical treatments--or allergen-free (see "Allergen-Free Trees"). Last, they might even be used to assist in bioremediation of heavy metals.
Researchers developed the first transgenic trees by the end of the 1980s. By 1998 a team at Michigan Tech University, led by Vincent Chiang, had designed a better tree for paper. Chiang and his colleagues determined how to insert the correct genes in aspens to halve the lignin content--which has to be isolated during papermaking by chemical treatments--and increase paper-strengthening cellulose by up to 15 percent. The trees would require fewer treatment chemicals, making them "greener" and less expensive to process than conventional trees. Michigan Tech patented the gene-insertion process; the trees are now in field trials.
Trees as Crops
|For a list of trials of genetically modified trees currently being conducted in the U.S., click here.|
Timber is big business, and another area that GM trees could help improve. The U.S. Department of Agriculture reported 2.9 billion cubic feet of timber cut in 1999 on national forest lands, valued at over U.S.$340 million. Banking on the potential profitability of GM trees, in 2000 several major timber and paper companies, including giants International Paper and the Westvaco Corporation, joined the New Zealand biotechnology company Genesis in a $60-million venture called ArborGen; it was the largest international commercial venture dedicated to transgenic trees for lumber at that time. A selling point for transgenic trees is that they would reduce land needs for tree plantations in the U.S. Southeast and reduce pressures on remaining forests in the West. "The environmental benefit in a shift to planted from wild is that you could get all the wood the world needs pretty much from 5, 10 or 20 percent of the land used now," says Steve Strauss, professor of forest genetics and biotechnology at Oregon State University.