Better Trees from GM Technology? 

HARVEY BLACK / UPI 7feb2005

Madison, WI — At an abandoned hat factory in Danbury, Conn, scientists are testing genetically engineered trees to see if they can be used to remove toxic mercury from the ground.

In a laboratory in Raleigh, N.C., another group is working to modify trees to make paper production less polluting and more energy efficient.

At Purdue University in West Lafayette, Ind., still more scientists are working on ways to engineer trees so they can store more carbon in their roots as a way of fighting global warming.

Genetically modifying trees has become an "extremely active" field said, Richard Meilan, leader of the Purdue group.

In all, researchers conducted 90 field tests of transgenic trees between 1987 and 2001, the majority of them since 1997, according to Resources for the Future, an environmental research group in Washington, D.C. The field tests were regulated and approved by the U.S. Department of Agriculture's Animal Plant Health and Inspection Service.

Many of the field tests were conducted by forest products companies with an eye on economic potential, said Roger Sedjo, an economist with Resources for the Future.

"Some of the work that's under way is to create conditions with the wood fibers to make them more amenable to processing," Sedjo told United Press International. "If you can have fibers that require less costs in the digester of a pulp mill, that's an advantage."

One way to do this is to modify trees to contain less lignin, the glue that holds wood fibers together and must be dissolved in the papermaking process.

In his lab at North Carolina State University, Vincent Chiang is using genetic modification to do just that. He has not only reduced the lignin content of the aspen tree — a stalwart of papermaking — but also has managed to alter lignin's composition to make it easier to remove.

"It's double dipping," he told UPI.

Genetically altering the trees is the only way to reduce further the costs and energy required to make paper, Chiang said. The conventional process is as efficient as it can be, but "still requires tremendous energy and bleaching chemicals. The only solution is to improve the raw material," said Chaing, who has been working to understand and reduce lignin for more than a decade.

Reducing lignin content by only 1 percent or 2 percent would mean "tremendous" savings for paper companies by reducing costs, Meilan said. It would also mean increases in the amount of paper produced, he said.

It might not be that simple, however. Gary Peter, of the University of Florida in Gainesville, noted that paper mills use lignin as an energy source, so reducing lignin in trees means that the mill owners must either buy more commercial power or generate more of their own, thereby adding to their electricity bills and, possibly, to air pollution.

Peter told UPI that mathematical modeling he has completed done shows that profits in some cases will increase by only 5 percent to 7 percent, which might not make it worthwhile in all cases for companies to use genetically modified reduced-lignin trees.

Still, at least one company thinks reducing lignin can be a benefit.

"What we're looking at is producing a tree that does not cause a financial burden on the mill," said Maud Hinchee of ArborGen in Summerville, S.C., a genetic research company that is field-testing trees with altered lignin content. "So the criteria that we use as a company is: Does this product provide a benefit to the industry?"

Hinchee said her company is attempting to work "within the range of lignin content that is acceptable from an energy generation point of view."

ArborGen also is working to modify trees to have them become woodier sooner, she said, as a way to cut costs and improve profits for forest products companies.

Another research area concerns developing herbicide-resistant trees, which Meilan said is worthwhile because it can help make herbicide use more cost efficient in tree-growing areas.

Making better trees for straightforward economic gain is one goal. Another is testing them to see if they can clean up a toxic environment. At the former Danbury hat factory, trees engineered by Richard Meagher, a genetics professors at the University of Georgia, are detoxifying a mercury-contaminated site. The trees contain a gene for a bacterial enzyme that changes the mercury in the ground to a far less toxic form, which is then released into the air through the leaves.

Meagher argues that toxic heavy metals can be managed, and in the end his method can reduce pollution. The idea does not sit well, however, with Neil Carman of the Sierra Club, who sees such an experiment as merely shuffling the location of a toxin.

Carman, with the club's Lone Star Chapter in Austin, Texas, also objects to genetically engineering trees that can resist insects. This can be done by inserting a gene for Bt, a naturally occurring insecticide. He said he is concerned that pollen from these trees, grown on plantations, can drift into natural forests.

"We're going to have silent forests," Carman told UPI. "If the trees create their own insecticides, insects are going to perish and the birds that feed on those insects are not going to make it. You're going to have whole food chains wiped out."

Meilan said insects will evolve their own resistance to insect-resistant trees.

Carman warned that pollen carrying inserted genes could create unforeseen problems. "A lot of ecological risk assessments need to be done. Trees live a long time and they have the potential to produce huge numbers of seeds and pollen," which can spread, he said.

"The vast majority of the pollen does fall within three meters of the tree," but pollen also can travel long distances, said Estelle Levetin of the University of Tulsa, Okla. Her research on cedar pollen, for example, showed it can be transported hundreds of miles by the wind.

Though the matter requires further study, Levetin added, if trees are harvested before they become sexually mature and produce pollen, then there is less of a reason to be concerned.

Harvey Black covers research for UPI Science News. E-mail sciencemail@upi.com