Though the rose gum carries an invasive risk, ArborGen's trees are an unknown quantity, Gordon said. Given the uncertainty involved, however, the Nature Conservancy has recommended to USDA that ArborGen be allowed fewer acres and trees to flower, and none in Florida, she said. The draft permit approved by USDA would allow flowering in 10 sites across the state.
"We don't know if it could become more invasive over time," she said. And until then, "it would be logical to me to not do those trials in Florida."
It is not irrational to fear invasiveness in eucalyptus, said Dan Binkley, a forest ecologist at Colorado State University. However, the rose gum appears to take on weedy traits only in arid regions like South Africa, where it can leverage its tremendous water efficiency. The South is far moister by comparison.
Even in Florida, the eucalyptus has proved to be somewhat delicate, ArborGen's Pearson added.
The tree "does not exist outside of the planted environment," he said. And in the closed confines of a plantation, "you need to manage these things very carefully to let them survive and thrive."
'More Wood. Less Land'
While he would like to see more data on the water use and fire impacts of eucalyptus plantations, Binkley understands the tree's allure, he said.
Unlike the pine trees used in Southern plantations -- which have quietly helped displace tobacco in the region's economy -- eucalyptus can deploy a full canopy of leaves within a few years. It is greedy for carbon, and within 27 months can grow to 55 feet in height.
The ultimate benefit of eucalyptus plantations would be the ability to grow more wood on less land, ArborGen's Hinchee said. (Not coincidentally, the firm's motto is "More Wood. Less Land.") Forests are continuously lost to development in the South, and natural hardwood acres have become harder to harvest. Increased productivity would have benefits "through the whole economic chain," she said.
Similar claims have been made for the practice of forest plantations as a whole, which remains controversial despite its ubiquity in the South, and little data exists to verify the claims.
In the end, if the United States seriously pursues bioenergy from plants, the country will face a choice of drawing that power more from trees that are treated like crops, or from grasses, which can behave far more invasively, Strauss said.
"If we're going to rely on biofuels as a significant part of a diverse portfolio of renewable technology," then harvesting trees is the best way to go, he said. "There's a lot of marginal land that could be used."
Reprinted from Greenwire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500