The rush to develop biofuels as an energy source could lead to devastating environmental and economic consequences, according to an article co-authored by Washington State University ecologist Richard Mack.
In the paper titled “Adding biofuels to the invasive species fire,” Mack and colleagues from around the U.S. warn that the characteristics that make a plant species a good prospect as a biofuel resource also make it a prime candidate to escape domesticity and become invasive when grown outside its normal range. They urge that any non-native species being considered for biofuel production be evaluated for their invasive potential before being approved for large-scale planting.
“We’re not categorically opposed to the use of wild species for biofuels,” said Mack, who is a professor in WSU’s School of Biological Sciences.
“Our intent here is to simply point out that often we don’t know how they’re going to behave in a new range. We know from abundant experience that spans decades, that some species will surprise you – once they’re in a new environment they can ‘jump the fence,’ as we say, and become invasive.”
The paper appears in the “policy forum” section of the Sept. 22 issue of Science magazine.
While acknowledging the need to develop alternatives to fossil fuels, the paper points out that the push for biofuels in the renewable energy initiative announced by President Bush in his 2006 State of the Union Address might lead to conflict with a presidential directive already on the books.
Executive Order 13112 on Invasive Species directs that no federal agency will “authorize, fund, or carry out actions that it believes are likely to cause or promote the introduction or spread of invasive species in the U.S.” without evaluating whether potential benefits of the action outweigh the potential harm, and taking precautions to minimize the risks.
In an interview just prior to publication, Mack said introducing new species into a new range always brings risks. A species is considered invasive when it spreads unchecked by predators or parasites and deprives native species of nutrients, water, or other necessary resources.
Nationwide, invasive species do an estimated $137 billion of environmental and economic damage each year. Biofuel crops are of special concern because they would be planted over vast areas and some of the species being considered are close relatives of species that have already shown themselves to be highly invasive.
Among the top candidates as biofuel crops are perennial rhizomatous grasses such as Arundo donax, or giant reed, which is native to parts of Asia.
Their high productivity, efficient use of water and nutrients, and storage of nutrients in below-ground structures during the winter are traits shared by many species that have become invasive after being introduced into new ranges. Invasive grasses are especially hard to eradicate; the most economical control method, biological control with an introduced insect or pathogen, is usually deemed too risky because the control agent might attack cereal crops such as corn and wheat.
Mack said few introduced species will become invasive, but we won’t know for sure which ones pose a threat until we see how they behave in their new home. He recommended that prospective biofuel species be subjected to small-scale test plantings in all the areas where they might be grown. A species might behave just fine in the Midwest, but become a notorious invader in the Southeast. Such tests would help biofuels producers identify both the positive and negative aspects of a candidate species.
“We need to know how they will perform before somebody plants a huge area with Arundo donax,” he said. “Once it’s planted and if it becomes invasive, you can’t call it back.”
Mack cited the case of cheatgrass as a worst-case scenario of what could happen if a non-native grass used for biofuel production becomes invasive.
A native of southern Europe, cheatgrass was introduced to western North America in the late 1800s. By the late 1900s it had become one of the most costly invasive species in the nation. It’s a persistent weed in fields of grain crops, and has devastated western rangelands.
Unlike the native grasses it displaces, cheatgrass provides little nourishment for wildlife or domestic livestock; and when its purplish-red stems die back at the end of each growing season, it leaves the soil vulnerable to sheetwash erosion. In cheatgrass-infested areas, autumn and winter rains wash so much soil into rivers that frequent dredging is required to clear access to hydroelectric dams and keep them operating.
“We don’t want anything close to that to happen with biofuel crops,” Mack said. “It’s fine to proceed down the lines of a new technology, but we need to be aware of possible negatives as well as the positives. We need to have a protocol in place to evaluate what the potential downside is.”
