ROME  In the past year, as the diversion of food crops like corn and palm to make biofuels has helped to drive up food prices, investors and politicians have begun promoting newer, so-called second-generation biofuels as the next wave of green energy. These, made from non-food crops like reeds and wild grasses, would offer fuel without the risk of taking food off the table, they said.

But now, biologists and botanists are warning that they, too, may bring serious unintended consequences. Most of these newer crops are what scientists label invasive species  that is, weeds  that have an extraordinarily high potential to escape biofuel plantations, overrun adjacent farms and natural land, and create economic and ecological havoc in the process, they now say.

At a United Nations meeting in Bonn, Germany, on Tuesday, scientists from the Global Invasive Species Program, the Nature Conservancy and the International Union for Conservation of Nature, as well as other groups, presented a paper with a warning about invasive species.

“Some of the most commonly recommended species for biofuels production are also major invasive alien species,” the paper says, adding that these crops should be studied more thoroughly before being cultivated in new areas.