In a newly issued document, the U.N. Intergovernmental Panel on Climate Change has shifted position on biofuels, for the first time acknowledging that they may have negative impacts that take away from their value in reducing greenhouse gas emissions.

The Working Group II contribution to the IPCC’s report, Climate Change 2014: Impacts, Adaptation, and Vulnerability , offers a subtle but significant caveat to the IPCC’s view of past view of biofuels as one of the “key mitigation technologies” for reducing fossil fuel use and greenhouse emissions, as articulated in this 2007 report.

The latest report, while it doesn’t repudiate biofuels, takes into account more recent scientific research, which points to problems that may result from reliance upon them as a replacement for petroleum and other fossil fuels.  The report, for example, warns that increased cultivation of crops to provide raw material for biofuel may boost water consumption and “exacerbate the already serious water scarcity” in countries such as China and Spain.

Additionally, IPCC says that land acquisition for biofuels production may have “negative impacts on the lives of poor people,” by depriving them of land and increasing food prices. Yet another worry is that reductions in greenhouse emissions from using biofuels may be cancelled out by the effects of deforestation and the draining of wetlands.

The report’s findings were hailed by environmental and anti-poverty activists who have been critical of the push to develop biofuels.

“I think the report strengthens the link between increased production of food-based biofuels, and increased competition for land and water for food crops,” said Alex Rindler, a senior policy associate for the Environmental Working Group. “It’s an issue of tradeoffs. What are you trading off by increasing the proportion of what’s going to grow fuel instead of food.”

Jeremy Martin, a senior scientist for the Union of Concerned Scientists, said the report reflected a shift that’s already been happening among scientific researchers and government agencies that are trying to develop energy policy. “There’s nothing really new here,” he said. “It’s a summary of what they’ve learned. I think it’s very clear that policy makers are figuring out that they have to be careful with biofuels, because of the impacts on food and land use.”

Even so, Martin said that “it would be a mistake to say there is no role for biofuels. This is not a complete reversal. It’s about being careful and smart. Scale is the important question. It seems clear to me that we can’t replace all our fossil fuels with biofuels.”

Kristin Sundell, an official for ActionAID USA, had a strong take on the report in a press release. “The IPCC has made it clear that biofuels are not a solution to climate change. In fact, biofuel production is deepening the impact of climate change on vulnerable communities,” she said.

But Brent Erickson, executive vice president of the Biotechnology Industry Association, a Washington-based trade group, disagreed with the spin that some biofuels opponents are giving to the report“If we decrease biofuel use, we will automatically increase petroleum use, primarily from Canadian oil sands. And that will dramatically increase emissions,” he said.

Ernie Shea, project director of the 25x’25, a Lutherville, Md.-based renewable energy coalition that includes agricultural and forestry interests, said that advances in the technology for producing biofuels will lessen the potential negative impacts. “Biofuels are a very important solution, one that needs to be evaluated on what the fuels are today and what they will be tomorrow, and not by looking in the rear window to 10-year-old technologies,” he said. (See related post: “Biofuel Startup KiOR Threatens to Veer Off the Road.”)

Shea also disagreed with the IPCC’s warning that biofuel production might drive up food prices. “The primary driver of food costs and availability is energy costs,” he argued.  (Take the quiz: What You Don’t Know About Biofuel.)