An international group of scientists is warning that the proposed Keystone XL pipeline from Alberta to Texas could cause huge environmental problems.

The Society for Conservation Biology released a report at its annual conference in Edmonton on Tuesday warning that the project could have long-lasting impacts on the environment and threaten endangered species.

If approved, the TransCanada Keystone XL pipeline would pump Canadian crude oil to the U.S. Gulf Coast. The pipeline expansion would start in Hardisty, Alta., and continue through Saskatchewan and the United States, where it would connect with another Keystone pipeline.

Construction could begin in 2011, with the pipeline being completed in 2013, according to TransCanada.

John Fitzgerald, policy director with the society, said as oil continues to spill into the Gulf of Mexico, many people are looking to the Alberta oilsands as a cleaner source of oil.

"Some people are pointing to this as a safer alternative. And to leap to that conclusion is not necessarily wise," said Fitzgerald, who's society recently sent its report to U.S. Secretary of State Hillary Clinton.

"One has to assess the full impact, the full life cycle of all of these energy choices before making these conclusions."

Recently, 50 members of the U.S. House of Representatives came out against the project, citing concerns the pipeline would double the country's consumption of crude from the oilsands.

In a June 23 letter to Clinton, they urged the Obama administration to do a full assessment of the environmental impacts of the oilsands before allowing the project to go ahead.

The U.S. Department of State hasn't adequately assessed the risks of the proposed pipeline, Fitzgerald said.

He warns that if the department ignores environmental warnings, the proposal could drag through the courts for years.

Alberta praises project in American paper

Since it was proposed, the Keystone plan has been controversial with plenty of opposition.

So much so that, Alberta Premier Ed Stelmach bought a half-page advertisement on July 2 in the Washington Post to defend it. The $55,800 ad paid for by Alberta taxpayers defends the province's oilsands environmental record.

A move Stelmach said may be necessary again.

"We will take every opportunity to ensure that the correct information, the facts are conveyed to those that are raising issues," Stelmach told CBC News.