The controversial Keystone XL pipeline would destroy agriculture and tourism jobs in the states through which it would run, according to a new report from Cornell University's Global Labor Institute (GLI).

The proposed 1,700-mile pipeline would cut through the U.S. breadbasket, transporting Canadian oil sands to a terminus in Louisiana. A bitumen spill -- which the report said is almost inevitable -- in the farm- and tourist-heavy region would cause workers to lose jobs, businesses to close and residents to relocate, the GLI researchers wrote.

"The damage of spills and other possible negatives haven't really featured in the discussions" around Keystone XL, said report author and GLI Director Sean Sweeney.

Based on experience from the Keystone I pipeline, a spill is more than a possibility, said Natural Resources Defense Council Canada Project Director Danielle Droitsch.

Heavy oil sands crude is much more corrosive than conventional light oils and is therefore more likely to leak during transport, she said. When it does escape, the substance tends to sink to the bottom of waterways and is extremely difficult to clean, Droitsch said.

The Cornell report points to at least 35 spills that have occurred in the United States and Canada since Keystone I began operating -- a spill frequency 100 times greater than pipeline owner TransCanada Corp. predicted.

Politicians need to be discussing "not just the likelihood but the reality that there will be a spill from Keystone XL," Droitsch said.

Sweeney did not provide an exact estimate of how many jobs would be lost in the event of a spill. That number, he said, would hinge on the size and location of a spill.

However large, the number would likely offset the 20 permanent pipeline operation jobs the U.S. State Department estimates Keystone XL will likely create, the report says.

TransCanada spokesman Terry Cunha said in a statement that the report severely underestimates the project's job creation potential. The company says the pipeline would bring 13,000 direct, on-site jobs. Some of those jobs would be temporary construction gigs, but the jobs' short-term nature should not matter, Cunha said.

"Why does Cornell's researchers and other activists denigrate the value of the work that Keystone XL will create for those Americans who work in the skilled trades?" he said. "Why do they feel that denying these Americans' work will help the U.S. economy or communities where these people live and work?"

TransCanada also disputed the Cornell report's spill estimates from Keystone I. Cunha wrote that the pipeline has had only 14 unplanned releases, none of which involved the pipeline itself. The incidents were contained within pump station facilities and each one leaked about five gallons of crude on average, Cunha said.

Overall, the threat of environmental damage and economic harm posed by Keystone XL is low, he said.

"It is not at all apparent why a new pipeline built to substantial safety standards would pose a greater risk than using older pipelines, tankers from other parts of the world or oil from offshore rigs," Cunha said. "Sending oil through a newly constructed pipeline is likely to be one of the safest mechanisms available."