As the city of South Portland geared up for a specially scheduled meeting on the latest proposal to keep tar sands – or oil sands – from flowing through the city’s industrial waterfront, supporters of the ban cried foul: Outsiders were interfering in the city’s business.

They accused out-of-state “Big Oil” interests of packing a meeting with so many nonresidents that it forced the South Portland City Council to delay its first vote on the proposal and schedule a bigger room. And they worried that the opponents might bring in more outsiders clad in red T-shirts to try to outnumber supporters in their sky-blue shirts and drown out the voices of the South Portland citizens whose environment is at stake.

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As if this was all about South Portland.

In fact, what’s happening in the city is one skirmish in an ongoing, international chess match over Canada’s plans to expand the production of its vast petroleum reserves in Alberta, about 2,000 miles west and north of Portland Harbor.

Both sides in the debate here have been organized and supported by outsiders who are concerned with much more than South Portlanders and the future of their waterfront.

South Portland’s city councilors could decide Monday whether to prohibit the city’s petroleum-importing terminals from converting into crude oil-exporting terminals some time in the future. And they may base that decision on the local implications – protect against the possibility of waterfront vapor stacks and additional air pollution or preserve future business options for one of the city’s biggest industries and one of the biggest petroleum ports on the East Coast.

While those local issues are real, it’s clear that the decision is about more than whether South Portland should allow one of its terminals to get into the oil export business.

Consider what happened – or rather what didn’t happen – in 2009 when the Portland Pipe Line Corp. asked for city and state permission to install two 70-foot-tall vapor combustion stacks and other equipment so it could use its 236-mile-long pipeline between Montreal and South Portland to export heavy crude oil from western Canada. It is precisely the kind of project that the proposed ordinance is written to prevent.

The city asked for feedback from its staff. It sent letters to 657 res-idents and potentially interested parties and invited them to comment. It ran newspaper ads about the project and the public hearing schedule.

There was some praise of the plan and of the company, but no evidence in city files that anyone objected. There was no sea of blue T-shirts, or red ones. The Planning Board – the same panel that last week voted 6-1 in favor of banning such a project in the future – voted 7-0 in favor of the city permits. And when the Portland Pipe Line came back in July 2011 to ask that its permits be extended for a third year related to delays caused by economic conditions, the board voted 5-0 to approve it. (Two members were absent. )

Nowhere in the city’s files on the project do the words “tar sands” or “oil sands” even appear. The oil to be exported through South Portland was referred to then as heavy crude from western Canada. No one asked exactly what kind of oil it was or where it was coming from.

While South Portland hasn’t changed all that much in the past three years, big changes happening outside the city have focused intense scrutiny on the tar sands fields thousands of miles away.

Tar sands have since become a rallying cry for environmentalists, especially those worried that climate-altering carbon is accumulating in the world’s atmosphere at a rate that could reach a kind of tipping point in the not-too-distant future. Also, a 2010 spill of the heavy tar sands oil from a pipeline in Michigan into the Kalamazoo River led to a complicated and expensive cleanup that has fueled fears of land and water contamination along the pipeline routes.

Signs of the huge political shift around tar sands became apparent in Maine in January 2013.

Maine environmental groups working with counterparts in Canada and Vermont went town to town along the Montreal-to-South Portland pipeline route asking town councils and boards of selectmen to pass resolutions against the eastward flow of tar sands. A representative of the Canadian consulate in Boston traveled to a special town meeting in Bethel to reassure leaders of that town about tar sands. As it happened, the Canadian representative and an out-of-state oil executive were never given a chance to speak at the meeting before townspeople voted for the anti-tar sands resolution.

That same month, more than 1,400 people converged on Portland from around New England and eastern Canada to protest the potential for tar sands to reach the coast of Maine. Activists carried signs saying the export of tar sands equals “Game Over” for the world’s climate. Not long after that, South Portland would emerge as ground zero in the region’s fight over tar sands.

Tar sands are a mixture of heavy crude oil, sand and water. Alberta happens to have a vast supply of the oil sands, giving Canada the world’s third largest crude oil reserve after Saudi Arabia and Venezuela. The oil sands require more energy and money to get out of the ground, process and refine, but they have become marketable as more conventional oil reserves strain to supply world markets.

The vast supply waiting to be exported and the extra energy required to get it to those markets is what has made tar sands oil the target of environmental activists around the world. Barrel for barrel, tar sands oil adds 9 percent to 37 percent more climate-warming carbon to the atmosphere than average oil adds, depending on whether the study was done by the Canadian government or environmental advocates.

The Canadian oil industry doesn’t dispute that tar sands oil has a higher greenhouse gas intensity than average oil, although it says it is within the range of the other heavy crudes it will most likely replace in the market.

While the Canadian government sees huge economic potential in its tar sands deposits, plenty of critics north of the border say the costs are too high – from the local impacts of mining to the global impacts on climate. The oil sands fields of Fort McMurray in Alberta have been nicknamed “Fort McMoney” or “Fort McMordor,” after the poisoned, blackened landscape in “Lord of the Rings.”

PIPELINES CRUCIAL FOR TAR SANDS

To fully develop the oil sands, Canada needs pipelines to get large volumes of the oil to foreign refineries and bigger markets in the U.S., Europe and Asia.

The Keystone XL pipeline, the most famous and most contentious of all of Canada’s options, would effectively move oil from Alberta south through the central United States to the big American refineries and export terminals on the Gulf of Mexico.

Keystone XL has become a source of tension between Canadian leaders and the Obama administration, which has delayed a decision on necessary U.S. permits and faces pressure to reject them. Even as South Portlanders make their stand against tar sands oil exports, a group of Nebraskan landowners is working through the courts there to block the latest Keystone XL pipeline route.

Indeed, each potential pipeline route has become the focus of multiple political battles.

The Canadian government and global oil companies are now pursuing two major pipelines options in addition to Keystone – the Northern Gateway pipeline west to the Pacific Ocean and the Energy East pipeline, which would carry the crude east through Ontario to Saint John, New Brunswick, and the Atlantic Ocean.

Both are being fought by environmental groups trying to prevent the export of tar sands because of the climate change potential and by people living along the pipeline routes who fear impacts to their local environments. Aboriginal groups in British Columbia, for example, have gone to court arguing that the Northern Gateway plan threatens their lands and fisheries.

The 236-mile pipeline between Montreal and a tanker terminal on the South Portland waterfront in Portland Harbor now appears to be one of many other possible routes for the oil. While there is no active proposal to bring tar sands to South Portland to be loaded onto ships, Canada has approved the use of pipelines that could eventually be used to bring the oil east to the Montreal end of the pipeline.

The Portland Pipe Line Corp.’s 2009 permits to add vapor stacks and other oil exporting equipment in South Portland have now expired. The company surrendered its state air discharge permit, which was granted after the Maine Department of Environmental Protection deemed the projected pollution levels well within acceptable levels.

MANY ANGLES TO CONSIDER

It’s hard to see how the pipeline-by-pipeline chess match will end. Some are saying that the future of Canada’s oil reserves shouldn’t be left up to city councilors in South Portland or judges in Nebraska and British Columbia. Maybe packing a community center with red and blue T-shirts and amending waterfront zoning in Portland Harbor isn’t the best way to set international energy policy or develop a strategy to fight global climate change.

Some scientists from Canada and the United States published a plea for a better way in an article in the journal Nature in late June. They said the piecemeal approach gives the impression that export of the tar sands oil is inevitable, even though it should not be.

“Current public debate about oil-sands development focuses on individual pipeline decisions. Each is presented as an ultimatum – a binary choice between project approval and lost economic opportunity,” the scientists wrote. “This approach artificially restricts discussions to only a fraction of the consequences of oil development, such as short-term economic gains and job creation, and local impacts on human health and the environment. Lost is a broader conversation about national and international energy and economic strategies, and their trade-offs with environmental justice and conservation.”

It seems increasingly clear the vote in South Portland on Monday will be a prelude to a lawsuit or a referendum campaign, or both. It’s also clear the South Portland City Council is being asked to consider a lot of angles, both by its residents and by outsiders.

Is it an issue of South Portland’s air quality? Of protecting against spills in Sebago Lake or Portland Harbor?

Is it about jobs and the future of the city’s working waterfront? Protection of free enterprise and the city’s commercial tax base?

Fairness to a key trading partner? Mining practices in Alberta?

Or, is it about global climate change? A desired transition to clean energy?

The answer seems to be “yes.” Take your pick.