Key gaps in information mean Canada has been unable to assess the impact of exploiting Alberta's oil sands, the nation's environment commissioner said Tuesday.

Lack of information due to "insufficient or inadequate environmental monitoring systems" mean the federal environmental and water agencies cannot build a clear picture of how regional ecosystems have been affected by oil sands projects, the Commissioner of the Environment and Sustainable Development said in a report to parliament.

And despite repeated warnings by both departments since 1999, "little was done for almost a decade to close many of those key information gaps," said Commissioner Scott Vaughan.

"As a consequence, decisions about oil sands projects have been based on incomplete, poor, or non-existent environmental information that has, in turn, led to poorly informed decisions," he concluded.

In July, Ottawa set out an environmental monitoring plan -- which Vaughan praised -- but no date has been announced yet for its start.

Vaughan noted some environmental trends in the region are well understood. He pointed to the fact that the oil sands are among the "largest and fastest-growing sources of greenhouse gas emissions in Canada."

The government has also reported that air pollutants from the oil sands have more than doubled in the last decade.

"For the first time, this pollution has led to acid rain, putting at risk freshwater lakes and boreal forests in northern Alberta and Saskatchewan and, perhaps, in the Northwest Territories," said the report.

Vaughan also cast doubts on Ottawa's ability to achieve new greenhouse gas emissions targets, saying it lacks a "coherent system... that has clear objectives, timelines, interim targets, and expectations with key partners."

A number of environmental and citizen groups are fighting against a planned 1,700-mile (2,700-kilometer) pipeline to bring oil from Canada's tar sands to the US Gulf Coast.

They argue that exploiting the unconventional oil sands of Alberta requires energy that produces a large volume of greenhouse gasses.

Canada agreed under the Copenhagen Accord to reduce carbon emissions by 17 percent from 2005 levels by 2020, after abandoning its commitment to the previous Kyoto Protocol and its much stricter targets.

Environment Minister Peter Kent said in a statement that Canada is "committed to achieving our emissions reduction target under the Copenhagen Accord."

He pointed to a sector-by-sector approach that started with stricter emissions standards for passenger vehicles and light duty vehicles, and minimum renewable content in gasoline and diesel.

He also signaled plans to limit emissions of heavy-duty trucks and phase out "dirty coal-fired electricity generation."

"We are already a quarter of the way to our target," he said.