A dream nearly four decades old will finally come true if the federal government follows through on a pledge to create a new national park on the fringe of Canada's largest city.

In Thursday's budget, the Harper government reiterated a commitment to turn the Rouge Valley, a strip of forest and marshland along a river that forms the eastern boundary of Toronto in the former borough of Scarborough, into the country's first near-urban national park.

The section of the budget document dealing with the plan is vague – saying only that the government will "take action" on the file – and doesn't provide a detailed timeline or cost. But advocates for the idea were pleased nonetheless.

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"It's wonderful the federal government is going to create a national park that's accessible by transit," said Jim Robb, general manager of Friends of the Rouge Watershed. "We hope the planning process will start."

Area residents and naturalists have been pushing to protect the Rouge since the 1970s, Mr. Robb said. Both the federal and provincial governments own land in the area, and the provincial portion is already designated a park. But putting it under the mandate of Parks Canada could lead to improvements, such as better trails and more access points, he said.

Mr. Robb said the next step should be a meeting of stakeholders – including environmentalists, planners and locals – to nail down the specifics of the project.

The current park extends from Lake Ontario to Markham. North of that is the greenbelt – an area of permanently protected green space – and a chunk of federal land in the geological landform known as the Oak Ridges Moraine.