TRAVERSE CITY, Mich. — The U.S. and Canada renewed a 40-year-old Great Lakes environmental pact Friday, pledging stepped-up efforts to reduce pollution, cleanse contaminated sites and prevent exotic species invasions.

The updated Great Lakes Water Quality Agreement binds both nations to continue a cleanup and restoration initiative begun when the freshwater seas were a symbol of ecological decay. Many of their beaches were littered with foul algae blooms and dead fish. The Cuyahoga River, which flows into Lake Erie in Cleveland, was so choked with oil and chemicals that flames erupted on its surface in 1969.

The pact calls for further action on problems that inspired the original agreement three years after the embarrassing river fire and a second version in 1987. It pledges to “restore and maintain the chemical, physical and biological integrity” of the five lakes and the portion of the St. Lawrence River on the U.S.-Canadian border.

It sets targets for reducing nutrients that cause foul algae blooms and recommends further cleanup of harbors contaminated with toxic chemicals.

“This agreement is more than just a commitment to each other,” Environmental Protection Agency chief Lisa Jackson said before signing the document with Canadian Environment Minister Peter Kent at the Canadian embassy in Washington, D.C.

“It is also a commitment to those who will come after us, showing them the importance of leaving the Great Lakes in better shape than they were when we inherited them,” she said.

The new version includes new sections on challenges that have emerged more recently: climate change, loss of wildlife habitat and a wave of invasive species such as zebra and quagga mussels and Asian carp. It also calls for the region’s governments to identify potential threats so they can be dealt with before developing into big problems.

“We’ve learned the hard way that we should not wait for damage to occur before we take action,” Jackson said.

The agreement’s success will depend on whether state and federal governments carry it out by enacting and enforcing strong laws and providing money, environmental activists said.

“Today we applaud,” said John Jackson, director of an advocacy group called Great Lakes United. “Tomorrow we get to work.”

President Barack Obama’s administration has spent more than $1 billion on a Great Lakes restoration program and has requested $300 million for the current fiscal year. But Canada is eliminating hundreds of government scientist positions, and proposals have been made in both countries to weaken clean water laws, said John Jackson, who is not related to Lisa Jackson.

Kent said Canada’s federal government would uphold its obligations under the agreement and had begun negotiations with the province of Ontario about carrying out the deal over the next five years.

Along with the federal Clean Water Act, the 1972 agreement was credited with leading governments in the region to ban phosphate detergents, which led to a significant drop-off in algae blooms. But the problem has worsened on Lake Erie and portions of Lake Michigan in recent years, a problem some scientists blame on runoff from farms and cities.

The new agreement requires governments to set phosphorus reduction targets within three years and action plans within five years.

It also sets a two-year deadline for putting together a system for early detection of new invasive species and rapid action to limit their spread.

But it imposes no timelines for finishing cleanup of the region’s 43 most heavily polluted areas designated under the 1987 update. The toxic hot spots have problems such as fish with tumors, foul drinking water and beaches unfit for swimming.

Work has been completed on just four — three in Canada and the Oswego River and Harbor in New York — although EPA officials say several others are nearly finished.

U.S. Sens. Carl Levin, a Michigan Democrat, and Mark Kirk, an Illinois Republican, praised the agreement as co-chairmen of the Senate’s Great Lakes Task Force.

“With its emphasis on prevention of environmental damage, the agreement reflects a more cost-effective use of resources, as preventing damage is generally less costly than cleaning up ruined ecosystems,” Levin said.