TORONTO - Environmentalists say Ontario's 728,000-hectare greenbelt should grow by about 60 per cent to guard against urban sprawl.

This weekend marks the fourth anniversary of the greenbelt's creation and the Ontario Greenbelt Alliance says it's time to expand the protected lands.

The group says a number of municipalities are facing significant threats and were left out of the original greenbelt plan, including Kitchener-Waterloo, Guelph, Brantford, Simcoe County, Port Hope and the upper watershed areas of the Golden Horseshoe rivers.

The provincial greenbelt plan was created to protect agricultural lands, control urbanization and give permament protection to natural ecosystems that sustain ecological and human health.

The Ontario Greenbelt Alliance says there's been little progress on revamping greenbelt policies since the government released its draft expansion criteria last August.