Prime Minister Stephen Harper has made the latest in a series of environmental pledges, this time announcing a plan to preserve ecologically sensitive land.

"Today, I am proud to announce that the new government of Canada is partnering with the Nature Conservancy of Canada in a national campaign to acquire and preserve half a million acres of ecologically sensitive land across southern Canada," Harper announced Wednesday outside of King City, Ont.

That community sits on the sensitive Oak Ridges moraine and is located within the Oak Ridges-Markham federal riding, currently represented by Liberal MP Lui Temelkovski.

The federal government will set aside $225 million to "reward the generosity" of landowners who agree to preserve their land from development by selling the land. Other landowners will get tax breaks for donating or agreeing to preserve the land.

Nature Conservancy Canada will work with Ducks Unlimited Canada and other partners on the plan. The federal investment will be matched dollar-for-dollar with contributions raised by NCC and its partner organizations from private donors.

Priority will be given to lands of national or provincial ecological significance and lands that offer a habitat for species at risk or migratory birds.

This project will protect as much as 202,300 hectares of wilderness in southern Canada, Harper said, even as Canada continues its century-long trend of urbanization.

Harper's announcement was made on the outskirts of Happy Valley Forest, the site of one of southern Ontario's few mature forests. It's also where four local residents recently donated 145 acres of land for preservation.

The forest there, Harper said, preserves the habitat of birds, contribute to cleaner air and prevent soil erosion.

"Without the forest cover, we would have to invest billions in flood protection infrastructure and water treatment facilities," Harper explained.

"So preserving forests in southern Ontario is not just the right thing to do from an environmental perspective, it's prudent economic policy as well."

Earlier this week, Harper announced $199.3 million for environmental projects in British Columbia, including a so-called "hydrogen highway," a network of recharging stations for fuel cell-powered vehicles.

On Tuesday, Harper also promised his government is set to announce new regulations to reduce greenhouse gas emissions.

And last week, Harper announced $1.5 billion for Toronto-area public-transit projects.

Harper made the announcement in Vaughn -- a Liberal-held federal riding just south of the Oak Ridges-Markham riding.

Reaction, analysis

In Mississauga, Ont., about 40 kilometres to the south, Liberal Leader Stephane Dion issued his party's law-and-order platform.

"I think I am the most influential leader of the opposition since a generation," he boasted to his audience.

The Liberals issued a news release saying: "Mr. Dion's leadership platform proposed the creation of the Pierre Elliot Trudeau Nature Conservation Foundation whose purpose would be to 'provide support to private land conservation organizations on a matching basis to support their efforts to acquire and protect lands of high conservation value.' The Dion plan would have endowed the Foundation with a one-time gift of $200 million."

In return, Harper questioned the sincerity of the new Liberal stances on law-and-order issues.

Pollster Allan Gregg told CTV News the announcements were defensive politics.

"They are trying to take what is obviously a vulnerability right now and ensure if they get into a writ in the near future that it is not going to sink them," the chair of The Strategic Counsel said.

Trying not to be eclipsed, the NDP released a green-themed TV ad.

"Climate change effects your family and it's been ignored by Liberals and Conservatives for too long," Layton says in the ad.

With a report from CTV's Ottawa bureau chief Robert Fife