The United States is nailing Canada's lumber industry with hefty tariffs that will cost Canadians jobs and Americans money.

On Monday, the U.S. Department of Commerce announced import duties of as much as 24 per cent on Canadian softwood companies. It's the fifth time since 1981 that Canada and the U.S. have sparred over softwood, and Canada has prevailed every time it has challenged the U.S. through the North American Free Trade Agreement, the World Trade Organization or the U.S. court system.

Canada is the largest softwood lumber exporter to the United States, so these changes could have significant impacts right across the country.

"I don't know the full results yet. Nova Scotia and the Atlantic provinces have historically been exempt from tariffs," says woodlot owner Gavin Davidson.

The reasoning behind the hefty tariffs is the imports are grown on Crown land, and therefore subsidized. For many years, Maritime lumber has been exempt from American duties because the industry ruled it wasn't subsidized.

But President Trump has made no such distinction so far. That's left New Brunswick Premier Brian Gallant talking tough in support of his province's valuable softwood lumber industry.

"Trump's presidency and his protectionist view and approach is the greatest hazard to the New Brunswick economy," says Gallant.

While there is a lot of uncertainty, the Department of Commerce has suggested it would apply specific tariffs on five Canadian companies, including J.D. Irving in New Brunswick, which would be charged three per cent.

"New Brunswick's forestry system has always been based on free and fair trade. Crown stumpage rates are reflective of this system. This has not changed and should be recognized by the U.S. Department of Commerce," a spokesperson for J.D. Irving said in a statement.

While the reaction and concern is high in New Brunswick, Nova Scotia politicians and industry members are waiting to see if the so-called "Maritime exemption" will still take effect.

"Obviously it's a significant impact if there isn't an exclusion, and they are faced with countervailing duties. That is going to cost significant money for Nova Scotia producers, which is why we are fighting for that exclusion," says Nova Scotia Minister of Trade Michel Samson.

Gavin Davidson hopes President Trump gets the right message.

"I'm hopeful that when he sees some of the facts surrounding all of these issues, he'll be able to make the right decision," says Davidson.

David Barrett has been in forestry for 70 years. It's not the first time he's seen his industry threatened by cross-border tariffs.

"Every 10 years it seems the American government wants to put a countervailing duty on it. It's time consuming and money," says Barrett.

Robin Wilber is president of Elmsdale Lumber, a Nova Scotia company that ships softwood to the United States. He says the Atlantic provinces have fought hard to prove prices are set based on supply and demand.

"We pay whatever the going price is in a free market place," says Wilber.

Under the Maritime Lumber Bureau, the Coalition Against Unfair Lumber Taxes was created. They were successful in obtaining an exclusion for the Atlantic region for 30 years. However, the latest agreement expired in 2016, and the individual provinces took over negotiations.

As a result, the exemption no longer includes New Brunswick.

Wilber, like everyone in the industry, is waiting to see whether the 20 per cent tariff will apply to the other three provinces.

"Just because we get an exclusion doesn't mean we're out of this by any means," says Wilber.

Canadians opposed to the levy call the trade measures ‘arbitrary.’ They say it will only cost Americans more to build new homes.

The President of the Nova Scotia Home Builders Association says in the short term, it could bring down the cost of lumber in Canada, but ultimately people could lose their jobs.

"From a housing perspective, if people are worried about their jobs or unemployed, it does have an impact on people being able to purchase or renovate their homes," says Sherry Donovan.

David Barrett worries about people living in rural areas where employment levels are already low.

"This will just make it a little worse,” he said. “A lot of them may not even survive."

With files from The Canadian Press, CTV Atlantic's Dan MacIntosh and Kelland Sundahl.