SPOKANE, Washington — Threats by President-elect Trump to impose sweeping new tariffs on the US’ top trading partners are revving up an old trade war that has pitted Washington, Oregon and Idaho foresters against Canada for more than 40 years. …It’s not clear whether that 25% tariff on lumber from Canada would cap at that amount or be added to the existing 14.5% tariff on those forest products. Regardless, it would make it more costly for Spokane-area residents to build a home, said Joel White, executive officer of the Spokane Home Builders Association. …Canada leads the world in production of forest products, which includes everything from raw lumber used for building to pulp used for making paper. The U.S. ranks second for world production, and Oregon and Washington lead the nation for where those trees are harvested. While both countries export forest products, they also represent the top importers of forest products from the other.