Baltic timber mattered most for specialized mast spars

If Baltic timber supplies had been cut off after 1700, how much more naval production and protection would Britain need in North America?

Only a limited increase, because Baltic imports were especially valuable for high-quality mast spars rather than the bulk of hull timber, and Canada offered a substitute source.

Britain obtained most ordinary shipbuilding timber from its own forests, with Indian teak providing another source later. Baltic wood, especially Swedish timber, mattered for the upper masts and spars that required particular qualities. Canada could supply suitable substitutes, so losing Baltic imports would probably produce a limited increase in North American activity. The suggested protection was a few additional 64-gun ships, or perhaps 74s, rather than a much larger permanent fleet.