One important aspect has to do with the nature of the boreal shield itself. Because the rock, soil and water in the boreal shield has zero capacity to neutralize the acid, the sulfuric and nitric acid that falls to the earth in the form of rain or is spread in fog and in other ways across the shield tends to go directly into the groundwater deep underneath the first layers of soil and rock.
The second aspect, or another related directly to acid rain is the effect on important industries that depend on the natural cycles in the boreal shield. The most obvious is likely the timber industry as changes in the ph of the soil and water have already had a very negative effect on timber in the shield, slowing growth rates and killing some trees outright. It is also the source for some of the provinces' water, and keeping it clean is vital to supplying clean and inexpensive water for people to use.