Acid Rain 2
If you think blackflies are getting worse, you’re absolutely right. A study has found that the « pestiferous and poisonous little demons’’ — as a French missionary called them 375 years ago — are being unleashed on Algonquin Park in numbers a hundred times greater than 50 years ago.
The reason: acid rain. Blackfly larvae love it. As lakes and rivers turn more acidic, they flourish, because they tolerate acidity better than predators and competitors.
In addition, acid rain is reducing the vigour of trees, accelerating their aging, impairing their ability to deal with stress, making them more susceptible to ultraviolet radiation damage, lessening their ability to withstand cold, and slowing their growth.
It is damaging the health of individuals — the young, the old, and those with respiratory problems. It is eating away at buildings, bridges, and other structures. It is killing fish and other aquatic creatures. And it is threatening the reproductive ability of birds.
However, in this litany of horrors, there’s good news. Although acid rain levels are holding steady at present, in Ontario we have reduced the prime ingredient, sulphur dioxide (SO2), by 62 per cent since 1980. Quebec has achieved a 68 per cent drop. Manitoba 20 per cent. New Brunswick 57 per cent. Nova Scotia 12 per cent.
But, at the same time, the nitric acid component in acid rain hasn’t gone down at all. It comes mainly from motor vehicle exhausts, where it is emitted as nitrogen oxides. They combine with water to form nitric acid. Improved exhaust systems have cut emissions, but the the continuing increase in the numbers of cars and trucks has kept total emissions steady.
Acidity is measured according to the concentration of hydrogen ions and is expressed in a pH scale that goes from 0 to 14. Neutral is pH 7. Zero is highly acidic, 14 is highly alkaline. Clams and crayfish begin dying at 6.5 pH. Trout have trouble reproducing at 5.5 pH, and start dying at 5 pH. At 4.7 pH, a lake is dead.
A 1997 government-industry task force report recommended that existing SO2 emissions be reduced by 75 per cent in both Canada and the United States (U.S. emissions account for half of the acid rain in Canada). That would reduce the areas at risk from acid rain in Canada by 99 per cent, to 7,000 square kilometres.
The task force said the cost to industry in Ontario alone, of a 75-per-cent reduction, would be $970 million to $1.3 billion annually, spread over the life of improvements made to equipment and plants. However the savings in health costs across Canada (no figures were given for Ontario alone) would be $890 million to $8 billion a year. (Not all members of the task force agreed on the figures for health savings.)
Although as yet uncalculated, savings to the forestry industry would also be big. In Ontario and Quebec it’s a $25-billion-a year business.
Even if SO2 emissions are cut by 75 per cent, nitrogen emissions will remain a serious problem. Not only car exhausts deliver them, so do chemical fertilizers. And as soils reach saturation, they too start releasing nitrates. Nitric acid is formed, and like acids of SO2, it leaches nutrients from the soil and frees aluminum, which blocks the uptake of nutrients by roots. The result is that on the Canadian Shield, where soil layers are so thin, trees can literally starve.
The stakes are high. What we need is first rate data, because of the difficulty in identifying the degree to which each stress affects the landscape.
For instance, we need to track the impacts and interactions among global warming, increased ultraviolet radiation caused by stratospheric ozone depletion, pesticide use, acid rain deposition, the incidence of disease, and insect infestation.
Without good data on everything, we can’t be sure what’s happening because stresses interact and reinforce each other. That’s why Ontario’s decision to cut all monitoring of acid rainfall is so lamentable (even though the federal government will maintain a few stations). It will save Ontario the paltry sum of $100,000. And reduce our ability to pinpoint cause and effect.