Needed: a Clean Air Act strong enough to protect plants
How clean must we keep the air?
The answer has been made complicated; it need not be. It is determined by the requirements for life - by the physical, chemical, and biotic conditions that are required to support living systems. These include not only man himself but those other organisms upon which man depends. It is not determined by partial cost-benefit analyses, or by compromise among competing polluters.
Standards for air quality are derived from two sources: (1) effects on man and (2) effects on other living systems. Criteria based on effects on man are less stringent than those based on effects on plants. This is because plants are more sensitive than people to low-level air pollution. This relationship is true in virtually every circumstance except for ionizing radiation, where standards for protection of man are adequate to protect all other organisms.
It is not surprising that those who may profit from pollution call for relaxed standards on the grounds that hazards to human health are small. Such arguments are largely irrelevant. The most important and demanding criteria are those derived from populations of plants and the factors that affect them. If plants are protected, people will be free of both direct and indirect effects of air pollution.
The costs to industry may be high, but the costs of failure to protect people and plants are far higher. The most immediate issue is the strengthening of the Clean Air Act, now up for renewal in the US Congress, and the governmental apparatus required to carry it.
Consider the Northeastern United States. There has been an increase over the last three decades in both the acidity of rain over North America and the area affected by the acidification. Effects are concentrated in the Northeast. All the acidity is not deposited in rain. A substantial fraction - one-third to one-half - apparently arrives as sulfur dioxide on small particles. It is removed from the air on to surfaces, including leaves, where it is converted to acid.
Other changes include increases in exposure of plants to a variety of contaminants such as ozone and heavy metals. All are produced as a result of the heavy use of fossil fuels in industrialized areas to the west and south. New England bears the brunt of the effects because the storm tracks commonly pass through it.
Effects of this atmospheric chemistry are sufficiently complicated and difficult to measure to provide ample basis for discussion among scientists and equivocation by others. The most clearly defined effect of acid rain is the acidification of lakes and streams in areas where the bedrock contains little limestone. Such areas have granitic rocks, their metamorphic equivalents, or sedimentary rocks that have a low alkalinity and therefore little capacity for neutralizing acids.
Most of New England falls in this category. Its lakes, streams, and ground water are turning acid. The effect is the loss of freshwater fisheries in lakes and streams, the virtual sterilization of the water bodies. High acidity in wells mobilizes aluminum and other metals containing lead from minerals in the ground and in pipes. Aluminum is toxic to plants and certain animals, including fish. Lead and other heavy metals are toxic to people as well.
In certain instances, the additions of the nitrogen and sulfur associated with the acidification have caused increases in growth of trees. There is, however, substantially no basis for assuming that the acid-leaching of forests or agricultural crops by the more acid rains will produce any effect in the longer term apart from impoverishment in essential nutrients, reduction in rates of growth, reductions in agricultural yields, and the loss of species and yields from forests. These effects are in part directly due to the acidification and in part due to increased incidence of diseases favored by any generalized stress.
The effects of ozone and other components of photochemical smog compound the problem. The national standard for ozone was set in 1971 as 0.08 p.p.m. The EPA reported that, in 1977, all but one of the 34 monitoring stations in New England reported violations of the standard. The standard was increased in 1979 to 0.12 p.p.m. The probability was 95 percent or more that ozone concentrations exceeded the new standards in 1977 and 1980 over extensive areas in the United States, including the Eastern US from south of Washington to Portland, Maine. Many plant species are sensitive to photoxidant damage at concentrations below the current standard.
Evidence for the effects of air pollution on forests is accumulating rapidly. Damage has been shown in stands of white pine along the Blue Ridge Parkway in western Virginia. An average reduction in growth of 40 percent was measured for the period 1955-1977. A similar reduction in the growth of pitch pine has been reported in New Jersey over approximately the same period. Other trees showing severe declines in vigor, even widespread mortality, over extensive areas in New England include the beech, the red spruce, the white ash, and the white and yellow birches. Insect and disease organisms are known to increase under air pollution, and it would be surprising to discover that the problems observed in forests in the Northeast are not caused by the combination of air pollutants now present.
The pattern of change to be expected in the terrestrial vegetation under this series of stresses is well known. These transitions are under way: losses of forest productivity, shifts in species, losses of tree species, all accompanied by losses of freshwater fisheries and the acidification of ground water, with toxic consequences for man.
The evidence is that agricultural yields in the Ohio River Basin are being reduced significantly and that photosynthesis by forests over large areas is also being reduced. A measure of this is seen in the magnitude of reductions in solar energy captured by plants and made available by both agriculture and forests. These range upward to as much as 40 percent in certain circumstances. A general 20 percent reduction in the magnitude of these resources would not be surprising.
If the reduction applies to all of New England's forests, it would, in energy terms, amount to the output of between fifteen and thirty 1,000-megawatt power plants, or 135 to 270 billion kilowatts a year. Valued as electricity, it would be worth $7 billion to $14 billion. This is a substantial subsidy for the New England states to be paying from their forests and pastures and cultivated fields in the interests of industrialization elsewhere.
These statements may appear as mere assertions by an overly sensitive scientist. Each statement, however, can be documented in detail from the extensive literature now available on air pollution and on biotic effects. While none of these statements are beyond argument, the weight of evidence is that our regulatory system, as it stood before it was cut by the present administration, was inadequate to protect the public's vital interests. The proposals to weaken the Clean Air Act further promise still greater erosion of the capacity of the nation to support people.
How clean must we keep the air? Clean enough for green plants.