Page 115 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

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Poland, up to 50% of the forests are dead or damaged.
in the eastern United States, some of the worst forest decline has occurred in the spruce and fir forests of north Carolina and Tennessee (Figure 3.2.1). in the adiron- dacks, red spruce and sugar maples have been especially hard hit. affected trees are susceptible to winter cold, insects,
and droughts. in red spruce, decline is evi- denced by poor crown condition, reduced growth shown in tree-ring analyses, and unusually high levels of tree mortality. For sugar maples, an indicator of forest dam- age is the reduction by almost half of the annual production of Canadian and U.S. maple sugar.
Nitrogen Oxides:
A Worsening Cause
in the United States, the problem of acid deposition appeared to be solved with the passage of the 1990 Clean air act (Caa) amendments, which targeted industrial emissions of
sulfur dioxide and nitrogen oxides. From 1990 to 2008, sulfur emissions from power plants decreased almost 70%, and wet sulfate deposition rates dropped across eastern Canada and the eastern United States—a real suc- cess story for science and public policy (Figure 3.2.2).
However, nitrogen emissions declined little and in some areas have increased. nitric oxide (nO) emissions come from three main sources: agricultural opera- tions (specifically, fertilizers and animal- feeding operations, which produce nitrogen and ammonia), motor vehicles, and coal-combustion power plants.
europe shows similar trends: Several studies have recently found areas with high levels of atmospheric nitrogen oxides in Switzerland and northern italy, presumably associated with intensive agriculture and fossil fuel burning, as well as in norway, where acid deposition in streams could have impacts on the economically important salmon industry.
However, 49 european countries began regulating nitrogen emissions in 1999, re- sulting in a regional decrease in nitrogen emissions of about one-third.
in China, overuse of nitrogen fertil- izers (an increase of 191% from 1991 to 2007) has led to acid deposition in soils, lessening crop production by 30% to 50% in some regions. if this trend continues, scientists fear that soil pH could drop as low as 3.0, far below the optimal level of 6.0 to 7.0 required for cereals such as rice.
acid deposition is an issue of global spatial significance. Because wind and weather patterns are international, ef- forts at addressing the problem also must be international in scope. reductions in acid-causing emissions are closely tied
to energy conservation and therefore directly related to production of green- house gases and global climate-change concerns. recent research pinpointing ni- trogen as the leading cause of acid depo- sition links this issue to food production and global sustainability issues, as well.
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▲Figure 3.2.2 Wet Sulfate Deposition. Spatial portrayal of wet sulfate deposition on the landscape, in kilograms per hectare, shows a marked decrease between 1990 and 2010 in the sulfate that fell as rain, snow, or fog. improvements result from combined Canadian and U.S. regulatory action on emissions that add acids to the environment. [Based on environment Canada.]
from paints and other household materials—that are important factors in ozone formation.
Industrial Smog and Sulfur Oxides Over the past 300 years, except in some developing countries, coal slowly replaced wood as society’s basic fuel to pro- vide the high-grade energy needed to run machines.
The Industrial Revolution led to the conversion from animate energy (from animal sources, such as animal- powered farm equipment) to inanimate energy (from nonliving sources, such as coal, steam, and water). Pollution generated by industry and coal-fired elec- trical generation differs from that produced by trans- portation.
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Chapter 3 earth’s Modern atmosphere 79
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