Air pollution, such as that evident here, can damage forests and rangelands up to 70 miles from the source. 



Air 



Air is a resource that significantly affects and is 

 affected by the Nation's forest and range lands. 



Impacts of air on forest and range lands — Air is 

 made up of many constituents that originate from 

 natural and unnatural sources. These constituents 

 eventually are deposited on the soil, vegetation, and 

 waters of the earth. Constituents causing undesirable 

 effects on living organisms or materials are called pol- 

 lutants. Air pollution is most common in industrial- 

 ized population centers and the forest and range 

 lands nearest these centers are most likely to be dam- 



aged. Pollution from some urban and industrial sites 

 has caused reductions in growth, increased suscepti- 

 bility to insect attack, and death to some vegetation 

 more than 70 miles distant. 



Most of the Nation's forest and range lands are in 

 areas of low population densities and have relatively 

 good air quality. Even so, air pollutants, transported 

 over long distances from urban and industrial cen- 

 ters, have direct adverse effects. Of major national 

 and international importance is acid precipitation, 

 caused by oxidation in the atmosphere of sulphur and 

 nitrogen oxides. Acid precipitation is now causing 

 adverse impacts on sensitive aquatic life, soils, and 

 vegetation, particularly in the northeastern United 



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