141 



According to Ledig (1992), "Introduction of exotic diseases, insects, mammalian herbivores, and 

 competing vegetation has had the best-documented effects on genetic diversity [of forest 

 ecosystems], reducing both species diversity and intraspeciTic diversity." Their impact has been 

 greater than that of other, more widely recognized, human-caused factors, including forest 

 fragmentation, changed demographic structure, altered habitat, pollution, and favoring of certain 

 "domesticated" species of trees. 



Timber Losses Due to Alien Pests 



In the U.S. and Canada, $2 billion in timber revenues has been lost due to tree mortality or 

 morbidity as result of exotic pest infestations (Pimentel 1986). Trees virtually eliminated as 

 timber supplies: chestnut, American elm, butternut or white walnut. 



Other Losses 



Timber supplies are not the only values associated with trees. The American elm was once the 

 primary ornamental tree in eastern and midwestern cities. The removal of elms killed by putch 

 elm disease has cost cities up to an estimated $100 million per year nationwide (Mazzone and 

 Peacock 1985). Nursery owners in the 1950s lost almost $1 million in Port-Orford-cedar nursery 

 stock due to spread of the fungal root disease, not including loss of future sales (Zobel et aL 

 1985). Fraser fir is increasingly popular as a Christmas tree. This species, along with balsam fir 

 and Douglas-fir, make up about thirty-five percent of national market ~ which sold more than 35 

 million trees in 1993 (Grimsley). 



Annual sales of maple syrup (made from the sap of the sugar maple) equals nearly $35 million 

 (Anonymous). 



Mitigation Costs 



Agencies of the U.S. Department of Agriculture spend between $20 and $25 million annually to 

 eradicate or suppress exotic pests or to mitigate their impacts. Port-Orford-cedar has been 

 severely reduced and the U.S. Forest Service is now spending $100,000 per year to manage 

 continued harvests. In 1989, Port-Orford-cedar brought an average price of over $2,600 per 

 thousand board feet (compared to $530 per thousand board feet for Douglas-fir). The value of 

 Expensive pest control, tree improvement breeding, silvicultural controls, and other programs have 

 also been needed to maintain harvest levels of red pine, white pines, and the oaks. These funds 

 are inadequate; threatened trees native to North Carolina which receive little or no funding 

 include the American chestnut, Fraser fir, and Canadian hemlock. The Forest Service is funding 

 a program on butternut, another valuable timber and nut tree almost eliminated from the forests 

 of North Carolina. 



In years when new outbreaks are discovered - such as the discovery of the Asian gypsy moth near 

 Pacific coast port cities in FY1992, funding levels can double (McGovern). 



