Our IJ\'iiii; Ri'Xdiincs — Habitat Assessments 



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volcano shortly after its eruption May 18, 

 1980. The 1988 image shows revegetation of 

 the northern slopes, and a landscape gradu- 



ally recovering to a new "natural" state. A 

 feature of this set of images is the small 

 bluish rectangular patches surrounding 



Mount Saint Helens, representing areas that 

 have been logged by clear-cutting. 



Fig. 2. Landsat MSS images of the Mount Saint Helens area in southern Washington in 1973. 1983, and 1988. The 1973 image shows the area before 

 eruption. The area north of the crater in the image with the bluish color was most devastated by the 1980 eruption. In the 1988 image the light pink color in 

 the blow-out area shows vegetation regrowth. 



vegetation type (Fig. 3). Although more than 

 61% of the conterminous United States is cov- 

 ered with the same dominant vegetation as 

 KiJchler suggests, the percentage varies consid- 

 erably by region. Almost 92% of the western 

 forests region remains covered with tree 

 species, while only 29% of the central and east- 

 ern grasslands region remains as grasslands. 



It must be understood that a low percentage 

 of agricultural or urban lands in a region does 

 not imply that the landscape exists in a pristine, 

 natural state. In some cases, the "natural" vege- 

 tation may be altered substantially by local 

 land-use practices such as grazing and logging 

 or changed by the introduction or invasion of 

 non-native vegetation. Kiichler (1964) recog- 

 nized overgrazing as having long altered the 

 central grassland. He also mentioned Kentucky 

 bluegrass (Poa pratensis) as an exotic that has 



become the dominant grassland in regions 

 including the Black Hills of South Dakota. As a 

 result, many areas that are not affected by agri- 

 culture or urbanization are far from their natur- 

 al state and do not perform the same ecological 

 role as did the original ecosystem. The coarse 

 nature of the AVHRR data and the lack of 

 detailed baseline data on original vegetation 

 conditions do not allow for the detection of 

 these important landscape qualities. While 

 these assessments have limitations, the compar- 

 isons represent the type of analysis and moni- 

 toring that can be done with a properly designed 

 operational vegetation monitoring system. 



The areas with the highest percentage of 

 land modified from its natural condition are in 

 the central United States. With one exception, 

 the most intensively cultivated areas coincide 

 with Klichler's grassland or mixed grassland- 



