An Ecological Assessment of the Louisiana Tensas River Basin: Chapter 2 
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conversions to agriculture. These watersheds are prima¬ 
rily located in arid and mountainous areas, where grazing, 
although an important agricultural activity, does not change 
the grassland cover type at this scale. About 10% (200) of 
the Nation's watersheds have been almost completely 
converted to agricultural land; these are located mostly in 
the fertile central United States. 
The Tensas River Basin (Figure 2.4b) is shown in red 
putting it in the 5th quintile and giving it a data range of 
greater than 69. This means that there is a very high 
agricultural land use practice in this watershed. 
The complicated spatial patterns in the southern United 
States are evident in the map of land cover diversity 
(Figure 2.5). The map shows the watershed ranking for 
the number of different natural land cover types (anything 
except urban and agriculture) per unit area. These 
rankings are based on the original 160-class version of 
land cover and not the 9-class version shown in Figure 2.1. 
The greatest diversity of natural land cover is found in 
the western United States, where large changes in 
elevation produce different vegetation types at the top 
and bottom of the same watershed. But there are also 
diverse watersheds in coastal areas, including parts of 
the Mississippi Gulf region. 
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Indicator Value 
