Attribute alterations 



The movement of work crews and marsh vehicles over the land surface 

 tramples and crushes vegetation in a zone wider than that cleared 

 for shot placement. The vegetation may be completely uprooted and 

 destroyed in some areas, depending upon the soil moisture condi- 

 tions. This results in an immediate decrease in food and cover for 

 the consumers in the area. The total area affected is usually small 

 in comparison to the remaining area of productive vegetation, and 

 the effects on animals, competition (shading), rough-mat formation, 

 and detritus accumulation are insignificant. 



The depth and number of ruts created by marsh vehicles are dependent 

 upon the total number of trips and the degree to which vehicles 

 retrace existing tracks. Deep ruts resulting from retraced trails 

 will form surface depressions for the movement of water and, if deep 

 enough, may result in standing bodies of water during wet seasons. 

 The orientation and depth of the depressions determine whether they 

 (1) remain for long periods of time and (2) alter the water regime 

 of a given area of land by increasing or decreasing the frequency of 

 submergence/emergence, average depth, and duration of submergence. 

 Areas dominated by marshhay cordgrass may be replaced by stands of 

 threesquare or other water-tolerant species when the frequency 

 and/or duration of submergence increases. The converse may occur 

 when frequency and/or duration of submergence decreases. Although 

 the total area affected is site specific, it is usually small when 

 compared to the total area of brackish marsh. Consumers that depend 

 upon these grasses and sedges for food and/or cover may ultimately 

 increase or decrease. 



The depressions allow a faster runoff of surface and standing water 

 in localized areas. The long-term effects on suspended sediments 

 and nutrients are slight. If vehicle tracks occur in areas of the 

 marsh where isolated ponds exist, intramarsh circulation could be 

 affected. Depressions could connect individual water bodies and 

 increase the intermixing of their contents. Waterfowl and wading 

 bird use would be expected to increase in these new depressions with 

 standing water. At the ecosystem level, however, this increase is 

 insignificant. 



The degree and significance of wildlife displacement resulting from 

 all oil and gas activities, including preexploration, are impossible 

 to predict or quantify. The point where noise and human presence 

 may change temporary and partial displacement to permanent and 

 complete displacement is unknown, but this factor should be consid- 

 ered during all phases of activities since it extends the effects of 

 the project beyond the boundaries of the immediate site. In general, 

 preexploration activities are short-term (two weeks or less), small 

 scale, and result in only minor wildlife displacement, even when 

 explosive methods are used. 



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