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 

 preexploration activities 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 considered during all phases of activities since it 

 extends the effects of the project beyond the boundaries if the immediate 

 site. 



Key attribute alterations 



The alteration which leads to the most significant impacts on the eco- 

 system is the creation of depressions in the land surface. Although 

 long-term effects on vegetation types may result from changes in water- 

 flow regimes, the areal extent of surface damage and impact on consumers 

 are minimal. As discussed above, direct vegetation removal may be bene- 

 ficial in some instances. 



Gravity preexploration . 



1. Activity sequence 



Gravity surveys may involve the placement of a relatively small piece of 

 equipment on the marsh surface. This unit (the gravity meter) may be 

 carried to stations by truck, marsh buggy, boat, or foot. Survey crews 

 are not required since data need not come from predetermined locations. 

 It is necessary only to plot the locations of the data collection 

 stations on a map. A small amount of vegetation is trampled during the 

 placement of the gravity meter. Several minutes are required for data 

 collection; the unit is then packed and carried to the next station. The 

 number of stations required for a gravity-meter survey is less than the 

 number of shot holes necessary for a seismic survey. Two men with 

 adequate transportation can efficiently conduct a gravity-meter survey. 



2. Primary ecological alterations 



2.1 Creation of ruts or depressions in the land surface 



2.2 Trampling and crushing of vegetation at the station locations 



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