6. ECOLOGICAL IMPACTS OF OIL AND GAS ACTIVITIES - DETERMINATION 

 OF IMPACT CAUSE, EVALUATION OF METHODS, AND MODIFICATION OR 

 PROPOSAL OF NEW METHODS OR STANDARDS 



USE OF ECOSYSTEM DIAGRAMS FOR IMPACT ASSESSMENT 



A description of the ecosystems diagram approach, its utility, its frame- 

 work, and its dynamic processes is addressed in Chapter 3 of this report. The 

 following discussion pertains to the analytical operations performed during 

 the present study to determine those impacts resulting from specific develop- 

 ment and exploration activities. 



As was previously noted, the ecosystems diagram (ESD) approach is an 

 analytical procedure that integrates a large amount of diverse information 

 regarding a natural system into a graphic model, the ESD, and then uses the 

 model to predict impacts resulting from system changes. Even though the ESD 

 is the core of the assessment procedure, several other analytical phases are 

 important to its utilization and therefore require discussion. The impact 

 assessment procedure consists of four major phases: (1) determination of 

 development activities, (2) determination of primary ecological alterations 

 resulting from specific development activities, (3) analysis and evaluation of 

 primary ecological alterations using the ecosystems diagram; and (4) impact 

 prediction based on the synthesis and interpretation of ecosystem alterations. 



Development Activities 



Activities can be described as specific actions which impinge on resources 

 either by construction-oriented development or by facility operation and 

 maintenance. Activities can be characterized as the lowest order, man-induced 

 physical processes which interact directly with definable aspect(s) of the 

 natural environment (for example, digging a pit, clearing brush, or burning 

 materials). A compilation of exploration and development activities is pro- 

 vided in Appendix A, and such activities were discussed in detail in Chapter 4. 

 Activities have direct influences (through primary ecological alterations) on 

 the ecosystem or parts thereof. Each activity is different in the sense that 

 it produces a unique set of environmental alterations. Certain types of 

 alterations may be shared with other activities, but other aspects remain 

 unique. The combination of unique and common alterations defines that partic- 

 ular activity. Activities may also be assembled into various combinations 

 that form higher order levels of organization, called "activity classes." The 

 activity class can generate environmental alterations common to many of its 



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