those components are possible. The same analytical process is repeated as 

 many times as necessary until endpoints are achieved for all primary, second- 

 ary, and higher-degree pathways. 



The above procedure will yield a set of environmental alterations of 

 different importance for each initial PEA analyzed. The fourth stage of the 

 ecosystems analysis involves synthesizing and interpreting these alterations 

 in order to determine those of greatest importance with respect to each PEA. 

 Reevaluation of complimentary or neutralizing alterations may occur again at 

 this stage. The net effects of the initial PEA in that particular ecosystem 

 are thereby determined - these are now referred to as impacts. 



Impact Assessment 



Following the determination of impacts, it is necessary to consolidate 

 them and evaluate their relative importance in terms of disruption of ecosys- 

 tem stability. Ranking may be desirable in order to establish the impacts of 

 greatest potential significance associated with a specific development phase. 

 Impacts of similar effects can be aggregated and summarized, and irrelevant 

 impacts can be deleted. The key attribute alteration, that primary ecological 

 alteration which has the potential of causing the most extensive ecosystem 

 change, can be determined. The foundations for subsequent stipulation evalua- 

 tion are thereby provided. 



SYSTEMATIC IMPACT AND METHODS ASSESSMENT 



In the following sections, the impacts of oil and gas development phases 

 have been determined for eight ecosystems. Because of their similarities, the 

 upland systems - maritime forest, coastal grasslands, and brush-grass complex - 

 have been treated together. Differences in their responses have been noted. 

 This review serves only as a reminder of the basic activity sequence and does 

 not attempt to give the detail that can be found in Chapter 4 in the section 

 entitled, "Detailed Account of Normal Oil and Gas Activities." 



For each ecosystem, a brief review is made of the activity phase. The 

 primary ecological alterations are noted, and a discussion of important ecosys- 

 tem attribute alterations is included. The key attribute alterations, the 

 most important changes, are identified. 



Chapter 7 provides a concise summary of the best-worded, most effective 

 stipulations that land managers can use to assure maximum control over oil and 

 gas activities on these lands. Some already are being used, others have been 

 modified, and others have been proposed. The stipulations are organized in 

 the same manner as the following discussion of impacts - by ecosystem first 

 and then by development activity. 



148 



