Inertia and Elasticity 



Two important characteristics of an ecosystem receiving oil or other 

 hazardous substances are its inertia and its elasticity. Inertia is its re- 

 sistance to change, or how much it can be stressed before it will change. 

 Elasticity is its ability to snap back to an approximation of the original 

 condition after major disruption from pollutional stress. This second charac- 

 teristic is of particular importance in spill response. These components are 

 difficult to quantify, but some estimates can be made. 



The critical factors contributing to rapid recovery of damaged ecosystems 

 are as fol lows: 



1. The existence of nearby epicenters for providing "seed" organisms 

 to reinvade a damaged system (e.g., for a river these might be 

 tributaries) . 



2. Mobility of life stages that may be important to movement of the 

 species. These may be spores, eggs, larvae, flying adults that lay 

 eggs, or any other stage in the life history of an organism that is 

 capable of moving either actively or passively to a new area. 



3. Condition of the habitat following pollutional stress. 



4. Presence of residual toxicants following pollutional stress. 



5. Physicochemical quality of the environment following pollutional 

 stress. 



6. Management or organizational capabilities for immediate and direct 

 control of the damaged area. 



Factors 3 through 5 are less important in this situation because it does 

 no good for the organisms to reinvade if they cannot survive once they do so. 



The presence of some regional management capabilities should be discussed. 

 In a paper "Opportunities for Maintenance and Rehabilitation of Riparian Habi- 

 tats," data on two streams located in different drainage basins in Pennsylvania 

 were used to show that by using only fish as an indicator, one can calculate 

 the time it would take an ecosystem to snap back and the difficulty of this 

 process. Enough case histories exist to document the efficacy of this proc- 

 ess although the components are difficult to quantify. 



The other property of the ecosystem is inertia, or the ability to resist 

 change. The fact is that indigenous organisms accustomed to naturally fluctu- 

 ating environments are much more resistant to change than those adapted to 

 stable environments. Structural and functional redundancy is the familiar 

 "spreading the risks" concept: if several organisms perform the same function 



164 



