STRESS AND ECOSYSTEMS 



75 



components selected for are those that somehow maximize energy 

 flow despite the presence of stressors. This is done either by diverting 

 all incoming energies to overcome stress or by extracting useful work 

 from the disordering force. Energy drains are normal processes 

 affecting living systems and should be identified as such even if they 

 normally do not reach critical thresholds beyond which recovery is 

 difficult. 



To evaluate the relative impact of push— pull effects on ecosys- 

 tems and to gain insight into the cost of recovery and ecosystem 

 resilience, we can calculate ratios of disordering-to-ordering energies 

 (Richey, 1970). This involves calculating the magnitude of energy 



TABLE 3 



RATIO OF DISORDER TO ORDER IN ECOSYSTEMS 

 SUBMITTED TO STRESS 



*Reduced to fossil fuel equivalents. 



flows that disrupt ecosystem structure and function and the 

 magnitude of energy costs associated with reordering and maintain- 

 ing order in the system. Table 3 summarizes literature reports on this 

 ratio. Most values are derived from experimental situations, where 

 the disordering input can be computed easily. Results show that 

 disordering energies have considerable amplification and that build- 

 ing and maintaining order is extremely expensive relative to the cost 

 of destruction. Obviously, the capacity of a system to regenerate 

 depends on the availabihty of enough energy sources to reorganize 

 the disordered structure. Since the availability of energy is a function 

 of the environment, the type of environment dictates rates of 

 recovery and degree of complexity at the steady state. In the term 

 complexity, I include such measures of ecosystem organization as 



