and energy flow in opposite directions in society; i.e., money output is 

 exchanged for energy input. Thus the ratio of Gross National Product 

 to National Power Consumption can be used to "convert" calories to 

 dollars. For the United States this is approximately 10,000 kilocalories 

 per dollar. Using this conversion, the ecological work of an acre of 

 forest has been calculated to be about $2,560 per year. Still to be 

 determined is the proportion of this work which is essential to man as 

 part of his hfe support system. 



Another approach to economic evaluation of natural ecosystems 

 involves assessing the work of nature in treating and recycling 

 municipal wastes. Experiments at Penn State University indicate an 

 acre of natural or seminatural vegetation can be an effective tertiary 

 treatment mechanism. An acre of land can absorb about 1.3 million 

 gallons of treated waste water per year, which is about the amount of 

 waste water produced by 35 city people. If this waste were subjected to 

 artificial treatment, it would cost about $1,400. Thus in addition to 

 "growing a tree crop," an acre of land could be worth an additional 

 $4,000 per acre for waste effluent disposal. 



A useful method to determine ecological versus technological tradeoffs 

 is to estimate per capita needs for land. It has been suggested that the 

 minimum per capita acreage requirements for a quality environment 

 based on present United States population and acreage is on the order 

 of: 



Food-producing land 1.5 acres 



Fiber-producing land 1.0 acre 



Natural use areas 2.0 acres 



Urban-industrial areas 0.5 acre 



Total 5.0 acres/capita to sustain the 



present quality of life. 



Although more intensive culture can increase food yield per acre, 

 additional requirements are generated to sustain the higher level of 

 technology. This thesis needs to be tested because, if true, our present 

 U.S. population can be more than doubled before depletion of life's 

 amenities. 



Associated with this calculation is the idea of some optimal proportion 

 between natural and constructed environments. In order to develop a 

 rational ecosystem management plan, the optimum ratio between 

 natural and artificial ecosystems must be determined. Preliminary 

 estimates suggest the ratio should be about 1 : 1 on an area basis for the 

 United States as a whole but should differ between regions. If this 

 concept is valid, then we are already overbalanced in some geographic 

 areas. An acceptable ratio depends on the character of use and 

 management, but it is clear that aggregation of people into urban 

 centers also requires natural ecosystems somewhere to sustain the life 

 support system. 



In ecological research, emphasis is placed on holistic studies of 6. Current Problems of 



ecosystems with special attention given to the processes of interaction 

 among the components. These types of studies are needed to evaluate 

 and predict the environmental impact of all types of development 



Ecosystem Research 

 and Management 



33 



