FORES I 



the demands of scientists and the 

 adequacy of public support. 



Ecosystem Models — The develop- 

 ment of ecosystem models is pre- 

 requisite to an adequate understand- 

 ing of environmental problems. A 

 single model is infeasible at the mo- 

 ment, but we see this as a future goal. 

 The development of a set of models 

 is the immediate necessity as a base- 

 line for application in both manage- 

 ment and teaching. 



The set of models to be developed 

 needs to include all of the classical 

 models mentioned earlier, but better 

 quantification is needed for many pa- 

 rameters. Tropical areas need much 

 more work for the elaboration of such 

 models than temperate zones. Spe- 

 cifically, the following sets of models 

 — in the form of abstract mathe- 

 matical equations, matrices, or proba- 

 bilistic or stochastic statements — are 

 needed for understanding and pre- 

 dicting human impact on the bio- 

 sphere or environment: 



1. Global Level 



(a) Production capacity of vege- 

 tation; responses to average 

 levels of growth factors like 

 radiation, temperature, wa- 

 ter, nutrients, pollutants; 

 utilization of vegetation by 

 animals and man; 



(b) Optimal carrying capacity 

 of the earth for men under 



various possible manage- 

 ment practices; 



(c) Interaction of vegetation 

 and the physical environ- 

 ment; circulation of carbon, 

 oxygen, and other sub- 

 stances through atmosphere, 

 biosphere, hydrosphere, and 

 geosphere; quantity and rate 

 (circulation speed) need to 

 be investigated. 



2. Biome Level 



(a) Production rate of vegeta- 

 tion; 



(b) Utilization practices of ani- 

 mals and other consumers; 



(c) Decomposition rate; 



(d) Reasons for homeostasis and 

 the equilibrium level of 

 forces that maintain it; 



(e) Efficiency of energy utiliza- 

 tion; 



(f) Man's management prac- 

 tices and their influence on 

 the system's turnover rates. 



3. Regional (Landscape) Level 



(a) Production, consumption, 

 and decomposition in bio- 

 cenoses; reactions to levels 

 and specific fluctuation pat- 



terns of external and inter- 

 nal forces like radiation, 

 temperature, water, nutri- 

 ents, pollutants, animal 

 feeding, etc.; 



(b) Developmental patterns of 

 species in space and time; 



(c) Qualitative responses of the 

 regionally available species 

 pool with regard to different 

 environmental matrices; 



(d) Chemical diversity within 

 the food web. 



Such a model can only be developed 

 if comparisons are available from all 

 contrasting biomes, although some 

 biomes are more important than 

 others for the development of a gen- 

 eral model. For example, inclusion of 

 a humid tropical forest is essential, 

 since these forests represent either 

 the absolute maximum, optimum, or 

 minimum realized on earth for many 

 of the ruling environmental forces. 

 Turnover of matter and energy in the 

 humid tropics is twice as fast as in 

 the temperate area. Tropical areas 

 contain at least 60 percent of the 

 world's natural resources. Again, the 

 humid tropics are especially suscepti- 

 ble to human impact, since their soils 

 and climate and orographic conditions 

 are highly sensitive. This is especially 

 true for modern agricultural tech- 

 niques, utilization of high-yielding 

 varieties, and constant shielding with 

 pesticides and insecticides. 



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