PART IX — TERRESTRIAL ECOSYSTEMS 



the knowledge gained there shows 

 reverberations and applications in the 

 temperate zone. 



Mathematical Models — Modeling 

 in the sense that it is used today with 

 regard to systems analysis — i.e., 

 mathematical or computer modeling 

 — exists for partial processes in many 

 cases in the temperate forest area, 

 only rarely in the tropics. No entire 

 ecosystem is yet completely under- 

 stood and modeled in any biome. 

 This work is just now being under- 

 taken by several thousand ecologists 

 working in different parts of the 

 world. 



The Analysis of Ecosystems Pro- 

 gram of the U.S. International Bio- 

 logical Program has as its ultimate 

 goal to provide the next generation of 

 scientists with an ecosystems model 

 that gives a satisfactory approxima- 

 tion of the following structural and 

 functional characteristics of the vari- 

 ous terrestrial ecosystems: (a) pro- 

 ductivity range; (b) turnover rates of 

 matter and nutrients; (c) species di- 

 versity; and (d) environmental pa- 

 rameter ranges with special emphasis 

 on energy, temperature, water and 

 substitute levels of nitrogen, phos- 

 phorous, potassium; and others. Fur- 

 ther, the program will help us to 

 secure sufficiently accurate data for 

 the elaboration of a general ecosys- 

 tems model that enables us to predict 

 functional and structural responses of 

 any given ecosystem to man-made or 

 accidental changes. 



It will take several more years of 

 intensive study to develop predictive 

 models for population changes and 

 chain reactions caused by the elimi- 

 nation or introduction of species or 

 groups of species. These "sensitivity 

 investigations" may provide the most 

 important results from present eco- 

 systems studies. In many cases, 

 changes are surprising and significant 

 but apparent only after several years. 

 It might be easier and quicker, there- 

 fore, to study the effects of some 

 interferences in tropical environments 



her than in temperate zones, be- 



cause development periods are shorter 

 and uninterrupted by a rest period. 

 Genetic studies have applied this 

 principle successfully in many cases, 

 and ecologists should do the same. 

 The results of such studies in tropical 

 areas will provide us with models that 

 will help us to manage our own envi- 

 ronment, especially in the southern 

 United States. 



For some of the large-scale changes 

 that man imposes upon the environ- 

 ment, predictions are already possi- 

 ble. Thus it is probably safe to predict 

 that, in South America, large-scale 

 traditional (temperate-zone) agricul- 

 ture in the Amazon-Orinoco water- 

 shed will fail, that the Rio Negro 

 region will change from a black-water 

 stream to a white-water system, that 

 all sorts of unpredictable changes in 

 the fauna will occur as a result of the 

 removal of several natural environ- 

 mental barriers, and that fantastic 

 changes will follow in every respect. 



It is probably unsafe, however, to 

 predict what would happen to the 

 atmosphere if all the tropical regions 

 of the world were cultivated. The 

 data base is too slim for any reason- 

 able prediction. We can only define 

 certain areas that are likely to become 

 problems: for example, the change of 

 tropical air masses from an almost 

 constant carbon dioxide level to an 

 as yet unpredictable fluctuation; or 

 the potential threat of airborne dis- 

 ease originating in the tropics (espe- 

 cially fungal diseases of plants) for 

 plants, animals, and man. The at- 

 tempt to establish large human settle- 

 ments in the humid tropics of South 

 America raises problems of unknown 

 magnitude. For example, sanitary 

 sewage disposal in an area saturated 

 with water and at such a temperature 

 level is a gigantic problem, and the 

 prospect of industrial sewage is even 

 more dire. 



Needed Scientific Activity 



The primary reason that ecology 

 was previously the "Cinderella" of 



the biological sciences is the fact that 

 an incredible number of species are 

 ruled by an unwieldy number of 

 forces, and the species in turn influ- 

 ence the forces. The analysis of an 

 ecosystem always seemed an unman- 

 ageable task, even assuming that only 

 the most important components were 

 to be studied. The recent develop- 

 ment of systems analysis, the teach- 

 ing of team studies, and the ever 

 growing computer capacities give us 

 a more realistic chance for a valid 

 ecosystem model. But all these tools 

 are useless without a willingness of 

 many scientists from several disci- 

 plines to cooperate in one study and 

 generate the necessary data pool for 

 individual cases. 



Data Base — The data base for the 

 prediction of human impact is com- 

 pletely incomparable in deciduous 

 and tropical forest areas. From the 

 standpoints of an ecosystems mod- 

 eler, the data base is totally lacking 

 to unsafe or, occasionally, satisfactory 

 in tropical areas and sometimes suffi- 

 cient to unsafe in the deciduous forest 

 areas. A general judgment is not 

 possible because the knowledge nec- 

 essary for the understanding of eco- 

 systems is so different in the various 

 disciplines. It is still necessary to 

 conduct major investigations and col- 

 lect a sound set of data if one cares 

 about accurate models that are mean- 

 ingful for management purposes. 



Instrumentation — The sensors and 

 techniques to acquire the necessary 

 data are generally adequate, though 

 their reliability and durability are 

 usually better in temperate zones 

 than in the tropics. It is, of course, 

 always necessary to develop new 

 tools for the constantly changing 

 tasks before us. For the elaboration 

 of better and more complete ecosys- 

 tem models, we foresee the need for 

 simulators and analogue computers of 

 larger dimensions. Many computing 

 facilities today still have only the 

 capacity to confirm the conclusions 

 that people had drawn from hand 

 calculations. How quickly progress 

 will be made naturally depends on 



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