PART IX — TERRESTRIAL ECOSYSTEMS 



grams should be greatly increased. 

 An obvious problem is that breeding 

 programs with trees progress slowly 

 because of the amount of time re- 

 quired for trees to grow to the point 

 where they can reproduce. 



Because of their high productivity 

 and even higher potential it might 

 be possible to develop tropical for- 

 ests as a major new food source. 

 For example, leaf extracts of a number 

 of species have a high protein con- 

 tent and large amounts of digestible 

 carbohydrate. Research is needed to 

 determine the best methods of leaf 

 collection and food extraction and 

 how to handle the disagreeable aro- 

 matic, gummy, or other substances 

 that are often produced by tropical 

 trees. Additional work will also be 

 needed to determine how to package, 

 advertise, and sell these products. 

 Traditional food habits of most peo- 

 ples are hard to change, even when 

 such change could result in a distinct 

 improvement in their nutrition. 



Some tropical trees have useful 

 pharmacological properties. About 

 half of the new prescriptions cur- 

 rently written contain one or more 

 plant products as a major active in- 

 gredient. The tropics have been an 

 especially rich source of these chemi- 

 cals and there is no doubt but that 



further investigation will be very 

 rewarding. 



Several other problems should at 

 least be mentioned. One has to do 

 with the use and misuse of resources 

 provided by animals of the tropical 

 forests in the form of meat, hides, 

 pets, and experimental animals. An- 

 other relates to the reservoir of dis- 

 ease, disease vectors, and pests pres- 

 ent in tropical forests. A third 

 results from the interaction of vegeta- 

 tion and the hydrologic cycle and on 

 the effects of irrigation, each of which 

 can produce appreciable effects on 

 local (and perhaps distant) rainfall 

 amounts. A fourth concerns the ef- 

 fects of wartime defoliation on large 

 stretches of forests and the problems 

 involved in providing for their rapid 

 recovery (or the development of 

 really good alternative uses of the 

 affected areas). 



Although it may not now be much 

 of an immediate problem, the rate at 

 which air pollution is increasing could 

 pose a serious problem to parts of 

 some tropical forests. As a result of 

 efforts of many of the less developed 

 countries (which are primarily tropi- 

 cal) to industrialize, local air pollu- 

 tion may increase rapidly. Many of 

 these countries may be too poor to 

 be willing to pay for unprofitable 



pollution-abatement programs and 

 processes. 



A possible longer-term problem is 

 related to the fact that tropical species 

 generally are more sensitive to tem- 

 perature fluctuations than are tem- 

 perate species. This means that if 

 man's various activities should cause 

 either a warming or, as now seems 

 more likely, a cooling of the climate, 

 the tropical forests could be in real 

 trouble. Removal of these forests 

 could itself contribute to this cooling 

 through resultant increases in albedo 

 and in atmospheric dust. In either 

 event, a useful ecological generaliza- 

 tion is that species from stable en- 

 vironments (as in the tropics) are 

 more sensitive to temperature and 

 chemical effects than are those from 

 fluctuating environments (as in tem- 

 perate zones). 



Finally, because of the magnifi- 

 cence and complexity of the biologi- 

 cal system that is represented by 

 tropical forests, they will serve as 

 excellent resources in the develop- 

 ment of man's understanding of the 

 ecological enterprise and as an area 

 to which he can go for rebuilding 

 and refreshing the human spirit. 

 Efforts should be made to preserve 

 parts of these forests, and to make 

 them readily available for these 

 purposes. 



Comparison of Temperate and Tropical Forests 



Whether we like it or not, feel it 

 dangerous or laudable, the human 

 race must prepare itself for a gigantic 

 task: managing the earth's surface! 

 This task is not, of course, the con- 

 cern of any single nation or race, 

 but it is obvious that the highly in- 

 dustrialized nations of the northern 

 hemisphere must take the lead in 

 tackling the job before us, because 

 they have the economic wealth, sci- 

 entific manpower, and industrial 

 force to begin to undertake the task. 



It is natural that we, as a people 

 of the temperate zone, take our own 

 environment, the deciduous forest or 

 grassland biome, as a reference point 

 in trying to understand other terres- 

 trial environmental features. This 

 way of thinking is sometimes dan- 

 gerous, especially if we try to draw 

 conclusions from management prac- 

 tices in one area and transfer this 

 concept to another. For present pur- 

 poses, however, it is valuable to start 

 from a few principles common to all 



productive areas of the world and 

 elaborate the differences from these. 



The State of Scientific Knowledge 



The temperate zone has at least 

 three very distinct forest formations 

 in which the ecology, especially the 

 sensitivity to human impact, is en- 

 tirely different: deciduous forest; 

 chaparral; and laurel forest. Tropical 

 areas are even more complex in this 



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