WORKING GROUP 3 
REYNDERS 
175 
Table I. Results of analysis of shifting cultivation areas 
Area 
Stage 
Units (in mm 2 ) 
Ratio to stage 1 
Age of stages in years 
A 
1 
60 
1 
1 
2 
62 
1 
2 
3 
115 
2 
3-4 
4 
196 
3 
5-7 
rest 
311 
5 
8-12 
total 
744 
B 
1 
53 
1 
1 
2 
96 
2 
2-3 
3 
111 
2 
4-5 
4 
161 
3 
6-8 
rest 
275 
5 
9-13 
total 
696 
G 
700 
ratio to A1 : 12 
ratio to B1 : 13 
13-25 
cultivated earlier by one of the clans now cultivating A or B, the shifting culti 
vation period will be about 25 years. This figure, arrived at by aerial photo 
analysis, fits into the picture derived from field experience. 
Although it lies beyond the scope of this paper, it will be obvious that with 
the same data and knowing the scale of the original photo, it will be possible 
to calculate the acreage cultivated per year, and, if the average area necessary 
for one family is known, the total number of inhabitants of the region can be 
given. This will be of importance for anthropological studies. 
Returning to the soil fertility the conclusion can be drawn that the (poten 
tial) fertility is very low, as it takes about 25 years before the soil returns to 
its initial state of fertility. 
Conclusion 
In conclusion it can be said that: 
- the aerial photographs give a better picture of shifting cultivation patterns 
than can be arrived at in the field; 
- these patterns often indicate better soils than in the uncultivated areas 
nearby; 
- the rotation period can be calculated from the aerial photos; 
- the rotation period, obtained from the analysis mentioned above, is a 
measure of the soil fertility of the soil type concerned. 
Discussion 
Mr. D. A. Boon (Neth., chairman W.G. 4) remarked that shifting cultivation is a very im 
portant problem in the tropics, as in certain regions large areas are completely damaged by 
this form of cultivation. What is the population density at which the fertility of the soil can 
still be secured for the future? Mr. Reynders answered that at the low population density of 
New Guinea (average about 1 person/km 2 ) there generally is regeneration of the original 
vegetation. Some figures could be given: Muju-district: 2 to 6 persons/km 2 , regeneration;