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Preservation of natural vegetation and wild-life. Nowadays in this country aerial photographs 
are also used with much success to obtain more profound information on the living condi- 
tions of rare plants and animals. Their particular environment is usually known and if 
this can be detected on the aerial photographs, a better knowledge can be obtained about 
their occurrence and distribution. Based upon this information steps can be taken to create 
possible reservations to protect against extinction. In addition to this, the department 
dealing with this subject has also used aerial photographs to study the distribution and 
movement of seals and rabbits. 
VII. 1b. Suriname 
Already during the period of the execution of the aerial survey in the scale of 1 : 40.000 
of the northern part of Suriname in 1947-1948 for the coastal regions, photographs in 
the scale 1 : 20.000 were taken in order to locate the main vegetation types of these low 
lands. The resulting type maps were found to give an excellent foundation for additional 
forest inventory work by making strip surveys and they were also very useful for the 
location of extraction roads. 
Based on this experience the Suriname Forest Service decided to make more intensive 
use of air photographs and to study particularly the possibility of identifying valuable 
species on air photographs. Special attention was given to the identification of "baboen" 
(Virola surinamensis), a tree species which occurs in the coastal swamps of Suriname, 
and of Triplaris surinamensis a species which grows mainly gregariously under the same 
conditions. 
A research project to obtain more detailed information on the influence of photographic 
scale, films and filter combinations, and different diaphragm settings seemed therefore 
worthwhile. In 1956 some test. flights were made by K.L.M. Aerocarto Ltd. with the 
following results. Compared with smaller scales 1 : 10.000 proved to be the best scale for 
identifying individual baboen trees. The effects of occasional morning haze were elim- 
inated by using a yellow filter. 
Based on the results obtained with these tests the Forest Service decided in 1956 to have 
all baboen forest areas photographed from the air. The location of the photo strips could 
be determined by means of the interpretation made on the 1 : 20.000 photographs. In 
total 8 different baboen areas with a total area of 1350 sq. km were photographed on a 
scale of 1 : 10.000. Photographs were made with a panchromatic film, Gevaert Aviphot 
33° and with yellow filter no. 2. 
The identification of the baboen trees on the photographs was assisted by the fact that 
dominant crown canopy in the typical baboen areas mainly consists of this species. Another 
indication is that the baboen trees are mostly slightly lighter in tone than the other species. 
Occasional mis-interpretations, however, are always possible. Only the baboen trees with 
a crown diameter above a fixed limit value were counted, and these were indicated by a 
white dot. The position of these dots was afterwards transferred to a 10.000 map using a 
Sketchmaster. Occasional checks were made in the field to compare the number of trees 
determined on the photographs with the actual number on the ground. 
Based on the total number of trees within a certain area a rough estimate of the total 
timber volume was made in order to plan exploitation. Further the maps proved to be 
very valuable for the siting of the timber extraction canals. 
The results obtained with the test photographs regarding Triplaris surinamensis were 
not satisfactory enough to justify large scale photography of this forest type. The negative 
results may be due to the gregarious habit of this species which creates difficulties in 
tree counting. 
37