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7. Study of recent changes in the landforms. The rapid processes are, of course, the most interesting in this respect. Sedimentation (erosion by rivers, abrasion) accretion of coast lines, growth of coral reefs, lagoon deposits, shifting of dunes and soil erosion studies are promising subjects of dynamie photo geomorphology.

The applicability of geomorphological mapping and research to geolo-gy, soil science, engineering, etc. has already been mentioned and will not be further dealt with in this paper. An interesting and comparatively young application is in the integrated surveys of natural resources which are now being carried out in many developing coutries. The aim is to make available a great many data on the geological and soil conditions of the area concerned, of its landforms and hydrological situation, of the land use and vegetation. Most of these projects have two things in common, viz. their large size and the necessity to have the basie infor-mation just mentioned, available at short notice. It is evident that the only justifiable answer to this problem is aerial survey, because it com-bines great accuracy with high speed and because it accelerates the costly field work. The work normally starts with the compilation of a basemap from the airphotos. This is essential because in most cases a suitable map does not exist. It occurs repeatedly that the experts enga-ged in natural resources inventory themselves spend time and energy on the preparation of such a map, which is then morę or less suitable for their own purpose, but the ąuality of which is insufficient for many other aims. It is therefore efficient to have a reliable map madę by the photo-grammetrist, which can be used by all the experts working in the area and by those who will do so in the futurę. The region — often a drainage basin — then is analysed by a team of closely cooperating specialists who carry out the photo interpretation and the associated field work and further research. Quite remarkable results are sometimes obtained from the airphoto work. J. J. R e y n d e r s, Utrecht University, recently computed the rotation period of shifting cultivation from photo observa-tion. This rotation period is, in sparsely populated areas, an indication of soil fertility, whereas it is a measure for population pressure in morę densely populated parts. The tsetse fly in East Africa is affiliated to certain vegetation types, which can be mapped from the air. It is thus possible to plan a sleeping sickness campaign with the aid of airphotos. Recently a study in this field was madę by J. L i b e n at the International Training Centre for Aerial Survey, Delft, The Netherlands. Har-vest estimates also are amongst the possibilities.

The results of the various analyses carried out by the specialists concerned, are finally combined in a report in which all the necessary basie information can be found and in which the possibilities of further deve-lopment are indicated. Inherent to all these studies is the ‘analysis in layers’, viz. separatedly for geology, soils, vegetation, etc. A common starting point the present land use, as mapped from the air, and the ultimate goal is to estimate the potential, futurę land use and to indicate how to achieve this.

The geomorphologist in such a team has a double role. His work can be very useful for the geologist and the soil scientist, because the landforms are basie in their fields of photo interpretation. He can further-more study and evaluate the geomorphological characteristics of the va-rious parts of the area in ąuestion and he can make a landform or geomorphological map. It is essential for the geomorphologist engaged in

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