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Review of the discussions

I. Definition of objectives
II. Evaluations
III. The methods used

The discussions can be regrouped into three large subjects:

I. The definition of the objectives.

II. The evaluations:

- interests,
- methods,
- means of decision,
- costs.

III. The methods used:

- scales,
- standard aerial photos and satellite pictures.

I. Definition of objectives


Before defining the objectives of the evaluation it would be necessary to define what a tropical pastureland is, what the limits of it are, and how to determine the importance and value of it.


A definition of the idea of the distance covered is equally desirable. Wouldn't it be necessary to enlarge the field of investigation by the " grazing experts " in order that the nutritionists can benefit from the results of their work ?


What are the sociological, climatic, geological agrostological, and zootechnical criteria necessary to individualize the two categories of evaluation defined by A. Blair Rains: surveillance and development of pasturelands ?


It is necessary to define precisely what the objectives of an evaluation are.


These are the objectives that determine the type of information to collect and the method of collecting.


Whatever the type of evaluation asked for, the principal objective is development (the point is stressed by Dr. Inuwa as well).


If the needs of the users, the nomads, have been seriously presented, at the time of implementation of the evaluation the objectives become evident,


One solution to the problem would be to localize the nomads who only move out of necessity. The objectives in this case are very precise: it is necessary to furnish the nomads grass and water - that implies a type of " multi-objective " development, according to the expression of Dr. Perry.


While accepting the idea of localizing the nomads and the objectives that implies, the question still comes up concerning the utilization of the dry zones in the North which cannot accommodate a nonmobile population.


A precise definition of objectives is necessary. That would permit, in addition, being able to estimate the cost of the evaluation to be undertaken.

II. Evaluations



For Dr. Inuwa as for myself the evaluation has a very specific role - to furnish basic ideas from which discussions and decisions must be forthcoming - but it is not an end in itself. It is otherwise because it has been too often considered as an end, and information that it contains is often not usable.


It is true that numerous evaluations have already been carried out, but few have been used. It is therefore necessary to strive to help governments better use the existing evaluations and to make them practical.


The interest of the evaluations would be much greater if one were to plan them so as to be able to measure over several years the progress of the development or deterioration of the pasturelands.

Numerous evaluations of the soil by aerial photos and even through attempts at using infra-red rays to measure the degree of dryness have been undertaken in the Sahel for the last three years. It was realized at that time that it was necessary to control the evaluations. It seems, however, that little effort was made to coordinate these evaluations, which made them lose much of their interest.



In order to manage the pasturelands, three aspects must be taken into consideration:

- make a balance-sheet of resources,
- study the conditions in which they are found,
- follow their evolution.


When we talk about the objective of an evaluation, it is necessary to remember that the composition of a pastureland is based on a large ecological concept involving water, animals, men, etc. Thus, if we want to carry out an evaluation of pasturelands, it is necessary to take borders into account. Unfortunately governmental structures are often an obstacle. It would be necessary, therefore, to be able to develop an original approach to the problem. A young organization such as ILCA could do it; certainly not the traditional administrative structures.


As Dr. Baker advocates, the evaluations must be carried out in a homogeneous zone by coordinating the efforts at the government level. The relatively limited results obtained in Mali are in part due to the method of approach.


Evaluations and map production are necessary but not enough, because the important aspect is the variation in the production of the pasturelands (year to year variability in quality and distribution of rainfall).

It is not necessary to limit the evaluations and the maps to possibilities for management and for pastoral production, but it is necessary to extend them to the problems of agricultural planning.

There is a lack of data concerning the change of vegetation, the evolution of pasturelands, and the factors that determine them.

It is necessary to carry out the evaluations on an interdisciplinary, not multidisciplinary level. In fact, the physical setting and the socio-economic conditions are of major interest as soon as it is a question of improving the pasturelands.


The surveillance- of ecological modifications can be seen on three levels: objectives, means, and methodology.

- Objectives: It is necessary to strive to become acquainted with the changes in vegetation in terms of climatic variations to guide, if not the detailed management of the pasturelands, at least the major axes of pasturelands for the animals;

- Means: It is necessary to study the evaluations the maps of the pasturelands and the aerial coverage already carried out. The possibilities of satellites like the ERTS must not be forgotten;

- Methodology: Some new exact and representative studies of the zone could update previous work and would permit studying changes in the pasturelands.


It would not be especially necessary to intermix the basic information gathered, with a view to carrying out an evaluation or a personal interpretation of the information in order to permit reusing the data.


It is useful, indeed necessary, to study the evolution of pasturelands; but the actual methods are inadequate.

Means of decision


Who decides on the objectives of an evaluation ? In my opinion, certainly not the team in charge of the evaluation. The recipients ought to be consulted, and as they are not in actual fact, many evaluations are under-utilized.


The state or private body asking for the evaluation must be consulted to fix the objectives. However, what is important is knowing how to carry out the evaluations and determining the necessary ways.


The relation between the specialists and the planner can be defined in the following manner: the decision of the planner lies in the framework of the global determination of the quality of the zones. The details are the work of the specialists.


The objective of the evaluation is development. Development is only possible if the landowner is identified (a person only develops well what belongs to him) and if the use that one wants to make of the land (livestock breeding, game reserves, or tourism) is well defined.

It would be necessary to create a committee of land-users - including those responsible for livestock management, for wildlife management, and for tourism - those who, in the government, would be consulted about evaluation problems.


To what extent can the nomads help to resolve these problems: categorizing of pasturelands, scales, economic objectives, development ?


Mr. Blair Rains has carried out evaluations that he judged unnecessary. It seems that the technicians ought first of all to gather evidence on the objectives of the applicant before beginning their evaluations.


In fact, the objectives of those using the land (to have the maximum amount of pastureland) and the objectives of the conservators (to protect the maximum amount of pastureland) were diametrically opposed. Being caught between the devil and the deep blue sea, I have not been able to satisfy either. It is therefore important to give a precise definition of objectives in accordance with interests at hand.



Before examining the methods of evaluating pasturelands, it would be necessary to have an idea of the cost, in particular for the photo-interpretation. Before any decision it would be necessary to know the cost/profit relationship and the timing of the evaluations so that they are always of present interest.


The profits of an evaluation being difficult to estimate, you can determine only with difficulty the worth of such an investment.


It is possible to have an idea of the cost of the evaluations if their objectives are well defined.


Coverage by aerial photographs is expensive, while satellite coverage is free. It is better therefore to equip ourselves with material destined for interpretation by satellites.


Being able to prepare the photos is not all. It is necessary to have the proper equipment and to educate for their interpretation. That is even more expensive.


The cost of an evaluation depends on its scale, its degree of precision, the socio-economic conditions of the country in question and finally, the available documents.

III. The methods used


Scales depend upon objectives and cost. H. LE HOUEROU:

If the objective is national planning, a scale of 1/500,000 is desirable; if the objective is regional planning, a scale of 1/200,000 is suitable; whereas, if it is an improvement project, a scale of 1/50,000 or greater is necessary.


In the developing countries, the costs are not always sufficiently taken into consideration, because the financing - in the majority of cases - is furnished by external sources.


So that everyone is speaking the same language, a " large " scale is a scale on the order of 1/100, and a " small " scale is on the order of 1/1,000,000 to 1/5,000,000.


For evaluations whose objective is administration or management of pasturelands, a scale of 1/250,000 is too small to permit improving the field. In fact, it does not even permit determining in what state the land is found, though that is what is most important, since the administration of the pasturelands has as its goal the increase of productivity.


Everyone talks about the scale of 1/250,000, whereas, based on international agreement, all of Sahelian Africa is already covered by a scale of 1/200,000. A standard coverage would be all the more desirable, since the scales being talked about are close, and since that would represent a considerable reduction in costs.

Standard aerial photos and satellite pictures


Is it possible to survey annually or seasonally the change in the limits of vegetation from a north-south line established by the ERTS system ?

In order to obtain regular data and on a large scale are we in a position, with actual technology and satellite photos, to use the satellites to transcend difficulties such as: small national units, dissemination of information, or placement of personnel ?


The ERTS system is valuable for surveillance of great tracts of land but as soon as a more or less precise evaluation is needed, we must resort to mixed information: satellite-airplane. In fact, surveillance calls for a greater scale than that necessary for an evaluation.

It is better not to survey very large tracts but rather to periodically survey small representative areas.


As Dr. R. Perry has pointed out, the use of ERTS system photos is very wise for planning development. Yet the interpretation of the photos should be done by persons who are familiar with the region and the evaluations carried out on the soil.

The preliminary evaluations of the soils are some of the most important factors in the interpretation of other types of evaluation.


It is said that the information coming from the satellites is not useful for the management of pasturelands. Is this due to financial or technical difficulties ?


What is the actual state of research on the possibilities of mapping based on the satellite photos of precipitation and the primary production of the pasturelands ?


A colleague of Mr. C. Hemmings was one of the first to use photo-interpretation to determine the areas of reproduction of locusts in Saudia Arabia, by relying on the evolution of the vegetation (food for the locusts) after the rains.

The results recorded by the ERTS system have been interesting although insufficient. The results that were foreseen as being promising are still mediocre.


There are two types of surveillance of the environment: by seasons or over a long period of time. Only information by satellite on the seasonal changes is available at the present time. For two years the satellite photos have been showing us potential agricultural zones in the Sahara. We have begun to survey more particularly the extent of brush fires. The satellite photos have permitted us to identify the principal ecological zones and to determine a classification for the soils, as for the types of vegetation. NASA furnishes the satellite photos at no cost or at reasonable prices. The problem still remains that of interpretation, but some simple techniques can be used.

Zaïre like Italy, is constructing its own station on the ground to receive the satellite data of the ERTS type. Brazil and Canada have them as well as the United States. In the area of the usefulness of the satellite as a means of surveillance of pasturelands or of observation of climatic changes, everything depends much more on the information furnished by analysis than on that furnished by photos.

In summary, the satellite photos are not very expensive for a small scale analysis. The interpretation is easy if it is carried out by a specialist in the field.


The satellite photos are interesting, but it is often necessary to wait two to three months or more before obtaining them.

The problems of the small zones and those of the large tracts should not be confused. Yet the systems are not opposed, and the principles of photo-interpretation remain identical.


The Kenyan government has created a committee for photo-interpretation, which has laid out the plans for a programme that will get under way in January. It has already received some photos from the ERTS system and has established the mosaic of Kenya on a scale of 1/1,000,000, which will serve to determine the zones and sub-zones for the programs of ecological surveillance.

From these photos it is possible, on a scale of 1/250,000, to follow the evolution of the plant life covering and to bring up to date old aerial photos. Kenya is working with the American census bureau on an evaluation of human population from the data gathered by the ERTS system. It has also used the ERTS system to construct soil maps.

It hopes in the near future to be equipped to directly receive information furnished by the ERTS system that will permit it to obtain a regular coverage on an actual time basis and will facilitate the surveillance.

Through these techniques, it intends to be able to determine the standing harvests for these regions with the help of adapted computers. This work has already begun and is continuing at the present time.


The question is knowing if the satellite programs can resolve the climatic changes or just permit observing them.

Practically speaking, is it better in the field to save what remains or to try to regenerate what has been destroyed, to give the land a chance rather than to get lost in theory and the computer programs?


To study the Sahel pasturelands, is it necessary to call on the aerial photo or the satellite photo ?

What are the advantages and inconveniences of these two processes?

Keeping in mind the scale and necessary means of investigation by satellite photos, I wonder if it is necessary to advise the African states right away or rather to suggest to them to resort to airplane photos for the solution of their immediate problems. As in Mali or in other countries of the Sahel there are two distinct problems: evaluating the whole and then taking immediate action.

Keeping in mind the fact that no computer exists to work with the results of the satellites, and that the aerial photos are relatively easy to interpret, I wonder from which direction we should approach the problem.

Between the satellite photos which are the future and the aerial photos which are the present, is it necessary to combine the two, to support the ERTS effort, or to educate photo interpreters ?


The Malian geologists were the first to ask about the use of satellite photos, and photo-interpretation has been used in Mali for two years. To those who are asking for a choice between the satellite and the airplane I will say that the two are complementary and permit obtaining successive views that are more and more detailed. The combination of the two has already been successfully used. The satellite photo is not the only valuable one.


I am trying to imagine how the information received from the ERTS system can be used practically and immediately in the field. It doesn't seem - if you put aside all the other uses of the ERTS system - that it can facilitate the movement of the livestock raisers from one area without grass to another where the rain has fallen and where the grass is growing. In fact, we forget that if the herders can move, they do move without taking opinions into account; and when they are not able to, they don't move even if the satellite suggests that they move 200 or 300 km. I think that it is unrealistic to suggest using the photos received by ERTS to this end.


In Africa the objectives are development and not the administration of particular improvements. The pasturelands are part of the natural resources, and one of the uses of photo-interpretation for the management of pasturelands could very well be to define the framework in which the management of the pasturelands takes place, that is to say, the agronomic and geological framework as well as the distribution of populations and great surface areas such as the Sahel. In fact, it must be difficult to obtain a broad evaluation of the distribution by any other method in a given length of time.

Yet if you consider management in time, that is, the management of the pasturelands themselves, in order to establish the livestock rotation, it is difficult to use photo-interpretation. Nevertheless, the data from photo-interpretation can be used to establish the general management schema, that is, to know where the grass grows the most rapidly after the rains. That can be observed in the ERTS or satellite photos. In conclusion, I don't think that it is necessary to prematurely reject the satellite photos. I think that the greatest use of the ERTS system will be to determine the resources and to specify areas where pasturelands are good, especially in terms of climatic changes.


Specialists and a lot of material are necessary in order to interpret the satellite photos. Thus in Mali we receive satellite photos without being able to work with them.


Every year it would be necessary to place the intervening changes in the vegetation at the disposal of the governments. It would be desirable to educate national specialists familiar with the very sophist) cased material necessary for interpretation in order that they could give valuable advice to their governments.


The information furnished by the satellites will be useful if a country has the specialists capable of dealing with it: but the personnel in Africa is scarce, and it is difficult to specially train those available. It is equally necessary to have educational programs.


I would like to point out that the British Ministry for Overseas Development is organizing educational courses for the African countries in the interpretation of aerial photos. These courses, which are having great success in Kenya, are based on the evaluation of the resources of pasturelands. A similar program is going to take place in Nigeria in the years to come.


Photo-interpretation from the satellite has not been very convincing in the last few years: we have had to continue to use aerial photos and soil evaluations. Where the methods seem weak, it would seem desirable that ILCA, interested persons, and the OAU work together to perfect the speed and efficiency of the methods.

I am happy to hear about the creation of an educational centre for photo-interpretation. Now it is necessary to select valuable candidates so that they can acquire this new technique.


In the months to come, a program for specialists in teledetection as well as in the use of satellite photos will be developed. This will be carried out by the FAO and the UNDP, very likely in Niamey.


Photos and the training of photo interpreters has been discussed. It would be better to work with what we have: to train field agrologists who can study pasturelands on the spot during the whole year in terms of changes, and to use the information gradually.

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