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New Approaches for Plant Production in Arid Lands A. Richmond
It is expected that a significant surge in biological productivity will take place in the world's arid lands. This will come about due to massive development in three directions: selection and development of new plant crops that tolerate drought and saline water; new biotechnologies for growing plants, based on the natural energies which prevail in arid regions; and practical methods for desalination of brackish and sea water. As the full realization of economic large-scale water desalination appears to lie in the distant future, immediate efforts must be made to select new plant crops and to develop new biotechnologies that can take advantage of the extreme environmental conditions common to many desert areas.
There are available many new plant species adjusted to arid climates in that they are tolerant of drought and soil salinity, some of which have great promise for impoverished arid lands. These include the Jojoba bush (Simmondsia chinensis), the seeds of which contain liquid wax that seems to have an impressive industrial potential. Jojoba oil is almost identical to sperm-whale oil (which has been outlawed in the USA), but requires little or no refining. it can be hydrogenated to a hard, colourless wax, or its longchain acids and alcohols can yield derivatives that are stable at high temperatures, for use as surfactants, emulsifiers, disinfectants, detergents, and lubricants. The meal thus obtained as a by-product can be used as a feed supplement.
Guayule (Parthenium argentatum), from which rubber can be extracted, grows in desert regions of north-central Mexico and the southwestern United States, All parts of the shrub contain rubber which, when purified, is virtually indistinguishable from the rubber obtained from Hevea trees. A potential source of rubber for various commercial purposes, it grows relatively well in poor desert soils and in otherwise unused marginal areas.
An entirely new type of agriculture may need to be created because of the fast-rising price of fossil fuels. One genus of plants which seems to be of significance is the Euphorbia genus which is closely related to the rubber tree. These plants contain a white latex which is an emulsion containing as much as 3000 per cent hydrocarbons, similar in many ways to crude oil. Present oil yields of Euphorbia are very small, the equivalent of only about 5 barrels per ha annually; however, under proper cultivation and with systematic selection of species, it is hoped that the equivalent of 50 barrels of crude oil per ha could be produced annually.
Experience in various arid lands indicates that the carrying capacity of the land for grazing animals can be significantly raised by planting suitable forage crops. One of the most promising, in the Israeli experience, is Cassia sturtii, a shrub from southern Australia. Under the conditions of the Negev desert it has demonstrated better year-round palatability than any shrub yet tested. It has good grazing resistance and the leaves have a high protein content (c. 12 per cent) and annual dry-matter yields of about 1 tonne per ha in a 200 mm rainfall area. Other fodder plants of great potential are the salt bushes of the genus Atriplex. These plants are highly salt-tolerant, and when grown in deep soil can thrive on only 150 - 200 mm annual rainfall.
Two new biotechnologies which are judged to have important potential for arid lands are "controlled environment agriculture" and the production of algal biomass. The former is essentially a greenhouse in which some of the solar energy and a good part of the water given to plants are conserved, and there is only a limited and controlled exchange of the gaseous environment inside with the outside air. Plants require only a fraction of the water they use in the open, and this can be more saline than is normally tolerated. CO: fertilization may be readily introduced into the closed system, affecting a substantial increase in yield. No extra energy is required to heat the greenhouse at night, heat stored during the day being used for this purpose.
Production of algal biomass is based on resources and conditions prevalent in hot deserts, that is, high daily temperatures and solar radiation throughout the year and the use of saline water-or even of sea water-not suitable for the production of conventional agricultural crops. An important advantage of algal production is that the culture can be readily grown without nutrient limitation, and, when cultivated in areas where temperature is not limiting, production is limited only by light. For locations which are rich in solar radiation, as are most arid areas, this forms a distinct advantage. Clearly it permits the plant cells to operate at their maximal photosynthetic efficiency.
Various biological parameters which affect the optimization of algal growth must still be elucidated. In addition, certain technical problems must be solved in order to develop commercial systems for mass cultivation of algae. The first relates to pond construction, its shape and depth, the system of mixing the algae-laden water, and most important, the type of lining. The second concerns a suitable method for separating the algal mass from the medium, and the third relates to the dehydration of the algal mass to facilitate distribution and storage of the product. Algal biomass has various uses as a feedstuff and is reported to be particularly suitable for pisciculture. Certain species of algae have been shown to be suitable as food for humans, and some peoples in African and Mexico have been using the algae Spirulina spp. as a nutritious, protein-rich food for ages. At present certain seaborne algal species are harvested off the shores of many oceans for the extraction of agar or alginates, products which have a very high demand in the chemical and food industries. In principle, any product that man can obtain from the higher plants, i.e., carbohydrates, fats, proteins, and cellulose, can be obtained from suitable species of algae.
An irrigation technique which may have far-reaching applications in the cultivation of arid zones is known as trickle irrigation. This involves the use of plastic tubes of small diameter, lying on the surface of the field alongside the plants, from which water is slowly and continuously emitted. A special benefit of this system is that brackish water, which is found in many deserts-albeit located at places in deep aquifers-may be successfully used. The build up of salt in the soil is controlled by continuous effective leaching.
In summary, new approaches are being developed which will facilitate a significant increase in future biological production from arid lands. New plant crops are being selected and improved, and in addition new biotechnologies are being developed that will either substantially decrease the limitation of water for plant culture, or utilize available saline water or sea water.
Discussion
The Working Group endorsed recommendations on the need for experimentation on plant introductions, for plant selection leading to genetic improvement, and for research into the ecological requirements of the various species tested.
Alternatives for the Development and Management of the Arid Lands of Mexico R. Nava, R. Armijo, and J. Gastó
This paper reviews work carried out by a research team at the Autonomous Agricultural University "Antonio Narro" (UAAAN) at Saltillo, northern Mexico, on natural-resource problems of the Chihuahuan Desert: In facing the problem of providing improved living standards for Mexico's increasing population, it is of the utmost importance to initiate a broad educational and production-oriented programme. The arid and semi-arid lands are an important segment of Mexican territory, covering about 40 per cent of the land surface. Approximately eight million people, representing 12 per cent of the Mexican population, live in these regions.
Rain-fed cropping and cattle-raising, the two main economic activities of the rural population, are strongly disadvantaged by the low and erratic rainfall and the short growing season. This makes agriculture a highly uncertain, risky operation, with low productivity and undependable incomes. Most of the economically active rural population is engaged in the primary pursuits of farming, livestock husbandry, and the gathering of native plants for local consumption. The peasants are limited by lack of working capital for resource development and animal improvement. The situation can be summarized as follows: deficient organization for primary production; agricultural activities at subsistence levels, supplemented by the gathering of native plants; incipient attempts at rural development; lack of association between the educational system and the problems of rural areas (McCiymont, 1975L
Some of the major concepts adopted by the research group in evolving a model for dealing with natural resources are:
1. Natural resource phenomena are part of dynamic systems,
rather than random or fortuitous in their occurrence;
2. The ecosystem is an appropriate image or model of these
phenomena, and forms the basic working unit;
3. The components of the ecosystem are characterized by a
definite structural arrangement and by specific functions and
interrelationships (Armijo, Nava, and Gastó, 1976);
4. The ecosystem can be modified directly, by transforming the
structural arrangement of its components, or indirectly by
introducing changes within its functions;
5. There exists a scale of resolution of natural phenomena that
is appropriate for dealing with problems of natural resources
most effectively, and that is the level of the basic ecosystem
(Gastó, 1978).
The sound management of natural resources has as its starting point the systematic planning of changes or developments. Two types of change can be identified: transformation, emphasizing man's rational intervention, and restructuring, involving the variables in the ecosystem. A basic objective in studying the structure of ecosystems is to discover the changes in time and space of the more important variables. From such an analysis it is feasible to explore two broad problems (Medina and Nava, 1977): (1) determination of the structure that gives the desired response to a given input; and (2) how to change the structure so as to achieve an end-state which produces the required response.
The basic ecosystem is characterized by five broad subsystems: the biogeostructure, or natural-resource base that integrated the abiotic components of the substratum and of the atmosphere with the biotic elements of plants and animals; the socio-economic structure or organization of man in various social, cultural, and political patterns; the technostructure, resulting from the interaction of the biogeostructural resources and the needs and objectives of man; the surrounding environment; and the incident external systems that provide the inputs of energy and matter required for the normal functioning of the ecosystem. The dynamic interaction of these systems results in the observed condition or status of any community.
The concept of a "goal" or "end-state" derives from a combination of value judgements and ecological criteria, combined in the form of a hypothesis, to determine the status of "health" of an ecosystem. The term "health" refers to the discrepancy between the present status of the ecosystem and its hypothetical end-state. The five ecological criteria employed are: geomorphology; present vegetational units; degree of erosion; relative proportion in the landscape; and hydrology. The value-judgement criteria comprise: multiple-resource use; stability; costs; and compatibility. By defining specific policies for management and utilization of natural resources it becomes possible to promote the development of man as part of his environment. In this regard some steps have been taken to establish a methodology as a preliminary to elucidating the multi-dimensional nature of the problem (Armijo, Dukstein, and Nava, 1979).
An experimental approach to the development of natural resources assists the formulation and shaping of basic concepts and principles. Empirical knowledge gained through systematic testing in experiments makes it possible to define the array of feasible management alternatives. The Noria de Guadelupe Experimental Station of UAAAN constitutes the physical unit where these alternatives have been tested. The systems of land-use designed there can be grouped into four categories: natural ecosystems; re-seeded rangelands; annual crops; and ecocrops. Ecocrops are regarded as one of the more efficient alternatives in resource utilization, their development being determined by the convergence of specific economic, social, and ecological factors. For this purpose it is necessary to know the structure of the various ecological land units in order to optimize their use. An immediate solution is thought to lie in the establishment of a series of programmes aimed at promoting various aspects of rural development, in effect a policy of "experimental development." A broad goal of this work would be to establish a wide range of possible directions and to provide empirical evidence which should lead to progressive increase in the applicability of choices made (Nave, Armijo, and Gastó, 1977).
It is also important to extend the area of applicability of the proposed management alternatives and to increase the number of feasible ecological management systems. Particularly, one needs to know the entire range of possible uses of the various ecological land units and their plant species, which emphasizes the importance of the search for methods of improving the utilization of scarce and limiting resources (Maynez, Armijo, and Gastó, 1975). A better understanding of the principles that regulate the functions and structure of ecosystems will lead to a more practical formulation of ecosystem responses that are appropriate to the needs of our changing society.
References
Armijo, R., Nava, R., and Gastó, J. 1976 "Fundamentos de transformación de ecosistemas, Univ. Aut. Agraria "Antonio Narro. " Monog. Tecnico-Cientifica, 2, pp. 1-57.
Armijo, R., Dukstein, L, and Nava, R. 1g79. ,"Aspectos decisionales en el manejo de los recursos naturales: Enfoque de multicriterios, R. Nava and R. Armijo, eds., Planeacion de los Recursos Naturales en las Zonas Aridas dol Norte do Mexico, Univ. Aut. Agraria "Antonio Narro."
Gastó, J. 1978"Ecodesarrollo y sociedad de consumo," Pontificia Universidad Católica de Chile, Fac. de Agronomía, Depto, de Zootecnía y O.E.A. Doc., 13, p. 39, Santiago de Chile.
Maynez, F,, Armijo, R., and Gastó, J. 1975. "Clínica ecosítemica silvoagropecuaria. Fundamentos y Metodología, Univ. Aut. Agraria "Antonio Narro. " Monog. Técnico-Científica, 1, pp. 72-136.
McClymont, G. L. 1975. "Educación oficial y desarrollo rural," Doc. Ocasional, 3, p. 24, UN-FAO.
Medina, J. G., and Nava, R. 1977. "Manejo ecológico de pastizales en zones áridas," Rangeman's Journal, 4, pp. 111-112.
Nava, R,, Armijo, R., and Gastó, J. 1977. Investigación silvoagropecuaria de las zones áridas de Mexico. Campo Experimental Noria de Guadalupe," Univ. Aut. Agraria "Antonio Narro." Monog. Técnico-Científica, 3, pp. 182-265.
Discussion
The strong contrast of approach between the two papers presented was reflected in the Working Group discussions that followed. Richmond had stressed the importance of research and experimentation in determining new ways of making use of the positive elements of the arid environment, in discovering new desert plants which might provide substitutes for scarce commodities, and in introducing new biological techniques for increasing production from the arid lands. The Working Group endorsed his recommendations on the need for experimentation on plant introductions, for plant selection leading to genetic improvement, and for research into the environmental requirements of the various species tested.
In strong contrast to this emphasis on innovation, Nava had urged caution in the introduction of technological change. He stressed the need for understanding the existence within traditional systems of a vast fund of knowledge which has remained largely untapped by the working scientist. We need to understand, appreciate, and sympathize with peasant cultivators when contemplating the introduction of modern technology to peasant agro-ecosystems. The Working Group recommended investigation into such aspects of what was variously called "folk ecology," "ethno-ecology," and "traditional ecology," although none of these terms was considered entirely satisfactory.
Proceedings of the Plenary Session
In the succeeding plenary discussion it was stressed that strategies for development and management in the drylands would need to differ in accordance with the social setting and with associated differences in environmental perception by those involved. It was also agreed that there was a need for the UN University to sponsor a more interdisciplinary approach to studies in this area, involving management science, particularly in relation to the intermediate stage of economic development, and the study of social processes, particularly of those exogenous factors which may influence local development programmes.
Among specific projects recommended for investigation were:
1. The relationship between rural industries and food
production systems in the Sudan;
2. At the theoretical level, an evaluation of past and existing
development strategies, and the development and demonstration of
new ones;
3. At the practical level, an attempt to translate management
strategies into terms which could be understood by the particular
groups affected, for example, planners, managers, and operators,
and to develop means of facilitating the transfer of information;
4. An investigation of the potential of integrated regional
development and urbanization as means of combating
desertification.
Two sets of recommendations from Working Group C were discussed, namely those supporting experimentation with new desert plants, selection for genetic improvement of crop species, and supportive studies in basic cynecology, and those recommending research into traditional ecology. Discussion on the latter stressed the dangers of overlap and duplication with existing activities, such as studies of traditional medicine by the World Health Organization (WHO) and activities under the MAB Programme. It was stressed that investigations into ethnoscience or traditional ecology should not be seen as ends in themselves, but as steps towards the solution of problems. So far, studies in ethnoscience have not been particularly successful, but it was suggested that the University of Khartoum might offer an appropriate "mix" for studies in this field.
From the viewpoint of the United Nation Sudano-Sahelian Office (UNSO), Mendez stressed the importance of investigation into the problems of drought, particularly in the Sahelian-Sudan zone, in the context of programmes to control and prevent desertification, and also recommended study of the problems involved in the innovation of new technologies, including their adaptation to local conditions, problems of social acceptability, and means of gaining the necessary technical co-operation.