2.3 Conservation and restoration
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The dimensions of conservation and restoration action in the arid and semi-arid lands are very varied, according to the local situation. The following approaches can be applied, some of which reinforce each other to attain objectives of sound land husbandry:
In the following paragraphs we will summarize thematic reviews covering some of the key tools and techniques which are most common in forestry programmes for restoration and conservation of the drylands.
2. CONTROL OF WIND EROSION
Shelterbelts and windbreaks provide several benefits, including protection against wind erosion and sand drifting, returns in fuelwood or poles, wildlife refuge sites and aesthetic and micro-climatic advantages to human beings. But their most important contribution lies in their contribution to increased crop and livestock yields.
In general, the information available consistently demonstrates the utility of shelterbelts in the Mediterranean climate. In the Sudano-Sahelian zone, the few measurements and observations available tend to indicate that shelterbelts are detrimental to rainfed crops. On the other hand, the scarce biological and micro-climatic measurements available provide encouraging evidence on the favourable effect of shelterbelts in irrigated areas. However, it must be concluded that for rainfed crop cultivation, means other than shelterbelts must be found for combating wind erosion. Symbiosis of agriculture and trees appears a potential method of reducing wind speed and improving the local micro-climate.
In the case of wind erosion and dune stabilization, several countries have instigated dune stabilization programmes which include schemes for dune fixation, afforestation and attainment of goods - such as fuelwood - as programme objectives.
Dune control effects to-date have largely been undertaken on the basis of trial-and-error experience at a few locations within the arid region. Despite the fact that several countries have launched large dune stabilization control programmes, much still remains to be learned both in terms of basic scientific facts and of technology. For instance, not very much is known about specific plant species which may best be used on the various ecological "niches" of the dunes, although we know from researchers that dune ecological conditions are quite varied. Consequently, only a few species are used in most dune work. There is scant knowledge on plant-sand-water relationships and on other physiological questions. No-one seems to have much information on the hydrological and ground-water topic vis-a-vis afforestation of dunes. Would thirty year-old plantations on dunes begin to "mine" all the capillary and ground-water, and then begin a die-off process? From a practical viewpoint, much could still be learned about more economical fixation procedures, better long-range management plans, pest and disease control, nursery/planting procedures, silvicultural systems, genetic development and multipurpose species. Dune afforestation, nearly an "infant field" of forestry, is now in a trial-and-error phase but is in need of a much better scientific foundation.
3. WATERSHED MANAGEMENT
The water relationships of arid zones are more critical to a greater number of people than in humid regions. Water is always in critical balance in arid ecosystems and this balance is being upset by man and livestock at alarming rates. Perhaps of greater significance is the loss through erosion of the soil of the soil reservoir. Not only is the soil reservoir the principal means of controlling the flow of water from upstream watersheds, but, more importantly, it is also the basis of the production of renewable resources on these watersheds.
It is obvious, therefore, that present land use patterns on watersheds in the arid regions of the world must be reshaped so that delicate water and soil relations are not pushed beyond their limits. As the number of people and animals living in arid zones climbs, and the quality of the land on which they live declines, the detrimental impacts of excessive grazing, deforestation and improper agriculture will continue unless solutions are found and implemented. These solutions should consider inter alia the upstream/downstream physical and socio-economic interrelationships.
The purpose of watershed management is to understand the hydrological, ecological and human relationships and then to apply this understanding to rehabilitating degraded areas, to conserving water, soil and other natural resources and to improving land use for increased long-term productivity. Watershed management efforts develop most often in connection with water development schemes and the protection of water supplies in areas where the water balance is deficitary. In most cases watershed restoration is justified to reduce sediment yield and prevent silting of reservoirs, intakes, waterways and harbors, ensuring that the life span of these works of infrastructure is not shortened. Wherever human settlements, intensively used cropland and touring facilities are endangered by flash-floods and mud-flows, as is common in many Mediterranean environments, heavy investment in slope stabilization, torrent control and river channel stabilization may be justified. On the other hand, in sparsely populated areas, where degradation of the vegetation cover and over-grazing have caused alteration of the soil-water-plant system, extensive and low-cost measures should be adopted to mitigate downstream effects. Increase in water yield may be a must when the water resources for human needs or for food production are scarce; however, very limited research exists (USA, Israel, Australia, India) on the techniques for vegetation manipulation and on the mechanical or chemical measures to reduce vegetation evapo-transpiration losses without affecting water quality.
The basic technologies required to manage watersheds under the various types of situations are known. A difficulty, however, is in getting local people to accept conservation measures, which call for participatory approaches in the planning and implementation of watershed management efforts.
4. WATER HARVESTING
The development of water resources in arid regions, at present and in the recent past, has been concentrated on large-scale irrigation projects. However, these projects provide few direct benefits to the small land holder or nomad, who must survive within the constraints of his environment without the benefit of new technologies appropriate to his needs. Fortunately, water harvesting offers one method of improving the livelihood of these people.
The purpose of water harvesting is to either augment existing water supplies or to provide water in situations where other sources of water are not available or developmental costs are prohibitive. The aim is to provide this water in sufficient quantity and of a suitable quality for the intended use.
In essence, a water harvesting system consists of a catchment area, which can be natural surfaces, artificial surfaces or combinations thereof and a water storage facility. There are many options regarding the geometric configuration of the system, as might be expected. The strategy taken in developing a water harvesting system depends upon a number of constraints, including:
Numerous water harvesting systems have been installed in the arid regions of the world. Although many are in experimental stages, most of the systems have met with success. Case examples can be found in Mexico, India, Iran, Pakistan, Australia and the United States and more water harvesting systems are currently being planned and implemented elsewhere.
A related aspect which is at an incipient stage is water harvesting from dew, which is an important source of water in areas such as the Atacama desert.
5. LAND RESTORATION AND REVEGETATION
Land restoration and revegetation of degraded arid lands is imperative to increased food production, not only to support the present population of 300-600 million people but also to provide for the anticipated future populations. Specifically, through land restoration and vegetation, the following goals are sought:
In general, the majority of the countries in the arid zones have declared policies on land restoration and revegetation. Intentions of protection, conservation and development of the natural resources are, in most cases, explicitly stated. A major problem, however, is converting policies into action. Biological and socio-economic constraints are usually present.
To a large extent, the technologies of land restoration and revegetation are known at least in a broad sense. Difficulties are encountered, however, in extrapolating these technologies for application in specific contexts. The availability of materials, labour and machinery may be limited and the acceptance by the people of the proposed technologies and their ability to implement the measures can be restricting. Nevertheless, the consequences of not imposing the necessary "corrective actions" is well illustrated through a number of case studies.
6. REHABILITATION OF SALINE ENVIRONMENTS
A special form of land restoration is the rehabilitation of saline environments. It has been estimated that nearly 10 per cent of the world's land area is salt-affected. Fortunately, through appropriate technologies, many of these salt-affected lands can be transformed from sources of erosion and desertification to areas producing valuable forage, fuel and other products.
Engineering solutions, the mainstay of rehabilitation programmes in the past, are unsatisfactory in many situations, because of water shortage, high costs and material shortages and technical problems. However, a possible alternative is to grow plants possessing sufficient salt or alkali tolerance to withstand the existing conditions without reclamation. Increasing attention is being focused on the use of highly salt-tolerant plants for growing on salt-affected soils or for irrigating with saline water.
The rehabilitation of saline environments is dependent on successful establishment of a vegetative cover. Depending on the site conditions, grasses, shrubs or trees may be suitable. In severe cases, it may be necessary to use "pioneer" species to ameliorate the site sufficiently for other more desirable plants to become established. For all situations, a careful screening of plants, against suitability criteria, is a pre-requisite.
To achieve success, it is necessary to also select an appropriate establishment method and to provide for sound management of the new resource. Recommended methods of rehabilitation are available, although these general methods may have to be "localized" for a particular area. Case studies in Ethiopia, Iraq, Pakistan and West Australia show that in many arid zones, the halophyts utilized in reclamation programmes can be grazed by livestock. Grazing experiments in saline environments continue, however, to formulate the most appropriate range management practices. Other uses of plants that are salt or alkali tolerant are also being studied.
7. WILDLIFE CONSERVATION
The wildlife resource in the arid zone has recently attracted increasing attention. However, only a few countries of the arid region are represented in the 1974 United Nations List of National Parks and Equivalent Reserves. Information on the ecological requirements of the indigenous animals is scarce and scattered. Few studies have been made on distribution, reproduction and potential utilization of wildlife.
Among the obstacles to the development of the wildlife resources of the arid and semi-arid regions are habitat deterioration, often associated with expanding human populations and changing land use practices, increasing use of pesticides which threatens the existence of certain species of birds and mammals, and poaching and exploitation for trade. On the other hand, there seems to be an excellent opportunity in the arid region for diversifying rural income by improving the management of national parks and wildlife resources.
8. GENETIC RESOURCES CONSERVATION
The importance of plant and animal breeding in respect of dry areas development cannot be over-emphasized. Breeding programmes for plants would require the introduction of new germplasm in order to develop varieties and strains resistant to drought apart from other desirable characteristics such as high yields, palatability to animals, low fuel value (against fires) and resistance to pests and disease.
Progress in breeding greatly depends upon the availability of broad genetic variability which exists in the natural flora and fauna of marginal areas. But this variability is rapidly disappearing. Coordinated action is, therefore, required at the regional level to preserve the genetic variability of plant and animal species, through the establishment of gene pools and exchange arrangements for genetic material.
9. ISSUES AND GAPS
In the following paragraphs some of the key issues related to the contribution of forestry to restoration and conservation of the arid environment will be pointed out for discussion. The major gaps in knowledge and in action are also identified, to promote research and cooperation in the strengthening of field programmes, as possible elements for inclusion in the Plan of Action.
9.1 General (*)
(*) These issues might also be considered in discussing the institutional aspects.
As indicated in the Introduction, there is a variety of approaches to cope with the problem, which may supplement each other. Some crucial points for discussion are:
9.2 Shelterbelts and windbreaks
Some particular issues for discussion on this topic are:
Some aspects which appear to require further study and research are:
(i) testing various species (and combinations thereof) for different sites and types of crops to be protected;
(ii) testing of various designs (spacing, frequency, width, height including agroforestry systems) of shelterbelts;
(iii) studies on shelterbelt economics under various conditions;
(iv) cultural and management problems of belts, including the question of root competition with crops.
9.3 Sand dune stabilization
The main issue for discussion on this topic is the experience obtained in areas where stabilization and afforestation programmes have developed for several decades: (i) what economic use can be made of the area without creating destabilization hazards; (ii) does the vegetation mine the ground-water and suffer as a result a die-off process?
Some topics identified which merit further study and research are:
(a) the technical biological/mechanical/chemical methodologies for dune stabilization, including testing of new methods;
(b) the economics of various fixation and rehabilitation techniques;
(c) the various physiological, biological, hydrological and physical processes of dune vegetation establishment, growth, survival and reproduction;
(d) exotic and native species trials and botanical testing to identify new or better dune vegetative species; nursery and planting techniques;
(e) development of land-use management and silvicultural schemes for long-term productive and profitable use of rehabilitated dunes, e.g. fuelwood production, charcoal;
(f) the sociological considerations of these activities in toto and the questions of planning desert rehabilitation as a multi-disciplinary effort;
(g) investigation of other varied productive uses of rehabilitated dune areas, e.g. honey-bee raising, forage tree production, relation of dune stabilization to irrigation development, shelterbelts and other agricultural pursuits;
(h) the need for a data bank, monitoring of programmes and the exchange of information;
(i) centres for education, training and extension work in the topic.
9.4 Watershed management
Some key issues to better orientate restoration and management of watersheds are:
Some technical aspects requiring further study and research are:
9.5 Water harvesting
Gaps in knowledge exist in the planning and implementation of water harvesting systems:
9.6 Land restoration
Regarding the topic of land restoration and revegetation, the following require serious consideration:
9.7 Reclamation of saline environments
For the rehabilitation of saline environments, important gaps in knowledge include:
9.8 Revegetation and management of natural vegetation
Some key aspects which require study and research are the following:
(i) surveys of vegetation forms and types;
(ii) ecological, botanical and physiological studies, particularly the capacity of various species to grow and reproduce under environmental stresses;
(iii) vegetation-environment interrelations. These are very delicately balanced. For instance, even slight changes in micro-climatic conditions affecting either water supply or water needs often tip the precarious balance either to success or failure in respect of many cultivated plants. And it is precisely in this dimension that a better understanding of the vegetation/environment relations assumes economic significance apart from purely scientific importance. Studies in this area could include:
The main areas for studies and research in this field are:
(i) species and provenance trials of trees and bushes
indigenous to the arid region;
(ii) site diagnosis techniques, including soil survey and bioclimatic investigations to facilitate choice of species and introduction of exotics;
(iii) site preparation and amelioration techniques, including the use of terracing (manual and mechanical), deep ripping, methods for reducing salinity or making use of run-off water;
(iv) improvement of nursery and planting techniques, including the efficient use of containers;
(v) improvement of tending, protection (particularly from fires and grazing) and management of plantations;
(vi) special studies on important genera/species, e.g. Acacias, Eucalyptus, Tamarix, Quercus, etc.;
(vii) use of sewage water in plantations and its environmental effects.
9.10 Wildlife, wildlands and national parks
Measures/actions to be initiated in this area could include:
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