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Forest functions related to protection and environmental conservation

A. Gottle and E.-H. Sène

Professor Albert Gottle is with the Bavarian State Ministry for State Development and Environmental Affairs, Federal Republic of Germany,
El-Hadji M. Sène is Chief, Forest Conservation, Research and Education Service, Forest Resources Division. FAO. Rome.

An adaptation of the position paper for the Eleventh World Forestry Congress, "Protective and environmental functions of forests ".

Dryland forest in Senegal

General considerations on the protective and environmental role of forests

The forest can deliver the functions of protection or conservation expected from it only if it is either in its natural state and under good natural ecological conditions or, when in use, it is managed in a sustainable manner. Under such conditions, health and vitality are very important. It is the vitality of forests that allows them to grow with sufficient strength and vigour in a way that will counter physical forces affecting soils through water erosion. It is this same vigour that allows a well-structured architecture and rich foliage that can counter wind erosion. The health of forests is fundamental to many of their environmental functions. However, forests are often affected by insects and other pests. They may be affected by a number of physiological alterations depending on climate changes, especially droughts. With health, vitality and a proper state of conservation, management and development secured. the forest intervenes especially in the following major environmental and protective functions.

Protection of water resources. Through their foliage. craggy bark and abundant litter, trees and forests decrease the speed of water dispersion and favour slow but total infiltration of rainwater; particularly in dry areas, the capacity of trees to retain other precipitations such as mist that then can be collected and stored for use is also important.

Soil protection. The forest canopy slows down the wind while its dense network of roots holds the soil in place; added to the buffering function of the water flow, these characteristics protect against wind and water erosion, land movement (mass slides and falling rocks) and, under cold climates, the risk of avalanches. With the combination of slower water dispersion and percolation to phreatic and intermediary water tables, the forest exerts an important buffering effect that protects against flooding or severe river bank erosion.

Influence on the local climate and reduction of gas emission impacts. Through the control of wind velocity and air flows, the forest influences local air circulation and may thus retain solid suspensions and gaseous elements; it can filter air masses and retain contaminants. The forest exerts a definite protective effect on neighbouring human settlements and crops in particular. This capacity is useful in the protection of inhabited areas that adjoin industrial zones and in urban forestry in general.

Conservation of the natural habitat and biological diversity. The forest offers a habitat to flora and fauna and, depending on its health, vitality and ultimately the way it is managed or protected, secures its own perpetuation through the functioning of the forest ecological processes. In Europe, almost half of the ferns and flowering plants grow in the forest. Owing to its size and structural diversity, more animal species are found in the forest than in any other ecosystem.

Recreational and other social functions of forests. Apart from direct physical and biological protective functions, forests in general have gained increasingly important recreational functions during the past five decades. In the vicinity of cities, tourism and health resorts have flourished, benefiting from the forest environment; in the forested areas of developed and developing countries alike, secondary residences are getting people back closer to the forests.

Protecting the cultural dimension of forests. While urban communities, particularly in the industrialized countries, are striving to be closer to nature, at the same time the evolution of the global and local forest economies may threaten other protective functions of natural forests in the developing world where forests have still maintained their cultural and religious functions. It is a challenge to twenty-first century forestry to cater also for these needs and maintain the cultural dimension of the protective functions of the forests. A number of innovative management options and many social and community forestry initiatives have addressed these needs.

Protective and environmental functions of forests in selected fragile environments

Mountain forests and sustainable mountain development.

Mountain ecosystems are among the fragile ecosystems targeted by UNCED Agenda 21; they are dealt with in Chapter 13, "Sustainable mountain development". The many activities developed intensively during the last five years since the Earth Summit have heightened awareness of the many functions of mountains. They are a repository of rare and rich plant and animal biological diversity. They contain unique gene resources underpinning agriculture and animal husbandry in the particular circumstances and farming systems prevailing in high valleys and plateaus. They provide a steady flow of water resources with related renewable energy potential. They are host to and protectors of a diversity of races and cultures.

In high mountains the forests protect settlements and communications systems against avalanches, falling rocks and landslides. In the European Alps, parts of the protection forests have been subjected to long-established management practices that have tended to maintain a correct mix of evergreen and broad-leaved species. But trends are strongly pushing towards unsatisfactory changes. Mixed stands are giving way to monospecific forests and many protection forests have been weakened and have become overaged. They grow more and more sparsely. In many cases the presence of game prevents natural regeneration through browsing and increases the degradation of the forest ecosystem and reduces its protective capacity. Measures to counter this negative trend or to restore the forest ecosystem include biological measures such as reforestation, engineering work and active silvicultural practices that promote and assist natural regeneration.

In other parts of the world the same decline may be observed but most of the degradation occurs as the result of the attempts of the rural poor to eke out a living, especially in marginal areas. In North Africa, in the African plateaus, in the Andes and in the Himalayas, the search for fuelwood, the grazing of animals, particularly well-adapted, ever-coping goats and marginal agriculture have been mentioned as being among the major factors of mountain forest fragmentation, degradation and loss. In many parts of the world mining also disrupts mountain ecology and leads to the degradation or destruction of unique biological diversity, in some cases affecting endemic species and the processes in which they are involved. Inappropriate mining in watershed areas may also often be the sources of contamination of major water courses (Hernandez, 1997).

Many ecological groups have highlighted the possible negative influences of communication lines and roads as their establishment entails the deforestation of large stretches which affect the habitat of species of high biological significance. However, the most potent root causes are highlighted by Hernandez ( 1997) in Latin America as being: i) the state of inherent fragility of young mountains; ii) the extreme poverty of the population and the loss of stamina and resolve in the face of drastically poor and yet rapidly degrading social conditions; iii) the segmented approach to development, the lack of institutional cohesion and coherence and the lack of suitable and participatory extension.

The protective functions of mountain forests and their relation to climate change require special attention. This subject has been largely studied worldwide. Gottle (1997, personal communication) reports the results of the research of the Bavarian State Office for Water Management on the possible consequences of climate change on the way mountain forests in Europe may then provide buffering functions:

· higher temperatures will lead to a rise of the snow and ice line resulting in more favourable conditions for vegetation but with higher "erodibility", the shifting of the permafrost line creating more instability in areas yet to be colonized by vegetation;
· frequent changes between thawing and freezing will release more weathering material and increase the related risks of rock fall and landslides while making the consolidation of vegetation more difficult;
· more water precipitation with the predominance of rains will lead to water-saturated soils which will eventually reduce shear resistance and loss of stability, and lead to conditions unfavourable to the establishment of vegetation. More surface runoff may also occur throughout the year leading to more erosion.

Similar changes in intensity but not in the direction of change may be experienced more strongly in mountain areas than on plains, meaning that more spectacular changes in mountain forest ecosystems, owing to the concentration on short horizontal distances of phenomena that otherwise happen in a differentiated manner and over greater distances on flat land.

Special attention to mountain forests for the future and greater efforts in watershed management. The Mountain Agenda which has been very active in the framework of Chapter 13, and the creation of the worldwide Mountain Forum and its regional chapters have stressed the need to balance the unidirectional flow of resources including forest resources and services from the mountain downwards. The need to find innovative funding mechanisms and fresh policy options that restore the overall balance between mountain economies and societies in lowland areas was strongly advocated. The efforts to conserve mountain forests in this case cannot be supported only by mountain communities.

Hernandez ( 1997) sends the same message regarding tropical mountain forests; he stresses that interested societies are more and more aware of the importance of the cloud forests in the production of high-quality water in tropical mountain watersheds. Hence, a better comprehension of the needs of sustainable forest management and development must be shared throughout the watershed, if mountain forests and beyond, mountain natural systems and socio-economic systems are to remain prosperous for mountain and national communities, and also for regional solidarity. In this context, many communities have called for more efforts for the management of watersheds that aim not only at the physical restoration of benign processes in the flow of water resources and solid material, but which aim at the sustainable development of mountain systems. This will be achieved through, inter alia; i) the stabilization of livelihood systems; ii) the improvement of living conditions in mountain areas; iii) the identification and promotion of innovative income-generating activities and alternative employment; and iv) the restoration of equity and solidarity between upstream and lowland communities.

A government nursery at Manoufya, Egypt. The seedlings will be planted as windbreaks to protect irrigation and drainage canals

Forests in the conservation and sustainable development of drylands

Trees and forests in dry regions have truly multiple functions. They provide a number of services that tend to buffer the harsh conditions and processes prevailing in dry zones especially in tropical areas. The environmental functions of trees and forests under dry conditions relate to a number of aspects, including the wellbeing of humans and animals, the productivity of cropland, the overall protection of land and water resources and the conservation of biological diversity. Berthe (1997), through Malian examples and lessons of universal value, has identified the many roles of forestry in drylands highlighting prerequisites to, and results of, well-guided forestry-related activities in the rehabilitation of natural resources and, especially, desertification control. He mentions the importance of training and technical advice and extension for rural populations; the improvement of the knowledge base of resources; the need for promoting new technologies; the major involvement of interested people; and the Revolution of responsibilities to their organizations.

Extreme heat, sandstorms and hot winds are the most taxing factors that challenge comfort and livelihoods in dry areas. Populations have used the trees and forests to protect themselves from these elements and many adaptations have been put to use. Natural vegetation has been conserved in most new human settlements. In many open forest systems, from the humid dry forests to the steppe formations, large stretches of tree-covered land have been left untouched and protected to shelter living areas. As it has often been difficult to protect natural formations and make them sustainable around dwellings when they evolve towards big cities and agglomerations, efforts to plant urban trees and pert-urban forests have developed in many dry areas. In Sahelian countries, for instance, efforts to install pert-urban forests date back to the early 1970s and have kept growing around all Sahelian cities. In the Maghreb countries and throughout the Near East to Iran, the role of trees and shrubs in the protection of the immediate living environment of humankind and the creation of an improved enlivened urban environment is well recognized.

In croplands, the agricultural patterns have developed the parkland system that was not only meant to continue maintaining the fertility of croplands but also to protect humans and animals. These types of formation prevail in all dry to subhumid areas from the campo-type formations of Iberian Europe to the Leguminosae-dominated parklands of subhumid to dry West Africa and southern Africa. Leguminosae and other nitrogen-fixing tree species play a key role in maintaining soil fertility. This function is of tremendous importance in areas where populations with worsening economic conditions can less and less afford chemical fertilizers. The most documented example is the pan-African Acacia (Faidherbia) albida of dry and dry subhumid areas of the region south of the Sahara; it provides shade and feed to animals and natural nutriments to crops. The parkland system referred to above contributes efficiently to the maintenance of these residual tree communities; however, a number of new and rapid socioeconomic developments have entailed the cutting and use for fuel and posts of tree species that hitherto had never been used for such a purpose. These social changes have modified the human/tree interface and efforts in social and community forestry have the challenge to counter and restore tree protection practices that tended to maintain the conservation of trees of particular importance to the communities in drylands. Modern agroforestry programmes must help understand these systems better and encourage their conservation, improvement and replication.

Without e protective tree cover, these uplands in Malawi are extremely susceptible to erosion

Deforestation induced by the use of forest and tree resources has been aggravated by the degradation of climatic conditions in many areas of the world. The most affected countries are those recognized by the United Nations in Africa and to which priority has been given in the negotiation and implementation of the UN Convention to Combat Desertification and Drought. Tree planting in areas threatened by desertification and the management of dry tree formations contribute to protecting the soils and restoring the productive capacity of the land. The most spectacular initiatives in desertification control are the efforts to stabilize sand dunes. These have been implemented with success in West Africa (Mauritania, the Niger and Senegal), in North Africa (Morocco, Algeria - with the huge initiative of the greenbelt that has shifted from massive plantations to an approach towards integrated rural development-Tunisia and the Libyan Arab Jamahiriya) and, in Asia (India, Iran and Pakistan, among others).

Tree planting is increasingly accompanied by associated techniques such as water harvesting, bunding and terracing and the establishment of microcatchments and moon crescents to collect all possible water resources. A number of projects are under way in this sector using a variety of approaches from heavy machinery to manual work and other associated options.

The National Action Programmes (NAPs) to implement the UN Convention to Combat desertification will promote these actions in the larger national initiatives to combat land degradation, food insecurity and poverty. Although tree planting has been heralded as the first and foremost tool for desertification control, many social, economic and ecological considerations have reevaluated its role and position. The NAP processes have recognized this and involve a larger set of integrated activities. However, seen as a potent multifunctional tool among others in land degradation control, tree, shrub and grass planting can constitute a powerful complex when implementing water conservation and erosion control measures, rehabilitation of exhausted croplands, diversification of village landscapes to include trees of various functions and services and the stabilization and reclamation of lands. Forestry, agroforestry and urban tree planting will then remain very high on the agenda of NAPs to combat desertification. It is certainly expected that this Congress, and the satellite meeting on the role of forestry to combat desertification which has preceded it, will come up with ideas and recommendations for action that will consolidate the contribution of foresters to the effective implementation of the Convention.

The biological diversity of drylands is often overlooked. Yet the tree and forest systems and the grassland expanses in dry areas are important repositories of biological diversity whose constituting species have developed the ability to live in the harshest conditions of water-deficit ecosystems. The provision of rangelands and food items such as teff in Ethiopia, the date palms and the various species of cactus and agave are only a few examples of the contribution of drylands to the protection of ecosystems, to animal feed and food supply.

This species (Bauhinia rufescens) is particularly attractive to cattle in the dryland Niger

Animal species of the dry Andes, the Sahara, the arid parts of the Sahel, the Asian and other deserts are of extraordinary beauty and utility to humankind and yet their habitats are being increasingly threatened. Formations around oases are also evolving very rapidly as these ecosystems are exposed to increasing pressure.

The same concerns are nurtured for dryland ecosystem germplasm. Woody species of these ecosystems, especially from the genera Acacia and Prosopis, provided due precautions are taken, have a huge potential to support desertification control measures. The protection of the forest and tree ecosystems of these lands must be secured to conserve these riches for present and future generations. The traditional knowledge and technologies developed locally should also be fully explored, restored and promoted.

A monkey In Yala Park, a protected area in Sri Lanka

Protection of forests in coastal systems and wetlands for their productive, protective and environmental functions

Coastal systems, wetlands and rivers have in common the special linkages with fresh, brackish or salt water resources. They benefit from the presence of water but may also suffer from it directly or indirectly. Forests generally benefit from the constant availability of water as allied formations have generally built adaptive physiological functions or biological variations that permit survival and development. However, as the status of the water bodies varies through droughts or excessive influx of new amounts from rains or other processes related to exceptional runoff, the systems may be negatively affected and their functions threatened. The fragility of wetland, coastal and riverine forests and other formations is linked to these phenomena.

Kabii and Bacon, Choudhury, Zheng Songfa et al. (1997) and many other authors of submissions to the Eleventh World Forestry Congress have documented the various aspects related to these ecosystems and the forests prospering in them, but the most important considerations relate to wetlands and, especially, to mangrove formations. As defined by the Ramsar Convention on Wetlands of International Importance especially as Waterfowl Habitat, and as recalled by Kabii, wetlands are "areas of marsh, fen, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six metres". Kabii includes in these areas a "wide range of wetland types including those under forest cover, such as mangrove forests, floodplain forests, peatland forests, bog forests, Melaleuca swamps and palm forests".

The wise use of these natural systems as delineated by the Convention includes: i) the formulation and implementation of comprehensive national wetland policies to be integrated in the national planning processes; ii) the application of the Convention's criteria to identify and designate wetland sites of international importance for conservation; iii) the application of a number of other tools and mechanisms generated by the Convention (management planning guidelines, monitoring of the wetlands experiencing changes owing to development initiatives, measures to obtain or provide specific assistance to solve problems encountered by the threatened sites mentioned above); and iv) in summary, contribution to the implementation of the eight-objective 19972002 Strategic Plan recently adopted by the Convention. Objective vii) of the Plan calls for the mobilization of "international cooperation and financial assistance for wetland conservation and wise use in collaboration with other conventions and agencies, both governmental and nongovernmental". This disposition is the gateway to conservation, management and sustainable development of wetland forests, including mangrove forests.

In the international efforts to assess wetland forests, more efforts will be needed not only to approach the evaluation of all wetland-related forests but also to assess their biological diversity better. The special efforts that FAO and the World Conservation Monitoring Centre intend to dedicate to protected areas in the next round of the world forest resources assessment will probably improve the data on protected forests in wetlands.

Mangrove forests are among the most intensively and diversely used forests in the world. They provide land resources for agriculture, in particular the development of rice paddies; they are extremely rich fisheries; some of their fruits are consumed directly and in many countries they are the main sources of fuelwood for growing coastal cities. The silviculture and management of mangrove forests have experienced many achievements and much progress. Many plantation initiatives have been successful although a number of technical problems remain, depending on species biology, training of staff and a number of local conditions including pollution problems as recorded by Zheng Songfa et al. ( 1997). Future efforts in mangrove conservation, management and development will include: i) efforts for increasing the management and silviculture of African mangroves, including reforestation; ii) a better knowledge of the resources, especially in Africa; iii) networking for further dissemenination of technologies concerning mangrove forests, given the huge gaps in technology between countries, especially between Asian countries and the rest of the world; and iv) more research in these ecosystems.

A number of other coastal systems are bare of vegetation following the deterioration of the grass and shrub formations that used to grow over these generally sandy geological formations. The sand deposits on the shore are shifted by the winds and carried inland, or deposited as coastal sand dunes that may invade and sterilize valuable croplands. To counter this, many countries have developed sand dune stabilization techniques along coastal areas. Many forests have been created and placed under sustainable management. In France huge pine plantations (Pinus maritima) now support a thriving fibre industry and provide a stable and friendly coastline. In North and West Africa coastal sand dunes have been stabilized with similar techniques with Acacia and Casuarina species; here, also, these coastal forests stabilize sand dunes, protect and promote rich croplands which allow fruit-tree cultivation and vegetable production and, at the same time, beautify the coast with an exceptionally increased potential for tourism.

Riverine forests are important biological formations that contribute to the conservation of river valleys and the mitigation of river bank erosion; along with the tree and grass formations on watershed slopes they guarantee clear water flows and reduce siltation. In Africa, the gallery forests, in addition to protecting the valley bottoms of many rivers and temporary water courses, are the refuge of species threatened elsewhere and hold a rich biological plant and animal diversity. It should be noted that flood forests in Africa have suffered particularly during the last two decades. The riparian formations of Acacia nilotica, for example, have disappeared along many major low valleys, which means that a number of bared floodplains will be subject to serious wind erosion problems or will be put under inadequate land use. The conservation of these systems requires broader efforts of land use planning and conservation strategy for which resources are not readily available in developing countries. However, some prioritization is necessary for the conservation of major river valleys as a number of major investments are made or are being planned.


Water resources will be a critical element in the next century. Growing populations with higher needs per caput as development continues will exert higher demands of this resource. Mountain ecosystems are the prime source of fresh and clean water and it is evident that sustainable mountain development will be one of the strongest challenges to human communities. The call for further attention to the conservation of mountain ecosystems and the promotion of integrative watershed management approaches should be heeded if the challenge of clean water for all, especially the 800 million people that have no access yet to this commodity, is to be met. For this, every effort is necessary to maintain and enhance the protection, conservation and environmental functions of the forests in mountain ecosystems.

The continuum that leads from mountain ecosystems to water bodies that respond to the Ramsar Convention on wetlands, through rivers and ground inflows, should be recognized and broad policy measures taken to secure a coherent conservation of the water resources. The forests will then be, by the same token, recognized in their various roles to protect, conserve and sustainably use the resources. Necessary efforts should then be taken to enact laws, regulations and conservation and development programmes are commensurate with the magnitude of the problems posed. Linkages between policies for the conservation of biological diversity and for the conservation and management of water resources should be made in a clear and effective way, as these are organically connected. The logical consequence of this is a coordinated approach to the implementation of both Conventions on wetlands and on biological diversity.

Forests are important in the restoration of degraded fragile ecosystems of drylands and in increasing their productivity. The coherent set of activities recommended by the Convention on desertification include forestry-related action, such as the management of natural forests, particularly with the participation of populations, afforestation and reforestation, and agroforestry practices to support cropland productivity and silvipastoral development. A number of other environmental and protective objectives are also included and have been reviewed by the IPF-related discussions and the Consultation on the Role of Forestry to Combat Desertification. Continued support to implementation should now be provided to translate the recommendations into practice.

The actions needed in the complex set of natural systems that were reviewed in this document will not be possible if efforts are not devoted to a number of basic prerequisites, including: i) the improvement of the knowledge of resources involved and the assessment of their situation; ii) the development of coherent research programmes to consolidate or improve technologies; iii) the promotion of regional and international cooperation to exchange the proven technologies and network among specialists; iv) the development of human resources through well-targeted capacity-building programmes. The international conventions that have been proclaimed before or after the Rio de Janeiro Summit provide a complete set of approaches and guidelines that should help promote, in a coherent manner at national, regional and international levels, the contribution of forestry to the maintenance of a sound environment and to sustainable development.


Special papers prepared for the Eleventh World Forestry Congress (13-22 October 1997, Antalya, Turkey) and referred to in this article:

Choudhury, J. 1997. Sustainable management of coastal mangrove forest development and social needs.

Hernandez, B.E. 1997. Strategies for strengthening watershed management in tropical mountain areas.

Berthe, Y. 1997. The role of forestry in combating desertification.

Kabii, T. & Bacon, P. 1997. Protection of wetlands and coastal lands and their habitats.

Zheng Songfa, Zheng Dezhang, Liao Baowen & Li Yun. 1997. Tidal land pollution in Guangdong Province of China and mangrove afforestation.

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