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Monday 30 January 2017

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Forests and water


Forests and water 

Unasylva No. 229
Vol. 58, 2007/4

Food and Agriculture Organization of the United Nations
Rome, 2007

Editor: A. Perlis
Editorial Advisory Board:F. Castañeda, R. Czudek, T. Hofer, D. Kneeland, A. Perlis, L. Russo, T. Vahanen, P. Vantomme, M.L. Wilkie
Emeritus Advisers:
J. Ball, I.J. Bourke, C. Palmberg-Lerche
Regional Advisers:
C. Carneiro, P. Durst, P. Koné, E. Mansur, K. Prins
Unasylva is published in English, French and Spanish. Payment is no longer required. Free subscriptions can be obtained by sending an e-mail to unasylva@fao.org

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Comments and queries are welcome: unasylva@fao.org

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Articles express the views of their authors, not necessarily those of FAO.
Designations employed and presentation of material do not imply the expression of any opinion on the part of FAO concerning the legal or development status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries.

The FAO publications reviewed in Unasylva may be ordered from any of the FAO sales agents listed on the inside back cover. FAO will process orders from countries where there are no sales agents. Contact the Sales and Marketing Group, Communication Division, FAO, Viale delle Terme di Caracalla, 00153 Rome, Italy.

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Contents


Editorial (Download- 120 KB)
I. Calder, T. Hofer, S. Vermont and P. WarrenTowards a new understanding of forests and water (Download- 616 KB)
O. Vigiak, O. Ribolzi, A. Pierret, C. Valentin, O. Sengtaheuanghoung and A. Noble
Filtering of water pollutants by riparian vegetation: bamboo versus native grasses and rice in a Lao catchment(Download- 533 KB)
M. Malagnoux, E.H. Sène and N. Atzmon
Forests, trees and water in arid lands: a delicate balance (Download- 537 KB)
H.M. Kangarani and T. Shamekhi
Policy proposals for integrating forest, water and people in the Tigris and Euphrates watershed(Download- 408 KB)
F. Kafeero
The impact of water shortage on forest resources – the case of Uganda 
(Download- 271 KB)
S. Stolton and N. Dudley
Managing forests for cleaner water for urban populations (Download- 549 KB)
T. Stohlgren, C. Jarnevich and S. Kumar
Forest legacies, climate change, altered disturbance regimes, invasive species and water (Download- 949 KB)
M. Fernández Barrena, N. Grados, M.S. Dunin-Borkowski, P. Martínez de Anguita and P. Flores Velásquez
Can the effects of El Niño be mitigated through a system of payments for environmental services? A study of the Piura River watershed, Peru (Download- 616 KB)
D.G. Donovan
Water, forests and the World Water Development Report (Download- 277 KB)
FAO Forestry (Download- 430 KB)
World of Forestry (Download- 368 KB)
Books (Download- 131 KB)


For further details log on website :
http://www.fao.org/docrep/010/a1598e/a1598e00.htm

Forests, trees and water in arid lands: a delicate balance

Author 
M. Malagnoux, E.H. Sène and N. Atzmon
Michel Malagnoux, prior to his retirement in September 2007, was Forestry Officer (Arid Zones) in the Forest Conservation Service, FAO Forestry Department.

El Hadji Sène was Director of the Forest Resources Division, FAO Forestry Department, until his retirement in 2004, and currently resides in Dakar, Senegal.

Nir Atzmon is in the Department of Agronomy and Natural Resources, Institute of Field and Garden Crops, Agriculture Research Organization, Volcani Centre, Bet-Dagan, Israel.
This article is adapted from Malagnoux, 2007.
In arid lands, where competition for water is acute, trees should be planted only when and where necessary and possible.

Arid lands are among the world’s most fragile ecosystems, made more so by periodic droughts and increasing overexploitation of meagre resources. Arid and semi-arid lands cover around one-third of the world’s land area and are inhabited by about one billion people, a large proportion of whom are among the poorest in the world.

Forests, trees and grasses are essential constituents of arid zone ecosystems and contribute to maintaining suitable conditions for agriculture, rangeland and human livelihoods. In providing goods (especially fuelwood and non-wood products) and environmental services to the rural poor and in contributing to the diversification of their household sources of income, forests and trees in arid zones boost poverty alleviation strategies and reduce food insecurity.

Roughly 6 percent of the world’s forest area (about 230 million hectares) is located in arid lands (FAO, 2001). Trees outside forests (scattered in the landscape, in arable lands, in grazing lands, in savannahs and steppes, in barren lands and in urban areas) have a vital role in arid lands, although it is difficult to assess their extent.

Availability of water – surface water, groundwater and air moisture – is usually the main factor limiting natural distribution of trees in arid lands, along with climate (rainfall, temperatures, wind) and soil quality. Each tree species is adapted to certain conditions and is located in its “niche”. When optimal conditions are widely distributed, forests or shrubs may cover large areas. More often, limited by water scarcity, vegetation is concentrated where runoff can accumulate or where groundwater is accessible. This leads to the uneven distribution of trees and bushes, for example in striped bush (fragmented bush stands), riparian forests, the deepest channels of valleys (thalwegs) and oases, and isolated in the landscape.

However, the natural distribution of vegetation has long been altered by human activities. Deforestation and degradation of tree and shrub formations (mainly through conversion to agricultural use) and overexploitation of forests and woodlands (through fuelwood collection and overgrazing) are among the major causes of soil degradation in arid areas. Furthermore, global warming is expected to result in rainfall decrease throughout most of the world’s arid zones, which will lead to more severe water scarcity and increased desertification risks.

Many methods for reversing deforestation, degradation and desertification rely on tree planting. However, before trees are planted it is essential to consider the water balance. 
Water availability limits distribution of trees; some individuals are able to survive even in the desert far from any other vegetation (Mauritania)
FAO/CFU000142/R. Faidutti

A TREND OF DECREASING FOREST COVER

Deforestation

Conversion of forests for agricultural crops and pasture land is the main cause of the increasing deforestation in arid lands. In many places the prevailing shifting cultivation and crop/fallow systems are no longer possible and continuous cultivation of the same piece of land, often with no crop rotation, leads to exhaustion of soil fertility and the need for new lands. Degraded wooded lands which were formerly neglected are now actively deforested. Increased grazing pressure and unmanaged harvesting of fuelwood and other products also result in degradation and deforestation.

The remaining forests and wooded lands are sometimes threatened by pest and disease outbreaks, although these are rare under extremely dry conditions. Forest fire is a constant threat in arid lands, although very large fires are rare compared with those occurring in other regions. Limited fuel accumulation due to high grazing pressure limits the extension of burned areas. However, fires cause considerable loss of forest, bush and tree cover, especially in the drier ecosystems, endangering ecological niches hosting relicts of forests of high biological diversity. 

Desertification

The United Nations Conference on Environment and Development (UNCED, 1992) defined desertification as “land degradation in arid, semi-arid and dry sub-humid areas resulting from various factors, including climatic variations and human activities”. Desertification is not an advance of existing deserts but is rather the effect of localized degradation of the land. It rapidly follows deforestation and soil exhaustion. Exposed to the sun, the wind and the rains, exhausted soils loose their organic matter and their structure while nutrients are leached away. Fine elements are blown into dust storms and sand grains become mobile and encroach on other lands through sheets and dunes. Overexploitation of forest, tree, bush, grazing land and soil resources has been increasing desertification.

Desertification is a worldwide problem directly affecting 250 million people, particularly in Africa where two-thirds of the continent is dry lands and deserts. However, more than 30 percent of the land in the United States is also affected by desertification. One quarter of Latin America and the Caribbean is deserts and dry lands. In Spain, one-fifth of the land is at risk of turning into deserts. In China, since the 1950s, sand drifts and degradation have taken a toll of nearly 700 000 ha of cultivated land, 2.35 million hectares of rangeland, 6.4 million hectares of forests, woodlands and shrub lands. Worldwide, some 70 percent of the 5.2 billion hectares of dry lands used for agriculture are degraded and threatened by desertification (FAO, 2007a). 

Climate change effects on arid lands

Undisturbed forests are able to adapt to climatic and edaphic changes to a certain extent, but not over the long term: palaeo­botanical records indicate that past climate change destroyed prevailing vegetation types and promoted new types to replace the former ones. According to most predictive models, global warming will affect arid lands through temperature increase and rainfall decrease all over the world (with the exception of southwestern Latin America, where more frequent El Niño–Southern Oscillations are expected to lessen drought risks) (UCAR, 2005). The models predict increases of the frequency and/or intensity of droughts. Increased fire risks are also expected for the remaining forests and wooded lands. Increased temperatures lead to increased evaporation and more severe scarcity of water. All these trends lead to increased risks of desertification. In many places the vegetation already faces harsh conditions near the threshold of lethal temperatures. Any increase of these maximum temperatures will directly lead to irremediable vegetation loss.

The main consequences of climate change in arid lands will be a decrease of agriculture, rangeland and forest productivity, biodiversity, soil organic matter and fertility. This will worsen poverty and food insecurity. Populations will be forced to migrate. It is predicted that 135 million environmental refugees will leave their land by 2020 because of desertification, of which 60 million will be displaced in sub-Saharan Africa (FAO, 2007b). Already facing the lost productivity of natural rangelands, nomadic and transhumant herders may be forced to settle. Concentration of herds around their new homes has already led to the disappearance of most of the vegetation cover around many settlements and around wells and other water sources that provide drinkable water for humans and animals year round. Policies to support settling of nomadic herders are weak in many countries.

Another problem is related to the ageing of the tree population as a result of overgrazing of young seedlings, which impedes the natural regeneration of trees. Overmature trees progressively lose their resilience to climatic stress, so that a single climatic event can destroy a whole area of forest. For example, most of the Acacia nilotica forests of the Senegal River Valley died in the early 1970s after a severe drought.

Restoring vegetative cover of arid-zone lands can help mitigate climate change by increasing carbon uptake and storage, even if only a small amount of carbon per unit area will be sequestered. The area of arid lands to be restored is so huge that it constitutes a good potential sink for carbon. The economics of related schemes should, however, be carefully considered and documented.
Acacia stands in the Sahel and their relationships with water
Water is a scarce and coveted resource in the Sahelian region. Competition for it is severe and when present it is rapidly used by humans, animals and plant species. Acacia spp. have a particularly sensitive interaction with water. In a year of abundant rainfall, they regenerate plentifully from seeds that may have been collecting for years, ready to germinate as soon as conditions are favourable. Acacia spp. also usually grow in abundance wherever topography, soil characteristics and local water economy facilitate their germination and growth, and this generates very marked landscapes.

Acacia nilotica stands prefer deep alluvial soils accumulated year after year by annual riverine floods. The seedlings survive these floods provided their tips are above the water. They regenerate profusely and grow quickly to become sturdy seedlings which can survive other floods. They then become strong even-aged clusters in regular stands.  Acacia nilotica is valued for its wood, leaves and pods, and forms part of the livestock-rearing systems of river valleys, floodplains and lakes in the Sahel. It is among the most productive Acacia species in the region.

Acacia seyal is a tender wood species growing on heavy soils in extensive stands. These stands support animal husbandry and have also provided most of the fuelwood and charcoal supply for Sudano-Sahelian cities; as a result their extent has been considerably reduced. The land they formerly occupied in the Sudan now supports extensive industrial sorghum cultivation. Acacia seyal stands are linked to black soils usually occurring on large flat plains subjected to temporary flooding. Such floods, although short lived, favour the development of even-aged stands like those of A. nilotica. Along with Acacia senegaland Combretum spp.,A. seyal produces large quantities of gums.

Acacia senegal is the main gum arabic producer in the Sahelian region. Especially in Chad, Mali, Mauritania, Senegal and the Sudan, this species produces the best quality gum arabic. The form and dispersion of its stands, often in extensive but localized patches, depend much on rainfall. Occasional favourable rainy seasons trigger explosive regeneration of A. senegal. This explains the occurrence of large even-aged stands on sandy soils with no apparent capacity to retain water. The species also grows in thick stands on alluvial soils in depressions that have collected fine alluvial material. 
Natural woodland of Acacia seyal and Acacia senegal, the Sudan
FAO/T. Hofer 

REVERSING THE DEGRADATION TREND

Removing the causes

To start with, the human-induced causes of desertification should be tackled. Poor people are obliged to exploit whatever resource they may have access to for their survival. Overexploitation should be avoided through assistance to meet their basic needs with income generation opportunities. Poverty mitigation measures can include planting trees (for their products and services) in major afforestation schemes, woodlots, linear plantations, windbreaks and hedgerows and as isolated trees in agricultural and other landscapes.

Natural regeneration through land protection

The most evident way to restore vegetative cover is to protect it from the causes of degradation: mostly exploitation (harvesting and grazing) and fires. Vegetation can spread naturally, even on bare lands, but the process is often slow. Protection is not always easy as it has to be maintained carefully over a long period. Planting trees, bushes and grass will speed up the process. Then, the restored lands need to be sustainably managed.

The Abéché protected area in Chad is a noteworthy example. In 1961, 305 barren hectares with a few Acacia trees (A. raddianaA. senegal and A. mellifera) were fenced off with barbed wire and carefully watched over to protect the watershed. Within ten years, without any planting, total land cover had been obtained. After 45 years of almost continuous protection, the protected area is now clearly differentiated from its surroundings in satellite images.

Afforestation, sand dune fixation and green belts

Afforestation through tree plantation can be a good tool for environmental restoration. During the second half of the twentieth century many forest plantations were established in arid lands all over the world, mostly for protection or for fuelwood production, and the pace of plantation programmes has been speeding up (FAO, 2006a,b). Plantation programmes have used many species (often exotics) and techniques, from low investment (rainfed) to high investment (rainfed with land shaping or irrigated from the water table, deep aquifers or wastewater). The varied successes and failures of such plantations now constitute good sources of information for future activities.

Many countries around the world (e.g. Chile, China, Denmark, France, the Islamic Republic of Iran, Mauritania, the Niger, Senegal and Viet Nam) have developed tree plantation techniques for fixation of shifting sands. In arid zones, both local and large national or international schemes apply such techniques to protect productive lands, infrastructures and settlements. Many of the plantations also produce wood and non-wood products.

Many arid zone towns and cities have planted local green belts to protect their population and infrastructures against dust storms and encroaching sands and to influence the microclimate. Arable lands, irrigation schemes, railways, roads, canals and coastal dunes are also being protected through dedicated schemes.

Larger-scale afforestation schemes for land reclamation have a long history; they were implemented in France and Germany in the eighteenth and nineteenth centuries and in the United States after the 1935 Dust Bowl. In Algeria, FAO and the World Food Programme (WFP) started the tree planting programme “Chantiers populaires de reboisement” in 1966. In 1971, Algeria initiated the “Barrage vert”, a planted 20 km–wide belt on the fringe of the Sahara desert intended to stretch 1 500 km from the western to the eastern borders of the country, to comprise 3 million hectares. By 2003 only 100 000 ha had been planted, however, mainly with Pinus halepensis (Belaaz, 2003). Following this national initiative, North African countries (Morocco, Algeria, Tunisia and the Libyan Arab Jamahiriya) started a regional programme, the Arab Magreb Union (UMA) green belt for the north of the Sahara, but since the 1990s there has been little evidence of its activities.

In 1978, China initiated the “Great Green Wall” project which afforested 9 million hectares in its first ten years. In the current phase of the project, now called “the New Great Wall”, an additional 5 million hectares are to be planted by 2010 (Ratliff, 2003). Dust storms still trouble Beijing as yet, but airborne dust is carried such distances that the effects of such greening efforts may require several decades to become evident.

The African Union launched a “Green Wall for the Sahara” project in Abuja, Nigeria in December 2006 to contribute to halting and reversing desertification at the southern and northern fringes of the Sahara. The project will work hand in hand with all concerned countries and other organizations and programmes such as the New Partnership for Africa’s Development (NEPAD), the Global Environment Facility (GEF) Operational Program on Sustainable Land Management (OP 15), the United Nations Convention to Combat Desertification (UNCCD) and the TerrAfrica Initiative. Rather than merely establishing a few lines of trees, the project will address sustainable and integrated resource management and restoration activities (through tree planting, rangeland restoration and agriculture, implemented only where feasible and sustainable) in a land belt as wide as possible. It will be a task for several generations.

The results obtained from green belt experiences have varied greatly depending on the scale of the afforestation schemes, the quality of the methods applied, their adaptation to local conditions and the quality of the plantation management. An in-depth study of the climate, soil, water, land use and socio-economic conditions is always required. Local water availability and water demand must always be considered (see below). Green belt initiatives must also take into account previous land uses and ownership and the causes for deforestation and desertification, including peoples’ needs for forest products, pasture and croplands, offering alternative solutions to cover these needs. Local people should be involved all through the process, from conception to the management of the new resources. Large monospecific tree stands should be avoided and a patchwork of different types of plant cover (including agricultural crops and grazing) preferred whenever possible. Local species should be preferred; several projects have clearly shown the problems related to exotic species, which may become invasive in their new environment. 
On formerly barren land at Abéché, Chad, protective measures initiated in the 1960s have resulted in restoration of land cover 
Google Earth™ mapping service

IMPROVING THE WATER BALANCE

Natural forests and tree plantations improve the water cycle in diminishing runoff and improving the replenishment of the water table. Tree planting has often been proposed as a way to increase rainfall. It has been estimated that 60 percent of rainfall over the moist evergreen Amazon forest comes from the forest itself through evapotranspiration
(TheAmazon.org, 2007). However, planting trees will produce tangible results in increasing rainfall on neighbouring areas only when very large areas are converted to forest (Avissar and Otte, 2007).

However, trees also consume water. The more the aerial system of trees is developed, the more water they transpire. The desirability of tree planting in arid lands is debated because trees may consume more water than they provide to the water cycle. Some countries, such as South Africa, have imposed a tax on the water consumed by forests. In certain circumstances where trees consume all the rainwater, it may be judged better to harvest this water through a bare watershed, store it in a reservoir and use it to irrigate high-value agricultural crops. For example, in Yatir, Israel, where average precipitation is only 270 mm per year, more than 3 000 ha of rainfed Pinus halepensis were planted in the early 1960s under a large-scale afforestation project. Although the forest provides carbon sequestration benefits and contributes to the livelihoods of nearby communities (particularly through fuelwood and non-wood forest products such as resins, fodder and medicinal and aromatic plants), it uses all the precipitation water. Furthermore, the forest has altered the biodiversity of the region, as new predation dynamics threaten endemic species. Rueff and Schwartz (2007) reported that the water that the watershed would have provided if it had not been afforested would have alleviated poverty better if it had been used for agriculture. They suggested that afforestation on a smaller scale, such as on farmers’ plots, may yield similar benefits with fewer drawbacks, as combining tree planting and agriculture is less disturbing to the environment, improves agricultural yields, conserves water and soils and provides fuelwood for farmers.

Local populations have implemented different methods of water harvesting to benefit their crops and their trees. One technique was adapted from the natural example of the striped bush at the transition between continuous bush stands and grass steppe (Malagnoux, 2008). Where rainfall does not provide enough water to maintain a continuous vegetative cover, fragmented vegetative cover is separated by land strips of varying width. Runoff from the bare land strips provides the vegetation with the water it needs; the strips thus constitute small watersheds. Agronomists have improved on these traditional techniques, and foresters have also adapted them to the size and needs of their trees. Mechanized technologies have been developed to increase the scale of land restoration dramatically through quicker and cheaper land processing, while deepening the strips to increase water-holding capacity.

In tree planting for desertification control, the present and future water balance of the stand should be systematically estimated for each phase of its evolution. Appropriate silvicultural measures should be promoted to maintain the yearly water consumption below the yearly water inflow – including species choice, surface to be planted, planting density, thinning, pruning, coppicing, pollarding and also, when necessary, conversion to more sustainable vegetative cover, for instance from a dense stand to a parkland or grassland. Every desertification control programme or greening activity should be considered at the landscape level. Trees should be planted only when really needed and where possible.

In addition to rain, other water sources such as recycled water and deep aquifers have to be considered. Many arid lands and deserts have deep aquifer resources that could be tapped. While some restoration activities could rely for a short period on fossil aquifers, these activities will be sustainable only when water recharge exceeds or equals water withdrawal. With urbanization accelerating in arid lands, urban forestry and other urban greening programmes using vegetation that consumes less water than trees (e.g. bushes and grasses) are of increasing importance. More recycled water is being used in such programmes, including sewage water in some countries, and this practice will progressively grow in the future.
Water drawn from a shallow well is used to irrigate trees planted as part of sand dune stabilization efforts, the Niger; once the roots reach the water table, the trees will no longer need to be watered
FAO/FO-0707/S. Braatz
FAO/FO-0716/S. Braatz

CONSERVATION AND SOUND MANAGEMENT 

The sound and sustainable management of land, vegetative cover, water resources and biodiversity means that only that part which is renewable, i.e. their effective production, is used, ensuring maintenance of the capital and its productive capacity. Sustainable land management includes:
  • conservation agriculture (minimum soil disturbance, maximum return of organic matter to the soil, permanent soil cover and crop rotation);
  • sound management of grazing lands (adjusting grazing pressure to carrying capacity);
  • multipurpose forest management planning. 
Of prime importance is the participation of the local people and communities, capitalizing on their traditional knowledge and practices. Clear land-use rights are essential to sound land management. Reinforcing people’s control over resources and guaranteeing them secure and fair access ensures their long-term commitment to resource conservation. Desertification control programmes must be mainstreamed into national development plans and strategies in particular to alleviate poverty, eliminate institutional, legislative or infrastructure constraints and facilitate co-management of development projects. 

CONCLUSIONS

Arid-land forests and trees have an important role in land stabilization, desertification control, watershed protection and other functions as well as providing wood (especially woodfuel) and non-wood products including fodder for domestic animals. They provide subsistence for local populations and are integrated in the fabric of rural societies. Yet the productive and protective functions and vitality of forests and trees in arid lands are often jeopardized by human-caused stresses and natural hazards. Despite their importance for local economies and for the people, arid land forests and forest products are still largely neglected in natural resource management policy and decision-making processes.

When tree planting is considered, the water balance should be assessed and its evolution should be estimated for each period of the whole life of the planted stand. Every desertification control programme or greening activity should be considered at landscape level. More than “plant a tree”, the motto for combating desertification should be “manage land and resources wisely: plant a tree only where and when it is sustainable”.
Bibliography
Avissar, R. & Otte, M. 2007. The impacts of afforestation in northern Israel on its local and regional hydroclimate. Paper presented to the International Conference on Afforestation and Sustainable Forests as a Means to Combat Desertification, Jerusalem, Israel, 16–19 April.

Belaaz, M. 2003. Le barrage vert en tant que patrimoine naturel national et moyen de lutte contre la désertification. In Proceedings of the XII World Forestry Congress, Quebec, Canada, 21 to 28 September 2003. Available at: www.fao.org/docrep/article/wfc/xii/0301-b3.htm

FAO. 2001. Global Forest Resources Assessment 2000 – main report. FAO Forestry Paper No. 140. Rome.

FAO. 2006a.GlobalForest Resources Assessment 2005 – progress towards sustainable forest management. FAO Forestry Paper No. 147. Rome.

FAO. 2006b. Global planted forest thematic study: results and analysis. Planted Forests and Trees Working Paper FP38E. Rome.

FAO. 2007a. State of the World’s Forests 2007. Rome.

FAO. 2007b. Adaptation to climate change in agriculture, forestry and fisheries: perspectives, framework and priorities. Interdepartmental Working Group on Climate Change. Rome.

Malagnoux, M. 2007. Arid land forests of the world: global environmental perspectives. Paper presented to the International Conference on Afforestation and Sustainable Forests as a Means to Combat Desertification, Jerusalem, Israel, 16–19 April.

Malagnoux, M. 2008. Restauration des terres arides dégradées pour la production agricole, forestière et pastorale grâce à une nouvelle technique mécanisée de récolte des eaux pluviales. In C. Lee  & T. Schaaf, eds. The future of drylands, Proceedings of the International Scientific Conference on Desertification and Drylands Research, Tunis, Tunisia, 19–21 June 2006. Dordrecht, the Netherlands, Springer. (In press)

Ratliff, E. 2003. The Green Wall of China. Available at:  www.wired.com/wired/archive/11.04/greenwall.html

Rueff, H. & Schwartz, M. 2007. The contribution of dryland forests to livelihoods – the case of the Yatir forest. Presented at the International Conference on Afforestation and Sustainable Forests as a Means to Combat Desertification, Jerusalem, Israel, 16–19 April.

TheAmazon.org. 2007. Information about the Amazon River. Internet document. Available at: www.theamazon.org/amazonriver.html

United Nations Conference on Environment and Development (UNCED). 1992. Chapter 12: Managing fragile ecosystems: combating desertification and drought. In Agenda 21. Available at: www.un.org/esa/sustdev/documents/agenda21/english/agenda21chapter12.htm

University Corporation for Atmospheric Research (UCAR). 2005. Press release: Drought’s growing reach: NCAR study points to global warming as key factor. 10 January. Available at: www.ucar.edu/news/releases/2005/drought_research.shtml

For further details log on website :
http://www.fao.org/docrep/010/a1598e/a1598e06.htm

Books


Two new FAO books on mangroves: a global assessment...

The world’s mangroves 1980–2005. 2007. FAO Forestry Paper 153. Rome, FAO.

Mangroves are coastal forests found in sheltered estuaries and along river banks and lagoons in the tropics and subtropics. The term “mangrove” describes both the ecosystem and the plant families that have developed specialized adaptations to live in this tidal environment. Mangroves fulfil important socio-economic and environmental functions: providing wood and non-wood forest products, protecting shores against wind, waves and water currents; conserving biological diversity; protecting coral reefs, sea-grass beds and shipping lanes against siltation; and providing habitat, spawning grounds and nutrients for a variety of fish and shellfish, including many commercial species. High population pressure in coastal areas has, however, led to the conversion of many mangrove areas to other uses, including infrastructure, aquaculture, rice and salt production.

This publication, prepared as a thematic study within the framework of the Global Forest Resources Assessment 2005, provides comprehensive information on the current and past extent of mangroves in all 124 countries and territories in which they exist. It presents both regional and global overviews of mangrove vegetation, species composition and distribution, together with an indication of the main uses and threats in each region.

FAO prepared The world’s mangroves 1980–2005 in collaboration with mangrove specialists throughout the world. It builds on a 1980 assessment by FAO and the United Nations Environment Programme (UNEP), the FAO Global Forest Resources Assessment 2000 (FRA 2000) and 2005 (FRA 2005) and an extensive literature search. Some 2 900 national and subnational data sets on the extent of mangrove ecosystems were collected during the process.

The results indicate that global mangrove area is currently about 15.2 million hectares, with the largest areas found in Asia and Africa, followed by North and Central America. An alarming 20 percent of mangrove area, or 3.6 million hectares, has been lost since 1980. More recently, the rate of net loss appears to have slowed down, reflecting an increased awareness of the value of mangrove ecosystems, but the annual rate of loss is still disturbingly high.

Removals of wood and non-wood forest products are rarely the main cause of mangrove loss. Human pressure on coastal ecosystems and the competition for land for other uses are the main causes of the decrease in area reported. The relatively large negative change rates that occurred in Asia, the Caribbean and Latin America during the 1980s, for example, were primarily due to large-scale conversion of mangrove areas to aquaculture and tourism infrastructure.
The information highlighted in the report, as well as the gaps in information revealed, will assist mangrove managers and policy- and decision-makers worldwide in ensuring the conservation, management and sustainable use of the world’s remaining mangrove ecosystems. 

...and a species guidebook for Southeast Asia

Mangrove guidebook for Southeast Asia. W. Giesen, S. Wulffraat, M. Zieren & L. Scholten. 2006. RAP Publication 2006/07. Bangkok, Thailand, FAO Regional Office for Asia and the Pacific & Wetlands International. ISBN 974-7946-85-8.

Southeast Asia is endowed with the world’s largest expanse of mangroves which are at the same time the world’s most biologically diverse and varied in structure. In the past few decades, however, much of the mangrove area has been degraded and destroyed. Many mangrove conservation and rehabilitation programmes have been launched in recent years. In the course of such activities, programme staff have faced continual difficulties in identifying plant species growing in the field. This field guide to the mangroves and associated plant species of the subregion was developed to fill an important gap. 
This extensive guidebook – almost 800 pages long – represents the first attempt to cover all mangrove plant species in Southeast Asia. In the first part, it introduces mangroves in general and Southeast Asia’s mangroves in particular. The second part provides descriptions of 268 plant species divided in seven groups – ferns; grasses and grasslike plants; other ground-dwelling herbs; epiphytes; vines and climbers; palms, cycads and pandans; and trees and shrubs. Skillfully drawn black-and-white illustrations of the plants greatly enhance the usefulness of the book.
This book will help more people, especially students, learn about mangrove forests in Southeast Asia and will support further advancement of mangrove conservation and rehabilitation programmes. It is a useful tool for mangrove forest managers, foresters, coastal resource managers, scientists, educators, students and interested lay people, not only in Southeast Asian countries, but in all countries where mangroves grow. 

Global assessment of bamboo resources

World bamboo resources. M. Lobovikov, S. Paudel, M. Piazza, H. Ren & J. Wu. 2007. Non-Wood Forest Products No. 18. Rome, FAO. ISBN 978-92-5-105781-0. 

Bamboo is a woody grass widely distributed in tropical, subtropical and mild temperate zones in all regions of the world. As a major non-wood forest product and wood substitute, it has always had an important economic and cultural role across Asia. Now the use of bamboo is growing rapidly in Latin America and Africa as well. In some countries, the processing of bamboo is shifting from low-end crafts and utensils to high-end, value-added commodities such as housing, pulp, paper, panels, boards, veneer, flooring, roofing, fabrics, oil, gas and charcoal (for fuel and as an excellent natural absorbent). The bamboo shoot is also a nutritious vegetable. Bamboo is an increasingly important economic asset in poverty eradication and economic and environmental development. 
Bamboo is a forest plant but is also widespread outside forests, including on farmlands and riverbanks, along roads and in urban areas. Taxonomists still debate the total number of bamboo species and genera – an estimate is about 1 200 species in some 90 genera.
This study, prepared by FAO jointly with the International Network for Bamboo and Rattan (INBAR), was undertaken as one of seven thematic studies within the Global Forest Resources Assessment 2005 (FRA 2005) process and is a first attempt at systematic reporting of the best available information on bamboo resources and utilization at the global level. The study is the result of a three-year process of data collection and validation involving many partners from participating countries and international organizations, in line with the FRA 2005 philosophy of global partnership. Although data availability and quality are often weak, the main value of the study is that it established a systematic methodology and launched the most comprehensive assessment of global bamboo resources to date. 
Sixteen countries in Asia reported a total of 24 million hectares of bamboo resources. Five African countries reported 2.8 million hectares. It is estimated that ten Latin American countries may have over 10 million hectares of bamboo resources, bringing the world total to some 37 million hectares or roughly 1 percent of the global forest area. However, the figures represent only rough estimates. They also include bamboo mixed with other species (in which bamboo is not necessarily predominant) and bamboo on non-forest land (including mixed with other trees or crops).
The publication also reports on species diversity, growing stock, biomass, removals, ownership and health status of the resource, and on bamboo products and trade.
It is hoped that the information and knowledge generated by this study will be useful to national policy processes, and that feedback from users will help improve future global resources assessments. 

Tracing the causes of illegal logging

Illegal logging: law enforcement, livelihoods and the timber trade. L. Tacconi, ed. 2007. London, UK, Earthscan. ISBN 978-1-84407-348-1.

Illegal logging is widespread – accounting for more than 50 percent of all timber in some countries – and causes great damage. Once cut, illegal logs feed the great demand for exotic hardwoods in developed and developing countries. The result has been an enormous loss of both revenue and forest resources. Consequently the issue has risen to the top of the global forest policy agenda as one of the major threats to forests, and donors and national governments are starting to develop initiatives to combat illegal logging. Yet considering the magnitude of the problem, surprisingly little is known about the causes of illegal logging and its impacts on biodiversity, people’s livelihoods and national economies.

Paradoxically, despite the negative impacts, illegal logging also benefits many stakeholders, including some marginalized communities. How can illegal logging be tackled without causing poverty in local communities? This book, published with the Center for International Forestry Research (CIFOR), examines the key issues including legislation and law enforcement, supply and demand, governance and corruption, forest certification, poverty, local livelihoods, international trade and biodiversity impacts. It includes key case studies from forest-rich regions in the Americas, equatorial Africa and Asia.

Illegal logging can only be tackled by addressing the underlying economic, political and social causes. While there are clearly no easy answers, this book explores the many dimensions of the causes, impacts and implications of illegal logging for forests, people, livelihoods and forest policy. While much is still unknown about the subject, Illegal logging adds to the growing literature, highlighting the key issues that must be understood in order to develop policy that can make a difference. 

Revisiting the state of the environment

GEO-4: Global environment outlook – environment for development. 2007. Nairobi, Kenya, United Nations Environment Programme (UNEP). ISBN 978-92-807-2836-1 (paperback), 978-92-807-2872-9 (hardback)

The 1987 report of the United Nations World Commission on Environment and Development report, Our common future (also known as the Brundtland Report), is widely credited for introducing sustainable development into the public consciousness. The fourth edition of Global environment outlook (GEO-4) takes stock of how far society has come in the 20 years since. The picture is grim, showing evidence of decline almost all across the board: more greenhouse gases, more widespread pollution, declining availability of freshwater, deforestation, degradation of farmland, depletion of natural resources, acidification of oceans.

Compiled and written by hundreds of researchers from a great variety of disciplines, GEO-4 provides an overview of global social and economic trends and the state and trends of the global and regional environment over the past two decades, as well as the human dimensions of these changes. The publication reminds readers that issues of forestry, freshwater supplies, agriculture, biodiversity and desertification are connected to each other and to climate change. It also explores the links between social trends and environmental decline, examining how increasing  population pressure and the increasing divergence between rich and poor influence the environment – resulting for example in more deforestation. 

As defined in Our common future, “Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs”. GEO-4 finds, however, that current human society tends to focus on meeting the needs of the present, and in doing so is indeed compromising the ability of future generations to meet their own needs. 

The nearly 600 page publication is divided in six sections. The first summarizes the evolution of issues since1987. The second section describes the state and trends of the environment from 1987 to 2007, with separate chapters devoted to atmosphere, land, water and biodiversity. The state of forests is extensively explored in the chapter on land. 
Section C presents the environmental status and trends from a regional perspective. Section D explores the human dimensions. One chapter probes areas of vulnerability and identifies opportunities for improving human well-being, while another examines environmental interlinkages and governance needs. The fifth section looks forward to 2015 and beyond; and the last summarizes options for action, categorizing possible solutions along a continuum from proven to emerging.

GEO-4 provides an outlook for the future and policy options to address present and emerging environmental issues. It will be of interest to policy-makers, professionals and academics in many sectors, as well as to the wider public.

For further details log on website :
http://www.fao.org/docrep/010/a1598e/a1598e17.htm

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