Towards a new understanding of and water

I. Calder, T. Hofer, S. Vermont and P. Warren

An overview of the state of he availability and quality of water in hydrology, and for embedding knowledge about forest and water in many regions of the world are this knowledge and the research find- interactions and salient issues in Tmore and more threatened by ings in policies. Similarly, there is a forest and water policy. overuse, misuse and pollution, and it need to develop institutional mecha- is increasingly recognized that both are nisms to enhance synergies in dealing strongly influenced by forests. Moreover, with issues related to forests and water climate change is altering forest’s role as well as to implement and enforce in regulating water flows and influen­ action programmes at the national and cing the availability of water resources regional levels. (Bergkamp, Orlando and Burton, 2003). In the past, forest and water policies Therefore, the relationship between were often based on the assumption that forests and water is a critical issue that under any hydrological and ecological must be accorded high priority. circumstance, forest is the best land Forested catchments supply a high pro- cover to maximize water yield, regulate portion of the water for domestic, agri- seasonal flows and ensure high water cultural, industrial and ecological needs quality. Following this assumption, con- in both upstream and downstream areas. serving (or extending) forest cover in A key challenge faced by land, forest and upstream watersheds was deemed the water managers is to maximize the wide most effective measure to enhance water range of multisectoral forest benefits availability for agriculture, industrial without detriment to water resources and domestic uses, as well as for prevent- and ecosystem function. To address this ing floods in downstream areas. challenge, there is an urgent need for Forest hydrology research conducted a better understanding of the interac- during the 1980s and 1990s (summarized tions between forests/ and water, for by Bruijnzeel, 2004; Calder, 2005, 2007; awareness raising and capacity building Van Dijk and Keenan, 2007) suggests

Key terms

Discharge (or water flow): volume of water passing through a given point at a given time Recharge: refill of a groundwater aquifer River basin: the complex system of watersheds and subwatersheds crossed by a major river and its tributaries while flowing from the source to the mouth Upstream/downstream linkages: the environmental, socio-economic and cultural flows, Ian Calder is Professor, Centre for Land Use synergies exchanges and conflicts between the upper and lower parts of a watershed and Water Resources Research, Newcastle University, United Kingdom. Watershed (or catchment): the geographical area drained by a watercourse – a concept Thomas Hofer is Officer (Conservation applied to units ranging from a farm crossed by a creek (a microwatershed) to large river and Hydrology), FAO Forestry Department, or lake basins Rome. Sibylle Vermont is Science Officer, Federal Watershed management: any human action aimed at ensuring a sustainable use of water- Office for the Environment, Berne, Switzerland. shed resources Patrizio Warren is Social Science Consultant, FAO Forestry Department, Rome.

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a rather different picture. Although biophysical interactions between forests STATE OF KNOWLEDGE ON the important role of upstream forest and water into policies. The International FORESTS AND WATER cover in ensuring the delivery of high- Expert Meeting on Forests and Water, Recent forest hydrology has focused quality water has been confirmed, earlier held in Shiga, Japan in November 2002 in on three topics that are particularly rel- generalizations about the benefits of preparation for these events, highlighted evant for policy-making: the comparative upstream forest cover on downstream the need for more holistic consideration advantages and disadvantages of forest annual and seasonal flows were generally of interactions between water, forest, cover in maximizing downstream water fallacious and misleading. Studies have other land uses and socio-economic fac- yields; the role of upstream forests in shown instead that, especially in arid or tors in complex watershed ecosystems. maintaining water flows during the dry semi-arid ecosystems, forests are not the During the past five years, the Shiga season; and water-quality preservation. best land cover to increase downstream Declaration has become a key reference This section summarizes findings in these water yield. Moreover, solid evidence for the development of a new generation three areas (based on Hamilton, 2005). has shown that in tropical ecosystems of forest and water policies (see article In the past, policy-making was often the protective role of upstream forest by Zingari and Achouri, this issue). based on the assumption that the more cover against seasonal downstream This article summarizes the state of cur- trees, the more water. Current forest floods has often been overestimated. rent knowledge about forest and water hydrology research challenges this This is especially true in connection interactions in watershed ecosystems. It assumption. The forest ecosystem is in with major events affecting large-scale summarizes some key issues that have fact a major user of water. canopies watersheds or river basins (FAO and emerged from discussion among forest reduce groundwater and stream flow, CIFOR, 2005). hydrologists, other water-sector experts through interception of precipitation The International Year of Freshwater and policy-makers in the years since and evaporation and transpiration from 2003 and the third World Water Forum the Shiga Declaration, the third World the foliage. As both natural and human- (Kyoto, Japan, 2003) helped drive the Water Forum and the International Year established forests use more water than incorporation of this understanding of of Freshwater. most replacement land cover (including agriculture and forage), there is no Upstream and question that forest removal (even partial) downstream, there increases downstream water yields. is a need for more holistic consideration Consequently, removal of heavy water- of interactions demanding forest cover has sometimes between water, forest, been suggested, especially in semi-arid other land uses and socio-economic areas, as a means of preventing or miti- factors (forested gating drought. However, such a policy watershed in India, should be weighed against the conse- irrigation in the Syrian Arab Republic) quent loss of the many other services FAO/19044/R. F aidutti FAO/FO-5535/T. H ofer FAO/FO-5535/T.

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and goods that forests supply, including Although forests can erosion control, improved water quality, mitigate small, local floods, they do not carbon fixation, recreation and aesthetic appear to influence appeal, timber, fuelwood, other forest floods from extreme products and biodiversity. Such a practice high-rainfall events like this one caused by should definitely be avoided in saline- a cyclone in Paznaun prone areas, where forest removal would Valley, Austria in bring salts closer to the soil surface; and August 2005 in mountain cloud forests, where tree

foliage, epiphytic vegetative surfaces, I nstitut twigs, branches, stems and shrubs provide

a “net” to capture “horizontal precipita- f ü r W asserwirtschaft , H ydrologie tion” from fog or cloud. It is also well established that partial or complete removal of tree cover may accelerate water discharge and increase flood risk during the rainy season and may reduce river flow or even cause river beds to dry out in the dry season. How- ever, the importance of forest cover in und regulating hydrological flows has often konstruktiven W asserbau been overestimated. Impacts of forest cover removal are evident only at the micro level and in association with short- duration and low-intensity rainfall events (which are usually the most frequent). As rainfall duration or intensity increases, or as distance of the rainfall area from the watershed increases, the influence of tree control is not one of them. raindrops. Natural forest cover pro- cover on flow regulation decreases. to prevent or reduce floods is effective vides the most effective barrier to At the macro scale, natural processes in only at a local scale of a few hundred hec- splash-induced soil erosion, largely the upper watershed are more important tares. The complex relationships between because of the contribution of the than land management practices in the forests and water in large river basins lower canopy leaves and the ground development of large floods. For instance, continue to be a matter of debate (see litter in reducing the force of splash- strong scientific evidence refutes the myth CIFOR, 2007), and it is clear that more ing. Forest removal and replacement that in the Himalayas causes work is needed for full understanding of with other land use systems leads in big floods in the lowlands of the Ganges these relationships. most cases to higher and accelerated and Brahmaputra; the large-scale floods It is in maintaining high water quality erosion unless great care in soil con- result rather from a combination of simul- that forests make their most significant servation is practised. taneous discharge peaks of the large riv- contribution to the hydrological charac- • Erosion is generally associated with a ers, high runoff from hills adjacent to the teristics of watershed ecosystems. This higher sediment concentration in run- floodplains, heavy rainfall, high ground- is achieved through minimization of soil off and with siltation of watercourses. water tables and spring tides, lateral river erosion on site, reduction of sediment Good forest cover is more effective embankments and the disappearance of in water bodies (wetlands, ponds, lakes, than any other kind of land cover storage areas in the lowlands (Hofer and streams, rivers) and trapping or filtering in keeping the water as sediment Messerli, 2006). Hence, although there of other water pollutants in the forest free as possible. The surface cover, are many good reasons for reforesting litter, particularly through the following debris and tree roots trap sediments watersheds (e.g. reducing soil loss, keep- mechanisms. and stop their downslope movement. ing sediments out of streams, maintaining • On sloping land, soil moves down- Moreover, deep tree roots stabilize agricultural production, wildlife habitat hill mainly because of gravity and slopes and help prevent shallow land- and so forth), flood risk reduction or even displacement by the splash action of slides.

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Forests maintain Incorporation of forest hydrology high water quality knowledge in water policies by minimizing soil erosion and Despite the significant advances in sci- reducing sediment; entific understanding of forest and water deforestation interactions, the role of forests in rela- generally increases erosion, resulting tion to the sustainable management of in higher sediment water resources remains, as elaborated concentration in in the previous section, a contentious runoff and siltation of watercourses issue. Uncertainty, and in some cases (Pakistan) confusion, persists because of difficul- ties in transferring research findings to different countries and regions, different watershed scales, different forest types and species and different forest manage- ment regimes. Another difficulty is a gap between research and policy, which persists at least in part because of a general failure FAO/ FO-6389/M. K ashio FO-6389/M. FAO/ to communicate results of hydrological • In addition to sediment, various ISSUES IN CURRENT FOREST AND research effectively to policy-makers types of pollution – depending on WATER POLICIES and to challenge conventional assump- nearby land use and drainage to the Following the International Year of tions with scientific evidence. To address watercourse – can also impair water Freshwater 2003, discussion among these issues, in 2006 the International quality. Potential pollutants include forest hydrologists, other water sector Union of Forest Research Organizations excessive concentrations of organic experts and policy-makers has focused (IUFRO) created a Task Force on Forests matter (leading to water eutrophica- on three core issues: incorporation of and Water Interactions. Its aim is to pro- tion) and agricultural or industrial forest hydrology knowledge in water mote consensus in the forest hydrology chemicals. Forest is certainly an ap- policies; inclusion of forest-sector con- propriate ground cover for drinking- tributions in integrated water resource Riparian forest buffer water–supply watersheds, because management policies; and payment for zones can greatly reduce or forestry activities (with the excep- forest- and water-related environmental eliminate non-point source tion of intensively managed planta- services. pollution from domestic, industrial and agricultural tions) generally use no fertilizers or use (Suriname) pesticides and avoid pollution from domestic sewage or industrial pro­ cesses. In addition, non-point source pollution (i.e. pollution from many diffuse sources) from domestic, in- dustrial and agricultural use can be greatly reduced or even eliminated by maintaining adequate riparian forest buffer zones along water- courses. Such zones, however, will not prevent groundwater contamina- tion. Moreover, where atmospheric pollutants are captured by trees be- cause of their height and aerodynamic FAO/FO-0788/N oebauer resistance, watershed forests will not protect water quality. This problem is most prevalent in mountain forests in industrialized countries.

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community on the key issues concern- ing forest and water interactions, and to Forests and water: key messages for policy-makers identify areas of scientific uncertainty on which to focus policy-relevant research. Water use by forests Seeking to generate and disseminate Factors influencing water use by forests include climate, forest and soil type, among others. In information that non-specialists can eas- general, forests use more water than shorter types of vegetation because of higher evaporation; ily and safely use, the task force has they also have lower surface runoff, groundwater recharge and water yield. Forest manage- produced a one-page fact sheet to con- ment practices can have a marked impact on forest water use by influencing the mix of tree vey key concepts in forest hydrology to species and ages, the forest structure and the size of the area harvested and left open. policy-makers (summarized in the Box at right). FAO, similarly, has produced Dry-season flows the booklet Why invest in watershed Forests reduce dry-season flows as much as or more than they reduce annual water yields. It management to raise the awareness of is theoretically possible that in degraded agricultural catchments the extra infiltration associ- policy- and decision-makers about the ated with afforested land might outweigh the extra evaporation loss from forests, resulting in needs for and benefits of watershed man- increased rather than reduced dry-season flows – but this has rarely been seen. agement (see Box, next page). For the linking of research and policy Flood flows related to forest hydrology, education Forests can mitigate small and local floods but do not appear to influence either extreme floods has an important role. Scientific and or those at the large catchment scale. One possible exception is reduction of downstream technical education is generally highly flooding by floodplain forest, where hydraulic roughness (the combination of all elements sectoral. Education across disciplines is that may cause flow resistance, such as forest litter, dead , twigs and tree trunks) may necessary to improve knowledge of forest slow down and desynchronize flood flows. and water interactions, e.g. to improve capacity to assess effects of Water quality and reforestation programmes on water Natural forests and well-managed can protect drinking-water supplies. Man- quality and quantity, flood control and aged forests usually have lower input of nutrients, pesticides and other chemicals than more soil protection. intensive land uses such as agriculture. Forests planted in agricultural and urban areas can reduce pollutants, especially when located on runoff pathways or in riparian zones. However, Inclusion of forestry in integrated trees exposed to high levels of air pollution capture sulphur and nitrogen and can increase water resource management water acidification. Development of integrated water resource management plans at the water- Erosion shed and/or river-basin level was one of Forests protect soils and reduce erosion rates and sediment delivery to rivers. Forestry opera- the targets set by the World Summit on tions such as cultivation, drainage, road construction and timber harvesting may increase Sustainable Development in 2002. These sediment losses, but best management practices can control this risk. Planting forest on multisectoral plans should be aimed at erosion-prone soils and runoff pathways can reduce and intercept sediment. ensuring “water for people, food, , and industry and other uses” (Global Climate change Water Partnership TAC, 2000). Global climate models predict marked changes in seasonal snowfall, rainfall and evapora- The need to include the “nature for tion in many parts of the world. In the context of these changes the influence of forests on water” dimension in these plans is water quantity and quality may be negative or positive. Where large-scale forest planting is increasingly recognized. The concept contemplated for climate change mitigation, it is essential to ensure that it will not accentu- of nature for water takes into account the ate water shortages. Shade provided by riparian forests may help reduce thermal stress to role of terrestrial ecosystems in enhanc- aquatic life as climate warming intensifies. ing water yields and water quality. For instance, the Lange Erlen forested area Energy forests in Switzerland is flooded a dozen days a Fast-growing forest crops have potential for high water demand which can lead to reduced month with water from the Rhine to allow water yields. The local trade-off between energy generation opportunities and water impacts forest soil to filter the water to improve may be a key issue in regions where climate change threatens water resources. its quality and recharge the groundwater of the nearby city of Basel. Source: IUFRO, 2007.

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Payments for environmental services Why invest in watershed management? In many countries, forest and water poli- cies, plans and programmes are coming By providing high-quality freshwater, significantly contribute to resolving these together through the increased popularity regulating discharge and runoff and host- often diverging concerns. of payment for environmental services ing fertile arable land and immense forest Why invest in watershed management can schemes (also called incentive-based resources, watershed areas have a pivotal be obtained free of charge by sending an cooperative agreements, stewardship role in the earth’s ecology and contribute e-mail to: [email protected]. It can payments, compensation schemes or significantly to the wealth and welfare of also be downloaded online at: www.fao.org/ performance payments) as financing human societies. In follow-up to the inter- forestry/site/37205 mechanisms for watershed management, regional watershed management review sustainable and other conducted in 2002–2003 (see Box, p. 22), sustainable development processes (see FAO has recently produced the booklet Why Box on Mexico). Payments do not neces- invest in watershed management to raise the sarily involve money; often they take the awareness of policy- and decision-makers form of services a community has been about the environmental services provided lacking, such as new or better roads, a by watersheds, the risks and threats cur- school bus or weekly transport for farm rently affecting them, and related eco- produce. nomics, management policies, governance Forest stewardship by upstream institutions and programmes. Succinct and populations, for instance, can be com- well illustrated, the publication addresses pensated by downstream water users primarily those policy- and decision-makers through direct payment for the provision responsible for finding a balance between of forest hydrological services such as socio-economic development and environ- discharge regulation or protection of mental conservation. The picture emerging water quality. In developing countries, from recent research supports the view that the ensuing “hydrosolidarity” between investing in watershed management can upstream forest managers and down- stream water users is often mediated by public agencies. For instance, since As are increasingly com- 1 200 km2 in 2005 and is expected to 1996 the Government of Costa Rica has mitted to the development of national reach 3 500 km2 by 2020. sponsored schemes to create economic forest programmes (NFPs) to imple- Many countries have begun to develop incentives for conserving forests and to ment sustainable forest management, integrated water resource management compensate those whose land or land there is scope for them to join forces plans at the national and/or watershed uses generate environmental services. with water experts to develop integrated level. Their implementation is complicated More sophisticated mechanisms invol­ water resource management plans and by the number and variety of stakeholders ving subsidies generated by income forestry programmes as part of a more within and beyond a watershed and their taxes and other public-sector sources comprehensive watershed/river-basin different and sometimes contrasting inter- are being put in place in industrialized planning process. Similarly, manage- ests, as well as by overlap of the adminis- countries (see Box on Switzerland). The ment of transboundary watersheds and trative responsibilities of different regional United Nations Economic Commission river basins should give greater consi- authorities in many countries. A step-by- for Europe (UNECE) Convention on the deration to the relationship between step planning process is advisable to ensure Protection and Use of Transboundary upstream forest cover and downstream buy-in for effective implementation of Watercourses and International Lakes water flows. For instance, the Program the plan. For example, the Water Frame- (2007) recently endorsed the concept of for the Sustainable Development of the work Directive of the European Union payments for ecosystem services includ- Rhine (ICPR, 2001), a transbound- foresees the development of river-basin ing the conservation and development ary initiative, adopts afforestation management plans from a consultative of forest cover. and forest conservation measures to process which will take place in 2008 and facilitate water retention and to pre- be finalized by 2009. This gives time for CONCLUSIONS vent floods in nearby downstream areas. European foresters to cooperate with their During the five years since the Shiga Dec- Protected forest area in the basin was water-specialist colleagues. laration, the third World Water Forum

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done in the past five years by regional in many regions of the world. New and Payments for environmental and global bodies such as the Ministerial innovative technical solutions for bal- hydrological services in Mexico Conference on the Protection of Forests ancing the use of the many services pro- in Europe (MCPFE), the International vided by forests and needed by society To counteract deforestation and water Network of Basin Organizations (INBO), – including those related to water – need scarcity, Mexico created a programme the Latin American Network of Techni- to be developed and promoted to policy- of payments for hydrological environ- cal Cooperation in Watershed Manage- makers, enabling informed decisions mental services in 2003. The programme ment (REDLACH), the Mekong River about integrated forest and water man- provides economic incentives for avoiding Commission (MRC), the Convention agement in an era of global change.u deforestation in areas with severe water on Biological Diversity (CBD), FAO’s problems but where commercial forestry, in Committee on Forestry (COFO), FAO’s the short or medium term, could not match Regional Forestry Commissions and the the opportunity cost of land-use conversion UNECE Timber Committee. to agriculture or cattle ranching. The pro- This cooperation needs to be further gramme provides direct payments to land- developed and strengthened at the Bibliography owners with forest in excellent condition; national and regional levels, for instance it pays for watershed conservation and for through the exchange of technical exper- Bergkamp, G., Orlando, B. & Burton, I. management and restoration of temperate tise and experience across countries 2003. Change: adaption of water resources and tropical forests associated with water and regions. There is a need for more management to climate change. Gland, supply to communities. It is funded through applied research on forests and water, Switzerland, World Conservation Union a portion of water fees collected under the as well as strengthened partnerships (IUCN). Federal Rights Law. The programme pays among research, educational, finan- Bruijnzeel, L.A. 2004. Hydrological functions 400 pesos (US$36.9) per hectare for cloud cial and political institutions. Sound of tropical forests: not seeing the soil for forest and 300 pesos (US$27.7) for other comparative valuations are needed for the trees? Agriculture, Ecosystems and types, and allows payments for up to 200 ha forest services (hydrological and non), Environment, 104: 185–228. per beneficiary. In 2007, about 480 000 ha including their contribution to forest Calder, I.R. 2005. Blue revolution – integrated were covered under the programme through people’s livelihoods, production of land and water resources management. 879 contracts (Martínez, 2007). biofuels, maintenance of biodiversity London, UK, Earthscan. (2nd ed.) and aesthetic and recreational value. Calder, I.R. 2007. Forests and water – ensuring These needs are even more pressing with forest benefits outweigh water costs.Forest and the International Year of Freshwater climate change adding to the complex- Ecology and Management, 251: 110–120. 2003, modern scientific understanding ity of the forest–water relationship and Center for International Forestry Research of forest and water interactions has been influencing forestry and water policies (CIFOR). 2007. Forests and floods, progressively permeating international and national environmental policies. This process has at last partially over- Water supply and urban forest maintenance come what Hamilton (1985) termed the in Lausanne, Switzerland four “M”s (myths, misunderstandings, misinterpretations and misinformation) The city of Lausanne, located on the shore of Lake Geneva in Switzerland, has 136 000 surrounding this topic in policy circles. inhabitants. The city owns some 16 km2 of forests which provide about 8 percent of its New perspectives on water and forest drinking-water. Funding from a combination of timber sales, subsidies and income tax interactions have enabled a clearer does not fully cover the forest management expenses (about €15 per year per inhabitant), understanding of what forest can (and especially when particular emphasis is given to protection of water resources. Accordingly, cannot) do to deal with the challenges a communal fund for sustainable development was established in 2001 with an initial the world will increasingly face in terms contribution of roughly €3 million. Further funding comes from €0.009 per kilowatt-hour of the availability, quality and manage- sold on the electricity network, €0.0003 per kilowatt-hour from gas sales and €0.01 per ment of water resources. cubic metre of water, as well as 1 percent of the annual profits of the city’s industrial On this basis, closer and more fruitful services, with no increase in expense to the consumers. Only part of the fund is used to cooperation between water management promote and manage the forest, which allows flexibility, especially for multiyear projects. experts and foresters has begun, as wit- In addition, forest and water supply services work closely together. nessed by the work on forests and water

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revisited. POLEX electronic policy alert, Thematic study for the Global Forest Martínez, J. 2007. Payment for environmental 14 November. Resources Assessment 2005. Rome, FAO. services in Mexico. Presented at a side FAO & CIFOR. 2005. Forests and floods: (Draft) event at the 26th session of the Subsidiary drowning in fiction or thriving on facts? Hofer, T. & Messerli, B. 2006. Floods Bodies of the United Nations Framework RAP Publication 2005/03. Bangkok, in Bangladesh: history, dynamics and Convention on Climate Change (UNFCCC), Thailand, FAO Regional Office for Asia rethinking the role for the Himalayas. Bonn, Germany, 11 May 2007. and the Pacific. Tokyo, Japan, United Nations University United Nations Economic Commission for Global Water Partnership Technical Press. Europe (UNECE) Convention on the Advisory Committee (TAC). 2000. International Commission for the Protection Protection and Use of Transboundary Integrated water resources management. of the Rhine (ICPR). 2001. Rhine 2020 Watercourses and International Lakes. TAC Background Papers No. 4. Stockholm, – Program on the sustainable development 2007. Recommendations on payments for Sweden, Global Water Partnership. of the Rhine. Conference of Rhine Ministers ecosystem services in integrated water Available at: www.gwpforum.org/gwp/ 2001. Koblenz, Germany. Available at: resources management. New York & library/TACno4.pdf www.iksr.org/index.php?id=336 Geneva, UN. Available at: www.unece. Hamilton, L. 1985. Overcoming myths about International Union of Forest Research org/env/water/publications/documents/ soil and water impacts of tropical forest land Organizations (IUFRO). 2007. Research PES_Recommendations_web.pdf uses. In S.A. El-Swaify, W.C. Moldenhauer spotlight: how do forests influence water? Van Dijk, A.I.J.M. & Keenan, R. 2007. & A. Lo, eds. Soil erosion and conservation, IUFRO Fact Sheet No. 2. Vienna, Austria. Planted forests and water in perspective. pp. 680–690. Ankeny, Iowa, USA, Soil Available at: www.iufro.org/science/ and Management, 251(1- Conservation Society of America. task-forces/water/publications 2): 1–9. u Hamilton, L. 2005. Forests and water.

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