185 185 FAO FORESTRY PAPER A guide to forest–water A guide to forest–water management management Water security looms as a major planetary challenge. Many people worldwide already lack adequate access to clean water, and pressure on water resources is increasing as populations grow, ecosystems are degraded and the climate A guide to forest–water management changes. Forests and trees are integral to the global water cycle and therefore vital for water security; they regulate water quantity, quality and timing and protect against erosion, ooding and avalanches. Forested watersheds provide 75 percent of our freshwater, delivering drinking water to more than half the world’s population. The purpose of A Guide to Forest–Water Management is to improve the global information base on the protective functions of forests for soil and water. It reviews emerging techniques and methodologies, provides guidance and recommendations on how to manage forests for their water services, and offers insights into the business and economic cases for this. The guide pays special attention to four ecosystems that are crucial for forest–water management – mangroves, peatland forests, tropical montane cloud forests and dryland forests. A Guide to Forest–Water Management nds that both natural and planted forests offer cost-effective solutions to water management while providing considerable co-benets, such as the production of wood and non-wood goods, climate change mitigation, biodiversity conservation and cultural services. The task of ensuring global water security is formidable, but this report provides essential guidance for water-centred forestry as a means of increasing the resilience of our precious water resources. ISSN 0258-6150 ISBN 978-92-5-134851-2ISSN 0258-6150 FAO FORESTRY PAPER FAO 9 789251 348512 CB6473EN/1/08.21 185 A guide to forest–water management PUBLISHED BY THE FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS AND INTERNATIONAL UNION OF FOREST RESEARCH ORGANIZATIONS AND U.S. DEPARTMENT OF AGRICULTURE Rome, 2021 Required citation: FAO, IUFRO and USDA. 2021. A guide to forest-water management. FAO Forestry Paper No. 185. Rome. https://doi.org/10.4060/cb6473en The designations employed and the presentation of material in this information product do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations (FAO) or the International Union of Forest Research Organizations (IUFRO) or U.S. Department of Agriculture (USDA) 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. 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Cover photograph: ©FAO/Mohamad Pazi iii Contents Foreword vii Acknowledgements viii Abbreviations and acronyms ix Executive summary x 1 Introduction 1 The importance of forest–water relationships 3 Managing forests for water 6 2 Monitoring and reporting on the forest–water nexus 7 The global situation 8 How to measure forest–water relationships 11 Riparian forests – a new global measure for monitoring forests and water 16 3 Managing forests for water 31 Managing forests primarily for water 34 Watershed-based forest management 47 The co-benefits of managing forests for water 57 Understanding trade-offs and synergies 61 Forest fires and water 68 Other disturbances with impacts on water 73 4 Valuing water from forests 75 Estimating the value of forest–water ecosystem services 76 Policy and market-based instruments to incentivize forest hydrologic services 83 Managing trade-offs and decision-support systems 95 Communicating and branding forests for water projects and initiatives 100 5 Key ecosystems for forest–water management 107 Mangrove forests 107 Peatland forests 113 Tropical montane cloud forests 120 Dryland forests 126 References 131 Annex 1. List of organizations that participated in writing the report 166 iv A guide to forest–water management Tables 1.1 Classification of water services 5 2.1 Sustainable Development Goal targets related to forests and water 8 2.2 Top ten countries and territories for the proportion of total forest area designated primarily for soil and water protection 11 4.1 Estimated average and aggregate values of various water services, selected biomes, 1997 and 2011 76 4.2 Total waterflow regulation by 90 types of vegetation–soil–slope complexes in the dry and rainy seasons, and its economic impact 80 4.3 Estimated increase in treatment cost due to change from baseline (forested) conditions to urban land use, Converse Reservoir, Alabama, between 1992 and 2004 81 4.4 Net present value of loss of agricultural yield over the life of the park due to low and high intensity flooding 82 4.5 Types of payment scheme for watershed services 85 4.6 Toolboxes and databases on payment schemes for watershed services 92 4.7 Examples of legislation that includes water fees for forest watershed management 93 4.8 Forest management decision-support systems potentially suitable for addressing trade-offs relevant to water services 99 4.9 Forest–water-related communication networks and toolboxes 106 5.1 The strengths and weaknesses of two payment schemes for water services in Veracruz, Mexico 123 Figures 1.1 Connection between ecosystem services and human well-being 5 2.1 Potential relationship between tree loss and the risk of erosion, forest fire and baseline water stress 9 2.2 Proportion of total forest area designated primarily for the conservation of soil and water, by region 10 2.3 Forest monitoring framework outlining indicators and subindicators in the Forest and Landscape Water Ecosystem Services tool 15 2.4 Sentinel-2 optical data showing the development of mining along a river network in the north of the Republic of the Congo 21 2.5 An example of the modelled Riparian Zones product 22 2.6 Process for identifying riparian buffer zones using accumulated waterflow 23 2.7 Tropical Moist Forest product (original and after fragmentation analysis) 23 2.8 Change in riparian forest cover at a site in the Democratic Republic of the Congo, May 2019–March 2020 25 v 2.9 Example of the use of spectral indices in conjunction with segmentation to highlight riparian forests in the forest–savannah domain 26 2.10 Example of how tools such as SEPAL and Collect Earth can be used to validate remote sensing observations 27 2.11 Riparian zones in the closed-forest