Forest Resources Assessment Working Paper 177 Assessing forest degradation Towards the development of globally applicable guidelines November, 2011 Forest Resources Assessment Working Paper 177 Assessing forest degradation Towards the development of globally applicable guidelines FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS Rome, 2011 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) 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 mention of specific companies or products of manufacturers, whether or not these have been patented, does not imply that these have been endorsed or recommended by FAO in preference to others of a similar nature that are not mentioned. This product is based on information obtained from various published and unpublished sources. The views expressed in this product do not necessarily reflect the views of the authors or FAO. All rights reserved. FAO encourages the reproduction and dissemination of material in this information product. Non-commercial uses will be authorized free of charge, upon request. Reproduction for resale or other commercial purposes, including educational purposes, may incur fees. Applications for permission to reproduce or disseminate FAO copyright materials, and all queries concerning rights and licences, should be addressed by e-mail to [email protected] or to the Chief, Publishing Policy and Support Branch, Office of Knowledge Exchange, Research and extension, FAO, Viale delle Terme di Caracalla, 00153 Rome, Italy. © FAO 2011 Contents Contributors v Foreword vi Acknowledgements vii Acronyms viii 1. Introduction 1 What is forest degradation? 1 Why does it matter? 2 Why measure it? 3 Towards guidelines 4 2. Issues in defining and assessing forest degradation 10 Indicators of forest degradation 10 Comparative analysis of definitions related to forest degradation 11 Discussion 12 Options for future action 15 3. Growing stock and biomass 16 What to measure 16 Measurement methods 18 Measurement frequency and reporting 23 Issues and challenges 23 4. Biodiversity 24 What and how to measure 24 Measurement frequency and reporting 43 Issues and challenges 43 5. Production of forest goods 45 What and how to measure 46 6. Soil erosion 55 What to measure 56 Measurement methods 61 Measurement intensity, frequency and reporting 71 Issues and challenges 72 References 74 ANNEX 1. Preparatory background information 82 ANNEX 2. Examples of equations for volume, biomass and carbon estimations 84 ANNEX 3. Additional descriptors of erosion features 87 ANNEX 4. Illustrative examples of erosion features 90 ANNEX 5. Soil erosion field worksheets 98 Boxes BOX 1.1 International definitions of forest degradation/degraded forest 2 BOX 1.2 Difficulties in measuring forest hydrological services 6 BOX 3.1 Defining growing stock and biomass stock 16 BOX 3.2 Growing stock in the FAO Forest Resources Assessment 17 BOX 3.3 Estimating tree volume 21 BOX 3.4 Estimating above-ground tree biomass 22 BOX 3.5 Forest biomass calculation 22 BOX 4.1 Definition of indicator species 27 BOX 5.1 Yield regulation in natural tropical forests 49 BOX 5.2 The logging of ipê as a catalyst of forest degradation in the Brazilian Amazon 51 BOX 6.1 Community mapping 58 BOX 6.2 Worked examples of scoring erosion features 62 BOX 6.3 Worked example – estimating soil loss in rills 63 BOX 6.4 Worked example – estimating soil loss in gullies and ravines 65 BOX 6.5 Worked example – estimating soil loss using plant root exposure 66 BOX 6.6 Worked example – estimating soil loss using armour layer 70 BOX 6.7 Worked example – estimating soil loss using soil build-up against a barrier 71 Tables TABLE 3.1 Basic tools for measuring growing stock 19 TABLE 4.1 Biodiversity indicators of SFM, from five indicator sets or processes 25 TABLE 4.2 Possible biodiversity indicators of forest degradation 27 TABLE 4.3 Proposed best fragmentation measures 33 TABLE 4.4 Possible species indicators of degradation in ecosystem function 40 TABLE 5.1 Potential indicators of degradation of the provision of forest goods and services 47 TABLE 5.2 Measurement of forest degradation based on the supply of forest goods 50 TABLE 6.1 Definition and scoring for erosion types 59 TABLE 6.2 Scoring for erosion state, extent and severity 61 TABLE 6.3 Erosion classes derived from summing scores for type, state, extent and severity 61 Figures FIGURE 1.1 Forest resilience and tipping points 7 FIGURE 1.2 Degradation thresholds 8 FIGURE 1.3 Range of natural variation is used to provide a reference level for degradation 9 FIGURE 4.1 Four spatial pattern processes of forest loss 31 FIGURE 5.1 Schematic illustration at the stand/compartment level of periodic change in growing stock due to harvesting (selective logging), tropical forest 46 FIGURE 5.2 A map of ‘degradation waves’ of forest goods depicting changes from 1991 to 2005 from Dar es Salaam (DES), the capital city of Tanzania 48 FIGURE 6.1 Calculation of the cross-section of the trapezoid shape of gullies and ravines 64 FIGURE 6.2 Sketch of a soil pedestal capped by a stone 67 FIGURE 6.3 Solution notch and staining in limestone rock 68 FIGURE 6.4 Diagrammatic representation of an armour layer and photograph showing removal of a portion of an armour layer 69 FIGURE 6.5 Build-up of soil behind a Gliricidia hedge, Sri Lanka 70 Contributors Many people contributed to the production of this document. In particular, chapters were authored as follows: Chapter 1: Victoria Heymell and Ken MacDicken. Chapter 2: Ken MacDicken (based on an earlier paper by Markku Simula). Chapter 3: Dan Altrell, Anne Branthomme and Rebecca Tavani Chapter 4: Ian Thompson, Robert Nasi, Kimiko Okabe, Valerie Kapos and James Gordon Chapter 5: Manuel R. Guariguata, Cesar Sabogal and Diji Chandrasekharan Chapter 6: Des McGarry v Foreword Forests provide us with a wide range of goods and services. Today, just as centuries ago, we still need forests for their products such as timber, paper, medical plants, fruits etc. Presently more people understand the values of services that forests provide, including wildlife habitat, hydrological functions and carbon storage. Likewise the degradation of forest resources is an important society concern that is perceived in many different ways. Forest degradation can be a serious environmental, social and economic problem with the potential to adversely affect millions of people who depend on forest goods and services. Given the contribution of forests to sustainable development and their role for human well-being, the state of the forests is important to all of us. Good information on the extent of forest degradation is needed to elaborate policies and implement forest-management plans allowing the restoration of degraded forests and the rehabilitation of degraded forest lands. Identifying and assessing the condition of forests is not easy – particularly since people have widely different views of what constitutes degradation. For some, any forest management activity may cause degradation. For others forest is only degraded when it can no longer deliver needed goods and services. There is no globally agreed definition of forest degradation which makes the discussion more complex. FAO, together with members of the Collaborative Partnership have taken a number of steps to tackle this problem. Results of this work are summarized in a series of working papers that can be found at http://www.fao.org/forestry/ fra/2560/en/. This document pulls together a range of views and approaches to the assessment of forest degradation. It should be regarded as precursor to the development of comprehensive, globally applicable guidelines for assessing forest degradation. There is much work yet to be done on this important topic – we trust the present paper contributes to the goal of reducing and mitigating the inevitable processes of forest degradation. Eduardo Rojas-Briales Assistant Director-General, Forestry Department, FAO vi Acknowledgements The preparation of “Assessing forest degradation – towards the development of globally applicable guidelines” represents a joint effort of the Collaborative Partnership on Forests (CPF) undertaken under the umbrella of the 2010 Global Forest Resources Assessment (FAO, 2010). FAO gratefully acknowledges the financial and in-kind contributions to this work made by CPF partners. Thanks go to all who have contributed to the development of this work: to those who provided answers to the initial questionnaires, to the authors of the 20 case studies, and to the authors and experts who contributed to technical meetings. A special thanks go to the authors of the chapters that describe key criteria for measuring forest degradation and to Victoria Heymell who saw the task through many arduous steps. Thanks also go to Mette Løyche Wilkie, Emma Foti, Marisalee Palermo and the rest of the FRA team in FAO for providing advice, guidance and assistance along the way and to Alastair Sarre who did the final editing. vii Acronyms AAC annual allowable cut ASTER Advanced Space-borne Thermal Emission and Reflection Radiometer C&I criteria and indicators CBD Convention on Biological Diversity CPF Collaborative Partnership on Forests dbh diameter at breast height FAO Food and Agriculture Organization of the United Nations