LULUCF

Sissejuhatus

Volume 4 provides guidance for preparing annual greenhouse gas inventories in the Agriculture, Forestry and Other Land Use (AFOLU) Sector. This volume integrates the previously separate guidance in the Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories for Agriculture (Chapter 4) and Land Use, Land-Use Change and Forestry (Chapter 5). This integration recognizes that the processes underlying greenhouse gas emissions and removals, as well as the different forms of terrestrial carbon stocks, can occur across all types of land and that often the same practices influence both Agriculture and Land Use, Land Use Change and Forestry. This approach is intended to improve consistency and completeness in the estimation and reporting of greenhouse gas emissions and removals. The refinement builds on this objective by providing updates to the guidance in terms of improved emission factors, new methodologies, and examples for compilers to better understand the estimation of emissions and removals in the AFOLU sector.

The principal changes made in the 2006 IPCC Guidelines and 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories (2019 Refinment), as compared with the Revised 1996 IPCC Guidelines (for both Agriculture, and Land-Use Change and Forestry, continue to reflect the elaborations of the Revised 1996 IPCC Guidelines introduced in the Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories (*GPG2000*) and the Good Practice Guidance for Land Use, Land-Use Change and Forestry (*GPG-LULUCF*). These include:

Adoption of the six land-use categories used in *GPG-LULUCF* (i.e., Forest Land, Cropland, Grassland, Wetlands, Settlements, and Other Land -- see Chapter 3). These land categories are further sub-divided into land remaining in the same category and land converted from one category to another. The land-use categories are designed to enable inclusion of all managed land area within a country;

Reporting on all emissions by sources and removals by sinks from managed lands, which are considered to be anthropogenic, while emissions and removals for unmanaged lands are not reported;.

- Additional reporting elements introduced in reporting all emissions and removals for managed lands, (see Table 1.2); - Generic methods for accounting of biomass, dead organic matter and soil C stock changes in all land-use categories and generic methods for greenhouse gas emissions from biomass burning that can be applied in all land-use categories; - Incorporating methods for non-CO2 emissions from managed soils and biomass burning, and livestock population characterization and manure management systems from Agriculture (Chapter 5 of the *Revised 1996 IPCC Guidelines* and *GPG2000*; - Adoption of three hierarchical tiers of methods that range from default emission factors and simple equations to the use of country-specific data and models to accommodate national circumstances; - Description of alternative methods to estimate and report C stock changes associated with harvested wood products; - Incorporation of key category analysis for land-use categories, C pools, and CO2 and non-CO2 greenhouse gas emissions; - Adherence to principles of mass balance in computing carbon stock changes; - Greater consistency in land area classification for selecting appropriate emission and stock change factors and activity data;. - Improvements of default emissions and stock change factors, as well as development of an Emission Factor Database (EFDB) that is a supplementary tool to the *2006 IPCC Guidelines*, providing alternative emission factors with associated documentation. The EFDB is described in Chapter 2 of Volume 1. - Incorporation of methods to estimate CO2 and CH4 emissions from flooded land.

The AFOLU Sector has some unique characteristics with respect to developing inventory methods. There are many processes leading to emissions and removals of greenhouse gases, which can be widely dispersed in space and highly variable in time. The factors governing emissions and removals can be both natural and anthropogenic (direct and indirect) and it can be difficult to clearly distinguish between causal factors[^1]. <ref>This general observation was made in the IPCC Report on *Current Scientific Understanding of the Processes Affecting Terrestrial Carbon Stocks and Human Influences upon Them* (July 2003, Geneva, Switzerland). As a specific example, emissions from wildfires on managed (and unmanaged) land can exhibit large interannual variations that may be driven by either natural causes (e.g. climate cycles, random variation in lightning ignitions), or indirect and direct human causes (e.g. historical fire suppression and past forest harvest activities) or a combination of all three causes, the effects of which cannot be readily separated.</ref> While recognizing this complexity, inventory methods need to be practical and operational.

The 2006 IPCC Guidelines and this 2019 Refinement are designed to assist in estimating and reporting national inventories of anthropogenic greenhouse gas emissions and removals. For the AFOLU Sector, anthropogenic greenhouse gas emissions and removals by sinks are defined as all those occurring on 'managed land'. Managed land is land where human interventions and practices have been applied to perform production, ecological or social functions. All land definitions and classifications should be specified at the national level, described in a transparent manner, and be applied consistently over time. Emissions/removals of greenhouse gases do not need to be reported for unmanaged land. However, it is *good practice* for countries to quantify, and track over time, the area of unmanaged land so that consistency in area accounting is maintained as land-use change occurs. The IPCC describes the Managed Land Proxy (MLP) as an approach to approximate estimates of anthropogenic emissions and removals, but this proxy estimate also contains emissions and removals resulting from natural disturbances.

This approach, i.e., the use of managed land as a proxy for anthropogenic effects, was adopted in the GPG-LULUCF and that use is maintained in the *2019 Refinement*. The key rationale for this approach is that the preponderance of anthropogenic effects occurs on managed lands. By definition, all direct human-induced effects on greenhouse gas emissions and removals occur on managed lands only. While it is recognized that no area of the Earth's surface is entirely free of human influence (e.g., CO2 fertilization), many indirect human influences on greenhouse gases (e.g., increased N deposition, accidental fire) will be manifested predominately on managed lands, where human activities are concentrated. Finally, while local and short-term variability in emissions and removals due to natural causes can be substantial (e.g., emissions from fire, see footnote 1), the natural 'background' of greenhouse gas emissions and removals by sinks tends to average out over time and space. This leaves the greenhouse gas emissions and removals from managed lands as the dominant result of human activity.

However, some of the emissions and removals from managed land are characterised by high interannualvariability. Interannual variability (IAV) refers to the variability in the annual emissionsandremovals estimates between years within a time series. In the AFOLU sector, the application of the MLP means that IAV can be caused by both anthropogenic and natural causes. The three main causes of IAV in GHG emissions and removals in the AFOLU sector are (1) natural disturbances (such as wildfires, insects, windthrow, and ice storms), which can cause large immediate and delayed emissions and kill trees; (2) climate variability (e.g. temperature, precipitation, and drought), which affects photosynthesis and respiration; and (3) variation in the rate of human activities, including land use (such as forest harvesting), and land-use change.

When the MLP is used and the interannual variability in emissionsand removalsdue tonatural disturbance is large, it is difficult to gain a quantitative understanding of the role of human activities compared to the impacts of natural effects. In such situations disaggregating<ref>Disaggregating means that an estimate is separated into its component parts</ref> MLP emissions and removals into human and natural effects may provide increased understanding and refined estimates of the emissions and removals that are due to human activities such, land use (including harvesting) and land-use change. In this way, disaggregation can contribute to improved quantification of the trends in emissions and removals due to human activities and mitigation actions that are taken to reduce anthropogenic emissions and preserve and enhance carbon stocks.

Guidance and methods for estimating greenhouse gas emissions and removals for the AFOLU Sector now include:

- CO2 emissions and removals resulting from C stock changes in biomass, dead organic matter and mineral soils, for all managed lands; - CO2 and non-CO2 emissions from fire on all managed land; - Optional guidance that may be used by countries that choose to disaggregate their reported MLP emissions and removals (i.e. all emissions and removals on managed land) into those that are considered to result from human activities and those that are considered to result from natural disturbances; - N2O emissions from all managed soils; - CO2 emissions associated with liming and urea application to managed soils; CH4 emissions from rice cultivation; - CO2 and N2O emissions from cultivated organic soils;. - CO2 and N2O emissions from managed wetlands, and CH4 emissions from flooded land; CH4 emission from livestock (enteric fermentation);. - CH4 and N2O emissions from manure management systems; and C stock change associated with harvested wood products.

The scientific background and rationale for these inventory components are given in the next section.