Land use and management activities have a substantial impact on carbon stocks and associated greenhouse gas emissions and removals. However, it is challenging to discriminate between anthropogenic and non-anthropogenic sources and sinks from land. To address this problem, the Intergovernmental Panel on Climate Change developed a managed land proxy to determine which lands are contributing anthropogenic greenhouse gas emissions and removals. Governments report all emissions and removals from managed land to the United Nations Framework Convention on Climate Change based on this proxy, and policy interventions to reduce emissions from land use are expected to focus on managed lands. Our objective was to review the use of the managed land proxy, and sum- marize the criteria that governments have applied to classify land as managed and unmanaged. We found that the large majority of governments are not reporting on their application of the managed land proxy. Among the govern- ments that do provide information, most have assigned all area in specific land uses as managed, while designating all remaining lands as unmanaged. This designation as managed land is intuitive for croplands and settlements, which would not exist without management interventions, but a portion of forest land, grassland, and wetlands may not be managed in a country. Consequently, Brazil, Canada and the United States have taken the concept further and delineated managed and unmanaged forest land, grassland and wetlands, using additional criteria such as functional use of the land and accessibility of the land to anthropogenic activity. The managed land proxy is imperfect because reported emissions from any area can include non-anthropogenic sources, such as natural disturbances. However, the managed land proxy does make reporting of GHG emissions and removals from land use more tractable and compa- rable by excluding fluxes from areas that are not directly influenced by anthropogenic activity. Moreover, application of the managed land proxy can be improved by incorporating additional criteria that allow for further discrimination between managed and unmanaged land. Keywords: Greenhouse gas emissions inventory, Carbon inventory, Managed land proxy, Land use, Agriculture, Forestry *Correspondence: Stephen.Ogle@colostate.edu Natural Resource Ecology Laboratory and Department of Ecosystem Science and Sustainability, Colorado State University, Fort Collins, CO 80523, USA Full list of author information is available at the end of the article © The Author(s) 2018. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creat iveco mmons .org/licen ses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Ogle et al. Carbon Balance Manage (2018) 13:9 Page 2 of 13 . However, the use of “managed land” as a proxy for Background anthropogenically-driven GHG fluxes does not always Greenhouse gas (GHG) emissions from land use are a require active management such as in cropland, settle- substantial contributor to global emissions, particularly ments or commercial forest land. It may also incorporate carbon (C) stock changes from land-use conversion [1– management decisions that are more nuanced, such as 3]. For example, deforestation, i.e., converting forests to protecting lands from wildfires, using wilderness for rec - non-forest uses (e.g., settlements) leads to oxidation of reation or designating areas for conservation. The IPCC organic matter in the tree biomass, litter and dead wood guidance provides latitude for governments to refine the pools both onsite and offsite, and emissions of carbon definition of managed land to meet their national circum - dioxide (CO ) to the atmosphere, as well as emissions stances, but the definition should be applied consistently of other non-CO GHGs where burning occurs. Affor - over time and across the territory in the country. Report- estation and reforestation have the potential to reverse ing should also be transparent and include descriptions this process resulting in a net uptake of CO from the of the methods and definitions used to determine areas atmosphere. Such a dynamic was exhibited in the United of managed and unmanaged lands. Determining the States during the twentieth century as former croplands managed land base will have implications for C stock were abandoned and reverted to forest in many cases changes and associated GHG emissions that are reported . Land-use conversion also influences soil C pools. For to the UNFCCC and addressed by policy actions to miti- example, cultivation of land leads to a release of soil C gate GHG emissions. ranging from 30 to 60% of the original stock in the topsoil Emissions and removals of GHGs from the land surface [5, 6]. Adopting conservation tillage, particularly no-till, occur even without anthropogenic interventions through can increase soil C stocks due to physical protection of land management. For example, forests accumulate and organic matter in aggregates [7, 8]. Changing crop pro- lose C through production and decomposition processes, duction practices, such as planting improved varieties or and these trajectories can change with natural distur- changing fertilization and irrigation practices can also bances . In addition, there is a limit to how much a have an impact on soil C stocks . Land use can have land manager can influence GHG emissions on managed a profound effect on trajectories of terrestrial C sinks land because the processes driving C stock changes and and sources, as well as other GHG fluxes, and conse - other GHG fluxes are not fully controlled by the man - quently, quantifying the impacts of land use and land-use ager. This has been recognized in the agreements for the change is a fundamental component of national GHG second commitment period of the Kyoto Protocol and inventories. participating countries have the option to exclude emis- The Intergovernmental Panel on Climate Change sions and subsequent removals from natural disturbances (IPCC) has developed guidelines for estimating anthro- on managed lands with fulfillment of the defined rules pogenic GHG emissions and removals [9–11] that are [11, 13]. Complete separation of anthropogenic and non- used to compile national GHG inventories for report- anthropogenic emissions on managed land is not trivial ing to the United Nations Framework Convention on [14, 15], and may not even be feasible. Regardless, the Climate Change (UNFCCC). National greenhouse gas managed land proxy allows inventory compilers to focus inventories focus on anthropogenic sources of emissions on areas in a country directly impacted by management because policy interventions directly influence human activity, and is considered by the IPCC as the most uni- activities contributing to emissions. Other, non-anthro- versally applicable approach for separating anthropo- pogenic sources of emissions, such as permafrost melt- genic and non-anthropogenic emissions associated with ing in the arctic and associated C O fluxes, are important land use . for understanding the global C cycle, but are less likely Given the disparity in the use of the managed land to be impacted by direct management actions. In the proxy among UNFCCC member governments, there is case of permafrost, indirect effects are possible by reduc - a need to understand the concept and associated appli- ing direct emissions from anthropogenic sources, such cation by governments. Therefore, our objective is to as fossil fuel combustion, fertilization management for review steps for delineating a managed land base as a croplands, waste management, but direct management foundation for reporting GHG emissions associated with of permafrost seems unlikely. Therefore, as part of the land use and land-use change. The managed land defini - IPCC guidelines, GHG emissions and associated C stock tion and implementation methods for Brazil, Canada and changes from land use and management activities are to the United States are examined in more detail. Develop- be estimated for all managed land in the country. ing a managed land base involves three general steps, (a) The IPCC defines managed land as “… land where defining managed land taking into consideration national human interventions and practices have been applied circumstances, (b) developing implementation criteria to perform production, ecological or social functions” Ogle et al. Carbon Balance Manage (2018) 13:9 Page 3 of 13 compatible with the definition, and (c) implementing land being subdivided into one of the following land-use the analysis to produce the managed land base for GHG categories: forest land, cropland, grassland, wetlands, reporting. settlements and other land. In addition, forest land, wet- lands and grassland must be divided into managed and Main text unmanaged sub-categories, and although there are no Use of managed land proxy GHG reporting requirements for unmanaged lands, While most governments report net emissions from countries are encouraged to report their areas. As more land use based on their national communications to the developing countries adopt the 2006 IPCC guidelines or UNFCCC , only 19 countries have delineated man- even start using the 2003 LULUCF guidance, a complete aged and unmanaged land areas for their territory based representation of land use will need to be developed, and on a review of the latest communications submitted by countries will have to determine which portions of their governments through 2015 and Common Reporting For- territory meet their definition of managed land. mat (CRF) tables submitted in 2018 (note: CRF tables Another 97 countries have adopted the later guidance are only submitted by Annex I parties to the conven- from the IPCC [9, 18] that include a complete representa- tion) (Fig. 1). There are several reasons that may explain tion of land use, but have not provided information about this situation. Approximately 85 out of the 195 member their managed land base. It is not possible to determine governments are developing economies and still use the the specific reasons for these decisions. Governments are Revised 1996 IPCC guidelines for reporting their emis- not required to mention this concept in their national sions , which is in accordance with UNFCCC report- communication to the UNFCCC unless they have delin- ing requirements for developing countries. The revised eated a portion of the country as unmanaged, although 1996 IPCC guidelines pre-date the development of the application of the managed land proxy should be dis- managed land concept as a proxy to anthropogenic emis- cussed based on IPCC Guidance [9, 18]. Regardless, all sions and removals that was introduced in the 2003 IPCC governments using the later guidance from the IPCC are Good Practice Guidance for Land Use, Land-Use Change implicitly using the managed land proxy, and many of and Forestry (LULUCF) , and incorporated into the these governments may consider their entire territory as 2006 IPCC Guidelines . The latter documents require managed land. full representation of land use in the country, with all Fig. 1 Proportion of governments that use approach I, II or III methods for land representation, or have not included this information in their national communications (IPCC 2003, 2006) (a). The subset of governments reporting their approach for land representation that have delineated managed and unmanaged areas in their territories compared to the governments that consider all land as managed (b). Data extracted from the latest national communication to the UNFCCC as of 2015 and common reporting format tables submitted in 2018 (http://www.unfcc c.int) Ogle et al. Carbon Balance Manage (2018) 13:9 Page 4 of 13 Defining managed land The United States has taken yet another approach Among the governments providing information about by focusing on direct intervention . The definition application of the managed land proxy to subdivide forest states “managed land occurs mostly in areas accessible land, grassland and wetlands into managed and unman- to human activity and includes altering or maintain- aged land, several have classified managed land simply ing the condition of the land to produce commercial or by considering some land uses as managed and others as non-commercial products or services; to serve as trans- unmanaged. For example, Australia and Belarus consider portation corridors or locations for buildings, landfills, all forest land, grasslands and wetlands as managed, while or other developed areas for commercial or non-com- land in the ‘other land’ category (e.g., rock outcrops, gla- mercial purposes; to extract resources or facilitate acqui- ciers, barren areas) is considered unmanaged. New Zea- sition of resources; or to provide social functions for land considers all grassland and forest land as managed, personal, community or societal objectives where these while wetlands are considered unmanaged. The Russian areas are readily accessible to society” . The United Federation, Ukraine and Peru use the same criteria as States government has incorporated accessibility of the New Zealand, except that they have designated some for- land as a criterion, and included specific functions in the est land in reserves or natural forests as unmanaged. definition. Some governments apply the managed land proxy with additional criteria, such as Canada, Brazil and the Implementation criteria and application to delineate United States. Canada has subdivided grassland, for- managed land est land and wetlands into managed and unmanaged Implementation criteria are specific rules that are used areas. Grassland is considered managed if used for graz- to delineate managed land. For most of the countries, the ing domestic livestock, designated as a national park or implementation criteria are based solely on the land use is used for an expressed purpose, such as a military base maps developed to support the national GHG inventory. . Canada considers wetlands in which human inter- Governments are typically considering a land-use cat- vention has directly altered the water table level as man- egory as completely managed or not managed based on aged, and there are two types: peatlands drained for peat these criteria. Brazil, Canada and the United States pro- extraction and flooded land associated with the creation vide examples for delineating managed land that includes of reservoirs. For reporting GHG emissions and remov- additional criteria, subdividing individual land uses into als, managed forests include all forest land that is subject both managed and unmanaged areas. The sections below to management for timber and non-timber resources provide further detail on the criteria and implementation as well as other ecological services. Therefore, managed methods for each country. land includes the timber harvest land base and other areas, including parks and reserved areas. Moreover, Canada because fire suppression efforts in Canada also affect The proportion of the area of managed forests varies GHG emissions and removals, areas that are under inten- among the ten provinces and three territories in Canada. sive protection against natural disturbances, mostly fire, Some provinces, including British Columbia, Alberta, are considered managed forests even if there is no timber New Brunswick, Nova Scotia, and Prince Edward Island extraction or other non-timber forest use (Fig. 3). consider all forest land as managed due to ongoing tim- Brazil defines all secondary forests and grasslands, ber harvest, fire protection and conservation activities. In planted forests, and forests subject to selective logging as contrast, Saskatchewan, Manitoba, Ontario and Quebec managed land. Natural grasslands and natural forest land delineate a northern border of managed forests based on are considered unmanaged except in the following cases: the northern boundary of fire suppression. In these prov -  legally created Conservation Unit areas in Federal and inces, areas to the north of this boundary are considered State Conservation Units (Except the Private Reserves unmanaged. The Province of Newfoundland and Labra - of National Preservation, due to the lack of consistent dor includes all forests on the island of Newfoundland as information regarding management interventions), in managed but limits managed forests in Labrador to those accordance with the Ministry of the Environment and the that are subject to ongoing or planned future timber National System of Nature Conservation Units; and  harvest. Yukon and the Northwest Territories delineate legally demarcated Indigenous Lands, as per information managed forest as areas designated for timber harvesting from the National Indian Foundation (FUNAI). Man- and areas under fire protection surrounding communi - aged wetlands include all reservoirs, which are created ties. Nunavut does not contain any managed forest. The through human activity, while rivers and lakes are consid- initial delineation of managed forests was based on GIS ered unmanaged. Other land is classified as unmanaged. boundaries of forest management units used for timber supply planning, parks and fire protection zones. Ogle et al. Carbon Balance Manage (2018) 13:9 Page 5 of 13 Managed forest areas can occasionally change over adjusted by manual editing of appropriate remote sensing time if management activities expand into areas currently data. considered unmanaged forests. Managed forest lands can only leave this category through land-use conversion. Brazil Once forests are considered managed, they remain in Brazil applies IPCC approach 3 methods for land repre- that reporting category. Unmanaged forests can become sentation, meaning that classification is spatially explicit managed forests if forest road construction and timber (i.e., all land area is explicitly classified). The Brazilian extraction commence, or if they meet other managed for- government utilizes several criteria (i.e., information est criteria. Unmanaged forests are monitored through plans/layers) and datasets to determine the managed Canada’s comprehensive deforestation monitoring pro- land base, including biome maps, municipal bounda- gram to ensure that resource extraction (mining), road ries, native vegetation maps (phytophysiognomy), soil construction and reservoir flooding events, which cause types and land use/cover maps from visual interpreta- conversion of forest to non-forest land uses, are identi- tion of Landsat-type satellite imagery. The integration of fied and the resulting emissions reported in the National all these georeferenced layers generates uniquely defined GHG Inventory [12, 21]. polygons in a Geographic Information System (GIS) The location and extent of cropland and grassland that cover the entire national territory. Specifically, each within a reporting unit is derived from remote sens- polygon belongs to a single biome, municipality, veg- ing data . Grassland is classified as managed within etation type, soil type, and land use/cover. The native reporting units that have soil and climate conditions forest land and native grassland that fall over legally cre- suitable for natural grassland and in which the Cen- ated Conservation Units and/or demarcated Indigenous sus of Agriculture identifies that agricultural activity is Land are included as part of the managed land database. present . All other mapped grassland is considered From one inventory year to another, changes in land use/ unmanaged. cover are identified, and a polygon in one inventory year The Atlas of Canada is used to determine the spatial may be split into several sub-polygons in the next inven- extent of wetlands based on an inventory of wetlands, tory year, if the entire polygon does not remain in the including those covered by forest at a national scale . same land use/cover category. All the native forest land The Canadian Sphagnum Peat Moss Association has and grassland that is part of the managed land base and provided a map showing the principal peat harvesting is subject to land clearing during the period of inventory areas  and an estimate of the wetland area managed is re-classified as another land use category in the same for peat extraction in 2004 . Estimates of the area period, even in the case that the land could be temporar- under peat extraction for previous and subsequent years ily unstocked with trees in the case of forest land. are made by adjusting the 2004 value on the basis of peat production. Flooded lands are delineated based on (1) United States forest conversion mapping , (2) the Canadian Reser- The United States has incorporated spatial data on spe - voir Database , and (3) hydroelectric industry consul- cific anthropogenic functions to delineate the managed tations . Emissions from reservoirs are reported only land base for the national GHG inventory . These for the 10 years following impoundment, and all flood - functions are based on the following criteria. All forest ing events that have occurred since 1980 are considered lands with active fire protection and timber harvesting managed wetlands. are considered managed. Other anthropogenic activities Settlements are identified through remote sensing data occur on forest lands, but are within areas already man- and population density mapping using Census data. A aged for timber harvest or fire protection, or are con - combination of the two approaches is applied because verted to another land use based on the activity or change remote sensing data may lead to misclassification of large in land cover. All grasslands are considered managed at areas of trees or grass within an urban boundary, while a county scale if there are livestock in the county. Other population density mapping may miss isolated areas of grassland and forest land areas are considered managed manufacturing, transportation or resource extraction. if accessible based on the proximity to roads and other Delineation of the settlement area is accomplished using transportation corridors, and/or infrastructure. Wetlands the boundaries of Statistics Canada’s ‘Populated Cent- are considered managed if the water level is artificially ers’  with populations over 30,000, which captures changed, or the wetlands are created by human activity. all major Canadian cities and represents 76% of Canada’s Protected lands maintained for recreational and conser- population. The total urban area for years prior to digi - vation purposes are considered managed (managed by tal boundary availability was estimated using boundaries public and private organizations). Lands with active and/ or past resource extraction are considered managed. Ogle et al. Carbon Balance Manage (2018) 13:9 Page 6 of 13 Overall, the implementation criteria provide a link Mines and Mineral Processing Plants , and Coal Pro- between the definition and the specific data that are duction and Preparation Report . A buffer of 3300 needed to delineate the managed land base. Criteria are and 4000 m is applied around petroleum extraction and implemented using remote sensing imagery that has been mine locations, respectively, to account for the footprint classified into land uses. Lands that are used for crop of operations and impacts of activities on the surround- production or settlements are all assigned as managed ing landscape. Accessibility is a criterion unique to the using the National Land Cover Dataset (NLCD) for the United States among these three countries, and is a key United States [28–30]. Active fire management is deter - determinant of managed area in remote areas of Alaska. mined from maps of federal and state management plans Accessibility is determined using a 10 km buffer sur - from the National Atlas  and Alaska Interagency Fire rounding road and train transportation networks with Management Council . Forest lands managed for the ESRI Data and Maps product , and a 10 km buffer timber harvests are informed by county level estimates surrounding settlements using the NLCD. of timber products reported in the U.S. Forest Service Timber Products Output Reports database . Lands Managed land bases in Canada, Brazil and United States maintained for recreational purposes are determined The managed forest land in Canada in 2015 includes from analysis of the United States Protected Areas Data- 225.9 Mha (Table 1) and represents 81% of the total base  in which lands are classified as managed if there managed land base of the country . The total area of is suppression of natural disturbances or that are used unmanaged forest in Canada is 118 Mha and all of this for extractive or recreational purposes. Multiple data area is in northern regions of the country with limited sources are used to delineate areas with active resource or no access (Fig. 2). Canada also reported 45.1 Mha of extraction, including the Alaska Oil and Gas Informa- cropland (16.1% of total managed land area) across 10 tion System , Alaska Resource Data File , Active provinces and 6.6 Mha of managed grassland (2.4%) in Saskatchewan, Alberta and British Columbia. Settle- ments accounted for 0.9 Mha (0.3%) of the managed land base, and managed wetlands accounted for 0.5 Mha Table 1 Managed and unmanaged land in Brazil, Canada and the United States (millions of hectares) (0.02%). There are 512.4 Mha of unmanaged land in grasslands, wetlands and other lands, predominantly in Country Managed land Unmanaged Total land area northern Canada . area land area Brazil has approximately 500 million hectares of man- Canada 279.0 630.4 909.4 aged land and 316 million hectares of unmanaged land Cropland 45.1 0.0 45.1 based on an analysis for 2010 (Table 1) . Brazil a a Grassland 6.6 Unknown Unknown reports the net emissions for each one of its six biomes Forest land 225.9 118.0 343.9 (Amazonia—AM; Cerrado—CE; Caatinga—CA; Mata Settlements 0.9 0.0 0.9 Atlantica—MA; Pampa—PA; Pantanal—PT), with per- a a Wetlands 0.5 Unknown Unknown cent coverage of approximately 49, 24, 10, 13, 2 and 2% a a Other lands 0.0 Unknown Unknown of the national territory (852, 187, 545 ha) respectively. Brazil (observed) 499.4 316.1 815.5 In 2010, unmanaged native forest land corresponded to Cropland 68.5 0 68.5 approximately 31% in AM; 30% in CE; 48% in CA; 16% in Grassland 188.3 41.1 229.4 MA, 12% in PA and 54% in PT. Unmanaged native grass- Forest land 235.3 258.3 493.6 land corresponds to approximately 1, 13, 1, 2, 16 and 21% Settlements 3.9 0 3.9 of the total territorial area of AM, CE, CA, MA, PA and Wetlands 3.4 16.1 19.5 PT, respectively. The percent coverage of other land (clas - Other lands 0 0.6 0.6 sified as unmanaged) in the total biome territorial area is Cloud-covered 36.7 near zero in all biomes except for PA, where it is approxi- areas mately 1%. United States 890 46 936 Figure 3 shows the distribution of the Conservation Cropland 159.2 0 159.2 Units and Indigenous lands (considered as part of the Grassland 320.6 25.8 346.4 managed forest land) in the Brazilian territory, where Forest land 292.7 9.6 302.4 their expansion from the periods 1994 to 2002 and 2002 Settlements 50.6 0 50.6 to 2010 have been observed. The largest expansion occurs Wetlands 43.0 0 43.0 in the Amazonia biome, where most of the unmanaged Other lands 24.7 10.8 34.5 forest land, grassland and wetlands also occurs (46.7%), The total area of unmanaged wetland, grassland and other land is 512.4 Mha, followed by the Cerrado biome (27.9%). Approximately but these areas are not disaggregated into the individual categories Ogle et al. Carbon Balance Manage (2018) 13:9 Page 7 of 13 Fig. 2 Distribution of managed and unmanaged land in Canada. The light gray areas are unmanaged and the darker gray areas are managed 36 million ha of land was cloud covered, corresponding Discussion to approximately 4% of the national territory . Two general approaches have been used to classify land The total managed land base in the United States is as managed by countries reporting GHG emissions and 890 million hectares, and about 46 million hectares are C stock changes to the UNFCCC. The first approach is unmanaged (Table 1, Fig. 4) . Managed land includes based on subdividing managed and unmanaged land the majority of the territory in the conterminous 48 according to the land-use classification with specific land states and Hawaii, where much of the land is actively uses designated as unmanaged. The second approach managed for crop production, grazing livestock, timber requires data on accessibility, vegetation structure and/ production, or occurs within settlement areas. Moreover, or functional activities, such as grazing, mining, timber the majority of the land in these regions is within a 10 km harvest, fire protection, crop production, conservation buffer of the road network, railroad corridors or settle - and social functions. Both approaches are in compliance ments. There are large blocks of land in Alaska that are with the reporting requirements established in the IPCC classified as unmanaged, which are grassland, forest land guidance [9–11], but arguably the second approach may or wetland. These areas are largely inaccessible, which allow national compilers to better discriminate between means that they are outside the 10 km buffer of road anthropogenic and non-anthropogenic emissions and networks or other transportation corridors, and have no removals. direct human management or function in which anthro- Examples of the first approach include New Zealand pogenic activities are influencing GHG emissions. that considers all wetlands as unmanaged, in addition Ogle et al. Carbon Balance Manage (2018) 13:9 Page 8 of 13 Fig. 3 Distribution of the Conservation Units and Indigenous Lands in the Brazilian territory, by biome, as represented in the Third National GHG Inventory for 2002 and 2010. Biomes include Amazonia (intermediate green), Caatinga (yellow), Cerrado (orange), Pantanal (brown), Mata Atlantica (darker green), and Pampa (light green). In black, managed areas in 1994; in medium grey (areas created between 1994 and 2002); and light grey (areas created between 2002 and 2010) Ogle et al. Carbon Balance Manage (2018) 13:9 Page 9 of 13 Fig. 4 Distribution of managed and unmanaged land in the United States. The gray areas are unmanaged and the blue areas are managed to Australia and Belarus that consider land classified as due to remoteness, lack of access, low human population “other lands” as unmanaged. Identifying some land uses density, or limited development in the region. Including as managed and others as unmanaged is a relatively sim- these areas in the inventory would lead to unnecessary ple and transparent approach. Lands are classified into use of resources to compile information that is needed land uses based on land cover maps derived from remote to estimate C stocks and associated changes, rather than sensing imagery and other information. The land uses focusing the time and effort in areas that are directly are expected to reflect specific functional activities, and influenced by human activity. Furthermore, governments therefore align reasonably well with areas that are man- could over- or under-estimate anthropogenic emissions aged and unmanaged in some countries. by conducting inventories for areas that are not managed. The second approach incorporates additional data Brazil, Canada, and United States have used the second on specific functional activities, such as the approaches approach to delineate their managed land areas, but even applied in Brazil, Canada and the United States. This with these applications, each country is using elements of approach is likely to be advantageous if land cover data the first approach. Specifically each country classifies all do not align with functional activity. For example, for- cropland and settlements as managed, which is intuitive est land may not be managed in some parts of a country given that these areas would not even exist without direct Ogle et al. Carbon Balance Manage (2018) 13:9 Page 10 of 13 human intervention. Forest lands, grasslands and wet- on areas designated as Protected Areas and Indigenous lands incorporate functional or locational criteria to var- Lands of Brazil. Implementing an additional criterion ying degrees to determine the managed and unmanaged related to impacts on vegetation structure may save land areas. For example, Canada and the United States resources and time in conducting GHG inventories, by determine the area of managed forest land based on further focusing the estimation on those areas subject to timber harvest and extraction of other resources, active anthropogenic emissions and removals. fire suppression and areas used for specific conservation Non-anthropogenic emissions can occur on managed and ecological functions. The government of Brazil uses land, and can be problematic for reporting anthropo- similar criteria and includes in the managed land base, genic emissions to the UNFCCC. For example, Brazil natural forest land and natural grassland in Conservation reports the area and associated C O emissions from nat- Units and/or Indigenous Lands, secondary vegetation ural forest land previously classified as unmanaged when (both in forest land and grassland), planted forests, and it becomes part of the managed land base. From 2002 forests subject to selective logging. The United States also to 2010, there were 59 million ha of new managed land, introduces a criterion of accessibility that leads to some mostly in the Amazonia region, and these areas seques- remote areas, particularly in Alaska, being classified as tered 190 Tg CO . Indirect human-induced effects, such unmanaged.as CO fertilization and/or N deposition, are most likely Grasslands are one of the more difficult areas to classify driving the net uptake of C O in these areas, and con- as managed or unmanaged because human intervention, sequently the sinks are not under the direct control of particularly livestock grazing, can be difficult to ascer - anthropogenic management activity. It may be possible tain from satellite remote sensing data. For example, even to determine the non-anthropogenic emissions from the with clear implementation criteria, the identification of managed land base although this is not trivial as noted managed grassland in Canada is problematic with rela- previously [15, 43]. These methods could help national tively low classification accuracy of 55, 58 and 69%, while inventory compilers to disaggregate the reporting into in contrast, Canadian cropland has been mapped at 71, those emissions and removals that are clearly the result of 82 and 93% accuracy for 1990, 2000 and 2010, respec- human activities, and those that are the results of indirect tively . The relatively low accuracy of imagery clas - anthropogenic activity or other emissions drivers, such sification is due to the similarity in reflectance between as natural disturbances resulting from insect outbreaks ‘native’ grassland that is used for livestock grazing and and wildfires. For example, in their 2017 National GHG permanent pasture. Permanent pasture is land that has Inventory, Canada reported separately the emissions and been improved by land clearing, stone removal, fertili- removals from forest lands that have been subjected to zation, breaking and seeding or fencing, but the level of natural disturbance and all emissions and removals on improvement often declines over time to the point where managed forest lands . Indirect effects of anthro - the vegetation is similar to native grassland. With similar pogenic activity, such as increased wildfires or pest and grazing practices, the distinction between the two is dif- disease outbreaks that lead to increased flux of CO to ficult, even with on-site visits. the atmosphere, or C O fertilization that increases net The United States has attempted to circumvent some of primary production and removals, in principle should these problems by classifying all grassland as managed in not be included in the reported estimates because they counties (smallest political unit in which Census data are are not directly under the control of land managers. available) that are known to have active livestock grazing However, aside from the attempts to disaggregate emis- based on Census data. However, this approach may lead sions and removals from natural disturbances by Canada to an over-estimation of managed grasslands, particularly and Australia, factoring-out has not been attempted in in the western United States where there are large areas any other National GHG Inventory, and more evalua- of native grasslands that may not be actively managed. tion is needed to determine the effectiveness of these Furthermore, even if livestock are active on these native approaches. grasslands, the impact on the structure of the vegetation The exclusion of unmanaged lands may lead to scien - may be limited compared to unmanaged grasslands, and tifically incomplete understanding of the greenhouse so there may be little or no anthropogenic impact on C gas fluxes between the land surface and atmosphere. For stocks and GHG emissions. Brazil uses a similar crite- example, much of the unmanaged land areas in Canada rion to classify Protected Areas (or Conservation Units) and Alaska contain deep organic layers and permafrost and/or Indigenous Lands as managed, with the ration- that are susceptible to a range of climate change impacts ale that creating specific legislation is leading to a direct from thawing, water table changes if ice melt allows water anthropogenic action. Similar to grasslands in the west- to drain, and wildfires [12, 44]. The response of these ern United States, this policy may not have much impact lands to climate change and the associated emissions Ogle et al. Carbon Balance Manage (2018) 13:9 Page 11 of 13 could have significant impacts on the global C cycle (both developing effective GHG mitigation policies enhancing CO and CH ). While it would not be appropriate to land-based sinks and/or reducing sources of emissions by 2 4 report these as anthropogenic emissions, the fluxes can improving land management. have important implications for global policies aimed at achieving GHG reduction targets or atmospheric CO Abbreviations concentration targets. If emissions from unmanaged for- C: carbon; IPCC: Intergovernmental Panel on Climate Change; UNFCCC : United ests, peatland or permafrost C (positive feedback) use up Nations Framework Convention on Climate Change. some of the remaining “allowance” for C emissions to the Authors’ contributions atmosphere , then mitigation efforts in all other sec - All authors assisted with the manuscript preparation. SO led the review of tors have to increase to meet the global CO reduction managed land approaches that are used by governments for reporting to the UNFCCC, and led the managed land analysis for the United States. GD and CW targets. While currently there are no UNFCCC require- assisted with the review of managed land approaches and the managed land ments for monitoring and reporting of GHG emissions analysis for the United States. JS assisted with the managed land analysis for from these areas by governments because they are desig- the United States. AS conducted the managed land analysis. WK led compila- tion of the managed forest lands areas in Canada, and TH led the compilation nated as unmanaged, including these areas could contrib- of cropland and managed grassland areas in Canada. TK and MR assisted with ute more certainty to the outcomes of policy programs the managed land analysis for Brazil, particularly those in the last III National intended to limit the impact of anthropogenic GHG GHG Inventory (MCTI, 2016), covering the period 2002–2010. All authors read and approved the final manuscript. emissions on the climate system. According to the IPCC, it is good practice to be trans- Author details parent about the methods that are used for estimat- Natural Resource Ecology Laboratory and Department of Ecosystem Science and Sustainability, Colorado State University, Fort Collins, CO 80523, USA. ing and reporting GHG emissions . Based on our USDA Forest Service, Northern Research Station, 1992 Folwell Avenue, St. review, governments could be more transparent about 3 Paul, MN 55108, USA. Natural Resources Canada, Canadian Forest Service, 506 their application of the managed land proxy in national West Burnside Road, Victoria, BC V8Z 1M5, Canada. Fábrica Éthica Brasil, Av. Cassatella 177, Jundiaí 13218-55, Brazil. Agriculture and Agri-Food Canada, communications. Many communications do not explic- 960 Carling Ave, Ottawa, ON K1A 0C6, Canada. Natural Resource Ecology itly mention managed land even though the concept is 7 Laboratory, Colorado State University, Fort Collins, CO 80523, USA. USDA For- implicitly applied by the 97 government that are using est Service, Northern Research Station, Forest Sciences Laboratory, 271 Mast Road, Durham, NH 03824, USA. National Institute for Space Research, Ministry the later guidance from the IPCC [9, 18] based on our of Science, Technology, Innovation and Communication (INPE/MCTIC), São review. Specifically, governments could provide a defi - José dos Campos, São Paulo, Brazil. nition for managed land and implementation criteria. If Acknowledgements some of the land is not managed, then it would also be We thank Alicia Klepfer who assisted with review of the national communica- useful to provide a map with the spatial distribution of tions in addition to a number of translators: Mikhail Yatskov, Kerry Dooley, managed and unmanaged land. In addition, changes in Craig Wayson, and Ana María Planas. We also thank Tom Wirth who provided comments on a draft version of the manuscript. the managed land base over time should be reported, and the effect of those changes on emission and removals. Competing interests The authors declare that they have no competing interests. Conclusion Availability of data and materials Delineating a managed land base is the only universally All national communications reviewed in this study can be accessed from the accepted approach for estimating anthropogenic emis- UNFCCC website (See http://unfcc c.int/natio nal_repor ts/annex _i_natco m/ submi tted_natco m/items /10138 .php). The managed land area data for the sions and removals associated with land use . The United States can be accessed by contacting the US Environmental Protec- managed land proxy has weaknesses because it is not tion Agency (https ://www.epa.gov/ghgem issio ns). For Canada, all cropland feasible to fully discriminate between anthropogenic (except for ~ 9kha in Yukon), managed grassland and settlements south of 60 N are publicly available (https ://open.canad a.ca/en). All other data pre- and non-anthropogenic emissions and removals. Non- sented in this report are publicly available based on the references cited. The anthropogenic emissions and removals from processes land database from Brazil can be made available upon request to the General such as natural disturbances, nitrogen deposition, and Coordination of Global Climate Change (http://siren e.mcti.gov.br/). CO fertilization do occur on managed land, and are Consent for publication difficult, if not impossible, to separate from anthropo - Not applicable. genic sources. Regardless, there is flexibility in the appli - Ethics approval and consent to participate cation of the proxy to meet national circumstances as Not applicable. illustrated in the examples from Brazil, Canada and the United States, by incorporating additional criteria to bet- Funding The manuscript was prepared through funding from the United States Forest ter delineate the managed land base, such as functional Service (Agreement Number 13-CR-11242305-098). Canada results were based criteria, vegetation structure, and accessibility. In turn, on Government funding for the National Carbon and Greenhouse gases this will focus attention on the regions that are influ - Accounting and Verification Study (NCGAVS) of Agriculture and Agri-Food enced directly by management activity with the goal of Ogle et al. Carbon Balance Manage (2018) 13:9 Page 12 of 13 Canada and the National Forest Carbon Monitoring, Accounting and Report- Buendia L, Miwa K, Ngara T, Tanabe K, Wagner F (eds). 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