Forest Definitions Applied in Reporting
A Comparison of Land Use and Land Cover Classifications
The terms “land use” and “land cover” are often applied when characterizing landscapes and monitoring change. However, they have distinct meanings within the forest and land management context and are defined as follows:
Land use describes the social and economic intent for which land is used, as well as the ecological potential of the land in some cases. It is the standard metric used for official government reporting on forest land area. Forests are dynamic systems which often experience disturbances, forest management activities, and other vegetation changes. In formal reporting undertaken by the United States, forests included in the ‘forest land use’ category are those that meet the Forest Inventory and Analysis (FIA) definition of forest (see definitions section below). This includes forest stands that have undergone recent changes in surface vegetation due to a disturbance such as wildfire and harvesting, and temporarily do not have forest cover but the land is expected to regain forest cover and remain in forest use.
Land cover describes the vegetation, exposed land surfaces, water, and artificial structures covering the land surface at a given time. Assessments of forest condition and fragmentation generally rely on spatially explicit data on land cover generated from remote sensing to monitor landscape patterns and dynamics. Land cover is a popular output from remote sensing products because remote sensing instruments generally identify land cover better than land use.
Although land use and land cover classifications are distinct, many datasets based on land use definitions also incorporate elements of land cover.
Figure 1: Simplified illustration of the differences between land cover and land use classifications. Land use has more distinct categories, shown by the breaks in the bars, and land cover can be interpreted more on a continuum, as indicated by the crosshatched sections. Note that the land classes depicted above are often dynamic and may reflect transitionary states.
Forest Definitions
Different definitions of what constitutes “forest land” may be applied for describing forests under domestic and international reporting commitments. Each definition is valid and adopted based on the reporting requirements, available data, time frame, and spatial extent of the analysis.
Note: all data used for United States forest reporting comes from Forest Inventory and Analysis (FIA) program surveys. Estimates of forest attributes differ based on domestic and international reporting definitions described below. The national compilation of FIA data, called the Forest Resources Report, is a product of the Resources Planning act (RPA) Assessment and reflects the international definition.
This domestic reporting definition is based on how the FIA program defines forest in its nationwide forest inventory. It is different from the definition used in international reporting, as described below under the Resources Planning Act heading. International reporting includes a minimum tree canopy height criterion.
Definition: Forest land has at least 10 percent canopy cover of trees of any size or has had at least 10-percent canopy cover of trees in the past, based on the presence of stumps, snags, or other evidence, and that will be naturally or artificially regenerated. Additionally, the land is not subject to nonforest use(s) that prevent normal tree regeneration and succession, such as regular mowing, intensive grazing, or recreation activities. Forest land includes transition zones, such as areas between heavily forested and nonforested lands that are at least 10 percent canopy cover with trees and forest areas adjacent to urban and built-up lands. Also included are pinyon-juniper and chaparral areas in the West and afforested areas. The minimum area for classification of forest land is 1 acre (0.4 ha) in size and 120 feet (36.6 m) wide measured stem-to-stem from the outer-most edge. Unimproved roads and trails, streams, and clearings in forest areas are classified as forest if less than 120 feet wide. This is the domestic reporting definition; the definition used in international reporting includes a minimum tree canopy height criterion.
The Forest Service Resources Planning Act (RPA) Assessment uses data from the FIA program. The RPA definition of forest is often referred to as the U.S. “international definition of forest”. The RPA, its supporting Forest Resources Report, as well as the Forest Sustainability Assessment Research program apply this definition of forest land to ensure that the land estimate matches the estimates provided under U.S. international reporting commitments (listed at the bottom of this page). This includes reporting of greenhouse gas fluxes for the Land Use, Land-Use Change, and Forestry sector to the United Nations Framework Convention on Climate Change.
Definition: Forest land is a land-use category that includes areas at least 120 feet (36.6 m) wide and at least one 1 acre (0.4 ha) in size with at least 10 percent cover (or equivalent stocking) by live trees including land that formerly had such tree cover and that will be naturally or artificially regenerated. Trees are woody plants having a more or less erect perennial stem(s) capable of achieving at least 3 inches (7.6 cm) in diameter at breast height, or 5 inches (12.7 cm) diameter at root collar, and a height of 16.4 feet (5 m) at maturity in situ. Forest land includes all areas recently having such conditions and currently regenerating or capable of attaining such condition in the near future. Forest land also includes transition zones, such as areas between forest and non-forest lands, that have at least ten percent cover (or equivalent stocking) with live trees and forest areas adjacent to urban and built-up lands. Unimproved roads and trails, streams, and clearings in forest areas are classified as forest if they are less than 120 feet (36.6 m) wide or an acre (0.4 ha) in size. However, land is not classified as forest land if completely surrounded by urban or developed lands, even if the criteria are consistent with the tree area and cover requirements for forest land. These areas are classified as settlements. In addition, forest land does not include land that is predominantly under an agricultural land use.
The United States international definition of forest (that is, RPA above) has been adapted to be compatible with that of the Food and Agriculture Organization (FAO).
Definition: Land spanning more than 0.5 ha (1.2 acres) with trees higher than 5 m (16.4 ft) and a canopy cover of more than 10 percent, or trees able to reach these thresholds in situ. It does not include land that is predominantly under agricultural or urban land use.
| Tree Criteria | Cover Criteria | Size | |
|---|---|---|---|
| Forest Inventory and Analysis (FIA) | A tree is generally described as a woody perennial plant, typically large, with a single well-defined stem carrying a relatively definite crown. FIA keeps track of all species tallied in its inventory on a comprehensive species list. Diameter sizes are used to determine whether individual trees are measured on various sample areas, but diameter and height constraints are not used for classifying forest. | ≥10 percent canopy cover or has had at least ≥ 10 percent canopy cover of trees in the recent past, based on the presence of stumps, snags, or other evidence, and that will be naturally or artificially regenerated. | ≥120 feet (36.6 m) wide and ≥1 acre (0.4 ha) |
| Resources Planning Act (RPA) | Trees are woody plants having a more or less erect perennial stem(s) capable of achieving ≥3 inches (7.6 cm) d.b.h., or ≥5 inches (12.7 cm) d.r.c. and a height of ≥16.4 feet (5 meters) at maturity in situ. | ≥10 percent cover (or equivalent stocking) by live trees including land that formerly had such tree cover and that will be naturally or artificially regenerated. | ≥120 feet (36.6 m) wide and ≥1 acre (0.4 ha) |
| Food and Agriculture Organization (FAO) | Trees are woody plants having a more or less erect perennial stem(s) capable of achieving ≥3 inches (7.6 cm) d.b.h., or ≥5 inches (12.7 cm) d.r.c. and a height of ≥16.4 feet (5 m) at maturity in situ. | ≥10 percent cover (or equivalent stocking) or by trees able to reach these thresholds, and predominantly under forest land use. |
Acronyms: d.b.h.: Diameter at breast height (4.5 feet /1.4 m); d.r.c.: Diameter at root collar; ha: hectare (0.4 acres).
Woodlands and Other Wooded Land Definitions
Woodlands generally occur in less productive areas of the United States, and the tree species that make up woodlands often have distinct growth characteristics. This includes being slow growing, smaller, and with a tendency to form multiple stems from the base of the tree rather than a single stem. Woodlands are included in the Forest Inventory and Analysis (FIA) domestic forest land estimates and FIA reports. Woodlands are included in Resources Planning Act (RPA) reporting, but woodland estimates are provided separately from forest land estimates and must meet a minimum height threshold.
Woodlands are defined by species composition and associated forest types, comprised of three softwood and six hardwood woodland types. To qualify as one of these woodland forest types, the majority tree stocking must comprise one or more of the 38 FIA-defined woodland tree species.
Definition of Woodland Tree Species: Tally tree species that are measured for diameter at root collar (d.r.c.). Most woodland trees are quite variable in growth form, that is, they are often multi-stemmed. Woodland species are identified with a "w" under the "Woodland" column on the FIA Comprehensive Tree Species List.
Although woodlands will typically have less canopy cover from trees than traditional forests, they must meet the minimum tree canopy cover threshold (≥10 percent) to be sampled (and therefore included in forest land) estimates. Forest land estimates provided by FIA include woodland.
In the past, “other wooded land” was reported by the Rocky Mountain Research Station and Southern Research Station FIA units based on canopy cover thresholds greater than or equal to 5 percent but less than10 percent of live tally trees of any size or met those thresholds in the recent past, based on the presence of stumps, snags, or other evidence. Current FIA protocols sample only areas that have at least ten percent canopy cover of trees, so the “other wooded land” category is no longer sampled by FIA. Any areas previously sampled as “other wooded areas” that have less than 10 percent canopy cover from trees are now considered non-forest land.
The definition of ‘woodland’ as adopted in RPA (and for international reporting), are woodlands as classified by the FIA program (see FIA woodland definition above) but must meet an additional height threshold: trees are capable of achieving of at least 5 meters (16.4 feet) in height or are able, based on-site productivity, to meet this criterion at maturity in situ. Although woodlands will typically have lower canopy cover than other forest types, they must meet the minimum tree canopy cover threshold (i.e., greater than or equal to10 percent) to be sampled by FIA and therefore reported in the RPA estimates.
While the FIA program considers woodlands as a subset of forests, RPA reports woodlands as a separate category.
FAO has an “other wooded land” reporting category, which is land not classified as “forest” spanning more than 0.5 ha (1.2 acres); with trees at least 5 m (16.4 feet) and a canopy cover of 5-10 percent, or trees able to reach these thresholds in situ; or with a combined cover of shrubs, bushes, and trees of at least 10 percent. It does not include land that is predominantly under agricultural or urban land use.
The RPA estimates based on FIA data are used for FAO reporting, though given the lower canopy cover threshold (≥ 5-10 percent) of the FAO definition for the “other wooded land” category, at least a portion of the area defined as “other wooded land” by the FAO is not sampled nor estimated by the FIA program since it is considered non-forest by FIA definitions.
| Tree Criteria | Cover Criteria | Size | |
|---|---|---|---|
| Forest Inventory and Analysis (FIA) | See FIA definition of trees in Table 1 however woodlands generally include species that are multi-stemmed and measured for diameter at root collar (d.r.c.). Woodland species are identified with a "w" under the "Woodland" column on the FIA Comprehensive Tree Species List. The diameter for woodland tree species is typically taken at the root collar. | ≥ 10 percent canopy cover of trees, where the majority tree stocking is comprised of one or more of the 38 FIA-defined woodland tree species aggregated into nine woodland forest type groups. | ≥120 feet (36.6 m) wide and ≥1 acre (0.4 ha) |
| Resources Planning Act (RPA) | Woodland species as defined by the FIA program but filtered to only include areas with trees capable of achieving a height of ≥ 16.4 feet (5 m) at maturity in situ. | ≥ 10 percent cover (or equivalent stocking) by live trees including land that formerly had such tree cover and that will be naturally or artificially regenerated. | ≥120 feet (36.6 m) wide and ≥1 acre (0.4 ha) |
| Food and Agriculture Organization (FAO) *other wooded land | Sparse trees capable of reaching ≥7.6 cm (3 inches) d.b.h. or ≥12.7 cm (5 inches) d.r.c., and a height of ≥ 5 meters (16.4 feet) at maturity in situ. | ≥ 5-10 percent, or trees able to reach these thresholds in situ; or with a combined cover of shrubs, bushes and trees ≥10 percent. | ≥0.5 ha (1.2 acres) in size with sparse trees |
Acronyms: d.b.h.: Diameter at breast height (4.5 feet /1.4 m); d.r.c.: Diameter at root collar; ha: hectare (0.4 acres).
Timberland
The FIA program reports area and volume estimates on timberland. Timberland is comprised of unreserved forest land capable of producing 20 cubic feet per acre per year of wood from trees classified as timber species and designated as a timber forest type. Timberland excludes reserved forest land or forest land that is not managed for production of wood products through statute or administrative designation such as wilderness areas. Any tree species that has diameter measured at breast height (d.b.h.), 4.5 feet above the ground line, is considered a timber species.
The FIA Glossary provides standard terminology applied within the Forest Inventory and Analysis (FIA) Program.
Selection of Domestic and International Voluntary and Formal Forest Reporting
The table below summarizes a selection of formal engagements and associated reporting commitments made by the United States relating to forests and the forest definition applied in reporting.
| Selected Agreement/Process | About the Organization and Reporting Where Applicable | Example Variables Used in Reporting | Forest Definition Applied for United States Reporting |
|---|---|---|---|
| Bonn Challenge | The Bonn Challenge is a global goal to bring 150 million hectares of degraded and deforested landscapes into restoration by 2020 and 350 million hectares by 2030. The United States periodically reports on its progress toward Bonn Challenge pledges. | Forest Area, Ownership | RPA |
| Collaborative Partnership on Forests (CPF) | The Collaborative Partnership on Forests is a voluntary partnership of 16 international organizations, institutions, and secretariats with substantial programs on forests. Their vision is that "by 2030 all types of forests and forest landscapes are sustainably managed, their multiple values are fully recognized, the potential of forests and their goods and services is fully unlocked, and the Global Forest Goals, the Sustainable Development Goals and other global forest-related goals, targets and commitments are achieved." Periodic reports are generated that incorporate United States reporting on progress toward Sustainable Development Goals. | Various | RPA |
| Convention on Biological Diversity (CBD) | The Convention on Biological Diversity is dedicated to promoting sustainable development. The Convention recognizes that biological diversity is about more than plants, animals and microorganisms, and their ecosystems – it is about people and our need for food security, medicines, fresh air and water, shelter, and a clean and healthy environment in which to live. The United States is a party to the CBD and participates in associated monitoring and reporting targets and protocols: • Aichi Biodiversity Targets: The Aichi Biodiversity Targets consist of five strategic goals to reduce biodiversity loss and promote sustainability of biodiversity. • Cartagena Protocol on Biosafety: The Cartagena Protocol is an international agreement which aims to ensure the safe handling, transport, and use of living modified organisms resulting from modern biotechnology that may have adverse effects on biological diversity, taking also into account risks to human health. • Nagoya Protocol: The Nagoya Protocol on Access to Genetic Resources and the Fair and Equitable Sharing of Benefits Arising from their Utilization to the Convention on Biological Diversity is an international agreement which aims at sharing the benefits arising from the utilization of genetic resources in a fair and equitable way. | Forest area, Growing stock, Biomass stock, Carbon stock | >RPA |
| The Montréal Process | The Montréal Process Working Group on Criteria and Indicators for the Conservation and Sustainable Management of Temperate and Boreal Forests established 7 criteria and 54 indicators that address the ecological, economic, and social dimensions of forest sustainability. The 12 member countries of the Montréal Process account for 49 percent of the world’s forests and 90 percent of the world’s temperate and boreal forests. As part of its institutional and political commitment to the Montreal Process, the United States produces Indicator reports and the National Report on Sustainable Forests on a periodic basis. | Forest Area, Forest Type, Ownership, Growing stock, Biomass stock, Carbon stock | RPA |
| Convention on Biological Diversity (CBD) | The Convention on Biological Diversity is dedicated to promoting sustainable development. The Convention recognizes that biological diversity is about more than plants, animals and microorganisms, and their ecosystems – it is about people and our need for food security, medicines, fresh air and water, shelter, and a clean and healthy environment in which to live. The United States is a party to the CBD and participates in associated monitoring and reporting targets and protocols: • Aichi Biodiversity Targets: The Aichi Biodiversity Targets consist of five strategic goals to reduce biodiversity loss and promote sustainability of biodiversity. • Cartagena Protocol on Biosafety: The Cartagena Protocol is an international agreement which aims to ensure the safe handling, transport, and use of living modified organisms resulting from modern biotechnology that may have adverse effects on biological diversity, taking also into account risks to human health. • Nagoya Protocol: The Nagoya Protocol on Access to Genetic Resources and the Fair and Equitable Sharing of Benefits Arising from their Utilization to the Convention on Biological Diversity is an international agreement which aims at sharing the benefits arising from the utilization of genetic resources in a fair and equitable way. | Forest area, Growing stock, Biomass stock, Carbon stock | RPA |
| Ramsar Convention on Wetlands of International Importance Especially as Waterfowl Habitat | The Ramsar Convention’s mission is “the conservation and wise use of all wetlands through local and national actions and international cooperation, as a contribution towards achieving sustainable development throughout the world.” The United States submits periodic reports to the Ramsar Convention including forest land use. | Forest Area, Forest Type | RPA |
| Resources Planning Act (RPA) Assessment | The Resources Planning Act (RPA) Assessment reports on the status, trends, and projected futures of the Nation's renewable resources on all forests and rangelands, as required by the Forest and Rangeland Renewable Resources Planning Act of 1974, as amended. The Resources Planning Act Assessment is released on a decadal basis, as well as periodic interim technical reports supporting the RPA Assessment. | The Resources Planning Act (RPA) Assessment reports on the status, trends, and projected futures of the Nation's renewable resources on all forests and rangelands, as required by the Forest and Rangeland Renewable Resources Planning Act of 1974, as amended. The Resources Planning Act Assessment is released on a decadal basis, as well as periodic interim technical reports supporting the RPA Assessment. | Various |
| Forest Inventory and Analysis State Reporting | FIA data are used for various state reports and state forest plans. | Various | FIA |
| The Forest Resources Report (FRR) | The Forest Resources of the United States Report is a national report prepared every five years summarizing national statistics on forest resources and timber industry outputs. | Various | RPA and FIA |
| Sustainable Development Goals (SDGs)/2030 Agenda | The United Nations Sustainable Development Goals (SDGs) are a blueprint to achieve a better and more sustainable future for all The United States voluntarily reports on progress toward the UN SDGs annually. | Forest area, Growing stock, Biomass stock, Carbon stock | RPA |
| United Nations Framework Convention on Climate Change (UNFCCC) | The UNFCCC is the entity in the United Nations tasked with supporting the global response to climate change. The goal of the UNFCCC is to stabilize greenhouse gas concentrations at a level that will prevent dangerous interference with the climate system in a time frame that allows the ecosystem to adapt naturally and enables sustainable development. (Framework Conventions are legally binding treaties, to which the general rules of international treaty law apply.) At the UN Climate Change Conference (COP21) in Paris, France, on 12 December 2015, the United States became a signatory to the United Nations Framework Convention on Climate Change (UNFCCC) Paris Agreement, a legally binding international treaty on climate change. Its overarching goal is to hold “the increase in the global average temperature to well below 2°C above pre-industrial levels” and pursue efforts “to limit the temperature increase to 1.5°C above pre-industrial levels.” As a signatory to the UNFCCC, the United States produces National Inventory Reports, Biennial Update Reports, and submits Nationally Determined Contributions. | Forest Area, biomass stock, carbon stock | RPA |
| United Nations Convention to Combat Desertification (UNCCD) | The United Nations Convention to Combat Desertification (UNCCD) was established in 1994 to protect and restore our land and ensure a safer, just, and more sustainable future. The UNCCD is the only legally binding framework set up to address desertification and the effects of drought. | Focused on land degradation. | |
| United Nations Economic Commission for Europe (UNECE) | The United Nations Economic Commission for Europe (UNECE) promotes pan-European economic integration. UNECE includes 56 member States in Europe, North America, and Asia. However, all interested United Nations member States may participate in the work of UNECE. Over 70 international professional organizations and other non-governmental organizations take part in UNECE activities. UNECE produces periodic reports relating to the forest sector, including contributions from the United States on national and regional forest sector trends as well as modeling and analytical work. | Various | RPA |
| United Nations Food and Agriculture Organization (FAO) Global Forest Resources Assessment. | The Global Forest Resources Assessment (FRA) examines the status and trends for forest-related variables across 236 countries and territories. The United States provides periodic national submissions to the Global Forest Resources Assessment. | Forest area, Growing stock, Biomass stock, Carbon stock | RPA |
| United Nations Food and Agriculture Organization (FAO) Regional Forestry Commissions | The UN FAO’s Regional forestry commissions provide a policy and technical forum for countries to discuss and address forest issues on a regional basis. The United States is a member of the North American Forest Commission (NAFC), the Latin American and Caribbean Forestry Commission (COFLAC), and the Asia-Pacific Forestry Commission (APFC). The United States actively participates in Regional Forestry Commission meetings and collaborates in technical discussions and technical publications on forest trends and measurement and monitoring developments. | Various | RPA |
| United Nations Forum on Forests (UNFF) | The United Nations Forum on Forests is a subsidiary body of the Economic and Social Council of the United Nations with the objective to promote the management, conservation, and sustainable development of forests and strengthen the long-term political commitment to this end. As a member of the UNFF, the United States periodically produces Voluntary National Reports to the UNFF. | Various | RPA |
Publications and References
- Mark D. D. Nelson, Kurt Riitters, John W. Coulston, Grant M. Domke, Eric J. Greenfield, Linda Langner, David J. Nowak, Claire O'Dea, Sonja Oswalt, Matt C. Reeves, David N. Wear. 2020. Defining the United States land base: a technical document supporting the USDA Forest Service 2020 RPA assessment
- Sonja Oswalt, W. Brad Smith, Patrick D. Miles, Scott A. Pugh. 2019. Forest Resources of the United States, 2017: a technical document supporting the Forest Service 2020 RPA Assessment
- Kathleen McGinley, Lara T. Murray, Guy Robertson, Eric M. White. 2023. National report on sustainable forests, 2020
- Forest Service U.S. Department of Agriculture. 2023. Future of America's Forest and Rangelands: Forest Service 2020 Resources Planning Act Assessment
- Lara T. Murray, Sonja Oswalt, Sara A. Goeking, Katherine Renwick. 2025. Forest definitions applied for national United States forest reporting: Status, gaps, and opportunities