An Analysis on the Long-term Management of Urban Tree Carbon Reduction ‘Forestry Inventory Analysis’ towards Climate Change Adaptation

Forest Inventory and analysis management program in the US

Forest investigations in the US are governed by the FIA Division with its headquarters in the R&D Sector of the USDA Forest Service of the United States Department of Agriculture. The FIA Division was established in the 1930s as a research institution to collect, analyse, and report data on the current status of forests in each state of the US, with a focus on the period from the 1970s to the present day. Long-term management conducted by the FIA has been the foundation for achieving carbon neutrality. The USDA Forest Service extended the scope from non-periodic to periodic, annual, and quarterly investigations in line with the FIA data collection system. A system that can periodically analyse the data and present them to the general public was established. In addition, the FIA program was substantially improved by extending the scope of data collection to allow an additional attribute set to be included in the subcategory scale in the figures, such as soil, underground vegetation, and tree crown conditions. The program was also amended to include a sample of urban trees for each type of land use in the selected city. It is also worth noting that a tree carbon assessment system could be developed at the national level using the long-term management system. Thus, a goal was set to analyse the background of the management system during the development of the assessment system.

Analytical framework: Place-keeping analytical framework (PKAF)

In this study, the PKAF was applied when analysing the long-term management system of the FIA program and to assist in providing a systematic understanding. The PKAF aims toward sustainability with environmental and social benefits through management to ensure its retention or enhancement (Wild et al., 2016). With the recent emphasis on the management system, an increased focus has been placed on management perspectives. To establish the concepts, the long-term and general concepts should be addressed in terms of policy, budget, governance, partnership, evaluation, and management (Dempsey and Burton, 2012). In other words, for the analysis of the long-term management system, analysis of the aforementioned concepts should first be carried out. Here, the focus of the monitoring and analysis is the approach used for the agreement to implement policies, the execution of policy to compile a budget, participation and information-sharing of stakeholders for partnership, decision-making participation of citizens and communities for governance, and long-term suitability of these concepts for evaluation and management.

A growing emphasis has been placed on such long-term programs and processes since 2010. Representative studies are Dempsey and Burton (2012) and Nam and Dempsey (2019a, 2019b and 2020), which have been commonly applied for the analytical framework to establish a long-term process for public places and park afforestation. The process has been widely applied in South Korea, from programme analysis for park regeneration (Nam et al., 2019) to landscape management processes for island areas (Nam and Oh, 2020), system analysis for park planning and management (Shim and Jo, 2016), community program analysis for fine-dust reduction (Nam and Kim, 2019), and trend analysis for park afforestation evaluation (Cho and Nam, 2022). Similarly, in this study the PKAF was applied based on the fact that it was first used for the FIA program to highlight the importance of investigation and monitoring in the Organic Administrative Act in 1897 and that it was subsequently evaluated as a long-term, successful model. Moreover, as the assessment system for the carbon storage and reduction of contemporary trees and the analysis of the management system for developing the assessment system have both been emphasised, the PKAF was set for applications in an in-depth analysis.

Network time-series analysis

To investigate the correlation analysis for the trend analysis on urban street trees and carbon-related factors, the VOSviewer software ver. 1.6.18 designed by Leiden University was used. VOSviewer is software used to compose and visualize a bibliometric network. Such networks can include, for example, academic journals, researchers, or individual publications, while they may also be formed based on citations, bibliometric coupling, co-citations, or co-author relationships. VOSviewer also provides a text mining function that can be used when constructing and visualizing concurrent networks of critical terms extracted from earlier literature. In this study, a similarity search was performed on 1,500 papers in the Science Direct database available for the world’s leading sources for scientific, technical, and medical research prior to the FIA keyword search of carbon and tree. The search of the literature was restricted to review and research articles, while the result was stored as an RIS file for the network analysis using the VOSviewer software. For certain keywords, duplication in the publication library would appear as a relatively large circular symbol, to be defined as the main cluster. Such symbols are marked in bold lines to represent the network connection for each keyword to allow a quantitative analysis across different networks. In addition, a frequency analysis was performed for the search strings using VOSviewer. The extracted keywords were categorized into Items, Cluster, Links, and Total Link Strength for the frequency analysis. In this way, the network visualisation was completed, and search results were ordered chronologically and resulting time-series data were analysed in the overlay visualization of the latest trends.

Cluster analysis

The PKAF was followed by a cluster analysis, which was used to verify the correlations across concepts, namely policy, budget, governance, partnership, and evaluation. The final concept to be highlighted in the PKAF is coordination, for which the connectivity and correlations across each concept should be analysed. This is to verify the background of the development of the long-term management system. To accomplish this, the qualitative analysis software NVivover. 12 by QSR International was used. This is software that is known to enable not only the analysis of general qualitative data but also the detection of themes and issues, and Nam and Bae (2021) employed this software to analyse qualitative data. In this study, a coding process was performed based on the concepts derived from the PKAF, and then the cluster analysis and visualization were conducted.

Trend of the tree assessment system in the USA

For 17 forests and trees in the US, carbon storage was as high as 1,224,700 Mg in 2010, which was 37.7 Mg ha⁻¹, and the carbon sequestration for these forests and trees was 42,093 Mg C year⁻¹ and 1.233 Mg C ha⁻¹ year⁻¹ (Nowak et al., 2010). The mean carbon storage and sequestration were 418,746 Mg C, 21.0 Mg C ha⁻¹; and 14,284 Mg C year⁻¹, 0.67 Mg C ha⁻¹ year⁻¹, respectively (Nowak et al., 2010). The urban forest carbon storage for 24.1 million ha was 506 million Mg C (TgC), and the carbon sequestration was assessed to be 16.15 TgC year⁻¹ (Scharenbroch, 2012). In Nowark and Crane (2001), the carbon storage capacity of forests in the US was found to range from 34–750 Tg C. It was also shown that 4.4% of the total forest carbon storage in the US was based on urban street trees (Birdsey and Heath, 1995). Every year, 1% of total greenhouse gas emissions in the US is attributed to carbon sequestration across urban forests (Scharenbroch, 2012). Thus, carbon storage and sequestration across urban forests are important issues alongside the increase in urban areas. These issues cannot be overlooked, as 80% of the total population in the US reside in urban areas (Acevedo et al., 2006).

The aforementioned previous studies applied various assessment systems to carbon emission and storage across urban street trees. For example, the following different indicators and quantitative data were used: the size of urban street trees (diameter at breast height, in general), longevity, growth rate, and street-tree management behaviours as well as factors related to the resistance of urban street trees from sunlight to pest and disease, physiological and environmental factors, water, salt, texture, compression, and biomass. Based on these, the following estimations were made: Last Positive Point, Relative Urban Stress Tolerance, carbon storage [C Storage (kg C) : Cst], and carbon sequestration (Sequestration of CO₂ : Cseq). For such a variety of assessment systems to be established, the data provided by previous literature are essential. Notably, studies by Stanek and State (1978), Schlaegel (1981), Tritton and Hornbeck (1982), Schlaegel (1984a), Schlaegel (1984b), Schlaegel (1984c), and Wenger (1984), conducted after the late 1970s, contributed to the development of assessment systems by providing the biomass data using the most important factors included in the carbon assessment system, namely growth rate, size, and longevity of trees. Through this research-based management system with a focus on assessment systems, the FIA has played a significant role in the collection, analysis, and provision of basic data for research on tree carbon storage in the US.

Trend of the tree carbon assessment system in South Korea

The MICS Act addresses carbon stock with increased sink or reduced emission of greenhouse gases through the activities stated in Article 2. However, as these activities are limited to forests, there is a limitation on the extent to which greenhouse gas sinks can be increased. In other words, compared to forests, carbon storage by street tree planting and management in South Korea would have little interest in the context of the current issue, in that additional investigation and regulation updates are needed for the South Korean Government to mitigate this issue. While the recently developed manual for street tree planting and management (Korea Forest Service, 2020) presents the information on the general points that have previously only been mentioned, the role of street trees with respect to carbon storage is not described. Similarly, the National Forest Health and Activity Distribution, a report of the National Institute of Forest Science in 2020, mentions the health of trees, vegetation, soil, and the atmosphere. Thus, the issue of trees and carbon storage in South Korea is either focused solely on forests, or is excluded altogether. Regarding the assessment system, carbon-related issues of urban street trees were discussed in studies published around 2010, including one on the level and effect of carbon dioxide sinks across urban trees (Park, 2009) and another on the assessment of urban street-tree carbon storage and annual carbon dioxide sinks (Park and Kang, 2010). The assessment system uses the biomass and carbon fraction used by the USDA Forest Service- i.e., the mean carbon storage across the representative street tree species is multiplied by the carbon fraction of 0.5 to account for the biomass. This method of assessment and the metric models of carbon storage and sink per planted tree species have been developed and recently applied by the Korea Forest Service (Korea Forest Service, 2020). In a study by the Korea Forest Service, a metric model is applied to each planted tree species, while these species are the urban trees exhibiting a high frequency of planting. It was also found that errors could be induced when applying metric models to urban trees, as the growth conditions vary across forests and urban areas. The evidence provided by this study is also insufficient for the development of the urban street-tree assessment system, as the scope of the study was limited to four cities in South Korea. This suggests the need to collect additional data for the assessment system and to build a long-term management system for establishing the national assessment system in advance of related research. Thus, a study which analyses the management system for the FIA program, currently being managed by the USDA, should first be conducted.

Policy: Political consistency and FIA-centred long-term inventory framework

Based on the Forest and Rangeland Renewable Resources Research Act enacted in 1978 sourced from Office of the Law Revision Counsel (all Acts below included), the FIA has practically been established as the representative program for the investigation and analysis of trees in the US. Its management has continuously been maintained, and an analysis of the policy showed that an analytical framework with a focus on the continuity and consistency of FIA-related policies has been formed (Fig. 2).

Fig. 2

Reviewing tree inventory-related legislative actions.

The continuity and consistency of the related policies place an emphasis on inspection and monitoring. The Forest Service Organic Administration Act is the first relevant law enacted by the president in 1897, and clearly states the need for the investigation and analysis of trees. Subsequently, the McSweeney-McNary Forest Research Act of 1928 states that the investigation and analysis should be conducted through the USDA. The Forest and Rangeland Renewable Resources Planning Act of 1974 states that the investigation and analysis should be extended via the participation of various stakeholders. These national policies on investigation and analysis were further enforced to signify the legal responsibilities of the USDA Forest Service by the National Forest Management Act (NFMA) of 1976. As such, the strong directionality of policies led to the Forest and Rangeland Renewable Resources Research Act of 1978, which states that the investigation and analysis must be reinforced using an FIA-centred approach. The FIA-centred investigation and analysis were actively extended thereafter. To illustrate this, continuing from the NFMA, the Forest and Rangeland Renewable Resources Research Act of 1982 stated that it should be extended to investigation, analysis, and evaluation. To ensure the continuity and consistency of the FIA-centred investigation and analysis, the Agriculture Research, Extension, and Education Reform Act of 1998 stated the need for efficient integration with other programs or institutions conducting the investigation. Subsequently, the National Forest System Land Management Planning Rule of 2012 stated that it would be extended to investigation, analysis, and monitoring as part of the FIA-initiated climate change adaptation. The Farm Bill of 2014 then highlighted the importance of biomass and carbon storage for climate change adaptation and stated that the FIA should lead the integrated data collection and analysis. Thus, an FIA-initiated systematic framework was formed through the consistency of policies that emphasized the investigation and analysis in 1987, while the framework for carbon storage and biomass assessment was established as part of recent climate change adaptation. Of greater importance is that a framework for policy development was set to ensure continuity and provide directionality regarding the partnership, budget generation, governance, and monitoring through the policies incorporating the management perspectives. This contributed to the construction of management structures with long-term perspectives. The relevant policies will be mentioned in each part of the conceptual analysis.

Partnership: Extending shared responsibilities and network alliance

The partnership in the FIA program is characterized by the shared responsibilities and activated state network alliance for overall tree management and data collection. This system underlies the framework of policies, from the extended sharing of responsibilities by the USDA Forest Service based on the Forest Service Organic Administration Act of 1987 and the McSweeney-McNary Forest Research Act of 1928 to the extended sharing of responsibilities by regional governments based on the Multiple-Use Sustained-Yield Act of 1960, and by the public and private sectors based on the Forest and Rangeland Renewable Resources Planning Act of 1974. Subsequently, based on the Forest Ecosystems and Atmospheric Pollution Research Act of 1988 and other relevant policies, the extended sharing of responsibilities was shown to involve the participation of various stakeholders, including the public, private and community sectors. In terms of such framework of shared responsibilities, first, the FIA management structure creates the network alliance structure, which leads to the formation of the central system of partnerships incorporating the network partnership basis, cooperation, and enhanced competence based on the Partnerships on Every Forest (PEF) program. For active trend-setting and execution regarding partnership by the PEF Team, an advisory group is created as a network to oversee the resource management, data collection, and education. This structure formed by the PEF Team leads to agreements through the sharing of opinions and responsibilities with the existing expert groups via the alliance system of partnership, beyond the general sharing of knowledge. Second, the multi-stakeholder partnership system is created through a liaison spanning the public, private, and community sectors. The partnership based on state cooperation broadly divides the country into the West, North-East, and Chesapeake bay watershed. The focus of such a partnership system is on the prioritization of shared values that constitute the extended data construction system based on cooperation between the state and other partners and sharing within the state and with other states. To this end, data collected from active community groups in each state are integrated. Representative groups include the stewardship-based National Wildlife and Fish Foundation and the national forest management group Penny Pines Plantation. This structure allows the regional government, state, and other partners to collaborate to resolve problems and search for opportunities towards improvement regarding forest carbon storage and restoration across all parts of the district under management. Thus, the state-based support program for decision-making is applied to data collection and strategy development, with an influence exerted across all parts of the given district and with the framework of shared responsibilities existing via multi-stakeholder partnership.

Budget: Generating extended funding based on partnership

A point to note in generating the funding through the public sector and other partners is the benefit-sharing partnership structure initiated by the public sector. Thus, it shows a concept of sharing benefits rather than pursuing benefits by a single sector in partnership with the FIA. Based on this, an extended budget may be generated. Analysing the 2019 FIA Budget Report showed that the budget for the FIA management was approximately 93.351 M USD, of which approximately 11% was generated through FIA partners (Fig. 3).

Fig. 3

Proportions of budget generated by stakeholders.

The actual budget for the FIA management was approximately 78 M USD. Considering that a large budget is required, the generation of a sufficient budget does not depend solely on what is provided by the central government, as additional funds must be generated based on the extended partnerships. In relevant policies, similarly, the importance of funding is mentioned frequently, from the emphasis on the USDA budget for the inspection and analysis in the McSweeney-McNary Forest Research Act (1928) to the creation of a budget for the foundation and management of the FIA in the National Forest Management Act (1976) and the budget organization for the expansion of the FIA in the Forest and Rangeland Renewable Resources Research Act (1978). Notably, Section 3(g) of the Forest Ecosystems and Atmospheric Pollution Research Act (1988) states that suggestions should be made on the long-term funding for the long-term management of the FIA. Subsequently, a political basis for funding was suggested based on extended partnerships which may be interpreted as the generation of additional funding through four sectors- namely, the public, community, private, and non-profit third sectors.

Other environment-related public sector programs, agencies, and universities provide the budget for the management of the FIA and acquire the necessary data in return. As such, it is a partnership structure of budget generation and data sharing. What is more important is that the data provided by the FIA to the universities and research institutions would contribute to basic research on biomass and carbon estimation. Since 2019, approximately 17 universities and institutions have conducted carbon-related research using FIA data, and 18 universities and institutions are conducting research on biomass. This reveals that the budget management of the FIA generated through the non-public sector significantly contributes to the research on carbon neutrality.

Governance: Collecting data on carbon neutrality based on active governance

Since the suggestion of the Administrative Procedure Act of 1946 on public participation in decision-making, the importance of the decision-making participation of various stakeholders has been highlighted. A structure of active governance with deep involvement in decision-making that goes beyond participation can be seen. Governance for the FIA is characterized by the opportunity of various stakeholders to engage in active decision-making regarding the collection of carbon-related data, for climate change adaptation based on active governance. Through active governance, the participation of stakeholders, especially the community, becomes active and regular, and creates a decision-making opportunity (Nam and Kim, 2018). Governance for the FIA program is, thus, managed by the FIA Management Team through the establishment of the overall governance structure (Fig. 4).

Fig. 4

Drawing the active governance structure of FIA.

The decision-making opportunity for various stakeholders is governed by the managers of the North, South, and West FIA programs. To this end, the opinions of policy-makers, forest business consultants, and academic researchers are first collected and integrated and volunteering and community activities are encouraged, while the respective opinions are actively incorporated. Such a governance structure is first characterized by the legally assured committee activities. The Federal Advisory Committee Act of 1972 and the Federal Lands Recreation Enhancement Act of 2004 have established a political device to basically determine the advisory role for two years. These Acts state that the committee should be established and public hearings and forums should be held, while various stakeholders should be given decision-making opportunities. Second, programs are activated to promote the participation of the younger generation. Through the activation of Youth Conservation Corps (YCCs) and Pathways Programs, teenagers to undergraduate students are encouraged to actively participate. The YCCs is a program designed for adolescents aged 15–18 years to experience carbon neutrality by engaging in meaningful activities in forests, prairies, and national parks. Moreover, the program provides an entry point to related job opportunities. The Pathways Programs works with the state government to provide paid employment opportunities to high school, undergraduate, and postgraduate students, as well as to recent graduates. As such, it exhibits connectivity between the FIA program and youth employment according to varying levels of education, based on the Internship Program (the opportunity for a student to explore career paths in the state during the school year, whereby the student is employed as a part timer for as long as one year), the Graduates Program (the opportunity for employment for individuals who have completed a degree or certificate program within the past two years), and the Presidential Management Fellows Program (the opportunity for individuals who have attained an advanced degree within the past two years). Third, the citizen stewardship activities are extended. In addition to such activities by volunteers, active participation is extended for data construction.

Regarding the decision-making participation, the 2019 FIA Budget Report showed that the percentage of participation in decision-making related to the FIA program was 47% for the government, 18% each for the academia and NGOs in the public sector, and 10% for the private sector. Thus, while a considerable part of the FIA decision-making opportunity is taken up by the public sector, a structure of active governance was found to offer the opportunity of decision-making participation to various stakeholders.

Evaluation (assessment system) and management

For data management and evaluation, the FIA program showed a specified, stepwise structure (Fig. 5). The steps in this structure included scope setting, error reduction, sample integration through the national cell grid, core variable setting, data collection, data quality assurance, information management, analysis, and R&D.

Fig. 5

Drawing the flow of data management and evaluation of FIA.

The Coverage for scope setting is conducted with the aim of expansion across the nation to include the 48 states and Alaska and Hawaii, as well as all private and public lands. The Sample Intensive is conducted to investigate samples across a wide range, covering approximately 20% of the entire nation. To verify the efficacy of the investigation and analysis and for error reduction, the national cell grid is used to specify each domain. The FIA program requires the setting of core variables for analyses; the climate change and ecological variables are defined and the variables of data collection are drawn. Data Collection is conducted to suggest various specific approaches. A wide array of data is collected based on the partnership between public sector entities as well as the academic and private sectors. For Quality Assurance and data homogeneity, all participants providing data should undergo a certification procedure. Through such procedure, data quality assurance is conducted. The input data are scanned for errors in real time using PDR software before being entered into the system. The PDR software not only detects errors, but also relays an accurate information system in the dimension of data management to subsequent generations. The information is also provided as open data. The National and Regional Users Group of the FIA applies the collected data in actual analyses and shares opinions in regular meetings. The collected data are used to complete a short-term, one-year report and a long-term, five-year report. The report of each state per period is compiled into an annual report. Finally, through trend analysis, estimation, remote sensing, geospatial analysis, and modelling, a sustainable data evaluation and management system is constructed. In summary, the management of the eight key steps of investigation and evaluation allows a positive assessment of the reliability and utility of the data produced by FIA.

Interactions from the perspective of long-term management

To verify the correlations across each concept ultimately highlighted by the PKAF, cluster analysis was performed on the policy, partnership, governance, budget generation, and evaluation, and the result indicated that the construction of the assessment system and long-term management of the FIA program were associated with the individual function of each concept as well as the integrated and combined interactions across the concepts (Fig. 6).

Fig. 6

Dendrogram coordinated framework for long-term management.

From the cluster analysis, 15 keyword groups were drawn for the FIA management system, which are defined as follows: The support for carbon neutrality in the policy (Po), governance-partnership liaison (G-Pa), participation of the private sector in the investigation (Pa-E), participation of the private sector in data collection (G-E), sharing of analysis and knowledge (E-Pa), political insights (Po), offer of central and regional government programs (Po), opportunity of participation for stakeholders (Pa), active participation (G), construction of governance system (G), partnership with state organizations (Pa), partnership-based management (Pa), budget generation and use of financial sources (F), participation of citizens in evaluation (Pa-E), and participation of regional groups (G). The keyword groups each highlighted the concepts of policy, partnership, governance, budget, and evaluation. However, what is of greater importance is the additional, mutual organic relationships revealed by the top keyword groups in A, B, C, D, E, and F in Fig. 6. The groups are again coordinated where a single FIA long-term management system can be seen to have formed based on such concepts. This coincides with the claim by Dempsey and Burton (2012) that efficient long-term management is only possible through the use of the concept of coordination, an essential item suggested for management in an open space.

Insights based on the PKAF

Analysing the FIA long-term management system based on the PKAF suggests that a partnership-based system is required in the long-term management structure to establish the assessment system for achieving urban street tree management and carbon neutrality in South Korea (Fig. 7).

Fig. 7

Proposing an integrated and long-term management framework.

For the data construction and assessment system for achieving carbon neutrality, the starting point lies in urban street tree management. Thus, based on the policy liaising the data drawn from the FIA policy analysis and the partnership specialized for data collection, a reinforced policy should first be presented to define a partnership-based assessment system. In addition, a framework for an integrated assessment system should be constructed. Furthermore, to go beyond the dimension of tree management and allow the concepts of long-term management to be established, a policy direction applying the concepts of budget generation, governance, partnership, evaluation, and management should be suggested in an integrated way. Second, for funding, a financial partnership system should be constructed via the participation of central and regional governments as well as communities. The relationship between the central and regional governments should not be binary from data construction to analysis, but unnecessary overlap in budget execution should be prevented through systematic partnership with collaboration aiming toward integrated data construction. In addition, such partnership-based budget generation should consider the sharing of benefits by each stakeholder. Third, the FIA analysis should indicate the governance structure in a form of active governance with community participation and extended roles. For active governance, unlike in a conventional community, active decision-making participation should be the basis from evaluation to budget generation, and should go beyond the participation in the dimension of management. Thus, as with the FIA, participation by the community and third sectors should be extended to data collection in addition to active decision-making participation with respect to management based on tree growth and obtaining other data for urban street tree data collection and construction. Fourth, the FIA pursues multi-stakeholder partnerships based on network alliance and sharing. An alliance system is required for data collection and the sharing of data and financial sources through an integrated partnership across the private, public, and community sectors, to reach the shared goal of carbon reduction through urban street trees. This will lead to a positive long-term effect, as shown by the theory of PPCP (Nam, 2021). Fifth, integrated directionality should be suggested to coordinate the assessment system for urban street tree carbon storage. Thus, variations in the construction of the assessment system based on the main body of the research leads to integrated results in the data collection, analysis, and evaluation. In addition, as indicated by the FIA analysis, the data should be open to the public, with a mandatory quality assurance procedure, and the reliability and utility of the produced data should be enhanced. Finally, it should not be overlooked that the correlations across each concept related to interactions should be essential considerations for the construction of the long-term management system.