Introduction

The negative impacts of ongoing climate change and direct human activities are steadily eroding Natural World Heritage Site (NWHS), which are known for their multiple values of natural beauty, biodiversity, ecosystems, and geological evolutionary processes, with their “walls closing in”1,2. The World Heritage Outlook 2020 report indicates that threats across all categories are increasing at NWHSs3. In response, a survey by the World Heritage Center in 2021 reiterated the importance of heritage conservation and sustainable development4, and the need to respond and adapt to possible future environmental changes by conserving and developing our valued NWHS in a sustainable manner5,6. Nevertheless, the threats and problems facing natural heritage sites have not diminished7,8. To cope with human pressures and the demands of regional development, addressing the connection between the conservation of NWHSs and the development of their surrounding regions is becoming increasingly crucial.

Buffer zone (BZ), as transitional areas between heritage sites and the external environment, buffer the negative impacts of external activities on heritage sites, maintain communication between heritage sites and the outside world, avoid ecosystem fragmentation9,10, and support the development of local livelihoods, making them key areas for achieving heritage conservation management and sustainable development5. But in most BZ around NWHS, forest loss, and increased human pressures are much higher, posing a significant threat to the overall ecosystem of the site8,11,12. However, many studies still indicate that the definition and implementation of BZ around NWHS are loosely applied13. In-depth research and practical efforts are still lacking in exploring BZ planning that adapts to the heritage site’s specific conservation management system, promoting stakeholder synergies, and enhancing adaptive management, etc.5. This essentially echoes Kareiva and Marvier’s14 pragmatic statement, which succeeds and develops the normative assumptions of conservation science referred to by Soulé15, i.e. conservation requires complementary strategies and, more importantly, people’s support for conservation goals to maximize conservation and development-. Therefore, to reach this conservation goal, there is an urgent need for nature-based solutions based on adapting the BZ of NWHS to harmonize the relationship between NWHS conservation and sustainable development of the BZ.

Finding solutions in the BZ that balance the environment and economic development is crucial to realizing the harmonious development of humans and nature in the NWHS. Nature-based solutions can effectively perform the combined functions of conservation and development16,17 In addition to preserving the natural beauty, biodiversity, and important geological sites, we also focus on community development and environmental justice14. In this context, agroforestry (AF) by combining trees with crops and/or livestock farming on the same land unit18, can be a land-sharing option in BZ for the conservation of species with high biodiversity value and the enhancement of habitat quality19,20,21, and highlights its unique value in terms of creating social and economic benefits for farmers18,22,23. More notably, the diversified ecosystem services of AF are directly aligned with multiple Sustainable Development Goals24,25, demonstrating its great potential to maintain the ecological balance of the NWHS BZ and promote economic development, aligning perfectly to harmonizing NWHS conservation and BZ development. From a conservation science perspective, AF has demonstrated the importance and utility of addressing the conservation role played by human alteration of landscapes in mitigating potential conflicts between BZs and intensive agriculture in NWHS26,27,28,29, essentially reflecting the centrality of coexistence as a cornerstone of conservation30. In this way, AF strengthens the overall ecological resilience of the NWHS, in addition to generating tangible economic opportunities for local communities31, further ensuring consistency and complementarity between conservation efforts and regional sustainable development goals32,33.

While the biodiversity conservation, community livelihood, and environmental values of AF in NWHS are well documented34,35,36,37 however, the contribution that AF plays in the BZ of the NWHS has not been recognized as a priority. More critically, the NWHS may have low environmental thresholds and an urgent need for sustained conservation efforts for the OUV (Outstanding Universal Value). How can the development of AF in the BZ be linked to the maintenance of the overall ecosystem stability and the promotion of the conservation of the geomorphological values of the heritage site, and can this be the best option for the NWHS? Previous attempts to answer this question have not yet reached generalizable conclusions, mainly because related studies have focused on AF’s in preserving the integrity and value of Karst World Heritage Sites and BZs development. For instance, studies by Chen et al.38 and Xiong et al.39 explore the connection between integrity preservation of Karst World Heritage Sites and AF development in BZs. Similarly, Luo et al.40 used field research interviews in the region to compare which AF development model adopted in the BZ of NWHS can better balance farmers’ interests and heritage value protection. Fang et al.41 explored and visualized the current research trends, hotspots, and structure of NWHS protection and BZ AF development using bibliometric analysis. Although these studies have claimed that AF is important for the protection and development of the Karst World Heritage Site, it is emphasized that AF has yet to be more fully answered and deeply understood before it becomes a definitive conclusion for conservation practices and BZ development of NWHS.

An analysis of current reviews and case studies found that AF does not effectively offer insights into heritage conservation and BZ development applications41,42,43,44. There is still insufficient evidence of conservation practices and development in the BZ of NWHS, especially in terms of the effectiveness of natural environmental protection, ecological maintenance practices benefits, and development applications. Indeed, these research orientations exacerbate the lack of clarity on the application of AF to BZ practices and heritage conservation. At the same time, there is still a lack of in-depth exploration of AF’s involvement in conservation actions and the practical manifestation of its potential advantages in the field of conservation management45,46,47. Here, we aim to bridge the knowledge gap on the importance of AF in the BZ of NWHS in terms of conservation practices and development applications, and will progressively finalize the work on the manuscript through the following steps. First, peer-reviewed articles were assessed to identify trends in the application of AF to heritage site conservation practices and development; Second, we examined whether AF has made significant progress or reached milestones in this area, focusing on specific research content; Finally, we analyzed the knowledge gaps of these achievements, emphasize the in-depth analysis of the content of the literature, and propose key scientific questions. Therefore, it is necessary to reveal the limitations of AF in heritage site conservation practices and development applications from a global perspective to enhance the social relevance of research and improve the effectiveness of conservation planning. Identifying the shortcomings of AF in conservation practices and development applications is key to developing new strategies and improving behaviors for conservation actors and AF practitioners.

Methods

Method framework

In this study, we used a systematic and comprehensive analytical framework originating in the field of health sciences to examine publications centered on AF in NWHS conservation practices and development applications. This framework involves a structured and exhaustive review process of existing publications, aiming to collect, assess, and synthesize all relevant research findings to address specific research questions, hypotheses, or phenomena48. As demonstrated by studies such as Fagerholm et al.49 and Mendonça et al.50, this framework is renowned for its logical rigor and practicality in terms of methodological operations. We chose this framework because it provides a structured approach to efficiently integrate and evaluate publication results for our review. The workflow outlined by this framework includes the following steps: define the protocol, review retrieval, assessment screening, analytic integration, and reporting results (Fig. 1).

Fig. 1
figure 1

Logic of literature review analysis.

Full size image

Workflow

Define the protocol

As the first step in the systematic literature review framework, the main focus is on clarifying the purpose of the literature review and defining its boundaries to ensure the fairness and reproducibility of the study. As below: (1) What is the trend in the increase of articles across the years? (2) What are the most and least common research themes? (3) What are the advances and landmark results of current research? (4) Around the results of the progress, what essential scientific inquiries should be explored in the future? By defining a protocol process, we strive to increase the transparency of the literature review and reduce possible bias and subjectivity. In doing so, the aim is to offer a thorough analysis and exploration of knowledge gaps in the application of AF to heritage site conservation practices and development.

Retrieval and review

Based on the research objectives and content, search characters were defined to comprehensively collect relevant literature and avoid bias. Searches were conducted in Scopus (1970-present) and Web of Science (1900-present) up to December 31, 2023. The search characters included: “Nature World Heritage” or “National Park” or “Reserve” or “Protected Area”, and “Buffer Zone” or “Agroforestry” or “Silvopastoral” or “Agrosilvopastoral”. This choice is based on several key reasons: (1) NWHS lacks a standardized nomenclature, exhibiting a wide array of titles. (2) The number of NWHS named “National Parks” and “Reserves” is high, with 82 sites specifically designated as “National Parks” and 19 as “Reserves”. (3) Numerous articles did not explicitly describe the international status of the study area in their titles, abstracts, or keywords, focusing solely on its location and name. Therefore, to collect as comprehensive a collection of relevant literature, we screened the research areas of the retrieved articles one by one. With this approach, we ensure the comprehensiveness and accuracy of the searches and reduce possible biases (Fig. 2).

Fig. 2
figure 2

Process, steps and results of literature retrieval.

Full size image

Assessment screening

The 2101 obtained publications were screened based on inclusion or exclusion criteria to ensure the rigor and accuracy of the review. The criteria for inclusion were as follows: (1) The search terms existed as a whole or as part of the publication’s title, keywords, or abstract; (2) For this manuscript, Scopus and Web of Science databases were selected, they are the largest peer-reviewed publications and citations that provide high quality literature and scholarly impact51,52; (3) The study area or subject of the article is an NWHS or a Cultural and Natural World Heritage Site; (4) Effective use of AF concepts, especially regarding various aspects such as AF in relation to climate change, soil, and water conservation, provision of habitats for plants and animals, livelihood development for farmers, and maintenance and management, which is closely related to its effectiveness in providing conservation practices and development applications. Exclusion criteria: (1) duplicate publications identified during the search process. (2) publications for which the full text could not be obtained. Additionally, we employed the “snowballing” method, which involves thoroughly reading a selected document to retrieve references provided in its citations53,54. Using this method, we obtained 11 publications, resulting in a total of 142 articles (Fig. 2). It should also be noted that title or abstract screening and full-text assessment were performed independently by two researchers using Rayyan QCRI software. Discrepancies were resolved through consensus discussions.

Analytic integration

The 153 publications (see supplementary document for details) screened were thoroughly analyzed and synthesized to gain a comprehensive understanding of the literature, identify trends, discrepancies or contradictions in research progress, landmark results, and key scientific issues. We analyzed and consolidated the categorization of publications in the following areas: (1) Identify the earliest year of publication, categorize the stages of publication, and assess whether the overall growth trend is stable; (2) Read the abstracts and keywords to determine the research themes, if unclear, conduct a thorough reading of the entire text to discover the main landmark achievements and cutting-edge research; (3) After thoroughly reading the full text, extract the key points of AF in heritage conservation practices and development applications; (4) By integrating the analytical steps, we analyzed and compared the key advancements and breakthrough results. (5) Core scientific issues have been identified and refined, seeking breakthroughs for future research work.

Results

Despite significant efforts by AF to participate in heritage conservation and development, there remains a substantial gap in research

In the retrieved publication results, the annual number of published articles fluctuated but showed a steady upward trend overall (Fig. 3). During the first phase, from 1992 to 2005, the number of publications was low, with a maximum of two articles per year, mainly reporting on the integration of traditional AF knowledge with modern conservation strategies for sustainable land use. However, the trend of research exploring the multiple benefits that AF provides to the NWHS has increased since 2006, the focus during this phase has been on discussing whether AF benefits the residents of heritage communities and whether it maintains the biodiversity of heritage sites. In Phase 3 (2016-2023), despite the number of publications grew rapidly during phase compared to the previous phase, the fluctuations show that research gaps are still evident. The research primarily focused on common problems of how AF can improve the ecological conservation function of heritage sites while also supporting the livelihood development of farming households, gradually deepening and diversifying. For example, how to quantify the ecological conservation effectiveness of AF, and to explore how the ecological awareness of community development management affects the protection practice and development application of AF in heritage sites.

Fig. 3
figure 3

Annual number of publications from 1992 to 2023 and delineates the segmentation of three phases.

Full size image

Insufficient inclusion of AF in conversations about the conservation-development relationship

By conducting an in-depth analysis of the 153 selected publications, the distribution of the main research themes was revealed. As in Fig. 4, 35% of the publications focused mainly on AF’s role in biodiversity protection, while 48% focused mainly on various aspects of plantation management in relation to the environment and community livelihood maintenance. Specifically, studies of AF’s conservation of species diversity at heritage sites cover a wide range of biological categories, such as birds, amphibians, anurans, and medicinal plants, showing that AF provides good habitat conditions for diverse species through land sharing55,56,57,58 (Fig. 4c). Despite AF making an important contribution to biodiversity conservation, to manage the quality of habitat provided by AF, it is necessary to analyze the crops (trees, cash crops, etc.), tree stand structure, and spatial structure on AF plots. These analyses became an important component of AF’s involvement in plantation management and community livelihood development maintenance, providing economic viability to the region through the development of large-scale AF plantations, such as cacao, cactus, etc., and, in conjunction with the tourism industry, providing additional means of development. In addition, aspects of policies and regulations, land use practices, and economic benefits have been used to assess and guide the adaptation of AF’s benefits and development practices in World Heritage Sites59,60,61 (Fig. 4b). More critically, the integration of AF into studies exploring the relationship of heritage conservation practices to development applications is relatively rare, accounting for only 14% of the total number (Fig. 4d). In reviewing the relevant studies, we fouvs focusing on BZs, accounting for only 8% of the overall studies (Fig. 4a).

Fig. 4: Illustrates the categorization of publication themes.
figure 4

a highlights the proportion of studies with BZs as the theme within heritage research; b refers to the categories under the theme of AF development applications and management in heritage sites; c details the analysis of AF in heritage sites regarding biodiversity conservation, specifically showing the number of studies focusing on plants, animals, and overall species; d represents the number of theoretical and practical studies focused on heritage conservation and development.

Full size image

Major advancements and hallmark achievements

Positive benefits of AF in heritage conservation practices

Economic benefit

Increase in local income. In the sustainable development of heritage sites, smallholder groups often combine agricultural production with ecological protection in AF to achieve optimal land-sharing options for multifunctional landscapes. This approach has become a key factor in the widespread adoption and economic gains made by farmers in heritage sites. First, AF provides diversified economic sources for local communities. Taking the cactus AF in Mexico’s Tehuacán Valley as an illustration, it generates income through the sale of cactus fruits and boosts the local economy by transforming these fruits into value-added products like jams, wines, and ice creams62. In addition, AF supplies communities with essential food and raw materials, such as timber, fodder, medicinal plants, and fruits, meeting the daily needs of households63,64.

Secondly, the diversity of natural vegetation around AF systems contributes positively to improving crop yields. In particular, connecting surrounding habitat patches with mosaic landscape mosaics provides essential ecosystem services, such as pollination and pest control, which increases yields65. In the long run, compared with a single agricultural model, AF not only better meets the development demands of farmers, and also ecologically friendly, supporting the local economy as well as promoting ecological sustainability. Through land-sharing options in such multifunctional landscapes, AF demonstrates great potential for economic and ecological win-win situations.

Expanding the physical vehicle for ecotourism in heritage sites. The ecotourism advantages attached to AF provide an important bridge in connecting nature and human interaction. Firstly, by providing unique landscapes and nature experiences, AF enriches the diversity of tourism experiences while promoting the harmonious coexistence of regional cultures and the natural environment. In Mexico’s Zapotitlán Valley, for example, local AF aids in ecotourism activities like birdwatching, enhancing tourists’ nature experience, and showcasing the profound cultural connections between humans and nature 5. Secondly, AF ecotourism significantly propels the development of BZs. In Rwenzori, Uganda, the region’s complex and dynamic AF landscape is one of the key attractors for tourism development, which in turn catalyzes economic prosperity and infrastructural enhancements66. Meanwhile, as the best way to complement heritage sightseeing tours and science education, AF should be appropriately regulated and managed while showcasing its unique appeal, emphasizing that the overdevelopment of AF for eco-tourism may pose a threat to landscape conservation66. Therefore, by balancing the needs of tourism and environmental protection, the ecotourism advantages attached to AF not only promote the economic development of heritage sites, but also significantly contribute to education and cultural exchange. This dual benefit makes AF ecotourism an effective means of achieving sustainable development.

Ecological benefit

Research has shown that AF conservation practices have significant positive impacts on heritage sites, particularly in terms of soil and water conservation and combating climate change. Initially, from the perspective of soil fertility and moisture maintenance, AF endeavors contribute to surface vegetation protection by preventing soil erosion, safeguarding against harsh winds, and maintaining soil resources67,68,69. Additionally, AF is crucial in the fight against climate change. The diversity and structure of vegetation can modulate the microclimate, reduce the intensity of solar radiation, and lower the rate of soil moisture evaporation, thereby regulating the regional climate and mitigating the impact of extreme weather events. For instance, the Gorongosa National Park in Mozambique, employing an AF system that merges forests or shrubs with crops, has been demonstrated to effectively mitigate the negative impacts of climate change70, it also reduces deforestation pressure on heritage sites71.

Social benefit

AF, with their regionally diverse landscape patterns and deeply rooted indigenous systems, not only offer a rich cultural tapestry closely intertwined with human well-being but also strengthen social cohesion, which is one of the primary reasons for their popularity among farmers. In terms of aesthetic value, AF ridge protected and fragmented areas72, enhancing landscape connectivity at the regional level. For example, in depressions, AF landscapes connect natural forests in karst formations, thereby increasing the heterogeneity of local spatial heterogeneity and maintaining overall landscape harmony73, while also creating a beautiful living environment for the local community.

In addition, within cultural traditions, certain flora and fauna in AF hold unique significance in local cultures. They play a pivotal role in traditional medicine, religious ceremonies, festival celebrations, and community interactions, contributing to the vitality of indigenous culture and strengthening social cohesion71,74. In everyday life, local farmers indicate that trees in AF offer recreational and spiritual experiences and hold aesthetic value, with their shade provides an ideal haven for cooling off and relaxation71,75.

Environment benefit

Provides niches for promoting biodiversity conservation. Traditional AF, dominated by homegardens and indigenous plants, plays a key role in maintaining the biodiversity of NWHS, not only providing essential habitats for endangered species, promoting their survival and reproduction, but also preserving the OUV of heritage sites. Firstly, Traditional AF provides a suitable living environment for regional plants. Observations from the plant communities in the Tehuacán Valley AF development in Mexico, such as the Apancles, Izotal, and Mexical AF systems, underscore a remarkable species richness mirroring that of natural forests, with about 85% being native species, indicating a high capacity for plant diversity conservation67,71,76.

Furthermore, AF provides habitats for the survival, migration, and reproduction of animals. Family gardens in the Tehuacán Valley of Mexico are very important for maintaining certain bird populations, as they offer food and resting spaces, thereby preserving bird diversity55,77. Compared to annual crops, AF maintains a higher diversity and abundance of soil invertebrates78. Therefore, understanding the interactions between different AF systems and natural vegetation and animals is crucial for maintaining the OUV of heritage sites.

Increase carbon sink reserves to combat climate change. Trees in AF systems not only help to absorb carbon dioxide from the atmosphere but also play a crucial role in combating climate change and ecosystem management, by absorbing more carbon from the soil through roots and litter that penetrate deep into the ground. Studies have shown that trees have a high potential for soil carbon sequestration, and also improve organic carbon in soil aggregates. For example, coffee AF in the tropics significantly increases soil carbon storage79,80. A research in Mexico revealed that scenarios with AF practices were found to have higher carbon sequestration by assessing the suitability of different land uses in the BZ81. Despite the relatively small area of AF in the BZ, it has played a positive role in improving soil carbon storage in heritage sites.

Opportunities and progress in AF development on the BZs of heritage sites

AF development in the BZ can take into account the ecological environment protection of heritage sites, while generating economic benefits for surrounding areas, effectively alleviating population pressure and poverty. Although BZ is gradually gaining attention and importance as an indispensable part of the sustainable development of heritage sites, its development still faces major obstacles, including strict protection regulations and insufficient investment and technical support. In addition, community residential development is often misinterpreted as a consumer of heritage resources that may threaten the heritage environment. To address these issues, AF initiatives are adopted within National Parks and their adjacent territories to reduce the reliance of farmers on woodland resources82. This is the main problem that had to be solved at the beginning of the development of AF in the BZ, how to balance the conflicts in resource use between the protected area and surrounding farmers. As this issue is alleviated, research began to focus on the maintenance of the heritage environment by AF. For instance, the Tehuacán-Cuicatlán Valley in Mexico maintains vegetation cover through AF systems, which help mitigate forest resources and promote the overall sustainable utilization of forestry and AF systems83. The Sundarban in Bangladesh protects natural mangroves through AF practices, bolstering environmental and biodiversity preservation, and addressing the challenges of climate change71.

As research continues to deepen, academics have begun to explore effective ways of utilizing the land surrounding conservation areas. AF, as an effective means of land management and heritage conservation74, can mitigate the negative impacts brought about by regional development, such as increasing vegetation cover, maintaining soil fertility, and protecting local water resources84. Integrating traditional local AF systems enhances biodiversity conservation and provides a source of income for local farmers, thereby addressing issues of sustainable livelihoods40,71. Consequently, the AF development not only serves as a bridge connecting ecology, economy, and culture55. It embodies a critical perspective for thoroughly examining and understanding of the intricate interplay between humanity and nature, regional advancement, and heritage conservation, enhancing the ecological protection buffer function of the BZ.

Management and maintenance of AF in BZ of NWHSs

AF plays is crucial in BZs of heritage sites, achieving the twin goals of heritage conservation and community development through land-sparing/sharing. It is necessary to explore the development of traditional industries in the context of heritage protection85. Firstly, from the perspective of heritage management, AF, as a key land-sparing measure in realizing BZ concept objectives86. By adopting a comprehensive protected area-BZ management approach87, an eco-friendly approach to industrial development can be explored.

Secondly, studying and overcoming the social and environmental factors that limit land sharing in AF can help develop management strategies to promote the development of AF. This includes environmental conditions, local culture, economic motivations, and community development aspirations, among others72. Adjusting species composition and spatial structure within AF systems through diversified management methods67,88 (incorporating local traditional cultures and farming practices, utilizing indigenous knowledge for management70,72,84, enhancing community participation and reducing conflicts between resource use and conservation goals63.

Understanding and respecting the worldviews, values, and needs of local farmers is key to ensuring the effectiveness and sustainability of AF management practices. Emphasis is placed on the dynamics of power relations and inequalities in regional development, especially in terms of resource utilization and distribution of benefits86. Adoption of sustainable land use practices is consistent with heritage conservation objectives and reduces threats to ecosystem integrity85. Overall, the management and maintenance of AF in heritage sites need to be contextualized and scientifically managed to support the environmental sustainable of heritage sites.

Discussion

Reasons for differences in research stages, themes, and comparison of research progress

Our analysis shows that the publication year displayed a fluctuating increase in the second and third stages (Fig. 3). Research on AF in the BZ of NWHS must urgently prioritize a deeper exploration of the connection between conservation practices and development applications. The background factors of different research stages’ divisions provide a basis for our conclusions. In the initial stage (1992–2005), due to food security issues caused by population growth and resource scarcity in the 1990s89, research focused on protecting heritage OUV while benefiting community farmers in the BZ90,91, which inspired attention to the environmental protection and socioeconomic benefits of AF. In the second stage (2006-2016), with the convening of the 2008 Davos Expert Meeting on World Heritage Sites and BZs, research shifted its focus to the protection of biodiversity through AF92, the relationship between wildlife and AF surrounding heritage sites93, and how to maximize the benefits of BZs through AF management90. These discussions may explain the fluctuating growth of research during this stage, marking the beginning of exploring the positive impact of AF on the OUV of heritage sites. The final stage (2017–2023) is diversified. Research in this phase responded to the United Nations Sustainable Development Goals18, covering quantification of conservation effectiveness, community participation, ecological awareness, and the integration of policy and practice84,85,94.

Despite the fluctuating growth in annual publications, we revealed an imbalance in the research themes of biodiversity conservation and community livelihood development, which accounted for 35% and 48%, respectively (Fig. 4). This imbalance can be explained by the following factors: first, AF provides rich ecological niches and habitat conditions through the ecological interactions of trees, crops, and livestock, which are beneficial for the conservation of sensitive species18,43,95. Compared to intensive agriculture, the structure of AF is more similar to forests, making it an effective option for achieving better buffering and diversification of livelihoods in the BZ of heritage sites96,97. Additionally, AF managed by smallholder groups creates multiple mosaic landscapes and connects multiple patches, providing connectivity for ecological corridors98,99, which supports the integrity of the environment around heritage sites and species protection39. Although the volume of publications concerning BZs is still insufficient, there is an urgent need to integrate the research frameworks for AF within the context of the relationship between sustainability practices and development applications, in preparation for future conservation management research.

From the summary of research progress and landmark achievements, a large number of studies have explored the role of AF in sustaining the biodiversity value of NWHSs in relation to criteria (ix) and (x). Biodiversity is crucial for maintaining ecosystem health and function, and NWHSs are often the last habitats of endangered species, attracting the attention of many researchers46,72,84. Another important reason is that AF helps to address the livelihoods of farmers in the BZ100. Under the premise of not threatening the preservation of the OUV of heritage sites, AF can provide livelihoods and sources of subsistence34, while reducing deforestation pressures and supporting the sustainable growth of the local economy, which is particularly important in heritage sites in developing countries. Therefore, the conservation and development of AF in the BZs of heritage sites has become a major focus of research, closely related to the conservation management of OUV in heritage sites.

Essential scientific questions that require resolution: emphasize the role of AF in the conservation of geomorphological values(vii) and aesthetic values(viii) of NWHSs

The ecological benefits of AF in the BZs of heritage sites are mostly focused on biodiversity conservation, with less exploration of its positive benefits in terms of geomorphological values and aesthetic values. It is clear from Fig. 4 with section “Environment benefit” that the current study focuses more on the important role that AF plays at different scales of biodiversity conservation and contributes positively to ecological restoration. In contrast to the value of AF in conserving biodiversity in the BZ of heritage sites77,92,101, heritage sites based on geomorphic and aesthetic values consider that geomorphic development and aesthetic features are the result of long-term evolution by nature and have a certain stability. However, this is not the case, as many geomorphic landscapes with rocky features are very fragile102 and easily disturbed by human activities103, as well as the aesthetic values that they exhibit are often subject to socio-cultural and ecological influences104. Williams argues that biological restoration is not a major issue when a NWHS is inscribed, grounded in criteria (ix) and (x)105. However, However, when World Heritage sites are inscribed based on criteria (vii) and (viii), biological restoration needs to be emphasized and more attention should be paid to geodiversity 4. Similarly, when a region is designated as a heritage site due to its natural beauty, it is important to preserve all areas that are vital to maintaining aesthetics 105. Therefore, we should pay more attention to how AF affects the geomorphology and aesthetic value of NWHSs through BZs.

Focus on the positive benefits of AF practices in BZs on OUV, integrity, and protection management of heritage sites

Conservation efforts extend beyond merely safeguarding the OUV, but also include maintaining the integrity of the heritage site and effective protection management. Currently, there are significant gaps in AF’s ability to achieve these conservation goals in the BZs of heritage sites. Although the role and benefits of AF in BZs for biodiversity conservation, the integrity conservation of heritage sites should focus on both boundary integrity and the integrity of ecology and landscape106. Current research has only explored the relationship between BZ AF of heritage sites and the integrity of karst World Heritage sites38, and the fact that the development of AF in the BZ is still lagging behind the conservation of heritage sites integrity39. However, these studies did not thoroughly analyze the effects of BZ AF on the ecological integrity of heritage sites, and there is still an urgent need to explore for answers. Preserving the ecological integrity and ensuring effective conservation management of heritage sites requires greater consideration of the interests of local farmers, who are mostly located in the BZs of heritage sites for their livelihood activities. Therefore, in order to minimize conflicts between farmers and heritage sites, it is important to focus not only on the ecological buffering role of BZs107 but also to consider the economic, social, and cultural benefits they bring108. Combining the multiple benefits provided by AF in the BZ of heritage sites with the connection between the heritage sites’s OUV, integrity, and protection management to increase the diversification of local livelihoods and encourage greater local involvement in heritage conservation efforts.

A comprehensive and interdisciplinary framework should be constructed to systematically analyze and assess the impacts of AF on the overall ecosystem health and sustainability of BZs of heritage sites

The role of AF practices in providing ecological benefits, including climate regulation and maintaining soil and water, has been widely studied and recognized (section Ecological benefit). However, when we focus on the role of AF within BZs in maintaining the overall ecosystem health and sustainability of heritage sites, the existing research seems inadequate39. Current research tends to focus on reductionist approaches to biodiversity conservation, with less exploration of the role of AF in promoting overall ecological health. For instance, the study by Wang et al examined the potential of AF in BZs for soil conservation and water storage through soil sampling and moisture sensors, but failed to further explore how these factors affect the complex relationships between heritage environments, and did not propose specific strategies for AF’s application to conservation practices and development in BZs of heritage sites68. On the flip side, Luo et al. assessed the environmental costs, carbon emissions, and net output of AF under different cropping patterns, but it is still insufficient in understanding how AF under different patterns can provide multiple natural environmental benefits, positive interactions with heritage OUV conservation, and BZ impacts40. In order to comprehensively evaluate the diverse benefits provided by AF, drawing on Therond et al.‘s proposed common analysis framework and diversified models for integrating AF systems would be an effective approach109. This method can help us gain a deeper understanding and analysis of the inherent connection between the conservation practice and development application of AF in the BZs of heritage sites, thereby better achieving the “win-win” goal of ecological and economic benefits.

Enhancing farmer-led restoration strategies to improve the management of AF in heritage sites, strengthening the role of AF in promoting socio-economic benefits, and designing differentiated conservation and development programs

From sections “Ecological benefit” and “Opportunities and progress in AF development on the BZs of heritage sites” of the articles, it is concluded that the initial and economic benefits of AF development in the BZ of the heritage sites are more considered to satisfy the livelihoods and development of the farmers in the region. We acknowledge that local farmers, as the main stakeholders in heritage conservation, their livelihoods are crucial for heritage OUV conservation and sustainable development. However, the existing AF management in the BZ fails to adequately enhance farmers’ participation in the combined land-saving/sharing approach to conservation management, as discussed in section “Management and maintenance of AF in BZ of NWHSs”, and there is a lack of consideration from the farmers’ point of view in the current policy formulation and management practices. This seems to contradict the emerging assumption of conservation science14, that conservation goals that lack farmers’ participation and support struggle to achieve lasting success. Effective responses to land degradation, undertaking conservation missions, improved food security, and poverty reduction, among others, can be achieved as a result of farmer-led restoration strategies110. Therefore, understanding the various factors that influence the behaviour of farmers in the BZ in carrying out AF practices provides an effective guide for developing AF participation in BZ conservation and development.

The development of ecotourism in AF in BZs has great market potential, combining the traditional ecology of the region with its resources, and designing a model of AF eco-tourism in the BZ, which is both ornamental and educational

In conjunction with the discussion in section Economic benefit, AF ecotourism in the BZ provides an integrated framework for sustainable heritage development, but there are many problems with the conservation and management of heritage sites. For example, Iacopino et al. proposed an integrated land governance model to address the long-term development of AF ecotourism by analyzing two management approaches (strict protection within the park and generous land use outside the park) for the Rwenzori Uganda Heritage Site66. Although this method is theoretically feasible, it may overlook an important fact in practical applications: changes in land-use practices in BZs may have an impact on ecosystem function and biodiversity within heritage sites. To effectively manage AF ecotourism in BZs, a holistic and comprehensive approach is needed. Firstly, the use of RS and GIS tools can provide managers with the ability to map the distribution of AF landscape points, vegetation cover, and land use data in the BZ, and these scientific methods can accurately calculate data on environmental change, providing a solid foundation for assessing the impact of AF ecotourism. Secondly, Tools such as the InVEST model, ecological sensitivity assessments, and tourism sustainability indices allow for the modeling and prediction of ecological impacts of tourism development in different regions, offering crucial insights into spatial dynamics amid tourism expansion and landscape risk111,112,113. Finally, by integrating traditional ecological knowledge and environmental conditions, sustainable AF ecotourism models and locations should be planned in the BZ. This provides the feasibility of promoting the sustainability of AF ecotourism in the BZ, which is compatible with the overall objectives of heritage conservation, while designing landscapes of aesthetic ornamental value and realizing the significance of heritage literacy and environmental education.

Bridging the knowledge gap regarding AF’s role in the conservation and development of BZ

In recent years, numerous reviews have explored AF’s role in conservation practices and development applications, seeking to close the knowledge gap in the understanding of the role of AF in these two areas. For instance, systematic reviews have highlighted AF’s significant role in the conservation and development of mountainous and ecologically fragile areas has been highlighted54,111. Meanwhile, Santoro et al. assessed the role of AF in the Globally Important Agricultural Heritage Systems program, while Kumar and Kunhamu explored conservation and development strategies from the perspectives of specific tree species, crops, and regions, respectively112,113. However, the report by Chen et al. emphasizes AF’s importance in conserving the integrity of Karst World Heritage sites and fostering the development of BZs, but there are still more shortcomings in revealing the effectiveness of AF participation in other NWHS protection and development38. Compared with Chen et al.‘s research, Fang et al.‘s analysis is more comprehensive, discussing current research trends, hotspots, and preliminary issues on this topic, but it focuses on quantitative analysis, with insufficient summary of the current research status and discussion of the implications for future research41. Our study bridges this knowledge gap from a systematic and comprehensive perspective, focusing on understanding AF’s advancements in conservation efforts and development applications within heritage site BZs, but also by pointing out the related key scientific issues, in order to bridge the obvious knowledge gap that exists. It also fills the gap in strict observation and reporting on the conservation practices and development applications of the BZ in NWHS in the past, which is critical to understanding the concentric circle effect of AF in conservation practices and development applications played by NWHS BZs (Fig. 5).

Fig. 5
figure 5

Concentric circle effect of AF development in NWHS BZs.

Full size image

Limitations of the research

Despite our efforts to comprehensively collect and analyze literature that fits the research theme, there are still some limitations in the research process. Firstly, this study relies solely on the Scopus publication database for searching relevant publications. Using multiple non-English publication databases might yield more literature114,115, which could further expand and enrich our research. Secondly, despite the use of the complementary technique of “snowballing” the identification of literature, only academic papers that we could identify and translate, and that were noticed during the writing process, were analyzed. This might have resulted in the omission of relevant literature written in less common languages that still align with the research theme116,117. In addition, although we considered multiple search terms as fully as possible, the fact that some of the studies did not specify whether their study area was an NWHS or a Cultural and Natural World Heritage Site, or omitted the use of term AF through other local designations for AF (e.g., Dehesas, Taungya, and Quesungual, etc.), may have contributed to the fact that some relevant literature was not included in our analysis. Finally, there may be a degree of error in the article screening and analysis process118,119,120. In addition, after analysis, we found that the AF composite strategy is mainly applicable to the BZ of heritage sites with human farming activities, and is operative in the terrestrial ecosystem type of heritage, whereas other conservation and development measures need to be applied to marine, glacier, and volcano types of heritage. Nonetheless, given the scope and conditions of the current study, these limitations are still within an acceptable range. By using a systematic literature review method, we have been provided with relevant information on the recent trends and unresolved key scientific issues in the conservation practices and development applications of AF in NWHS.

Conclusion

BZs play an increasingly important role in ecological conservation and community livelihood development in NWHS. AF, as a land-sharing measure integrating intensive production, biodiversity protection, and ecosystem services, is consistent with the vision of achieving ecological needs and high socio-economic standards in BZs. In summary, our research indicates that although previous studies have had knowledge gaps and thematic imbalances, there is an emerging body of research is examining the connections between conservation practices and development applications of AF within the BZ of NWHS. These studies have helped to provide insight into the dual impacts of AF in BZs on environmental preservation and community development, providing a solid information base for the field.

On this basis, this review reports multiple key developments and achievements, including the opportunities for AF development in BZs, its multiple benefits for heritage site conservation, as well as effective ways to manage and maintain AF in BZs. These findings validate AF’s distinct contribution to conservation efforts and development initiatives within the BZs of heritage sites. In addition, we identified critical scientific issues in AF that require urgent attention in both conservation and development, which echoes the progress we reported. Specifically, these issues involve extending AF’s conservation of biodiversity to comprehensive conservation management of geomorphological values and aesthetic values, assessing the comprehensive benefits of managing AF through an interdisciplinary framework and multidimensional assessment, and further exploring its conservation and development potential for resource endowment differentiation, sustainable planning, and differentiated conservation strategies, thus pointing to specific directions for future research. Although there are various options for the conservation and community development of BZs in NWHSs, AF is undoubtedly the best option for realizing the concentric circle effect, and it is time to break down the walls that close in.