*Review* **Mainstreaming Smart Agroforestry for Social Forestry Implementation to Support Sustainable Development Goals in Indonesia: A Review**

**Dona Octavia 1,\*, Sri Suharti 1, Murniati 1, I Wayan Susi Dharmawan 1, Hunggul Yudono Setio Hadi Nugroho 1,\*, Bambang Supriyanto 2, Dede Rohadi 3, Gerson Ndawa Njurumana 1, Irma Yeny 1, Aditya Hani 1, Nina Mindawati 1, Suratman 4, Yelin Adalina 5, Diana Prameswari 6, Etik Erna Wati Hadi <sup>1</sup> and Sulistya Ekawati <sup>7</sup>**


**Abstract:** The increasing need for forest resources and cultivated land requires a solution in forest management to realize sustainable land use. Smart agroforestry (SAF) is a set of agriculture and silviculture knowledge and practices that is aimed at not only increasing profits and resilience for farmers but also improving environmental parameters, including climate change mitigation and adaptation, biodiversity enhancement, and soil and water conservation, while assuring sustainable landscape management. SAF, a solution for land management systems to reduce the rate of deforestation, is a smart effort to overcome the food crisis and mitigate climate change that is prospectively applied mainly in the social forestry area. Optimized forest land utilization could be achieved by implementing SAF and applying silvicultural and crop cultivation techniques to optimize productivity and meet sustainability and adaptability goals. This paper reviews the existing conditions, opportunities, and challenges in the mainstreaming of SAF in social forestry implementation to support the Sustainable Development Goals in Indonesia. Mainstreaming SAF should include policy innovation and regulation implementation, the use of appropriate technology, and compromises or trade-offs among benefits, risks, and resources. SAF is a strategy to revive the rural economy and community prosperity through the optimal use of local resources as well as a form of smart landscape and land-use management that has significant roles in soil and water conservation, bioenergy, climate change responses, and enhanced biodiversity conservation.

**Keywords:** agrisilviculture; climate change; food security; livelihoods; tropical forest management

**Citation:** Octavia, D.; Suharti, S.; Murniati; Dharmawan, I.W.S.; Nugroho, H.Y.S.H.; Supriyanto, B.; Rohadi, D.; Njurumana, G.N.; Yeny, I.; Hani, A.; et al. Mainstreaming Smart Agroforestry for Social Forestry Implementation to Support Sustainable Development Goals in Indonesia: A Review. *Sustainability* **2022**, *14*, 9313. https://doi.org/ 10.3390/su14159313

Academic Editor: Victor Rolo

Received: 9 June 2022 Accepted: 27 July 2022 Published: 29 July 2022

**Publisher's Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

**Copyright:** © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

#### **1. Introduction**

Indonesia has the third largest area of tropical forest [1] as well as the second largest biodiversity and the second highest number of indigenous medicinal plants in the world [2]. It covers 10% of the global tropical forest with 50% of the world's biodiversity, flora, mammals, amphibians, reptiles, primates, and birds, and provides 25% of the medicinal plants for human health. Blessed with high rainfall throughout the year, Indonesia tropical forest regulates water supply for agriculture, domestic needs, and industries. Meanwhile, more than 25 thousand villages are close to the forest area, with a total population of about 9.2 million households, of which 1.7 million are classified as poor. Tropical forests store about 30% of the world's carbon and Indonesia's forest has the most significant tracts of rainforest and has become a pillar toward Agenda 2030 for Sustainable Development Goals (SDGs) [1]. In spite of its potential, Indonesia's tropical forest management encounters some challenges due to the high community demand for forest resources, including the need for land in state-owned forest areas. Meanwhile, [3] states that conversion to agricultural land is the main cause of deforestation, therefore, it faces a high challenge in preserving the existence of forests. In addition, the demand to meet community needs requires proper strategies to manage forest resources. Several efforts have been developed by the government of Indonesia for these two interests through several forest management policy changes including the Social Forestry (SF) Program.

Along with policy changes in forest management, the deforestation rate in 2017–2018 has decreased by 0.49 million ha [4,5] as forest management policies became increasingly popular in the Social Forestry scheme. Deforestation decreased by 75.03% in the 2019–2020 period, covering an area of 115.46 thousand ha. This achievement is the lowest deforestation rate in recent history. Subsequently, to provide more opportunities for the community to gain access in forest management and get direct benefit from it, the Indonesian government issued the Minister of Environment and Forestry (MoEF) Regulation 9/2021 concerning Social Forestry Management. It is a derivative of Law 11/2020 concerning job creation and Government Regulation 23/2021 concerning forestry management. In this regard, Regulation of MoEF No. 8 of 2021 concerning forest management and preparation of forest management plans as well as forest utilization in protection forests and production forests encourage the increased productivity of forest land through the application of agroforestry and forestry multi-business. Utilization of state forests, especially protection forests and production forests, can be carried out through program activities in the Social Forestry schemes.

SF is a sustainable forest management system implemented in state forests or private/customary forests by local or traditional indigenous communities as the main actors to improve well-being, environmental balance, and sociocultural dynamics in the form of village forests, community forestry, community plantation forests, traditional forests, and forestry partnerships [6–8]. A review of the Indonesian literature showed that social and economic perspectives on SF development received more attention than environmental perspectives. Economic opportunities are deemed to be the main benefit of social forestry, while social and environmental challenges seem to be the major barriers to implementation [8]. Three main keys in the SF program are how to improve the institutional governance, forest governance, and business governance. SF management needs innovation, technology, and collaboration to provide broader benefits for communities in terms of forest land and the use of forest products.

Agroforestry is a silvicultural plan that responds to the challenges of sustainable forest management, especially adjacent to community settlements. Agroforestry is a prospective solution to reduce the rate of deforestation and overcome the food crisis problem [3,9]. This is an integrated approach to a sustainable land-use system (traditional and modern) in which there are interactions between ecological and economic components (timber/forestry plants with seasonal/perennial tree crops, livestock or fisheries inside or outside forest areas). Agroforestry provides ecosystem services, including climate change mitigation and benefits for smallholders, as well as prospects for sustainable food production [10–12].

In the context of Indonesia, the legal framework for agroforestry is laid out in Government Regulation 23/2021 and MoEF Regulations 8 and 9/2021. These regulations state that agroforestry involves optimizing the utilization of forest land through a combination of planting patterns of forest trees and agricultural tree crops and/or animals to increase the productivity of forest land without changing its main function. This is a suitable utilization of forest areas and products in SF management to increase forest land productivity and support meeting the needs for food and energy, medicine, and/or fodder. It is also an alternative solution to resolving social and land conflicts and/or increasing local community income [6,7,13]. Agroforestry offers a great opportunity to support the SDGs for synergy in the agriculture and forestry sectors in the areas of food, energy, water, and income [14,15]. Agroforestry technologies implemented according to an SF scheme have many advantages in both ecological and economic aspects that support the achievement of several of the SDGs, specifically #1 (no poverty), #2 (zero hunger), #3 (good health and well-being), #5 (gender equality), #6 (clean water and proper sanitation), #7 (affordable and clean energy), #13 (climate action), and #15 (life on land).

Another benefit of agroforestry development is the availability of new off-farm jobs in rural areas, such as drying crop yields, wood cutting, and making furniture. In addition, new jobs can also benefit women, as it opens up opportunities for them to be involved in production activities, which will increase gender equality and ultimately contribute to improving the rural economy. Furthermore, agroforestry can also contribute by encouraging community sociocultural development and participation through collective action for people to learn together, rediscover the power of traditional wisdom and knowledge, and then integrate all of that with the development of new knowledge and technology.

Smart agroforestry (SAF) is actually AF "plus" or good AF practices, a set of agriculture and silviculture knowledge and practices aimed not only at increasing profits and resilience for farmers but also at improving environmental parameters, including climate change mitigation and adaptation, biodiversity enhancement, and soil and water conservation, while assuring sustainable landscape management. SAF has subsequently evolved into a science-based pathway for both traditional and modern agroforestry to achieve important goals for natural resource management and socioeconomic benefits. The SAF model has been recommended for development in social forestry areas [7,13], with the aim of providing access for communities around forests in the form of forest farmer groups, facilitated with an extension to enhance farmer capacity and links to capital and the market. The use of SAF technologies has proven to have the potential to improve productivity and livelihood in compliance with environmental guidelines while enabling subsistence and small-scale communities to improve their resources. From the economic perspective, SAF technologies can increase economic resilience through product diversification, especially by increasing the profitability of agroforestry.

The involvement of the community in collaboration with government agencies and the private sector is also important to achieve SAF goals. This is mainly to lower the risk of overharvesting activities on common-pool resources. In the context of Indonesia, several legal frameworks are beneficial for the government and private sector to formulate regulations, programs, and strategies to help the community manage its natural resources with support from those institutions. Thus, well-structured formal and informal institutions provide a better collaborative attitude, good management, and natural resource protection, as well as better livelihoods.

Mainstreaming SAF within the SF program becomes a promising alternative to accommodate the interests of good management and natural resource protection as well as better livelihoods. Furthermore, tree planting in the SAF model has become the latest trend in overcoming the climate crisis, motivating legions of people around the world to utilize the incredible carbon-absorbing potential of trees. In this regard, Indonesia signed the Paris Agreement (PA) in April 2016 and ratified it through Law 16/2016 in October 2016, followed by enacting its first nationally determined contribution. As climate change intensifies, Indonesia continues to seek a balance between current and future development and poverty reduction priorities.

We aimed to review and provide information on the existing conditions, opportunities, and challenges in implementing SAF within SF to support the SDGs in Indonesia. The paper was based on a synoptic review approach to SAF- and SF-related publications and nationwide experiences. The reviewed materials come from international and national research papers, regulations, technical reports, and relevant books. The scope of the review covers the historical context of regulations, institutions, and policies of SAF and SF management, and discusses the implementation of SAF in relation to the SDGs, including its benefits in terms of increasing community prosperity, soil and water conservation, climate change adaptation and mitigation, biodiversity conservation, landscape-based resource management, and best practices for agroforestry in some areas.

#### **2. Agroforestry and Social Forestry: Historical Backgrounds**

*2.1. History of Agroforestry and Social Forestry Development*

Agroforestry and social forestry may be two inseparable terms. While agroforestry refers to land-use techniques by which woody plants are combined with agricultural crops or livestock to form ecological and economic interactions between various existing components [16], social forestry emphasizes the strategy of strengthening the tenure of forest management by granting access and management rights over forest areas to local communities (MOEF regulation 9/2021). Social forestry prioritizes the application of agroforestry techniques in land management in order to achieve two main objectives, community welfare and forest resource sustainability. The implementation of agroforestry in SF has been highly encouraged, as it is believed to contribute to the achievement of the Sustainable Development Goals [16].

Although research on agroforestry began to be popular around the 1980s [17], agroforestry has been practiced in Indonesia for a very long time. Farming systems that are known by local names, such as *parak*, *pelak*, *repong damar*, *tembawang*, *simpukng*, *talun*, *wono*, *tenganan*, and *amarasi* in various regions, basically reflect agroforestry practices that have become part of community culture in land management [16]. Local community wisdom has viewed the agroforestry system as a land management approach that can meet daily needs while proving to be able to conserve natural resources, including forests.

The concept of social forestry, on the other hand, was introduced in Indonesia in the 19th century. The Dutch colonial government in the late 1890s introduced the *taungya* or *tumpangsari* system in Java [17]. The taungya system was a model of granting access (cultivation rights) to farmers over teak forest areas in Java. Farmers were allowed to cultivate food crops between young teak plants up to a certain plant age. Farmers could enjoy the results of their cultivation but were obligated to look after the young teak plants. More recently, initiated by the 8th World Forestry Congress in Jakarta, with the theme "Forests for People", community rights to forest resources have received greater attention among policy makers, bureaucrats, scholars, and forestry practitioners at the national level [18]. The attention of these various groups was also triggered by the increasing tenurial conflict between local communities and the government and forest area permit holders in land uses.

Various initiatives to give the community a greater role in managing forest areas then emerged. Perum Perhutani, with the assistance of various donors in 1985, built 13 pilot models of social forestry in several areas in Java, while other pilot models were built around the early 1990s in South Kalimantan, South Sulawesi, and West Irian [19]. Analyses of these pilot practices indicated that social forestry can potentially improve the welfare of forest-surrounding communities and resolve tenurial conflicts, but there are weaknesses in terms of equal rights (between community groups and Perum Perhutani) and a lack of community interest in investing in the long term, due to uncertain continuation of land management rights [20,21].

With the establishment of the Directorate General of Land Rehabilitation and Social Forestry under the Ministry of Forestry (MoF) in the early 1990s, community involvement in forest area management began to receive better attention in terms of the policy and regulatory aspects. However, as stated in [22], at that time, the government had not given forest management rights to the community. Forest management was still dominated by the "forest first" approach, where community involvement was more directed toward forest rehabilitation programs [23]. The limited budget and human resources for the implementation of forest rehabilitation were the main considerations for community involvement in the management of the forest area, and as a result, the community's tenurial rights to manage the forest area have not been fully granted.

Community involvement in the early era of social forestry programs can be seen from several introduced policies, such as HPH Bina Desa, Community Forestry, and People Plantation Forest [24]. In 1995, the government introduced the Community Forestry (CF) program. In this program, the community was actively involved in forest management activities and obtained the right to use non-timber forest products (NTFPs). The CF management permit was determined based on a contract agreement between the applicant (individual, community group, or cooperative) and the local Provincial Environment and Forestry Service. Although the policy still focused on community activities in forest rehabilitation, the program was successfully implemented through the granting of CF concessions in the Nusa Tenggara region, with an area of approximately 92,000 ha [25].

The concept of social forestry that is close to the current practice might have existed since 2003. At the International Conference on Livelihoods, Forests, and Biodiversity, at a series of Conference of Parties meetings in Bonn in 2003, the official representative of Indonesia introduced a social forestry program with a more comprehensive approach that included ideology, strategy, and implementation in the context of community empowerment in forest resource management. The program provided access for local communities to manage forest areas in order to improve their welfare and conserve forests at the same time [24]. In 2006, the government launched the Community Plantation Forest (Hutan Tanaman Rakyat or HTR) program, which was linked to its efforts to alleviate poverty (propoor), create new jobs (projob), and increase economic growth (progrowth) [26].

Subsequently, in 2015, the development of social forestry entered a new phase. The 2014–2019 Working Cabinet, led by President Joko Widodo, merged the Ministry of Forestry with the Ministry of Environment to become the Ministry of Environment and Forestry (MoEF), and one of the Directorate Generals formed under the MoEF is the Directorate General of Social Forestry and Environmental Partnerships (DG PSKL). The establishment of DG PSKL in 2015 significantly accelerated SF development. Under the Nawa Cita program promoted by the Presidential Cabinet, the DG PSKL set a target for developing social forestry in Indonesia, covering an area of 12.7 million ha, through five SF schemes: community forestry, village forest, people plantation forest, private/customary forest, and forestry partnership [27]. From the emerging ideas of SF up to 2014, the total established SF area was only around 0.4 million ha, while the current total established area reached 5.004 million ha [28].

Similar to SF, agroforestry policies ideally should be well-organized and institutionalized. Many successful collective actions on forest and land management in Indonesia were associated with the implementation of good agroforestry practices by communities [29]. In Indonesia, there are at least two ministries that have been pioneers in the development of agroforestry: the Ministry of Environment and Forestry (MoEF) and the Ministry of Agriculture (MoA). Although the mandate of the MoEF is within the forest area and the MoA is more focused on areas outside forests, there are many overlapping areas on the ground that require close coordination between the two ministries.

Agroforestry has a potential role in increasing farmers' income and sustainable landscape management [30]. Forest ecosystem services significantly support community livelihoods and provide very important sources of livelihood for indigenous people [31]. In other places, such as Paru Village Forest, West Sumatra Province, community plantations

of rattan within the agroforestry model show promise as a source of economic income [32]. The application of best practices of agroforestry in SF areas seems promising to reduce people's dependence on expanding the opening of forest lands, and thus could be a better alternative for reducing deforestation as well [33,34]. Last but not least, the integration of the market chain is also among the crucial priorities in developing best practices of agroforestry [35].

#### *2.2. Rules and Regulation*

The legal system in Indonesia has a clear hierarchical structure for its rules and regulations, including the Constitution, laws, government regulations, ministerial regulations, and regulations of the Director Generals. The regulatory hierarchy covers everything from philosophical principles to tactical and technical aspects of the implementation of government policies and programs. The system of rules and regulations applied to the agroforestry and social forestry sectors also follows this legal system.

Four main laws are used as reference rules for implementing agroforestry and SF: Law 41/1999 on forestry [36], Law 32/2009 on environmental protection and management [37], Law 37/2014 on soil and water conservation [38], and Law 11/2020 on job creation [38]. Observing the substance of the four laws, what is interesting is that three of them, Laws 41/1999, 32/2009, and 37/2014, seem to be in a diametrically opposite position to Law 11/2021. On the one hand, the three laws regulate how forests and land are managed, with a strong sense of ecological protection, while on the other hand, the law on job creation encourages investment for economic purposes. Based on this situation, implementing SAF becomes important and strategic as a counterbalance to achieving the mandate of the four laws. On the one hand, it ensures that the mandates of Laws 41/1999, 32/2009, and 37/2014 can be fulfilled, while at the same time ensuring that the objectives of Law 11/2021 regarding investment and job creation can also be fulfilled. What then becomes important is how the derivative regulations of the four laws can regulate and provide a legal umbrella for the implementation of SAF as a balance between the two poles of interest.

Under these laws, there are various government regulations (PP) that are the source of various derivative regulations focusing on agroforestry and SF. Some of the most relevant rules and regulations around agroforestry and social forestry are presented in Figure 1. They include PP 26/2020 on forest rehabilitation and reclamation and PP 23/2021, concerning the implementation of forestry, which states that agroforestry is a form of reforestation (rehabilitation in forest areas) and afforestation (land rehabilitation outside forest areas) [39]. AF is one of the recommended activities in the business of utilizing protected and production forests, as well as SF management [40].

The job creation law changes a number of regulations in the forestry sector. PP 23/2021 states that the management of social forestry is carried out by planting patterns in agroforestry, silvopasture, silvofishery, and agrosilvopasture. The regulation also states that village forest, community forestry, and people plantation forest approval holders are prohibited from planting oil palm trees in the SF concession area. PP 24/2021 regulates the term for managing oil palm plantations (*jangka benah sawit*) in forest areas that do not have permits in the forestry sector. The previous monoculture oil palm cultivation system must be gradually changed to an agroforestry system to increase land productivity and maintain biodiversity. Oil palm plantations are obliged to return the business part of the forest area to the state 25 years after planting. These two government regulations prove that the Indonesian government prevents forest conversion and encourages the application of agroforestry as a means of conflict resolution.

At the ministerial regulation level, PERMEN Kehutanan P.37/2007, which accommodates agroforestry practice in community forestry, seems to be the first ministerial regulation that mentions wanatani/agroforestry directly. Other regulations on agroforestry include P.11/2020 concerning people plantation forest and P.9/2021 on SF management. PERMEN LHK P.11/2020 regulates the application of agroforestry in cultivated areas based on the principle of sustainability. P.9/2021, concerning SF management, states that it can be

carried out with agroforestry, silvopasture, silvofishery, and agrosilvopasture according to forest function and type of space [7]. At the policy level, the two PPs and three PERMENs mentioned above, although some were enacted before Law 11/2021, provide a fairly strong legal basis for the implementation of SAF in Indonesia.

**Figure 1.** Regulations related to agroforestry and SF at the operational level and their umbrella rules (box colors indicate different rule levels and arrow colors indicate derivative rules).

At the operational level, there are two regulations governing agroforestry, Director General of Watershed Control and Protected Forests (PerDirjen PDASHL) Regulation P.7/2017 concerning technical guidelines for agroforestry implementation, and P.8/2016, concerning technical guidelines for the implementation of forest and land rehabilitation activities. Perdirjen PDASHL P.8/2016 stipulates that agroforestry is a form of forest and land rehabilitation activities on cultivated land and forest areas. The technical guidance is further regulated in PERDIRJEN PDASHL P.7/2017 for implementing agroforestry in protected forests and outside forest areas, as a technical direction for agroforestry activities. The goal is to realize sustainable forest management and increase the carrying capacity of watersheds through agroforestry, for the welfare of the community in terms of economic, ecological, and social aspects [41].

The support of two existing PERDIRJEN as operational guidelines for the implementation of SAF as a derivative of the ministerial regulations, PPs, and the above laws, could

become the basis for implementing SAF to improve community welfare while assuring the continuation of the ecological functions of forests and land.

#### **3. SAF Implementation**

SAF practices have numerous benefits for many aspects of human life and the environment. They have a substantial function in providing a community's daily needs [42–44], enhancing the biodiversity of flora and fauna [45–48], moderating microclimates, mitigating and adapting to climate change [14,49], promoting soil and water conservation and soil health [50–52], and restoring the landscape [53–55]. The SAF paradigm should drive people, especially policy makers, to create rules and regulations that promote a larger scale of agroforestry implementation, in areas of either forest land or private land. It was suggested in [43] to strengthen the appreciation of smallholder agroforestry farmers as significant contributors to worldwide environmental targets and community economic objectives. Agroforestry is a prospective form of land use that can improve soil health and productivity in a sustainable manner, which makes it a viable strategic option for agricultural communities and policy makers to restore and maintain soil health [52].

Implementing agroforestry systems using different forest management schemes in Indonesia is in line with shifting the paradigm on agroforestry as a smart tool for sustainable land-use management. We distinguish smart agroforestry from agroforestry based on several variables, which are presented in Table 1.

**Table 1.** Differences between SAF and AF.


\* In SAF implementation, plant regeneration can be carried out by using assisted natural regeneration (ANR) and intensive artificial regeneration (IAR). ANR is an accelerated technique focusing on the ecological aspect, while IAR is artificial planting carried out in heavily degraded forest areas with hard-to-find natural seedlings, integrating economic and social aspects of the community, along with the ecological aspect [69].

In order to provide broader insight to the SAF paradigm, we conducted a review of AF system practices that contribute to achieving the SDGs, in particular, those related to increased rural income and prosperity, soil and water conservation, bioenergy, climate change response, biodiversity conservation, and landscape management, from AF practices in Indonesia and other countries. The schematic linkage of SAF activities with SDG objectives is presented in Figure 2.

**Figure 2.** Linkage of SAF activities with SDG objectives.

#### *3.1. SAF for Community Welfare*

The promulgation of Law 6/2014 concerning rural development programs, with the main objective of fostering community prosperity, is in line with the target for achieving Sustainable Development Goals (SDGs) 1, 2, 3, and 15: alleviating poverty and hunger, promoting good health and well-being, and conserving limited terrestrial resources. In its implementation, Law 6/2014 recommends the optimum use of local resources through the implementation of applicable technology, especially locally based innovations. According to [70], the potency of AF practices in supporting community livelihoods will make it the most approachable strategy.

As a land management system that has long been recognized, AF provides many benefits for farmers [12,71] and will be significant for a long time because of its capacity to support livelihoods, as well as provide environmental benefits and revive the rural economy [70]. As a system that is eco-friendly [72] and can satisfy the socioeconomic needs of the people [73–75], AF can also open up new jobs for gender-friendly rural economic development. Apart from generating income, agroforestry can also play an important role in sociocultural stimulation among communities that starts by studying problems together, rediscovering existing knowledge and traditional wisdom, and integrating new knowledge. In this way, the community becomes more involved and better educated through peer-to-peer discussion and group participation.

The SAF approach is a solution to forest management practices and the development of livelihoods for local communities that depend on forest resources. SAF is expected to accelerate the increase of land cover by increasing the diversity of wood plant species and non-timber forest products in forest areas. This will have implications in terms of increasing the production of forest products and improving the ecological functions and ecosystem services of the forest area. In addition, SAF is an effort to anticipate changes in the sustainability status of the traditional AF system, which is at a moderate level [76–78]. The application of SAF will strengthen the function of forest areas, especially in providing benefits and added value to sociocultural, economic, and ecological aspects, as well as their ecosystem services [79]. Implementing SAF is in line with the vision of realizing sustainable forest management and prosperous communities in Indonesia.

A study in East Nusa Tenggara Province was conducted to examine the relevance of agroforestry management to rural prosperity [70]. The AF practice in the area is dominated by coffee and cashews, and it was found that these two commodities could potentially be promoted to increase the community's welfare. AF practices can support the community livelihoods (income and food security) of smallholder farmers, produce raw materials, and strengthen biodiversity while maintaining productivity and sustainability of soil and water resources [80,81]. Research on AF development in Wan Abdul Rachman Grand Forest Park (WAR GFP), Indonesia, showed that farmers' income increased by 75.63%. There was also increased food crop production, possession of luxury goods, and access to information and financial loans, as well as strengthened farmer institutions [42,54]. AF can also improve livelihoods (income and food security) of smallholder farmers through diversified commodities [80]. As shown by the SAF characteristics presented in Table 1, agroforestry practices in East Nusa Tenggara Province and WAR Grand Forest Park are examples of SAF where the community already uses its knowledge for effective and efficient agricultural practices to gain environmental benefits and high economic profits.

Studies of agroforestry practices in Kenya and other sub-Saharan Africa countries have also confirmed that AF has the potential to provide social and economic benefits that can address household incomes, livelihoods, and food insecurity and provide fuelwood [82,83]. A systematic review of 22 peer-reviewed articles published between 2000 and 2019 assessing the contributions of AF to food security in Indonesia, mostly in Java and Sumatra, found that there are differences between AF and SAF in their contributions to food security [44]. SAF can contribute up to five times more revenue, which enables farmers to ensure their food security. The contribution of agrisilviculture lies along the continuum of timber versus non-timber forest products, showing similar trade-offs between diversity and income. One study highlighted that AF options have up to 98% and 65% greater net present value (for periods over 30 years) compared to traditional agriculture [84,85].

Similarly, AF also contributes to the aspect of public health. AF development increases the diversity of foodstuffs by introducing newly developed fruit and vegetable species, cultivating animal feed for livestock systems (providing more milk and other livestockderived products), or increasing incomes, enabling the purchase of a wider variety of foods and medicines [43,83,86].

Learning from many studies of existing AF practices in Indonesia and other countries, it has been proven that SAF makes a significant contribution to people's welfare, especially by increasing family income, ensuring food availability and family nutritional intake, increasing access to financial loans, and strengthening farmers' institutions at the local level. To further develop SAF on a broader scale, full support from relevant stakeholders is needed, especially for the development of local mainstay commodities, which will ultimately be able to realize the welfare of rural communities.

#### *3.2. SAF for Soil, Water Conservation, and Bioenergy*

Globally, agriculture plays a major role in 70% of fresh water use and is a driving factor in various environmental problems. It also became an important factor related to the current global problem of water resources and climate change [81]. Converting from forest to agricultural land, which drastically reduces tree cover, can lead to soil degradation and reduced soil organic carbon, and decreases water accessibility in terms of proper quality and quantity [87–90]. Worldwide, out of a total of approximately 75 tons/ha/year of soil lost due to erosion, agricultural land contributes 13 to 40 tons/ha/year, which causes production losses of 33.7 million tons/year and increases global food prices by 3.5% [51].

AF is one way to maintain a hydrological balance in accordance with efforts to maintain productivity and achieve sustainable soil and water resources. Through AF, a model of sustainable agriculture and landscape management, soil fertility, and water security can be maintained by increasing the infiltration rate, suppressing the erosion rate, and regulating water flows, reducing the amount of water lost as surface runoff, and improving water quality [81,91,92]. This is in line with the target for achieving SDG 6: clean water and sanitation. AF/mixed tree-based farming systems maintain the soil's physical properties better than conventional agriculture [87,91]. Multistrata tree crop systems make up an important category of agroforestry systems, in which 25% of the total biomass production that goes to the roots can be retained in the soil for a longer time than in an annual cropping system [88].

An AF system is structurally and functionally more complex, and spatially and temporally more heterogeneous than a monoculture system of plants or trees, hence it is more efficient in the utilization of nutrients, sunlight, and water [88]. At least 20% tree canopy cover is required to maintain organic matter in the system as a whole [91]. The important element in AF patterns is the presence of deep-rooted plants that have the ability to regulate the water status in the root system for the benefit of shallow rooted crops [91,93]. Based on the rate of infiltration and runoff, the capacity of AF systems to maintain the hydrological cycle, although still under forest, empirically and scientifically is much better than conventional agriculture [94]. Tree–crop combinations reduce the destructive power of rainfall, reduce runoff, and increase the infiltration rate, which in turn reduce erosion [90]. Rubber-based AF systems can increase nitrogen supply and water-use efficiency in each soil layer [95], and can enable rubber trees to acquire shallow soil water up to 24% [96].

One of the good AF models in soil and water conservation is the intercropped contour hedgerow, which is characterized by multiple hedges along the contour at intervals of 4–6 m [97], with agricultural and commercial crops in between [90,97]. In a contour hedgerow system, the eroded soil from the top is blocked by hedgerows at the bottom, which not only functions to block runoff and store trimmed biomass piles, but also to retain and settle sedimentation [90]. This accumulation of biomass can increase the organic C content in the soil. An increase of 1 g kg−<sup>1</sup> (0.1%) of soil organic carbon was shown to increase available soil water capacity by 6% [98]. Nitrogen-fixing plants have been widely applied in contour hedgerow systems to minimize soil erosion, restore soil fertility, and improve crop productivity [97], due to their high nutrition content [90] and ability to increase soil nitrogen content [91].

SAF also contributes to providing bioenergy through the application of bioenergybased AF. This system simultaneously functions to mitigate climate change, improve food security and soil quality, increase energy access, and alleviate rural poverty [99]. A study found that short rotation woody crops in shelterbelts that are typically designed to optimize soil protection and enhance conditions for crop growth can produce a number of environmental benefits, including increased biodiversity and carbon sequestration, reduced GHG emissions, and increased soil organic matter and water conservation [100]. Thus, in the context of bioenergy development, the role of agroforestry in the rural economy is to generate bioenergy crop production, which offers increased market access and income diversification strategies for rural populations [101]. AF systems using coppiced tree belts, which combine the advantages of traditional alley cropping with the short rotation coppice, is a new strategy for bioenergy [102] that supports the achievement of SDG 7 (clean and affordable energy).

#### *3.3. SAF for Climate Change Response*

The climate change phenomenon and its problems are being faced by all nations around the world [103], triggering a global mitigation commitment to keep the temperature from going up 1.5 ◦C [104]. Plants can absorb carbon dioxide (CO2), which results in carbohydrate accumulation in plant biomass. Plant constituents and the age of the land determine the amount of CO2 absorption. CO2 gas is the main GHG, with the largest amount originating from human activities that produce high rates of emission, so it is used as a standard or reference for changes in atmospheric composition and global climate change. AF practices such as carbon sequestration have indirect effects in terms of reducing deforestation and forest degradation in primary forests. Apart from that, the AF system that is encouraged in the social forestry scheme in Indonesia is also a solution for revamping areas within forests that have already been used by the community for non-forestry activities, especially agriculture, called the Jangka Benah policy. The Jangka Benah policy is an effort to improve the function of forest areas by encouraging communities to implement AF systems instead of monoculture farming. This policy is also intended to ensure that

illegal agriculture or agroforestry activities in forested areas can be reduced slowly and gradually. This system can conserve carbon in the soil to support carbon stock enhancement in both soil and vegetation [105]. One effort to ensure that AF practices can support sustainable forest management was to certify legal and sustainable AF products [106]. One of the sustainable forest management certification bodies in Indonesia has provided certification services for small farmers, hence it is hoped that farmers who practice AF will still pay attention to conservation and environmental principles. The government can also apply a regional priority scale for AF practices based on geological criteria, pedology, land slope, level of anthropogenic factors, forest fragments, potential land-use capacity, and legal reserves [107], so that SAF development is based on the forest condition, land, and environmental carrying capacity.

AF contributes significantly to supporting actions for mitigating [106] and adapting to climate change [107]. Hence, the practices of AF systems and technologies support the achievement of SDG 13 (addressing climate change). In mitigating climate change, AF practices can increase carbon stock in the above- and below-ground biomass and soil carbon pool. AF systems that are integrated into cropping and livestock can enhance carbon sequestration significantly [104]. AF has more carbon stock than land-use systems without trees, such as pastures and fields with annual crops [108], but less than forested areas. There is an estimated 12–228 Mg ha−<sup>1</sup> of carbon stock [108,109] in tropical humid AF systems, and 68–81 Mg C ha−<sup>1</sup> in tropical dry lowland areas [108]. Meanwhile, the estimation of carbon stock in AF systems across the world amounts to 0.29–15.21 Mg ha−<sup>1</sup> yr−<sup>1</sup> in above-ground biomass and 30–300 Mg ha−<sup>1</sup> yr−<sup>1</sup> in 1 m soil depth [110].

The increasing risk of climate change related to drought, flooding, and crop pests will affect farming systems. In this regard, AF management requires conservation oriented toward adapting to climate change [111,112]. Farmers can implement AF systems to continue living on their land as a form of climate adaptation at the farm level. AF can create a resilient microclimate for crop cultivation and livestock activity [113]. In addition, trees as a component of AF can support environmental services to increase resilience to climate change and reduce the vulnerability of local people [11] in terms of water, soil, climate, and hydrology disaster control. AF allows important improvements in microclimates in terms of climate buffering and reduced climate variability [105].

Technology in AF practices for climate change mitigation and adaptation (defined here as SAF for climate change) must meet specific criteria such as availability, applicability, low cost, and environmental friendliness. The Technology Needs Assessment (TNA) for Climate Change Adaptations in Indonesia indicates that "site species matching" is the selected technology and relevant to the mitigation aspect [114]. The smart site species matching technology considering land suitability and local community preferences is indispensable in the development of AF systems to obtain optimal results for climate change mitigation and adaptation [115].

#### *3.4. SAF for Landscape Management*

SAF in sustainable landscape management is the main strategy for implementing sustainable development [116]. This supports the achievement of SDG 15 (especially for sustainable use of terrestrial ecosystems, halting and reversing land degradation). Various kinds of landscapes, land uses, and land covers in Indonesia are changing very quickly as a result of the global crisis, which has caused several crises in the country, with the impacts felt by urban and rural communities [117,118].

Implementing SAF in integrated landscape management must be in accordance with local land conditions, topography, climate, and community culture. It is a more cost-effective land utilization strategy and production input to enhance multipurpose production and optimal revenue for each unit area, which relates to the rule of sustainable production [42,119]. The productivity of AF patterns by using silviculture techniques has been optimized by means of tree species selection, land suitability and topography, and environmental manipulation, as well as innovation in maintenance techniques, including plant protection from pests, diseases, and weeds [119–123].

Developing SAF toward sustainable landscape management requires the application of several silvicultural and crop cultivation techniques, as follows.

#### 3.4.1. Planting Pattern Arrangement and Species Selection

The planting pattern of an AF system should be arranged to optimize the use of space and time. Plants should be arrayed in such a way as to maximize the growth space. The interface area will be maximized if there are many plant species planted in a hexagonal pattern [124]. AF systems can be classified into agrisilvicultural (crops, tree/shrub crops, and trees), silvopastoral (pasture/animals and trees), and agrosilvopastoral (crops, pasture/animals, and trees) or another specialized system [125]. AF systems were classified in [126,127] into two patterns based on the component number and the canopy strata: simple and complex or multistoried. An along cycle or permanent AF system was introduced in [128], which referred to an intercropping system between some tree species and annual crops, where the crops can be cultivated continuously during the tree cycle. In the intermediate and advanced phases of AF, where the tree crowns are close to each other and the relative sunlight intensity reaching the ground surface is lower, shade tolerant crop species should be chosen. This is because the shade from trees has a negative effect on crop growth and yield [129].

#### 3.4.2. Use of Legumes and Cover Crops in Agroforestry

Intercropping legumes can increase input and reduce the use of external nitrogen fertilizers, hence they can be part of a low-emission farming system. In addition, such intercropping provides legume yield [130] and can improve monoculture cropping when shade trees of legume species are planted [131]. It can also control weeds without reducing crop yields, thereby reducing maintenance costs for farmers [132], and has a function in the cycle and availability of P in the soil [133]. Moreover, as reported in [134], using *Centrosema macrocarpum* (5 kg seeds per ha) as a cover crop could cover 100% of an area in 3 months, and it also controls weeds. In 8 months, the total average *Centrosema* biomass was 8.12 T/ha, with total nitrogen accumulation of 232 kg/ha, soil compaction was reduced at 20 cm depth, and organic matter and potassium levels were increased.

#### 3.4.3. Use of Biofertilizers in Agroforestry

The use of biofertilizers in AF has an ameliorating effect on soil, and biofertilizers multiply easily [135]. Biofertilizer acts as a component of or instrument for soil fertility management in fluctuating weather [136]. Several research results show that applying biofertilizer along with inorganic fertilizer could increase the soil biota and the production of various types of cultivated plants [137]. Nitrogen-fixation plants provide an environmentally friendly and renewable source of low-cost nutrients as well as fertilization efficiency, improve soil health, and maintain environmental sustainability. Biofertilizers can also increase plant resistance to adversarial environmental stresses [138]. Integrated nutrient management, which involves applying organic material, compost, manure, biofertilizer, and inorganic fertilizer together, can increase tree and crop yields, improve the nutrient quality, and minimize losses to the environment [139].

In addition, there are some advantages of AF development, such as its potential to stimulate the production of important secondary metabolites, especially in dry areas where water, light intensity, nutrition, and shade stresses occur [140]. Branches, twigs, and leaves of trees can be sources of secondary metabolites or potential bioactive compounds. The content of primary and secondary metabolites in plants is an important factor that determines their nutrition and health and promotes the plants' value [141]. At a certain level of growth and/or stress, it was found that plants produce secondary metabolites in certain cells and taxonomic groups [142]. The intensity of light received by plants in the shade affects photosynthesis, including the yield of secondary metabolites [143,144].

Another advantage of AF systems is the low risk of pest and disease attacks. It was confirmed in [145] that plant diversity in an AF can decrease pests and diseases. Furthermore, as revealed by [146], complex landscapes in agricultural areas and AF systems by their nature allow multitrophic interactions, which presents opportunities to develop natural pest control. Meanwhile, it was reported in [147] that pest and disease attacks could be reduced by 73% with mixed-crop planting. A more recent study found that an intercropping system with legumes in western Kenya suppressed brown line disease in cassava [148]. The intensity of pest damage in AF systems is lower than in monoculture agriculture [149], because AF planting patterns affect pests and diseases not only based on the plant species, but also other factors, including pest types, pest preferences, and microclimate [150,151]. The diversity of plant species composition in an AF system can cause different types and intensity of pest and disease attacks [151].

#### *3.5. SAF for Biodiversity Conservation and Enhancement*

As a mixed land utilization system that integrates tree and crop species based on their designation and use plan, AF increases plant diversity [152,153] and directly supports the achievement of SDG 15 (halting biodiversity loss). Farmers with larger cultivated areas tend to practice multistrata AF with larger amounts of plant species [54]. A multistrata cacao-based AF associated with some shade tree species in the buffer zone of Lore Lindu National Park, Central Sulawesi, Indonesia, succeeded at inviting pollinating insects to help pollinate the cacao plants, so the yield increased to the optimum level [154]. Besides economical purposes, AF practices are also beneficial for the conservation of local native plant species, such as *Acacia seyal* and *Balanitras aegyptiaca* in Ethiopia, which are used for fuelwood, food (the fruit), medicine, charcoal, poles, bee feed, fodder, etc. [155].

An AF system contributes to plant protection by decreasing the pest, disease, and weed populations, increasing natural predators of pests, and increasing plant and land productivity [151,156]. An alley cropping cacao AF practice showed a higher abundance of arthropoda, which has an important role as a decomposer and natural predator, compared to monoculture oil palm plantations [157]. AF systems can regenerate multiple fauna populations and diversity compared to monoculture systems because they have habitats for the provision of food and good food chain cycles [158,159].

Many studies have reported an increase in floral, faunal, and microbial diversity induced by AF in temperate and tropical regions compared to monocropping [47,48,52,160,161] due to favorable soil–plant–water–microclimate conditions [47] and the availability of nutrients from shade trees [162]. Silvopastoral and agrosilvicultural systems have the potential to conserve floral and faunal species [163]. A simple modelling demonstration of the habitat amount hypothesis proved that AF is important in reducing biodiversity loss at farming sites [48].

AF for shade-grown coffee has been practiced worldwide to increase biodiversity conservation [164]. It can preserve biodiversity [47,158,165] and improve the quality of the surrounding environment and ecosystems [166]. Coffee in agroforestry practice requires shade, thereby increasing biodiversity and building multistrata SAF. Furthermore, coffee and cocoa AF systems were found to increase the diversity of fauna such as birds, mammals, and other species [167]. Rubber agroforests in Thailand have greater butterfly richness compared to rubber monoculture [45]. Coffee AF could provide habitats for slow lorises. The trees provide numerous sources of foraging, social activity, and movement for slow lorises [168]. This is in accordance with the findings of [158], showing that coffee AF carried out in the Kemuning Forest of Central Java has an important role in preserving the Javan slow loris (*Nycticebus javanicus*), an endemic primate species that is endangered.

On the southern and eastern slopes of Guatemala, coffee, cardamom, and fallow AF systems significantly increased the connectivity of forest biodiversity in a fragmented landscape and overall landscape biodiversity [169]. AF sites in Pearl Lagoon Basin, Nicaragua, tended to have comparable plant diversity relative to neighboring secondary forest [170].

The research findings of [171] highlighted that the biodiversity of AF systems should be maintained to guarantee the availability of all three types of ecosystem services (provisioning, regulating, and cultural), food security, and community livelihoods. AF practices lead to increased biodiversity and can be linked to food, shelter, habitat, auspicious microclimate, better soil–plant–water relations, and other benefits produced by mixed tree crops [47]. Based on the above findings regarding the numerous contributions of AF to biodiversity (flora, fauna, micro-organisms), we concluded that AF systems represent smart land-use management with a significant role in biodiversity conservation and enhancement.

#### *3.6. Best Practices of SAF*

Many studies have found that the main practitioners and innovators of AF are indigenous people with local wisdom. They have practiced AF for thousands of years and have passed on their knowledge of developing, modifying, and adapting AF systems through learning and adjusting [172–174], including developing variations in plant structure and composition according to environmental and socioeconomic factors [175]. One key aspect of their best practice that the world can learn is that they always apply a sustainable and integrated approach to managing ecosystems in a multifunctional way and the innovation decision processes are common to any sector [55,176,177]. A good understanding of the soil conditions, as the main consideration that leads to careful selection of tree planting sites, coupled with good tree maintenance efforts, results in high growth rates, which is widely recognized as a sustainable land management practice, particularly in the tropics [172,178,179].

In deciding on a tree–crop combination, farmers mainly consider the availability of land and the potential for income diversification [180]. Several best practices of AF (SAF) in Indonesia have been widely developed by farmers throughout the country. In Java, people's local wisdom regarding land use is based on biophysical conditions, experience, and cultural heritage, specifically sacred forests, mixed gardens, rice fields, residential areas, and home gardens [181]. The main timber commodities developed are sengon (*Falcataria mollucana*), with a 6-year rotation, and teak (*Tectona grandis*), with a 20-year rotation, which generate economic values of USD 1015/ha−<sup>1</sup> and USD 2815/ha<sup>−</sup>1, respectively [182].

Indigenous AF in dryland areas can be found in the eastern part of Indonesia, including Mamar on Timor Island [76,77,183] and Kaliwu on Sumba Island [79]. The socioeconomic contribution of sedentary gardens, silvopasture, and Mamar on Timor Island ranges from 77.74 to 78.99% [76], while Kaliwu agroforests contribute 46.88% to farmers' income on Sumba Island [184]. In terms of ecological functions, in the Mamar and Kaliwu ecosystems, there are 112 plant species structured in multiple strata and 146 plant species [185,186], respectively. Community initiatives to regenerate and conserve NTFPs by implementing AF also need to be enhanced, especially to improve the rate of plant growth [187].

On the easternmost island of Indonesia, the Papuan community has several examples of best AF practices aiming to meet substantive needs. The area for AF development was obtained from degraded forest with an average land size of 0.25–1.0 ha undergoing a shift to the next plantation location within 2–3 years [188]. They applied a traditional AF system through trial and error to meet their basic needs and ensure food security first [189,190]. The most commonly used cropping pattern for the top canopy stratum is timber, fruit, and plantation tree crops, while the lower crown stratum consists of tubers, vegetables, and herbs [191–193]. The selected plants are species that do not need intensive care or attention, and are local mainstays [188]. The most commonly developed species are multipurpose tree species (MPTS) such as *Pometia* sp., *Artocarpus communis*, *Durio zibethinus*, *Nephelium lappaceum*, and *Mangifera indica* [191]. The AF practice in Papua makes a significant contribution (53.5%) to the farmers' income [192]. SAF can reduce degraded forest areas in the future through intensive planting with three pillars to increase land productivity: the use of superior seeds from quality sources, environmental modification, and integrated pest and disease control (intensive silviculture) [194].

In the western part of Indonesia, best AF practices for benzoin (*Styrax benzoin*) can be found in a customary management system adopted by a local community in North Sumatra which has traditionally owned benzoin forests for generations. They collect seeds or seedlings around benzoin-producing trees and then plant them in areas where there are Styrax trees [195]. Beginning at 8–15 years, farmers start to tap the resin of benzoin trees, and if they do it right, they can extract the resin for about 60 years, or across generations. Study [196] revealed that benzoin trees help in forest conservation and promote local economic and cultural values. Another interesting best AF practice is found in WAR GFP, Lampung, where farmers with limited land availability have successfully developed a cacao-based AF and ensured the fulfilment of their basic needs by gaining access to food, fodder, and fuelwood [42], while restoring the previously degraded conservation forest [54]. Benzoin agroforestry and AF practices in WAR GFP are other examples of SAF being successfully practiced by local communities, which provide multiple benefits, as depicted in Table 1.

Best practices of SAF are also developed in many countries, including northern Bangladesh and some African countries. Farmers improved their livelihoods significantly by practicing AF, as it provides multiple benefits for them [11,75,197]. AF practices were found to ensure economic returns and sustain farmers' livelihoods [75,198] as well as increase plant species diversity, since high-canopy trees enable the underneath crops to capture optimal sunlight, while deep-rooted plants can ensure optimal nutrient absorption [124,199,200]. In addition, indigenous AF also plays a role in land and water conservation, especially landscape conservation around springs and hilly areas [183,184]. Examples of successful SAF practices in other countries include agroforestry for the sustainable management of sloping land areas in Southeast Asia and the Pacific [201], agroforestry practices in the form of biomass transfer of nitrogen-fixing trees combined with rainwater harvesting techniques and integrated nutrient management in a semi-arid region of Zimbabwe [202]. The use of smart agroforestry technologies in Mali is also an example of SAF to address the constraints to adopting proven agroforestry techniques for improved market access to increase food and nutritional security and build resilience of farming systems [203]

Best practices of AF systems, both traditional and modern, that have a significant impact on the economy, ecology, and social aspects can be categorized as smart agroforestry (SAF) or agroforestry plus (AFP). Other examples of SAF practices in Indonesia include Repong Damar in the Krui coastal area of Lampung Province, Tembawang, in West Kalimantan, Parak in Maninjau, West Sumatera Province, and Mixed Garden in West Java [204]. Another SAF practice is the AF Smart Farming initiative by the research group Tropical Agroforestry of Brawijaya University. Some activities of AF Smart Farming have been soil fertility management of AF land after the eruption of Kelud Mountain, and the management of AF and soil fertility by farmers in Ngantang, Malang [205].

Based on the numerous significant contributions of SAF practices to community welfare, soil and water conservation, bioenergy, climate change responses, landscape management, and biodiversity conservation and enhancement, as well as the variety of best practices, scaling up AF implementation should be mainstreamed for both on forest land or private land. It is expected that SAF practices will become the mainstay of forest and landscape management in Indonesia, especially through the SF scheme, in order to achieve several Sustainable Development Goals. Hence, the main key to the successful mainstreaming of SAF for SF implementation lies in suitable policy innovation, the use of appropriate technology, and compromises or trade-offs among the benefits, risks, and available resources.

#### **4. The Way Forward**

The academic world only began paying attention to the AF system in the 1970s–1980s, when it was realized there was a need to find alternatives to increase agricultural productivity, reduce degraded land, and increase the benefits for small landowners. Since then, the importance of implementing AF systems has become more urgent, especially in tropical rural areas around the world [206,207]. Although it was an old technique, AF has

been introduced as a new science and many publications have presented various results of technical studies related to AF systems.

Developing SAF is not only aimed at increasing profits and resilience for farmers, but also improving environmental parameters, including biodiversity enhancement, soil and water conservation, and sustainable landscape management. Hence, the aim is to obtain collective and comprehensive environmental and economic benefits. This confirms a study revealing that in addition to the multiple benefits derived from current AF practices, SAF also supports sustainability and dynamic land management [208]. We consider that the agriculture and silviculture knowledge employed in SAF are based not only on modern technology, but also on local indigenous knowledge proven to survive over generations, to realize sustainable management of natural resources, including forests. Furthermore, SAF is a win-win land-use option between productive and environmental functions, and it plays an important role as part of a so-called climate-smart landscape approach that simultaneously embraces mitigation and adaptation policies and programs [209].

However, despite the contribution of multiple functions and benefits, the development of SAF faces various challenges, especially related to limited land availability and a lack of alternative sources of income for farmers. The demands of life necessities and lifestyles, global climate change, and government policies are also triggering factors for land conversion. The tendency for land conversion also occurs in the Mamar system [78], although it does not always provide a significant increase in income, as it often requires substantial capital beyond the capacity of farmers. A study in Bungotebo, Jambi, also found that rubber and oil palm prices have induced farmers with limited land ownership and no other on-farm income sources to change their AF land into rubber and oil palm plantations [210]. Another example is in Bantaeng, South Sulawesi, where farmers who previously cultivated candlenut (*Aleurites moluccana*) and kapuk randu (*Ceiba pentandra*) on their land converted it to maize cultivation in order to more quickly obtain a cash income [211].

In addition to the challenges mentioned above, the expansion of oil palm, which in many cases involves the clear-cutting of forested areas in order to open areas for farming, is an activity that might hinder AF development. Many farmers are reluctant to plant oil palm in combination with forestry crops because they believe it will reduce the productivity of their plantations. To overcome this, farmers need assistance with developing commodity diversity by using forestry plants that are multipurpose tree species (MPTS). Social forestry in Indonesia, which focuses on developing business governance for AF farmers, aims to make them no longer depend on oil palm. The completion of monoculture oil palm plantations in forest areas can be addressed by applying the concept of palm oil management (jangka benah).

There are two stages of improvement: The first is to enrich forest plant species by forming mixed oil palm plantations (oil palm AF), aiming to improve the structure and function of forest areas previously disturbed by monoculture plantations. The second is to increase the species and number of mixed plants to form a more complex, multilayer vegetation structure (complex AF) that is close to the structure of natural forest. Meanwhile, coffee in AF practice requires shade, which increases biodiversity and builds multistrata SAF. This is supported by a study from Cambodia [212], which reported that shade-grown coffee delivers the same yields as coffee grown without shading. Therefore, coffee AF is profitable, both ecologically and economically. Incentives for farmers also affect farmers' decisions related to tree species and biodiversity, as shown by an ecological–economic assessment model [213].

Ministry of Environment and Forestry Regulation 9/2021 concerning social forestry stipulates forest criteria and types of social forestry businesses that can be developed. Permitted activities for social forestry in areas with good vegetation cover or conservation areas should be more in the form of environmental services, such as ecotourism activities, whereas AF activities are directed at unproductive forest land or land that has been degraded in order to increase land cover. Since SAF applied to social forestry aims to improve the welfare of the community around the forest and increase community participation in forest rehabilitation activities [22], its implementation is prioritized on degraded forest lands, and it is considered as vegetative conservation for watershed rehabilitation as well [214]. A study found that one of the causes of forest destruction in Indonesia is the conflict between forest communities and forest managers. Social forestry is a form of comanagement that can improve community welfare and sustain the forest while reducing conflicts between communities and forest managers [215].

SAF development is also challenged by farmers' low capacity regarding farming techniques, low awareness, and low motivation to integrate tree or tree crop species into their monoculture farming in forest areas [128]. A study from Rwanda [216,217] also revealed that a lack of skills and technical know-how, limited capital, and the need for quality seeds have decreased the adoption of new AF practices by farmers. Other challenges are related to a lack of trust in the government's commitment to SF implementation [218], limited finances to practice good farming (business capital), limited market options for AF products, and limited post-harvest AF product processing techniques and capacity [219,220]. Similarly, another study [221] confirmed that developing AF with SAF in Indonesia will be more challenging with the complexities of socioeconomic and ecological problems along with broader goals to solve problems at the local to global scale. Climate change, for example, has indirectly affected farming patterns [222]. In addition, inadequate policy support for providing comprehensive and intensive mentoring facilities was also reported to be a cause of the decrease in adopting AF practices [222–224].

The weaknesses of SAF often make it difficult to implement at the farmer level for several reasons: (i) From an economic perspective, AF sometimes harms farmers due to unfavorable market conditions. (ii) From a social perspective, planting trees on agricultural land can sometimes be difficult for farmers, due to unsupportive government policies (e.g., the sandalwood planting policy in NTT). (iii) In terms of soil fertility, farmers do not like to plant trees, because they require a lot of nutrients to grow. (iii) In terms of the growth of other plants, trees that grow tall with spreading branches can harm other plants [225], and need to be altered, such as by pruning and thinning.

In the context of good practices, the customary/traditional AF system developed in various regions in Indonesia is still often neglected. We also consider this system as smart agroforestry (SAF) practice based on local indigenous knowledge. For further development, indigenous SAF would need scientific improvements and innovative treatments to respond to social economic dynamics, including the decrease in farm land due to factors such as increased population and higher standards for product marketing [221].

In spite of these challenges, the sustainability of indigenous SAF can be observed in the social, economic, ecological, technological, and institutional dimensions of dryland farming, with a sustainability level of 54% for mixed gardens, 52% for Mamar agroforests, and 51% for silvopasture, which is classified as moderate [76]. The moderate value represents the impact of the balance of environmentally friendly social–ecological functions that contribute positively to the subsistence needs of farmers [78]. The sustainability dimensions of the traditional AF system can also be seen in its function as an important habitat for key cultural species that are rare in nature. The Mamar AF system is an example of community awareness to independently maintain the sustainability of AF, while non-Mamar agricultural land requires intervention in various ways, such as guidance and counseling on sustainable land use [226].

Considering that the biophysical characteristics and resources as well as the socioeconomic aspects of communities vary, the success of SAF development needs mainstream supporting policies, taking into account sociocultural, economic, and ecological suitability. The best traditional practices for building community economic resilience need to be encouraged as a power node for community-based development. On the other hand, various negative impacts related to the development of market-oriented agricultural and plantation technology that can lead to the simplification of indigenous AF values should also be anticipated, especially a reduction in the values that make up SAF as a node for sociocultural, economic, and ecological adaptation. Technological development is a necessity, but it needs

to be harmonized to strengthen the sociocultural values of the community, including the cultural and ecological identity in AF management. Market-oriented simplifications can lead to humans becoming mere economic beings, even though they are socioecological creatures who interact with nature.

As of May 2022, the development of the SF program through five schemes (community forestry, village forest, people plantation forest, customary forest, and forestry partnership) achieved 5.004 million ha for 9223 forest farmer groups (data obtained from Directorate General of Social Forestry and Environmental Partnership, MOEF) out of a targeted 12.7 million ha by 2030 [227]. The large areas allocated for the SF program represent a big opportunity to apply SAF technologies. In addition, the relatively long period of SF agreement (35 years) can be extended for one more period to provide a guarantee for communities that implement AF systems with long-term plants or perennials to get more secure access rights to manage the land and harvest the plant yields [42,228].

Even though in Act 11/2020, Government Regulation 23/2021, and MoEF Regulations 8 and 9/2021, the legal framework for "smart agroforestry" is clearly stipulated as a landuse management option to increase land productivity, there is still a need to anticipate and resolve various challenges in SAF development. Mainstreaming SAF technology on a large scale in SF areas should be followed by enhancing community capacity in farming technologies coupled with providing other supporting facilities for sustainable land-use management [40,229,230]. Kiyani et al. [217] confirmed that corrective actions needed for the success of SAF implementation include providing subsidies and regular training and informal education to help farmers build their skills and capacities, while ensuring their involvement in decision-making related to SAF policies and programs. In addition, it is necessary to establish tree nurseries to increase the production of quality seeds and ensure the successful cultivation of tree crops in SAF development. The concept and advantages of SAF technologies and its success story need to be intensively socialized not only for the community, but also for related stakeholders. Furthermore, technology and innovation should be provided for postharvest treatments and diversified product processing, which would allow some AF products that are perishable to be preserved and marketed more widely.

Subsequently, the mainstreaming and scaling up of SAF as part of SF program development need support not only from the government, but also from all related stakeholders in order to overcome structural barriers and limited community capacity [231]. Multistakeholder collaboration is needed, involving NGOs, research institutions, the private sector, international donor agencies, and good government, to encourage innovation in designing, pioneering, and implementing further farming initiatives in Indonesia. In many cases, collaboration can form networks and forums to strengthen partnerships and achieve goals [222]. Community participation can be facilitated by providing more and easier access to technology, capital, markets, information, and supporting infrastructure to increase the economic added value of products generated from AF. In the 4.0 era, market and marketing websites for AF products should be created for farmers with government facilitation, mainly local governments and related stakeholders. With this technology, AF products can be recognized and made available to a wider market [33].

The increase in AF products of various types and functions will in turn encourage the plant-based forest commodity industry to develop postharvest and product processing businesses, on both a small and large scale. This will create many jobs and business opportunities and strengthen the economy of communities. Increased coordination among stakeholders at different levels of bureaucracy, an increased understanding of the challenges faced by smallholder farmers, and the adoption of innovative approaches to managing resources are critical to facilitating farmers' capacity and organizational improvement. Mainstreaming SAF within the implementation of SF programs would provide both a backward and forward linkage in the development of forest-based agribusiness that would significantly contribute to achieving the Sustainable Development Goals in Indonesia especially related to alleviating poverty and hunger, promoting good health and well-being, providing water and energy, mitigating and adapting to climate change, and conserving limited terrestrial resources.

Finally, although there is ample evidence to suggest that certain species of agricultural crops can be grown in combination with forest trees, the biophysical and socioeconomic characteristics of participating communities and their environmental conditions vary widely. Therefore, there is a great need for further research to develop appropriate management practices and establish the complementarity of various agricultural and forest species compositions in different ecological zones.

#### **5. Conclusions**

SAF contributes significantly to the economy, both ecological and social, and therefore supports the achievement of several SDGs (1, 2, 3, 5, 6, 7, 13, and 15). There is an opportunity to apply SAF on a large scale in forest land (state forest) through the SF program, because it is supported by government regulations.

The key to the success of silviculture in SAF lies in the proper selection of plant species and planting pattern arrangements that can provide advantages by addressing aspects of productivity, sustainability, and adoptability. The productivity of AF patterns could be optimized by applying silvicultural and crop cultivation techniques, including species site matching and selection of land suitability, environmental manipulation, and innovation in maintenance techniques, including protecting plants from pests, diseases, and weeds.

SAF can potentially be implemented in social forestry areas. It enables the development of multiple forestry businesses to mitigate land-use changes and support the achievement of Sustainable Development Goals in Indonesia. However, for further development, it needs to be mainstreamed or scaled up. The mainstreaming of SAF through policy support should consider sociocultural, economic, and ecological suitability. Subsequently, appropriate technology and innovation for postharvesting treatments and diversified product processing of SAF products should be introduced for communities to increase the economic added value. SAF is a strategy to revive rural economies and community welfare through the optimal use of local resources along with smart landscape and land-use management, which has significant roles in soil and water conservation, bioenergy, climate change responses, landscape management, and enhanced biodiversity conservation. Hence, the main key to successfully mainstreaming SAF for SF implementation lies in suitable policy innovation, the use of appropriate technology, and compromises or trade-offs among benefits, risks, and available resources.

**Author Contributions:** Each author (D.O., S.S., M., I.W.S.D., H.Y.S.H.N., B.S., D.R., G.N.N., I.Y., A.H., N.M., S., Y.A., D.P., E.E.W.H. and S.E.) had an equal role as main contributors who equally discussed the conceptual ideas and the outline, conducted the literature reviews, performed the analysis, prepared the initial draft, provided critical feedback on each section, as well as revised and finalized the manuscript. All authors have read and agreed to the published version of the manuscript.

**Funding:** The APC was funded by the Strengthening of Social Forestry Project of the Directorate General of Social Forestry and Environmental Partnership, MoEF of Indonesia.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Acknowledgments:** We thank all of the anonymous reviewers for their comments and suggestions to improve the manuscript. We also thank the Strengthening of Social Forestry Project of the Directorate General of Social Forestry and Environmental Partnership, the Ministry of Environment and Forestry of Indonesia for support in publishing this manuscript.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**

