1. Introduction
Agricultural systems are one of the most extensive forms of land use globally, covering 36.5 percent of the global land area [
1,
2]. It has been shown to provide a wide range of functions and services to the population, such as the production of food, fiber, feed, and medicines [
3,
4]. The Green Revolution, which introduced new technologies and policies to increase food crop yields in developing countries, began in the 1940s as a response to the problems posed by rapid population growth. This movement towards intensification of agriculture eventually led to the gradual unsustainable of current production patterns [
5,
6]. For example, the extensive use of pesticides and fertilisers and the intervention of industrial technology [
7]. On the one hand, that has increased food production and productivity to a certain extent and promoted agricultural development [
8]. On the other hand, this intensive mode of agricultural production has exacerbated existing social, economic and ecological problems [
9,
10,
11]. For instance, in India, where agriculture is under pressure from water scarcity in many regions, water-consuming crops were introduced during the Green Revolution, resulting in the loss of nearly 100,000 indigenous rice varieties and seriously affecting the sustainability of traditional agriculture [
12,
13,
14,
15,
16,
17,
18,
19]. It is widely recognized in the academia that existing production patterns need to be transformed in a more sustainable way, in order to cope with the above impacts [
20,
21,
22].
To date, agroforestry is increasingly being discussed as an effective solution for modern agriculture [
23,
24]. Compared to other production methods like intense monoculture farming and slash-and-burn, agroforestry has a better potential to provide high yields and preserve ecological stability in a variety of ecological and socioeconomic contexts across the world [
25,
26]. In addition, the Millennium Ecosystem Assessment noted that sustainable agroforestry can meet human needs for food and fuel, and contribute to the conservation of biodiversity [
27]. Agroforestry is essentially a combination of agriculture and forestry [
8]. It is the intentional use of woody perennials (trees, shrubs, palms, bamboos, etc.) in a particular form, e.g., spatial arrangement or chronological order, on the same land management units as crops and/ or animals [
25,
28]. Yet, its ultimate purpose is to produce food, instead of generating/creating trees. Agroforestry is therefore an important complement to existing ecosystem services. For example, timber production and water supply in provisioning services, carbon sequestration, water retention, soil conservation and biodiversity protection in regulating services, and forest recreation, entertainment and cultural and religious services in cultural services [
29,
30,
31].
Moreover, forests could provide multiple functions within existing ecosystem services [
32]. Forest functions (FF) are terms used to define the link between forests and people, which is related to and vital for community livelihoods [
33,
34]. For instance, the biological diversity provided by forests is a source of support for the livelihood security of surrounding communities [
35]. FF also plays an important role in increasing agricultural production and maintaining agro-ecological sustainability [
36]. For instance, forests play a key role in terraced farming systems by controlling water supply, lowering hydrogeological hazards, providing windbreaks, preventing soil erosion, regulating the climate, providing adequate habitat for crops, and fertilizing them [
37,
38,
39]. Similarly, FF also fundamentally support the achievement of the Sustainable Development Goals (SDGs), such as providing livelihoods for populations to eradicate hunger (SDG2); increasing employment (SDG8); conserving biodiversity (SGD15); hydrological cycle (SDG6), etc. [
40,
41,
42]. Likewise, in the Globally Important Agricultural Heritage Systems (GIAHS) project, forests and agroforestry complexes have important multifunctional roles in almost half of the sites [
43].
The "Rice-Fish-Duck" (RFD) agro-ecosystem is an important component of the GIAHS, it has high ecological, socio-cultural and economic values [
44,
45,
46]. The rapid expansion of land for construction and the development of terraced tourism at the expense of large areas of forest above the system has led to severe soil erosion, destabilising the RFD ecosystem and affecting the sustainability of RFD ecosystem services (RFDES) [
47]. However, it was found that the Hani terraces in China's Yunnan Province serve as a complementary example of how RFDES can also be carried out in a sustainable manner. The reason for this is that they systematically manage forests, terraces, water and villages as a whole [
48]. Additionally, they created a sustainable rice farming organism and harmonized the interactions between the components [
49]. Therefore, agroforestry systems will contribute to environmentally friendly practices for restoring agricultural landscapes and land management strategies with high benefits [
50].
In this regard, co-management of forests and terraces is an important process in the transition from RFD agricultural systems to rice-fish-duck-forest (RFDF) agroforestry systems. Research on the ecosystem services provided by RFDFS has been widely discussed and validated. Examples include a proven role in restoring degraded ecosystems in RFD areas, providing additional economic benefits to First Nations, such as increased agroforestry products and tourism revenue [
48]; Socio-cultural benefits include food and livelihood security, natural beauty, religious culture, and so forth [
51]. However, RFDFES was found that it is not a complete concept, forest ecosystem services were treated as a complement to RFDES, and there was fragmentation of RFDFES. This leads to our research question: i). what is the RFDFES in the context of sustainable development? ii). what are the recurring issues for RFDFES in interdisciplinary discussions? iii). what is theoretical framework to integrate the themes, content and objectives of RFDFES to support the sustainable development of RFDFES, and iv). whether this framework could contribute to the achievement of SDGs.
Given the above, this article employs a systematic literature review (SLR) approach, to answer the research questions and fill the knowledge gaps. It could enhance the overall understanding of RFDFES knowledge. From a global perspective, the RESEARCH focuses on the current research themes of RFDFES, summarises and analyses the specific research progress that has been made in RFDFES, and extracts the common problems that exist in the sustainable development of RFDFES. The RFDFES sustainable management framework is then built to address these concerns and is compared to the SDGs to investigate the framework's role in assisting in the accomplishment of the SDGs.
2. Materials and Methods
The SLR analyzes specific issues or explores specific hypotheses via critical review, not merely summarizing 'all the information' about a subject, in order to eliminate systemic mistakes and effectively integrate facts and views from different disciplines [52–54]. This paper, in order to gain a more thorough understanding of RFDFES and to support its sustainable development, systematically compiles and analyzes the literature related to RFDFES, identifies the pertinent research themes of RFDFES, and builds a framework for sustainable management of RFDFES in conjunction with existing frameworks for the sustainable management of agriculture and forestry.
In this way, this study suggests the following methodological steps previously employed by Petticrew and Roberts [
52]: i). depict the important components of RFDFES in the context of sustainable development; ii) explore the solutions to the identified problem; iii) conduct a comprehensive literature search to locate publications relevant to the research question; iv) screening of search results against inclusion and exclusion criteria; v) Evaluate articles related to the topic based on selected literature; vi) synthesize the outcomes from the literature and extract research data; and vii) analyze the results of the extracted data (see
Figure 1).
2.1. Search and Appraisal
Based on the research questions in Steps 1 and 2, relevant keywords were identified (steps 3, 4, 5), including "ecosystem services", "rice", "fish", "duck", and "forest". The search string "title-abstract-keyword": "(" Ecosystem Servic*") and ("Rice" or "Paddy" or "Fis*" or "Duc*") and ("Fores*" or "woo*")" was used to search article in Scopus, 73 publications were retrieved. To minimize the ambiguity and ensure accuracy, three researchers finalized 41 publications according to the criteria in
Table 1.
2.2. Synthesis
To identify and classify core elements from which information and conclusions might be deduced, we carefully reviewed the subjects and contents of 41 articles (Step 6). We found that RFDFES involves research on four core elements: ecological, economic, socio-cultural and regulational (
Figure 2) [
55,
56,
57]. The categorization of economic and ecological service functions and the debate of service valuation remain the key areas of attention for current RFDFES research, and there are gaps in the socio-cultural and managerial elements of RFDFES. We will go into the socio-cultural and regulational aspects in the discussion section to more thoroughly elaboration.
In Step 7, we discussed the problems in the RFDFES study, combined with the existing agricultural and forestry management frameworks, constructed a sustainable management framework for RFDFES. It consists of 4 themes, 10 sub-themes, and 29 indicators for management (3 sub-themes, 6 indicators), ecology (2 sub-themes, 7 indicators), economy (2 sub-themes, 6 indicators), and socio-culture (3 sub-themes, 10 indicators). Furthermore, Its relevance to SDGs is further discussed.
2.3. Report
In Step 7, we discussed the current issues in the RFDFES study, combined with the existing agricultural and forestry management frameworks, constructed a sustainable management framework for RFDFES. It consists of 4 themes, 10 sub-themes, and 29 indicators for management (3 sub-themes, 6 indicators), ecology (2 sub-themes, 7 indicators), economy (2 sub-themes, 6 indicators), and socio-culture (3 sub-themes, 10 indicators). Furthermore, Its relevance to SDGs is further discussed.
5. Conclusion
This study synthesizes and analyses recent academic research on RFDFES from the perspective of the shift from agriculture to agroforestry, with the aim of gaining a more thorough understanding of RFDFES in the context of rapid population growth and sustainable development. Through a systematic literature review, we evaluated a total of 41 articles that were pertinent to the study topics. First, we synthesised the core elements of RFDFES research from 41 publications into four categories: regulatory, ecological, economic and socio-cultural. Then, we analysed and summarised the core issues of RFDFES research, and found that there are problems of deforestation for agricultural expansion, socio-cultural marginalisation, and low community and local participation in RFDFES management.
To do this, we developed the RFDFES sustainability framework based on accepted mainstream frameworks for sustainable management in agriculture and forestry and within the scope of our research topics. The proposed framework tackles the RFDFES's current issues and significantly advances the field of study of sustainable agroforestry management. Additionally, this study compares the Framework to the SDGs and concludes that the Framework aids in the accomplishment of a number of SDGs. It further reflects that the framework will help to ensure food and livelihood security for local populations and improve their lives and well-being.
The main limitation of the RFDFES sustainable management framework proposed in this study is that it uses only one bibliographic database (Scopus) and relies exclusively on existing published academic research, which may inhibit other relevant research. Despite the limited scope of our research, it fills a temporary gap left by the lack of an agroforestry-specific framework for sustainable development. In the subsequent phase of more extensive study and application of particular practical examples, the framework will be refined and augmented with the goal of demonstrating and promoting it internationally.