Indigenous and local knowledge in sustainability transformations research: a literature review

Scholars, politicians, practitioners, and civil society increasingly call for sustainability transformations to cope with urgent social and environmental challenges. In sustainability transformations research, understandings of transformations are often dominated by Western scientific knowledge. Through a systematic literature review, we investigated how indigenous and local knowledge (ILK) is represented in peer-reviewed empirical scientific papers that apply ILK in contexts of transformation, transition, and change. Our results show, first, that all papers applied ILK to confirm and complement scientific knowledge in contexts of environmental, climate, social-ecological, and species change. Only four papers (5%) applied ILK to conduct research on transformations. Second, we identified four research clusters that apply ILK in contexts of transformation, transition, or change in (1) Arctic, (2) terrestrial, (3) coastal, and (4) grass and rangelands environments. These clusters are located along two axes: tropic to Arctic and marine to terrestrial. Finally, our results indicate that indigenous and local understandings of transformations are currently neglected in the scholarly transformations discourse. The reviewed papers do not focus on how indigenous peoples and local communities understand transformations, instead they focus on what changes indigenous peoples and local communities observe and describe, resulting from their daily experiences and activities. We argue that because of its in-depth local, place-based character, ILK can substantially contribute to a more plural understanding of transformations and the assessment of transformative change. We conclude that future research needs to investigate how to gain a more plural understanding of transformations that leads potentially to more inclusive actions toward more just, equitable, and sustainable futures on a local and global level.


INTRODUCTION
For more than two decades, sustainability transformation research has sought to better understand how large system changes toward just, equitable, and sustainable futures can be fostered (Loorbach et al. 2017). Diverse definitions of and approaches to transformation exist in the literature (Patterson et al. 2017, Blythe et al. 2018. They are decisively influenced by Western scientific knowledge because it is currently the dominant knowledge system that sets prevailing standards for research (Davis and Ruddle 2010). Knowledge systems exist through "agents, practices and institutions that organize the production, transfer and use of knowledge" (Cornell et al. 2013:61). Knowledge from other knowledge systems, such as indigenous and local knowledge (ILK) systems are rarely involved in research, especially in transformation research (Blythe et al. 2018).
The contributions of ILK for sustainability and research are increasingly considered in sustainability science (Mistry andBerardi 2016, Tengö et al. 2017). Indigenous and local knowledge is defined as a "cumulative body of knowledge, practice, and belief, evolving by adaptive processes and handed down through generations by cultural transmission, about the relationship of living beings (including humans) with one another and with their environment" (Berkes 2018:8). Its contributions are especially highlighted by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES). For example, Brondizio and Le Tourneau (2016) argued that involving indigenous peoples and local communities is essential to develop and implement more effective environmental governance systems for ecosystems and biodiversity. Another example is the exchange of ILK and scientific knowledge in the case of pollinator conservation (Hill et al. 2019). Indigenous peoples and local communities practice biocultural approaches to pollinator conservation in all continents, except Antarctica, which maintain biodiversity and Nature's contributions to people (Díaz et al. 2018, Hill et al. 2019. The contribution of ILK is also exemplified by the combination of observations from Tibetan pastoralists and scientific knowledge on climate change to support the hypothesis of delayed summers on the Tibetan Plateau (Klein et al. 2014, Mistry andBerardi 2016). Reasons for this growing interest are the long-standing relationships of indigenous peoples and local communities with their surrounding environments, the holistic knowledge accumulated in centuries to govern social-ecological systems, and the ability of these communities to overcome crisis and changes of all different types (e.g., livelihood change, climate and ecosystem change, availability of resources; Pearce et al. 2015, Berkes 2018. Despite these positive examples of how ILK can contribute to sustainability and research, studies that investigate how indigenous and local understandings of transformation can support working toward just, equitable, and sustainable futures are less abundant. In fact, the transformation discourse seems to pay insufficient attention to social differentiation, issues of power and plurality which threatens the legitimacy of the discourse (Blythe et al. 2018). To overcome some of these challenges, we argue that a more inclusive and plural understanding of transformations is needed, which views transformations from the perspective of diverse knowledge systems.
The aim of this study is to review to what extent indigenous and local understandings of transformation are represented in the scientific sustainability transformation literature. To reach this goal, we conducted a systematic literature review of ILK in contexts of transformation, transition, and change. The findings intend to stimulate the debate on transformations to enable a more plural and comprehensive understanding of transformations, which includes insights from diverse knowledge systems.

SUSTAINABILITY TRANSFORMATION RESEARCH
The interest in sustainability transformations is increasing among scholars with different theoretical backgrounds and has led to the emergence of different conceptual approaches to transformations . Reviews from Feola (2015), Loorbach et al. (2017), and Patterson et al. (2017) provide detailed overviews and discussions of these conceptual approaches to transformations that show the diversity of how transformations can be understood within the Western scientific knowledge system. Following Patterson et al. (2017), we briefly introduce how four prominent conceptual approaches to transformations from the global sustainability literature understand transformations: (1) socialecological transformations, (2) sustainability transitions, (3) transformative adaptation, and (4) sustainability pathways (Table  1). First, the social-ecological transformations approach focuses on social-ecological systems (e.g., forest, fishery, agriculture systems) while often taking a place-based research perspective (Berkes et al. 2002, Gunderson andHolling 2002; Table 1). Its disciplinary roots are in ecology but are strongly widened by social sciences (Patterson et al. 2017). Social-ecological transformations literature is based on complex adaptive systems theory that discusses resilience, adaptability, and transformability as key properties of social-ecological systems , Gunderson and Holling 2002, Walker et al. 2004. This approach understands transformations as "shifts that fundamentally alter human and environmental interactions and feedbacks" (Walker et al. 2004. Second, the sustainability transitions approach generally focuses on social-technical systems while often taking a sectoral perspective (e.g., energy, water, waste, food systems; Grin et al. 2010, Köhler et al. 2019; Table 1). This approach investigates longterm societal change toward sustainability. Its disciplinary roots are in innovation studies, complex systems theory, technology studies, institutional analysis, and evolutionary as well as institutional economics (Patterson et al. 2017). This approach understands transformations as transitions (see Hölscher et al. 2018 for a comparison of the terms transformation versus transition) and thus as "co-evolution processes that require multiple changes in socio-technical systems or configurations," "multi-actor processes," "radical shifts from one system or configuration to another," "long-term processes," and "macroscopic" (Grin et al. 2010:11-12).
Third, the transformative adaptation approach focuses on power issues within transformative processes as an adaptive response to climate change (Pelling et al. 2015; Table 1). It takes a systemic and structural perspective on human vulnerability and equity concerns linked to climate change (Pelling 2010, O'Brien 2012. Transformative adaptation aims to change fundamental systemic structures and paradigms that produce vulnerability for people. Its disciplinary origins are in development studies, human geography, and political ecology (Patterson et al. 2017). This approach understands transformations, for instance, as "physical and/or qualitative changes in form, structure or meaning-making (...). It can also be understood as a psycho-social process involving the unleashing of human potential to commit, care and effect change for a better life" (O'Brien 2012:670).
Fourth, the sustainability pathways approach focuses on human development while often taking a contextually grounded sustainable development perspective (Leach et al. 2007, Scoones et al. 2015; Table 1). This approach investigates the governance aspects of transformations and highlights the role of citizens at the same time (Scoones et al. 2015). Its disciplinary roots are in development studies, political science, complex systems theory, anthropology, and economics (Patterson et al. 2017). This approach does not relate to one specific definition of transformation due to the differences of context and perspectives (Scoones et al. 2015). However, this approach highlights the role of pathways to sustainability in which a pathway is "the way in which a given system changes over time, depending on the issue in question, several different scales may be important, sometimes simultaneously and in overlapping ways" (Leach et al. 2007:12).
This brief overview does not claim to be exhaustive, but shows how transformation is understood differently within the Western scientific knowledge system. Scholars with different theoretical backgrounds have different foci in transformations (e.g., socialecological, social-technical systems), apply different perspectives (e.g., place-based, sectoral), and pursue different aims (e.g., resilience and sustainable production and consumption; Table 1). Despite these differences, they jointly contribute to a more comprehensive understanding of what a transformation in the sense of a large system change means. They all call for large-scale societal change toward sustainability while understanding transformations as nonlinear, complex, long-term, multilevel, multiphase, and cross-scale processes , Loorbach et al. 2017. Indigenous and local knowledge systems https://www.ecologyandsociety.org/vol25/iss1/art3/ may contribute different insights to the scientific understandings of transformations because of their (1) accumulation of knowledge, practices, and beliefs; (2) strong connection to the environment of indigenous peoples and local communities; and (3) emphasis on relationships of living beings with another and with their environment (Berkes 2018).

Systematic literature review
To identify the existing body of research on ILK in sustainability transformation research, we conducted a systematic literature review (Pullin andStewart 2006, Luederitz et al. 2016; Fig. 1). First, we searched for primary research articles on ILK and sustainability transformations in the Scopus database. The search string used for the review comprised two main elements: (1) transformation (e.g., transformation, transition, or change) and (2) ILK (e.g., indigenous ecological knowledge, local ecological knowledge, or traditional ecological knowledge). The terms "transition" and "change" were selected because of their possible interpretation in the sense of transformation (i.e., large system change; Appendix 1). The search was applied to abstracts, titles, and keywords of published papers written in English between 2000 and 2016. The year 2000 was set as the starting date because at this time research in combination with ILK was becoming ubiquitous in different scientific fields, such as resource management (Cruikshank 2001). The search returned 592 papers (Fig. 1), of which 492 were disregarded after the screening of titles and abstracts because they did not meet the following criteria: (1) they did not apply or observe indigenous, traditional, or local knowledge; and (2) they were not connected to transformation, transition, or change. We also excluded papers that were not published in English (n = 4).
Then, we classified the remaining papers (n = 96) into the groups of review, theoretical, and empirical papers to filter only empirical papers for our literature review (n = 81; Appendix 2 for complete list of reviewed empirical papers). We excluded review and theoretical papers because we were only interested in empirically supported evidence for indigenous and local understandings of transformations.

Data analysis
We conducted qualitative content analysis and coded the content of the final set of 81 papers using the software MAXQDA 12 (Mayring 2014). We developed the coding scheme (Appendix 3) according to the research aims and the variables that help to answer the research questions. Main categories of the coding scheme were general paper characteristics, methodological approach, location of case study, the occurrence and use of the terms transformations and ILK and their synonyms, and the connection of ILK and transformations in the reviewed literature. We continuously adapted and refined the coding variables during the iterative process of coding the papers until we reached a consistent information level.
In addition, we quantitatively analyzed the full text of the final set of 81 papers. All words that appeared in at least one of the papers were extracted to examine the abundance of the individual terminologies across all papers (Abson et al. 2014, Partelow et al. 2018. The extracted list contained n = 5570 unique words, which was further reduced by excluding adjectives, pronouns, articles, numbers, and abbreviations that were content-wise not relevant to the topic. In addition, words with ambiguous meaning that had no connection to the topic were excluded (e.g., background or cycle). Our final list contained n = 842 words. With the final multivariate word by paper matrix, we conducted a detrended correspondence analysis with R software to derive a visualization of the principal gradients found within the abundance of words in the papers (Hill and Gauch 1980). Using the detrended correspondence analysis to visualize the first two axes of the multivariate space, we in addition clustered papers into groups that shared the same wording, using Wards clustering (Abson et al. 2014). Different groups were visualized within the ordination by different colours. Detrended correspondence analysis is a standard ordination analysis predominantly used in ecology with sparse datasets, extracting main gradients out of multivariate datasets based on reciprocal averaging (Hill and Gauch 1980). Statistical significance of cluster groups was supported by an indicator species analysis, which allowed the identification of words that were significantly occurring and hence indicating a specific cluster group.

Geographical and temporal distribution
The 81 papers investigated 82 case studies (1 paper with 2 case studies). The biggest part of the research was conducted in North America with 31 papers (38%), followed by Asia with 13 papers (16%), Africa with 11 papers (13.5%), South America with 11 papers (13.5%), Oceania with 10 papers (12%), and Europe with only 6 papers (7%; Fig. 2). We also identified a general increase in publications per year, especially since 2008 (Fig. 2).

Fig. 2.
Geographical distribution of case studies (n = 82, because one paper investigated two case studies) and temporal distribution of publications (n = 81).

Understandings of transformations
We found few empirical papers that included ILK to understand transformations among the reviewed scientific papers. The application of the words "transformation," "transition," and "change" in the reviewed papers showed a clear focus on the use of the word "change" in combination with ILK. In all 81 papers (100%) the word "change" was mentioned, "transition" in 21 papers (26%), and "transformation" in 17 papers (21%; Appendix 4). In 49 papers (60%), only "change" was used (Fig. 3a). The combination of "change" and "transition" was used in 15 papers (19%). The words "change" and "transformation" were used together in 11 papers (14%). Six papers (7%) used all three words. Only four papers (5%) used the term "transformation" in the sense of a social-ecological system change (i.e., . Eleven papers (14%) used "transformation" or "transition" in the sense of a system change, but did not define it, such as a transition of a pastoral system (Homann et al. 2008).
Furthermore, 11 papers (14%) used these terms in ecological contexts, such as "transition of temperature and landscape" or "environmental transformations" (e.g., . Additionally, the "transformation of living conditions" was researched in four papers (5%; e.g., Klein et al. 2014. Regarding the term "change" the predominant focus of the analyzed literature body lies in observations and perceptions of environmental (n = 30, 37%) or climatic (n = 25, 31%) changes by ILK holders (Fig. 3b). The papers dealing with environmental changes focus, for instance, on marine (e.g., Taylor et al. 2011, Moshy and or terrestrial environments (e.g., Paré et al. 2010. Papers focusing on climatic change often investigated indigenous and local perceptions of climate change and interpretations of climate variables, such as temperature or precipitation (e.g., Boillat andBerkes 2013, Boissière et al. 2013). Fourteen papers (17%) dealt with socialecological changes, for example, changing livelihood circumstances due to environmental alterations (e.g., Ford et al. 2006). The remaining 12 papers (15%) dealt with change in terms of changes in species abundance and behavior (e.g., Kendrick et al. 2005, Carter andNielsen 2011).

Conceptualization of indigenous and local knowledge
The term of ILK summarizes all the different descriptions of indigenous, traditional, or local knowledge systems occurring in the reviewed literature body. Some authors constrain to one description, for instance, traditional ecological knowledge (Gill and Lantz 2014) or indigenous knowledge , but most of the papers (n = 60, 74%) used the different terms synonymously.
Only 39 papers (48%) explicitly defined ILK (Fig. 3c), of which 24 papers (30%) referenced literature from Fikret Berkes who defined ILK (or traditional ecological knowledge) as "a cumulative body of knowledge, practice, and belief, evolving by adaptive processes and handed down through generations by cultural transmission, about the relationship of living beings (including humans) with one another and with their environment" (Berkes 2018:8). Thirteen papers (16%) used other definitions and references to define ILK, for instance, ILK defined as "place-based knowledge that is rooted in local cultures and generally associated with long-settled communities which have strong ties to their natural environments" (Orlove et al. 2010:244). Two papers (2%) did not link their definition of ILK to other literature.

Methodological approach in indigenous and local knowledge research
The methodological approach of the data collection in the reviewed literature showed a strong tendency to qualitative methods (Fig. 3d). Fifty-five papers (68%) used qualitative methods exclusively, particularly semistructured interviews and focus-group discussions, and 26 papers (32%) conducted a mix of qualitative and quantitative methods.
In 48 papers (59%), data analysis included both qualitative and quantitative methods, indicating that data collected through qualitative methods often were analyzed through statistical methods (Fig. 3e). In 33 papers (41%), solely qualitative methods were used, such as content analysis of the interviews (e.g., McCarthy et al. 2012, Altschuler and Brownlee 2016).

Fig. 4.
Research clusters resulting from detrended correspondence analysis: research in Arctic environments (red), research in terrestrial environments (green), research in coastal environments (blue), and research in grass and rangeland environments (gray). *wording adjusted.

Clusters of scientific literature on transformations and indigenous and local knowledge
The cluster analysis, which is visualized in the detrended correspondence analysis of the words used in the reviewed papers, yielded four distinct research clusters: (1) research in Arctic environments (red), (2) research in terrestrial environments (green), (3) research in coastal environments (blue), and (4) research in grass and rangeland environments (gray). These clusters were distributed along two axes: (1) marine vs. terrestrial environments (X-axis) and (2) Arctic vs. tropic climatic conditions (Y-axis; Fig. 4). Appendices 5 and 6 present more information for each research cluster (e.g., geographical distribution of case studies, key research aspects) and a complete list of significant indicator words, respectively.
The cluster of research in Arctic environments comprised 26 papers (32%; red). This cluster focused solely on case studies in Arctic environments, including Alaska, the Canadian Arctic, and Siberia. Actors involved in the research were members of different indigenous communities in Arctic regions, such as the Inuit, the Cree, or the Chipewyan Dene. The key research aspects of this cluster were observations and understandings of changing climatic and environmental conditions. Because of the widespread subsistence activity of hunting mammals on land and ice, especially changes in sea ice and the distribution and abundance of different animal populations in the Arctic regions were objects of research in this cluster.
The cluster of research in terrestrial environments included 22 papers (27%; green). The spatial focus of this cluster lay mostly in case studies in Oceania and South America. Actors involved in this research cluster were either from indigenous communities or local communities. The research focused on the perception of climatic changes and the adaptive capacity of the local communities to these changes. Unlike the other clusters, this cluster paid high attention to societal aspects and culturally important issues in the communities, such as education, globalization, government, beliefs, spirituality, and traditions.
The cluster of research in coastal environments comprised 14 papers (17%; blue). This cluster focused strongly on coastal and island regions of all continents. Actors involved in the research of this cluster included local fishers or divers with local ecological knowledge of the marine environments in these regions. Key research objects in this cluster were changes in marine ecosystems, such as coral reefs and lagoons, which served as habitats for endangered fish and plant species, and appropriate management strategies for a positive development of these ecosystems.
The cluster of research in grass and rangeland environments included 19 papers (24%; gray). The spatial focus of this cluster lay in Africa and Asia. Participants were predominantly actors with an agricultural background, for instance, local herders, smallholder farmers, and households owning small land areas or livestock. Hence, the research focus lay in environmental changes of grass-and rangelands and the consequences for livestock management and farming. Problematic issues mentioned in this cluster were desertification and vegetation changes as well as mitigation processes against these changes.

DISCUSSION
Three major insights gained through our literature review: (1) a lack of research to understand transformations from the perspective of ILK systems, (2) challenges of researching ILK in contexts of change, and (3) a pledge for a more plural understanding of transformation. Based on these insights we formulated relevant starting points for future research.

Lack of research to understand transformations from the perspective of indigenous and local knowledge systems
This study demonstrates a gap in understanding transformations from the perspective of ILK systems in the sustainability transformation literature. Despite our comprehensive search Ecology and Society 25(1): 3 https://www.ecologyandsociety.org/vol25/iss1/art3/ string (Appendix 1), we identified only four papers (5%) in our review that applied indigenous and local observations of change to investigate transformations from social-ecological literature (i. e., . This result might be explained by two main reasons: (1) potential caveats of this study, and (2) an actual lack of consideration of ILK in sustainability transformation research.
The first explanation relates to an important caveat of this research, which is that we only sampled peer-reviewed papers published in English referenced on Scopus. This sampling method can lead to a systematic sampling bias because the consideration of ILK to foster sustainability transformations could mostly appear outside of this body of academic literature and in languages other than English (Vinyeta and Lynn 2013). Research on ILK with a focus on understanding transformations, for instance, from cultural anthropology or ethnobiology may exist in other sources, such as books or papers that are not accessible through Scopus and are written in other languages. A similar sampling bias has previously been reported in systematic reviews of ILK with regard to conservation initiatives (Benyei et al. 2020). Furthermore, most of the case studies of the reviewed papers conduct research in North America, which might also be a bias. This would be true if the reason for this is the fact that North America is generally the continent with the highest amount of academic literature worldwide (King 2004), which therefore may also lead to more research in this area. However, another possible reason for this focus could be that the regions of Alaska and the Canadian Arctic are some of the most affected regions by global climate change worldwide (Hinzman et al. 2005). The loss of sea ice due to climate change has an especially strong impact on the livelihood of indigenous peoples and local communities in Arctic regions. Because indigenous and local observations of climate change and its consequences are treated a lot in the reviewed literature body, it could be a logical outcome that case studies in these affected regions dominate the reviewed literature.
The second explanation could be that sustainability transformation research has indeed not engaged thoroughly with ILK yet despite the recognition that more plural perspectives and worldviews need to be considered to advance sustainability transformation research (Loorbach et al. 2017). We only found four papers from social-ecological transformations literature that investigated transformations with ILK. Indigenous and local understandings of transformation have the potential to relate the values, contexts, worldviews, and cultures of indigenous peoples and local communities to the transformations discourse , such as in environmental governance (Brondizio and Le Tourneau 2016), climate change (Savo et al. 2016), conservation (Benyei et al. 2020), and resource management research (Ban et al. 2018). The engagement of ILK in sustainability transformation research is still emerging and in its infancy. Including more than simply Western scientific knowledge systems to change perspectives and find solutions for sustainability challenges still gets relatively little attention (Golden et al. 2015). However, the number of recent papers that showcase the value of bridging ILK and scientific knowledge for climate change mitigation and biodiversity conservation is increasing (Gavin et al. 2015, Brondizio and Le Tourneau 2016, Garnett et al. 2018, Hill et al. 2019. A challenge is that in contrast to scientific knowledge, ILK is often regarded as "subjective, arbitrary, and based on qualitative observations of phenomena and change" (Mistry andBerardi 2016:1275). Also, current research approaches that try to apply ILK are often driven by Western research methods and political agendas, such as predominant conservation and development approaches, which is questionable because all knowledge is value driven and linked to socially situated actors (Weiss et al. 2013, Mistry andBerardi 2016). For example, the perception and interpretation of climate change is very different whether the observation approach is local or global, or from an ILK or scientific knowledge perspective ). Another example is from Golden et al. (2014), who presented the challenge of mutual understanding and negative connotations to Western terms and concepts. In their study, they described the absence of the word or concept "adaptation" in the culture of First Nations in Canada and argued that it makes a common approach to research on adaptation almost impossible.

Challenges of researching indigenous and local knowledge in contexts of change
Our results support the trend of increasing research that engages with ILK in contexts of environmental, climate, social-ecological, and species change in different environments (Figs. 2, 3, 4). However, our results indicate three challenges that accompany research with ILK in contexts of change: (1) the added value of ILK, (2) the use of qualitative methods, and (3) the focus on change and adaptation.
First, understanding the added value of ILK for sustainability research is difficult because ILK is very different from scientific knowledge (Berkes 2018) and in our review, 42 papers (52%) did not even provide a definition for ILK. Indigenous and local knowledge is "local and context-specific, transmitted orally or through imitation and demonstration, adaptive to changing environments, collectivized through a shared social memory, and situated within numerous interlinked facets of people's lives" (Mistry andBerardi 2016:1274). However, the trend is still to assimilate ILK within scientific knowledge instead of acknowledging ILK as an equally relevant knowledge system (Tengö et al. 2014, Mistry andBerardi 2016). Hence, engaging with ILK means encountering different worldviews, practices, ethics, identities, power relations, and rights (Tengö et al. 2017). The results from the detrended correspondence analysis also show that the green cluster (i.e., terrestrial environments) was the only one that presented social aspects of ILK, such as belief, culture, and language ( Fig. 4; Appendix 5).
Second, the different methodological approaches used in the reviewed papers show the predominant use of qualitative methods both in data collection and data analysis, which indicates the complexity involved in investigating and understanding ILK. Csonka (2005) mentioned the mostly oral character of these knowledge systems, which requires the use of qualitative methods and the contribution of "qualitative, historical field data" (Vinyeta and Lynn 2013:14). However, Davis and Ruddle (2010) criticized that the standards of accountability and transparency for research on ILK need to be improved, starting with "the requirement that researchers provide descriptions of research designs and methodologies sufficient to enable assessment of the reliability and representativeness of findings, and to facilitate comparison, generalization, and evidence-based conclusions" https://www.ecologyandsociety.org/vol25/iss1/art3/ (Davis and Ruddle 2010:892). Others see great potential in the open and qualitative character of research on ILK because of the "readiness, reliability and low cost" of associated methods (Hallwass et al. 2013:402) and the possibility to support and complement the usually more quantitative data of Western scientific research . Furthermore, qualitative approaches may also be more likely to capture and articulate aspects of ILK systems that are holistic and not directly commensurable with reductionist science (Whyte et al. 2016).
Third, the detrended correspondence analysis revealed four research clusters that generally focus on observing changes with indigenous peoples and local communities in Arctic, terrestrial, coastal, and grass and rangeland environments ( Fig. 4; Appendices 5, 6). Research on change that includes ILK can be better differentiated by the environments in which the research is conducted than by the theoretical or methodological approaches used. This indicates greater diversity of the biophysical conditions studied compared to the theoretical and methodological approaches used. The focus of observing change lays with natural phenomena, such as melting of ice, change of flora and fauna, and climate variations. This research on change in different environments tends to be driven more by natural science research, such as ecology or biology, with less focus on social aspects. Additionally, the research clusters generally focus on the practices of indigenous peoples and local communities in their respective environments and how these practices have adapted to changes. One example is the change in hunting practices of the Inuvialuit people in Canada's Western Arctic due to climate change (Berkes and Jolly 2002). However, none of the research clusters indicates a focus on understanding which practices or strategies indigenous peoples and local communities apply to navigate and manage their environments toward desired states, i.e., often breaking out of and transforming negative situations.
Summing up, future sustainability transformation research that engages with ILK should be transparent about how ILK is understood and which research designs and methodologies are applied. Research, which engages with ILK, needs to also apply different innovative methods to deal with the complexity of ILK and to make insights from local and place-specific ILK useful for other regions of the world that also undergo processes of change. Possible methods could include the analysis of stories and songs that are a repository of ILK (Fernández-Llamazares and Cabeza 2018, Fernández-Llamazares and Lepofsky 2019). Additionally, insights from more contextualized and place-based research modes such as transdisciplinary research might provide helpful approaches (Lang et al. 2012, Balvanera et al. 2017a. With the societal problems or phenomena as a point of departure and not a specific theory or methodology, transdisciplinarity can serve as a research practice that allows for collaboration between ILK systems and scientific knowledge systems on equal footing. Transdisciplinary research highlights close collaboration between scientific as well as societal actors and is therefore promoted by global sustainability research initiatives (e.g., IPBES, Future Earth) to cocreate knowledge for sustainability transformations (Mauser et al. 2013, Pascual et al. 2017.

Need for plural understanding of transformations
Sustainability transformation research and practice aims at changing how people interact within the systems they live in, such as food or energy systems. For transformative change to improve the living conditions for people from different knowledge systems, it becomes critical to connect with their view on how the world works and changes, how to act for transformations (i.e., what to do to foster change), and what just, equitable, and sustainable futures could be (Braun 2015, Blythe et al. 2018). Thus, we argue for a plural understanding of transformations because this (1) could substantially improve understandings of transformations, (2) is ethically required, (3) could increase agency for contributing to sustainability transformations, and (4) could support research on transformative change.
First, we believe that including people with different knowledge systems can improve the sustainability transformation discourse and practices because it potentially widens the conceptual understanding and provides more variety for actions to foster just, equitable, and sustainable futures. The scientific sustainability transformation discourse has its own understandings or approaches to transformations (Feola 2015), such as socialecological transformations, sustainability transitions, transformative adaptation, and sustainability pathways (Table 1). Due to different disciplinary roots, they apply different perspectives on transformations (e.g., place-based, sectoral), foci (e.g., socialecological systems, human development), and pursue different aims (e.g., resilience, sustainable pathways; Table 1; Patterson et al. 2017). What unites them is their call for large-scale societal change toward the normative goal of sustainability and a scientific approach to transformations by viewing transformations as nonlinear, complex, long-term, multilevel, multiphase, and crossscale processes , Loorbach et al. 2017. Indigenous and local understandings of transformation could bring additional perspectives, foci, and aims concerning transformations due to alternative normative goals and emotional as well as spiritual connections to nature (Reid et al. 2006, Gray 2016).
The dominant sustainability transformation discourse aims for the normative goal of sustainability (Loorbach et al. 2017), which is primarily influenced by Western worldviews, values, and knowledge systems (Kothari et al. 2014). A plural understanding of transformation could carefully consider and reflect on alternative normative goals, such as "Buen Vivir," which is a concept that captures a culture of life for collective well-being of people and nature together with different interpretations across South America (Gudynas 2011, Monni andPallottino 2015), or "Ubuntu," which is a moral concept of caring that connects humanity and has origins in South Africa (Metz 2011). Normative goals of transformations vary between people in different places and from diverse knowledge systems and worldviews. They may also vary among different actors within a place. Perceptions of the normative goal shape possible and preferred actions that may foster change toward a desired direction. Engaging with indigenous peoples and local communities for transformation can therefore be a promising endeavor to collaboratively explore alternative actions for and desired directions of transformations. A reflexive view on the normative aspect of transformations is critical to consider for scholars conducting social-ecological transformations, sustainability transitions, transformative adaptation, or sustainability pathways research in places where indigenous peoples and local communities live, to avoid repeating or reinforcing previous or existing patterns of injustice and marginalization. https://www.ecologyandsociety.org/vol25/iss1/art3/ Indigenous and local knowledge systems can also provide guidance for how to include emotional and spiritual aspects into the often very positivistic sustainability transformation discourse because ILK systems are knowledge-action-belief complexes and entail different conceptualizations of human-nature connectedness (Gadgil et al. 1993, Reid et al. 2006, Gray 2016, Berkes 2018. Recent literature highlights that successful transformations will not only rely on changing structures and practices, but also on the change of human-nature connectedness as well as values and mindsets (Abson et al. 2017, Horcea-Milcu et al. 2019, Ives et al. 2020. The sustainability transformation literature discusses the need to change people's connection to nature as well as values and mindsets instead of only developing and scaling out new social-technical innovations, such as new technologies (O'Brien 2016, ). However, discussions on how to achieve these changes for transformations at the societal level are still in its infancy. Indigenous peoples and local communities have very different connections to nature and worldviews than do Western societies. Some of them regard themselves as one unit with nature with deep relations to their place and all living beings, which includes mountains, rivers, lakes, and animals (Berkes 2018). These different human-nature connections and worldviews might provide critical reflections for the current Western scientific approaches to transformations (Table 1). A possible reflection could be on how to understand relations between people and nature (e.g., one unit versus divided, or as biocultural relations; Sterling et al. 2017), or the systems of interest (e.g., socialtechnical systems), which in science often separate people from nature and thus insufficiently recognize the relations and patterns between living beings. Finally, such reflections could lead to new actions to foster transformations that go beyond scaling out of new technologies (e.g., renewable energies) and changing dominant practices by including, for instance, spiritual and emotional values of nature (i.e., scaling deep) or by emphasizing local identity, place, and kinship relations (i.e., scaling down).
Second, there is a strong ethical imperative for engaging with different people and actors concerned with transformations and their aspirations, knowledge, and conditions (Castree et al. 2014, Daedlow et al. 2016. A more collaborative approach to working with indigenous peoples and local communities as partners, might dismantle the power imbalance between ILK and scientific knowledge concerning the notion of transformations (Tengö et al. 2017). This is particularly important in engagement with indigenous peoples and local communities, who have often been marginalized and deprived of livelihoods and self-governance in the name of development and change (Smith 2012). Working toward a plural understanding of transformations might acknowledge cognitive justice, which legitimizes the existence of different knowledge systems, suggests going beyond epistemic supremacy, and is part of processes of decolonizing knowledge (de Sousa Santos 2008, Rodriguez 2017. Cognitive justice "demands recognition of knowledges, not only as methods but as ways of life. This presupposes that knowledge is embedded in an ecology of knowledges, where each knowledge has its place, its claim to a cosmology, its sense as a form of life. In this sense knowledge is not something to be abstracted from a culture as a life form; it is connected to a livelihood, a life cycle, a lifestyle; it determines life chances" (Shiv Visvanathan in Rodriguez 2017:2).
A rewarding yet challenging endeavor for sustainability transformation researchers is to reach out to indigenous peoples and local communities and learn from their worldviews and knowledge systems what transformations possibly mean for them, and from there to explore a common ground for transformations to sustainability or any other normative goal. Working with indigenous peoples and local communities as partners can be key to better understand and act for transformations. For instance, the collaboratively developed fire management system in the Canaima National Park in Venezuela shows how ILK and practices of fire management from the Pemon indigenous peoples informed a counter narrative of landscape change that led to a shift in the environmental discourse and policy making regarding fire management in the park (Rodriguez 2017). Another example is related to effective environmental governance Le Tourneau 2016, Garnett et al. 2018). Indigenous peoples and local communities manage vast areas of land, ecosystems, and biodiversity, and in many cases, their governance systems are sources of sustainable practices, developed and implemented by communities with limited external involvement and embedded in their worldviews (Berkes 2018, Mistry and Berardi 2016, Timoti et al. 2017. Third, by involving people with diverse knowledge systems, we hope to also draw attention to the challenges related to agency in transformations (Westley et al. 2013. Understanding the creation and distribution of agency between different people across scales is key to work collectively and inclusively toward just, equitable, and sustainable futures (Moore 2017). The notion of transformation in sustainability science is currently promoted dominantly by Western scientific knowledge systems, which limits the distribution of agency. A plural understanding of transformations, should involve a more diverse and inclusive set of actors representing diverse knowledge systems, and it should lead to more diverse actions to solve current sustainability problems, other than the often applied approach of solving problems with technological innovations.
Fourth, plural understandings of transformations could contribute to research on transformative change that specifically collaborates with indigenous peoples and local communities. The number of studies investigating transformations is increasing and predicted to grow in the future (Köhler et al. 2019). Most recently, the IPBES outlined, in its next work program until 2030, to assess "factors in human society, at both the individual and collective levels, that can be leveraged to bring about (...) transformative change in favour of biodiversity while taking into account broader social and economic imperatives in the context of sustainable development" (IPBES 2019:18). One explicit ambition from IPBES is to include knowledge from natural sciences, social sciences, humanities, and ILK systems in its assessments through participation and inclusiveness , Díaz-Reviriego et al. 2019. Assessing factors that lead to transformative change in favor of biodiversity with ILK systems will entail understanding transformation and transformative change from the perspective of indigenous peoples and local communities as a prerequisite. However, our results show that this is currently neglected in research. We therefore see epistemological, ontological, and methodological challenges that an assessment of transformative change, which includes ILK, could face if it considers cognitive justice and wants to avoid the supremacy of Western scientific knowledge systems. https://www.ecologyandsociety.org/vol25/iss1/art3/ In summary, we need a plural understanding of transformations because the sustainability challenges we face are as diverse as people are. It is important to be inclusive to different kinds of engagement with sustainability transformations to avoid a supremacy of Western scientific knowledge systems in identifying and prioritizing ways forward. Bridging diverse knowledge systems concerning transformations, could lead to involvement of more people, increased mutual understanding, cocreation of actions across knowledge systems with stronger impact and effectiveness, and support collaborative research on transformative change. As the urgency to solve sustainability problems increases, collaborations between diverse knowledge systems may provide helpful ways of thinking about how to foster transformations.

Future research
Our literature review reveals that the discourse on sustainability transformations lacks understandings of transformations from ILK systems. To address this gap, we suggest two concrete research activities to move forward toward a more plural understanding of transformations: (1) exploring other sources to understand sustainability transformations from an ILK perspective through consultations and collaborations with experts on ILK (i.e., researchers who have studied ILK systems) and ILK holders (i.e., knowledge holders representing their knowledge system, its integrity, and rights), and (2) active engagement of ILK holders and ILK experts in research processes (Tengö et al. 2017). These two research endeavors could also reveal more local understandings of transformations, which in return can potentially contribute to a better understanding of global transformations (Balvanera et al. 2017b).
First, consultations and collaborations with experts on ILK and ILK holders who are familiar with the concept of sustainability transformation and who have worked with indigenous peoples and local communities for a long time in their research and other activities can reveal other sources and existing work on different understandings of transformations. The experts on ILK and ILK holders should be used to seeing ILK and scientific knowledge as both legitimate and complementary. Particularly important persons to consult are indigenous scholars and ILK holders with experience in interacting with science and policy, for example in the Convention on Biological Diversity and IPBES. The consultations and collaborations could provide entry points to potential alternative understandings, concepts, and ways to describe and talk about transformation among indigenous peoples and local communities. This could provide insights about diverse views on human-nature connections and alternative perspectives on time, future, change, scale, and amplification (i. e., a different scaling understanding to foster transformations), which are fundamental elements of the Western scientific understanding of transformations.
Second, active engagement with ILK holders and experts on ILK could deepen and broaden the understanding of practices and strategies for transformation as well as contribute to shifting the power dynamics between knowledge systems and addressing the ethical requirements in sustainability transformations research. Tengö et al. (2017) emphasized the need to engage with the actors and institutions that represent ILK systems, rather than scientist interpreting ILK and the main interfaces with scientific and other knowledge systems (Tengö et al. 2017). One possible approach to bridge different understandings of transformations is the multievidence base approach, which recommends five tasks for successful collaborations across knowledge systems: to mobilize, translate, negotiate, synthesize, and apply (Tengö et al. 2017). This set of tasks can guide a knowledge collaboration to facilitate mutual respect and understanding, usefulness for all actors involved and thus both expand the joint knowledge base for transformation as well as strengthen the ethical practices in sustainability transformation research. Joint and deepened understanding can also create a foundation for agency for transformation. Such an encounter of knowledge holders would contribute to going beyond the dichotomy and power asymmetry of ILK versus scientific knowledge (Agrawal 1995). It would help to see the different knowledge systems as equally relevant and complementary, to bridge them (rather than integrate), and hopefully at the end enable them to work together. Furthermore, it would also increase cognitive justice concerning transformations to avoid suppressing nonscientific knowledge systems and amplifying epistemic supremacy of Western knowledge systems (de Sousa Santos et al. 2008, Rodriguez 2017. As discussed, fostering sustainability is only one possible goal besides others that could arise from traditionally marginalized groups, such as Buen Vivir or Ubuntu. By going beyond acknowledging ILK systems within their own frames and worldviews and treating them as an equally relevant and parallel type of knowledge with differing fundamentals , Tengö et al. 2014), a basis for true collaboration could be built for an enhanced understanding and fostering toward just, equitable, and sustainable futures.

CONCLUSION
This systematic literature review investigated the current role of ILK in sustainability transformation literature. Our study reveals a research gap in understanding transformations from the perspective of ILK systems. We gained an understanding of how ILK is studied in different contexts of change, which is currently applying ILK to confirm and complement scientific knowledge on environmental, climate, social-ecological, or species change. We propose future research endeavors that could yield a plural understanding of transformations and hence, provide an enriched picture of how we could foster inclusive transformations in times of pressing sustainability challenges. Collaborating with indigenous peoples and local communities for transformations has the potential to substantially enrich and question scientific approaches to transformations by providing, for instance, alternative and complementary goals to sustainability, such as Buen Vivir or Ubuntu. Sustainability transformation research needs to avoid the risk of neglecting nonscientific knowledge systems and the risk of perpetuating the supremacy of Western scientific knowledge systems as we endeavor to foster transformations toward just, equitable, and sustainable futures.

Acknowledgments:
We thank the reviewers for their constructive comments. This research is supported by the Volkswagenstiftung and the Niedersächsisches Ministerium für Wissenschaft und Kultur (Grant Number A112269). This research draws on work undertaken in a large transdisciplinary research project (Leverage Points for Sustainability Transformation). The author(s) acknowledge and thank all project members for their ideas and input in the early stages of this work, even where they are not listed as authors. Full details of project members and their research are available at https:// leveragepoints.org. DPML has been supported by a research fellowship granted by the Foundation of German Business (Stiftung der Deutschen Wirtschaft). ("indigenous knowledge" OR "indigenous ecological knowledge" OR "indigenous environmental knowledge" OR "indigenous local knowledge" OR "local knowledge" OR "local ecological knowledge" OR "local environmental knowledge" OR "traditional knowledge" "traditional ecological knowledge" OR "traditional environmental knowledge" OR "local indigenous knowledge" OR "local traditional knowledge" OR "indigenous traditional knowledge" OR "traditional indigenous knowledge" OR "traditional local knowledge" )