Is ‘conversion to sustainable agriculture’ a gradual process of change or a radical move from one point to another? Throughout the 15 chapters of this book, including conversion experiences in the USA, Canada, Latin America, Europe, the Middle East, Japan and Australia, the reader can conclude that ‘conversion’ is a gradual transition toward more resilient farming systems. This volume goes beyond the analysis of conversion at the on-farm level and attempts to provide guidelines for an analysis of conversion at the food-system scale. There is valuable material bringing to the surface the advances in the field, information on existing loopholes and ultimately inspiration for new inquiries. Common issues emerge although the experiences under review come from many different contexts. Interestingly, the authors share no common concept of sustainable agriculture and their diverse concepts are reflected in their use of different terminologies, which include ecological agriculture (European Union), ecological conservation agriculture (Japan), organic farming systems (USA) and agroecology (Cuba).

The three main themes of the book are presented in the first three chapters: Chapter 1: ‘The framework for conversion’ (S. Gliessman); Chapter 2: ‘What do we know about the conversion process?’ (M. Rosemeyer) and Chapter 3: ‘The history of organic agriculture’ (Jamilson and Perkins).

The framework for conversion that Gliessman elaborates in Chapter 1 builds on three steps proposed by Hill (1985)Reference Hill¹: level 1 focuses on making conventional practices more efficient and less costly; level 2 on the substitution of conventional inputs and practices with alternative ones; level 3 on a redesign of the agroecosystem based on ecological processes and relationships. To this, Gliessman adds a fourth level, which focuses on the goal of re-establishing a culture of sustainability that takes into account the interactions among all components of the food system (p. 7). This fourth level attempts to make more explicit the critical mobilization of conventional structures of thinking, developing and practicing agriculture underneath each of the other levels.

Approaches to sustainable agriculture supposedly foster analysis based on integrative and holistic views to properly address complexity. However, the conversion framework presented is a linear trajectory of change, which facilitates the analysis of the parts but hinders a systemic analysis. Gliessman admits this defect when he says ‘we know how to study the pieces of agroecosystems separately, but we are still limited in our ability to work with complexities of entire systems simultaneously’ (p. 9). Why does linearity persist? Perhaps it is because the way the inquiries are designed is still very aligned to conventional scientific rational, or perhaps it is for the lack of sources and evidence to answer new questions.

In fact, in some of the cases presented in the book the linear view of the transition process only partially works. According to Chapter 6 ‘California, USA: The conversion of strawberry production’ and Chapter 12 ‘Japan: Finding opportunities in the current crisis’, the former practitioners of organic agriculture were small producers who had developed direct markets, a characteristic placed at level 4. As a corollary, we can say that in both the Californian and Japanese cases the move to organic impacted simultaneously the farm and the culture of sustainability, but this process cannot fit in a linear analysis. Once the certification process began to rule the practice of organic farming in both places, large agri-business entered the market causing an involution from level 4 to level 2 and the sticking of the conversion process at level 2.

Furthermore, since the framework was created from observing the transition from conventional modern agriculture to more ecological agriculture, it appears to be less useful for understanding the transition to sustainability from non-modern agriculture (e.g., peasant farming systems or mixes of traditional and modern agriculture). The two chapters treating the case of Mexico—Chapter 8 ‘Mexico: Perspectives on organic production’ and Chapter 9 ‘Mexico: Traditional agriculture as a foundation for sustainability’—reveal the limitations of this framework when it comes to the peasant experience converting to sustainability. Since traditional agriculture has a remarkable ecological content, often without use of agro-chemicals, levels 1 and 2 of the framework do not reflect the starting point of its transitions. Maria del Rocio Romero, Chapter 8's author, situates it in the fourth level, thus leaving a hole in our understanding of how this process began.

Very little seems to be known about what the transition from non-modern to sustainable agriculture means and implies. Following Rosemeyer's survey of what we know about the transition process in Chapter 2, we can conclude that research so far has stressed the process of transition from modern agriculture to organic farming systems. This might obscure that organic is only one of a set of agroecological options. Besides, it could cause a bias in the way research and resources on sustainable agriculture are oriented. In almost 30 years of research (this survey covers publications from 1980s up to the present), transitions from different systems other than modern do not appear to be important, but transitions from conventional to organic systems in both developed and developing countries do.

In GliessmanReference Gliessman², we learned that traditional agricultural systems are an example of sustainability, as their agroecosystems are similar to the structure and function of the natural ecosystems of their biogeographic region. Indeed, characteristics of traditional agriculture have served as a basis for the development of sustainable systems, proof of which is seen in the transition experience of Cuba to agroecology, discussed in Chapter 10 ‘Cuba: A national-level experiment in conversion’.

If peasant-like traditional agriculture is ecologically sustainable, what should a transition from traditional to sustainable agriculture imply? Gonzalez Jacome (Chapter 9) raises the issue of modifying traditional agriculture to operate in better market conditions, while simultaneously reproducing its ecological knowledge foundations. In a world with 1.5 billion smallholders, many of them practicing traditional agriculture, we need to make more efforts to better understand what the transition from traditional agriculture to sustainability means. Koocheki, author of the chapter ‘The Middle East: Adapting food production to local biophysical realities’ raises concerns about this too, stating that prevailing models of sustainable agriculture may lack applicability in many developing countries.

Other important gaps in the research on conversions are acknowledged in the survey. For example, for a long time research on sustainable agriculture has been extremely oriented to the physical aspects of the farm during the transitional process, such as pest management, soil diseases, nutrient dynamics and soil nutrient availability. Certainly this is one type of knowledge needed for farmers to undertake the shift with confidence, but without integrating the social dimension, the understanding of conversion will not be fully accomplished. Interestingly, the issues on the economic and social dimensions in the recent literature are very similar to those mentioned in a 20-year-old article by MacRae et al. Reference MacRae, Hill, Mehuys, Henning and Brady³. This might indicate that old issues remain unresolved.

A key tension in transition is certification, especially related to organic farming. While for some farmers organic certification works as a stimulus to finance the transition (by getting premium prices), for others it is a restriction or an unnecessary step. For example, small Japanese producers studied by Muramato, Hidaka and Mineta (Chapter 12), rejected the certification process, arguing they should not pay for a recognition they had achieved before the boom of organic certification. Dumaresque and Ecker, authors of Chapter 14 ‘Australia: Farmers responding to the need of conversion’, take another angle on the issue through the story of the emergent ‘middle way’ agriculture in Australia. The term was coined to recognize the effort toward sustainability, ‘(…) which rejects the conventional model of agriculture and yet falls short of or rejects the organic agricultural model as well’ (p. 324). Such an issue reveals the importance of diversifying formal approaches to recognize a wider range of sustainable options.

A common theme in most of the chapters deals with the influence of institutional change and human resource mobilization to enhance the process of conversion to sustainable agriculture. This was true for the conversion of conventional strawberry farms on the central coast of California, USA, where the role played by centers of research was clearly fundamental. In Chapter 7 ‘Ontario, Canada: Lessons in sustainability from organic farmers’, institutional participation is a central piece of the authors’ analysis. There, Clark and Sumner point out how institutional arrangements can also act as a barrier to sustainability. Similarly, the contributors of Chapter 11 ‘European Union: Key roles for institutional support’ (G. Guzman and Antonio Alonso), center their analysis on how a system of subsidies allowed a quick move toward the redesign of the agroecosystem, because of tailored financial supports. These analyses allow seeing how both government and research institutions have the ability to influence the culture of sustainability. Therefore, institutions would better be considered as one of the cross-cutting issues of conversion.

Altogether, the book offers a big picture of the conversion to sustainability undertaken across the world. A chapter about China or India would have offered a more complete picture of the states of transition, since we know little of the extent to which their buoyant agricultural sectors are moving toward sustainability. The contributors are experts in the processes of sustainable agriculture of the regions and countries they examine. Without doubt, this is a ‘must read’ piece for scholars and students interested in understanding the multiple layers of conversion through a well-informed update on the evolution of sustainable agriculture.