Yellow leaves resemble green ones in that, in contrast with brown leaves, they have an intact cuticle, and their cells are essentially still alive. California bay leaves infected by P. ramorum have been shown to senesce and abscise from trees more frequently than uninfected leaves. In infested forests, a great portion of senescent leaves probably enters the stream already colonized by P. ramorum. As leaves that fall into the water do not dry out, their cells likely remain alive for an extended period, allowing further colonization by P. ramorum. However, stream resident clade 6 Phytophthora species also compete for this substrate and may limit the extent to which P. ramorum can grow on, persist, and reproduce from them. As dry, brown, senesced California bay leaves begin to make up a greater proportion of leaf litter in late summer and fall, the ability of clade 6 Phytophthora species to exploit these, while P. ramorum cannot, may be one explanation for why the latter is recovered less regularly and with lower frequency from these and other California streams in the fall and early winter. Moreover, as the summer progresses, green and yellow leaves will be more decomposed and less suitable for P. ramorum. The warming of streams late in the summer may additionally favor clade 6 Phytophthora species that are known to have generally higher optimal growth temperatures than most other species. We maintained temperatures constant for experimental purposes, but the persistence and sporulation of these Phytophthora species, and P. ramorum in particular,dutch buckets may be significantly affected by temperature fluctuations and extremes.
We have isolated P. ramorum and clade 6 Phytophthora from leaf litter of other tree species in naturally infested streams, including leaves of coast redwood, madrone, white alder, big leaf maple, and coast live oak. Occasionally, we have found portions of other submerged riparian plants, such as chain fern or elk clover , to be colonized. It is well-established that California bay leaves are an optimal substrate for P. ramorum, and though clade 6 Phytophthora species are known from a great variety of vegetative litter, it is uncertain how conducive other vegetative litter would be to survival and sporulation of either species. Stamler et al. recovered primarily clade 6 and 9 Phytophthora species from rivers in the southwestern USA using leaves of Salix and Populus species, common asriparian trees, as bait. It would be expected that natural leaf litter in such ecosystems would also harbor these organisms. Themann et al. recovered primarily P. gonapodyides but also P. cinnamomi from vegetative litter in sediments in an irrigation reservoir. Therefore, leaf and other vegetative litter should be considered as potential sources of Phytophthora, including pathogenic species, whether they are found in natural streams or other surface waters. Alternatively, the suitability of local vegetation may be a determinant of what Phytophthora species become established or prominent in streams.Current farming and food systems confront and are implicated in multiple challenges and unsustainable changes, including biophysical dimensions such as climate change , environmental pollution, escalating losses of biodiversity, and deteriorating ecosystem services.
Social forces and structures as well as unsustainable socioeconomic processes also strain present capacities to manage growing population pres sure, unplanned urbanization, food and nutrition insecurity, dietary shifts, and health disparities associated with poverty, and growing inequality among multiple stakeholders, including women, youth, migratory workers, and indigenous peoples. Both urban and rural actors are impacted in relation to land ownership and land use change issues and drivers underpinning global industrial agriculture and connected food systems. Human activity has approached critical limits over an increasing number of the so-called Planetary Boundaries , beyond which the functioning of ecosystem ser vices may be substantially altered, increasing the risk of destabilizing life on our planet. Agriculture and food systems are both a villain and a victim in approaching or breaching PBs, and this is already impacting the ability to farm and produce food. How can humanity sustainably grow nutritious food and return to a safe operating space within the PBs? As an alternative to this scenario, a growing number of studies and reports indicate significant potential gains from transitioning toward agroecological agriculture as a way of nourishing current populations sustainably while allowing for future generations to support their livelihoods. One core quality of transitioning to agroecological farming systems is the regenerative trend of increased “outputs” per unit “input” for a more efficient agriculture for using and conserving diversity on a long-term basis, through the use and combination of different agricultural techniques in ways which restore and nourish the soil and enhance the local environment, instead of continuously degrading it.
In addition, the diversification strategy makes food producing systems resilient to external shocks and influences, such as floods or droughts, using, for example, approaches built on the principles and science of agroecology. There is growing evidence that such production systems allow for lower cost and more diverse fruit and vegetable supply. Furthermore, conventional thinking about food is increasingly being challenged, shifting from being regarded only as a commodity toward becoming acknowledged for its nourishment, social and cultural values, the links it creates between people, and its deep connectedness with ecosystems, ecosystem services, and natural resources. The current globalized industrial food system exhibits the same drivers which impact and shape farming industries and food production, and underscores the importance of focusing on how food flows into food systems, and which structures and related policies are shaped to support and reinforce current farming as well as food systems. It is not only conventional and industrial production of animal feed, genetic material, or major commodities such as wheat, rice, coffee, sugar, maize, and chicken which are controlled and shipped across continents by large trans-national corporations. Our globalized industrial food systems sometimes also include food which originates from farming systems based on organic farming regulations and principles like the IFOAM principles, calling for more coherent, equitable and holistic food systems,grow bucket and applying agroecological farming methods. In other words, the intentions behind such farming systems and their contributions to agricultural and environmental sustainability are not always extended to food systems, which generally contribute to out-competing local produce, distorting prices and producing huge amounts of food waste and other waste. This can be seen as a contradiction and emphasizes the importance of thinking of not only organic and agroecological production, but also has consequences for thinking the principles into the entire food systems. At the same time, there are many examples of organic farming and food as well as agroecology presenting alternatives to the industrial farming and food systems , and by increasing and emphasizing this, we can move toward a food system that falls within the PBs. This calls for profound analyses of how agroeco logical food systems function, and how they can contribute to coherent, resilient and equitable production and exchange of food, while human and social capitals are built up throughout the food systems, and resources are cycled rather than transported through, from or to disconnected parts of the systems. How can such food systems meet challenges such as losses of complex and system-oriented, context-relevant knowledge about farming and food, and how can they contribute to re-connect consumers and the food that they eat across urban-rural settings in city-region food systems? An increasing number of papers and reports link agroecology and food systems , referring to the fact that agriculture and food systems are intricately linked, and to a large extent driven by the same global structures.
Given the intricate and mutually-reinforcing relations between agriculture, food, and socioeconomic systems, the present article aims to characterize and explore how the concept of agroecology stimulates the conceptualization of agroeco logical food systems, or perhaps even a more inclusive term like “socio-agroecological food systems.” Food systems following the principles of agroe cology calling for resilience, multi-functionality , equity, and recycling of resources face particular challenges and have significant options for impacting sustainable development in city regions. This needs to be seen in a light where an increasing amount of the global population lives in urban areas, from smaller towns with a few thousand inhabitants, to mega-cities of millions of people. Urbanization has changed diets and nutrition, while food consumption has become detached from food production worldwide. Taking a systems approach to reconnecting these gaps requires major changes in consumption patterns, resource management and social responsibility, if everybody is to be nourished in agroecological food systems. We aim to explore the connections and linkages between the concepts of agroecology and food systems, and focus particularly on how the food system framework can locate and ground the concept of agroecology within a rural– urban landscape setting. This exercise requires us to critically examine the reciprocal flows and the multiple environmental, social, and governance related connections needed for an agroecological food system transformation.A food system is a system that involves activities, social and institutional structures, and processes related to the production, distribution, exchange, and consumption of food. Agricultural systems are part of food systems, integrated in ecosystems, and constituted socioecological systems. Over the past few decades, the understanding of food systems has clearly developed as result of the development of a more and more globalized food system. Ericksen compared some features of “traditional” versus “modern” food systems, and addressed the governance of different food systems, with or without support for local production, and Foran and co-authors point to the existence of different concepts of how food systems are constructed, with examples from so-called developing countries. The structure and governance of the food system clearly influences consumption patterns by providing both producers and non-food-producing consumers with options of availability. The range of social and environmental welfare outcomes stemming from food system activities were also discussed and visualized in Ericksen , and Jennings and co-authors analyzed how planned and well gov erned city-region food systems could contribute to different aspects of food security for different groups of citizens, stable incomes, circular economies, and resilience at various levels. Characterizing a food system can follow through its different social aspects and arrangements, like the type and degree of contact between those who grow and produce food and those who receive and eat the food without participating in the production of it, or who and how many people are involved in the cycle between the soil and the plate. Where local food systems with short supply chains have potential for involving resource feedback loops, raising collective awareness among different actors within the food system, and give possibilities for mutual learning , a larger and decoupled food system lacks the direct interaction and feedback, reduces exchange of experiences and knowledge, or the embedded ness inherent in a localized food system. A decade of research on New York’s Chinatown produce economy gives an example of the importance of this con nectedness: the studies revealed that 80-plus produce markets offered an incredibly diverse assortment of lower-cost produce because they are connected to a web of nearby, independently-run small farms and wholesalers.In a food chain , a product flows through different steps, where various forms of transformation may occur, and connection and feedback loops between these different steps may not necessarily exist. In such systems, farmers or industrial food producers can risk becoming producers of “food from nowhere,” as expressed by Bové and Dufour , and later unfolded by Campbell , and “consumers” can become reduced to a non-informed and non-responsible person, only “consuming food no matter of origin,” as a contrast to so-called “food citizens” defined as a consumer who makes decisions that support a democratic, economically just and environmentally sustainable food system, with a possibility of being actively involved in the food system at different levels. The call and practice of re-localizing of food systems is similarly seen as a harbinger of rural– urban reciprocity as consumers and producers are re-embedded physically and socially in the food system while raising awareness of their respective impacts on one another.Agroecology is widely acknowledged equally as a science, a practice and a movement. Its academic roots go back nearly 100 years, drawing on the fields of agronomy, horticulture, and ecology.