The persistent threat of emerging plant disease pandemics to global food security.

Plant disease outbreaks are increasing and threaten food security for the vulnerable in many areas of the world. Now a global human pandemic is threatening the health of millions on our planet. A stable, nutritious food supply will be needed to lift people out of poverty and improve health outcomes. Plant diseases, both endemic and recently emerging, are spreading and exacerbated by climate change, transmission with global food trade networks, pathogen spillover, and evolution of new pathogen lineages. In order to tackle these grand challenges, a new set of tools that include disease surveillance and improved detection technologies including pathogen sensors and predictive modeling and data analytics are needed to prevent future outbreaks. Herein, we describe an integrated research agenda that could help mitigate future plant disease pandemics.

Diverse adaptation strategies helped local food producers cope with initial challenges of the Covid-19 pandemic: Lessons from Québec, Canada.

The Covid-19 pandemic has demonstrated the vulnerability of food systems to disturbances. Advocates have promoted short food supply chains as more resilient and adaptable thanks to their embeddedness in local economic and ecological networks. As part of a broader case study on challenges facing farmers in local food supply chains in Québec, Canada, we asked farmers about the pandemic's impacts on food production and marketing in the province, including how food producers coped with these challenges. We sent an online questionnaire to 1,046 farmers who distribute food through direct marketing in Québec, identified through consumer-facing online platforms. We conducted follow-up interviews with 15 of the 133 farmers that completed the questionnaire to gain a better understanding of their pandemic-related challenges and opportunities, as well as their adaptation needs and strategies. We identified four main types of challenges among farmers: workforce shortages, balancing food demand and supply, changes in sales outlets and marketing channels, and other operational and development issues. In turn, six key adaptation strategies helped farmers reorganize their marketing and sales, which we categorize as: redistribution, streamlining, replacement, collaboration, farm adjustment, and outlet adjustment. Most surveyed local farmers felt well-prepared to adapt to the four major challenges that the Covid-19 pandemic forged or escalated, and our findings suggest that they demonstrated remarkable resilience to additional challenges posed by the pandemic. Our study therefore contributes important insights about how flexibility and redundancy among local farmers stabilized the local food system during the onset of a global pandemic.

Socio-environmental consideration of phosphorus flows in the urban sanitation chain of contrasting cities.

Understanding how cities can transform organic waste into a valuable resource is critical to urban sustainability. The capture and recycling of phosphorus (P), and other essential nutrients, from human excreta is particularly important as an alternative organic fertilizer source for agriculture. However, the complex set of socio-environmental factors influencing urban human excreta management is not yet sufficiently integrated into sustainable P research. Here, we synthesize information about the pathways P can take through urban sanitation systems along with barriers and facilitators to P recycling across cities. We examine five case study cities by using a sanitation chains approach: Accra, Ghana; Buenos Aires, Argentina; Beijing, China; Baltimore, USA; and London, England. Our cross-city comparison shows that London and Baltimore recycle a larger percentage of P from human excreta back to agricultural lands than other cities, and that there is a large diversity in socio-environmental factors that affect the patterns of recycling observed across cities. Our research highlights conditions that may be "necessary but not sufficient" for P recycling, including access to capital resources. Path dependencies of large sanitation infrastructure investments in the Global North contrast with rapidly urbanizing cities in the Global South, which present opportunities for alternative sanitation development pathways. Understanding such city-specific social and environmental barriers to P recycling options could help address multiple interacting societal objectives related to sanitation and provide options for satisfying global agricultural nutrient demand.

Agronomic phosphorus imbalances across the world's croplands.

Increased phosphorus (P) fertilizer use and livestock production has fundamentally altered the global P cycle. We calculated spatially explicit P balances for cropland soils at 0.5° resolution based on the principal agronomic P inputs and outputs associated with production of 123 crops globally for the year 2000. Although agronomic inputs of P fertilizer (14.2 Tg of P·y(-1)) and manure (9.6 Tg of P·y(-1)) collectively exceeded P removal by harvested crops (12.3 Tg of P·y(-1)) at the global scale, P deficits covered almost 30% of the global cropland area. There was massive variation in the magnitudes of these P imbalances across most regions, particularly Europe and South America. High P fertilizer application relative to crop P use resulted in a greater proportion of the intense P surpluses (>13 kg of P·ha(-1)·y(-1)) globally than manure P application. High P fertilizer application was also typically associated with areas of relatively low P-use efficiency. Although manure was an important driver of P surpluses in some locations with high livestock densities, P deficits were common in areas producing forage crops used as livestock feed. Resolving agronomic P imbalances may be possible with more efficient use of P fertilizers and more effective recycling of manure P. Such reforms are needed to increase global agricultural productivity while maintaining or improving freshwater quality.

Identifying leverage points for sustainable nutrient policy integration in Canada.

Addressing the 'wicked problem' of nutrient pollution requires coordinated policies spanning across diverse sectors and environmental systems. Using a case study of Canadian legislation, we apply semantic network analysis to identify thematic links across an inventory of 245 nutrient-related policies. Our analysis identifies twelve topics with unique types of connections across multiple facets of Canadian society. 'Hub' policies include broad environmental protection, land use planning, and climate-related legislation with close ties to multiple other topics. 'Bridge' policies create connections among otherwise disconnected topics in the network, representing opportunities to inform new policy proposals. Some legislation, such as food processing regulations, indirectly relates to nutrient use but could inform policy integration towards more coordinated and holistic nutrient management across the food system. A computational text network approach can be useful for addressing challenges in complex policy analysis, including by identifying unique entry points to guide more cross-cutting nutrient policy development.

Untangling the role of social relationships for overcoming challenges in local food systems: a case study of farmers in Québec, Canada.

Advocates for re-localizing food systems often encourage consumers to support local farmers and strengthen local food economies. Yet, local food systems hinge not only on consumers' willingness to buy local food but also on whether farmers have the social support networks to address diverse challenges during food production and distribution. This study characterizes the challenges and support systems of farmers selling to local markets in Québec, Canada, across multiple growing seasons using a mixed-methods research design. We sent an online questionnaire to 1046 farmers and conducted follow-up interviews with 15 of the 133 respondents. Our findings show that farmers relied on an average of four support actor groups, particularly employees, customers, and other farmers. Actors played distinct roles in terms of the importance, frequency, and formality of interactions, providing immediate and long-term support through formal and informal relationships across multiple spatial scales (farm, local community, and regional/international). Our thematic analysis showed that support actors helped farmers in four key domains: (1) Knowledge sharing and emotional support; (2) Labour and workforce; (3) Material and financial aid; and (4) Consumer education and business promotion. Farmer associations provided resources to tackle various challenges, acting as bridges across multiple support actor groups. Yet, our results suggest that political desires to encourage local food systems are in some cases poorly matched with resources to address specific types of challenges farmers face. Specifically, overlooking the role of diverse social support actors in helping farmers build food production and distribution capacity could undermine efforts to foster localization. Supplementary Information: The online version contains supplementary material available at 10.1007/s10460-022-10343-0.

A new dietary guideline balancing sustainability and nutrition for China's rural and urban residents.

Diets have important but often complex implications for both environmental quality and nutrition. We establish a production-oriented life cycle model to quantify and compare the farm-to-gate environmental impacts and food nutritional qualities underlying rural and urban diets in China from 1980 to 2019, a period of rapid urbanization and socioeconomic changes. The environmental impacts of rural diets were generally higher than those of urban diets, but this gap reduced after 2000. Environmental and nutritional values varied considerably across the 31 Chinese provinces due to their different food intakes and dietary structures. Dietary changes coinciding with urbanization increased greenhouse gas emissions, eutrophication potential, and nutritional quality, but decreased energy consumption and acidification potential. Based on our results, we propose a new dietary guideline to mitigate environmental impacts and improve nutritional quality.

The U.S. consumer phosphorus footprint: where do nitrogen and phosphorus diverge?

Phosphorus (P) and nitrogen (N) are essential nutrients for food production but their excess use in agriculture can have major social costs, particularly related to water quality degradation. Nutrient footprint approaches estimate N and P release to the environment through food production and waste management and enable linking these emissions to particular consumption patterns. Following an established method for quantifying a consumer-oriented N footprint for the United States (U.S.), we calculate an analogous P footprint and assess the N:P ratio across different stages of food production and consumption. Circa 2012, the average consumer's P footprint was 4.4 kg P capita-1 yr-1 compared to 22.4 kg N capita-1 yr-1 for the food portion of the N footprint. Animal products have the largest contribution to both footprints, comprising >70% of the average per capita N and P footprints. The N:P ratio of environmental release based on virtual nutrient factors (kilograms N or P per kilogram of food consumed) varies considerably across food groups and stages. The overall N:P ratio of the footprints was lower (5.2 by mass) than for that of U.S. food consumption (8.6), reinforcing our finding that P is managed less efficiently than N in food production systems but more efficiently removed from wastewater. While strategies like reducing meat consumption will effectively reduce both N and P footprints by decreasing overall synthetic fertilizer nutrient demands, consideration of how food production and waste treatment differentially affect N and P releases to the environment can also inform eutrophication management.

Feeding the Corn Belt: Opportunities for phosphorus recycling in U.S. agriculture.

The supply of phosphorus (P) is a critical concern for food security. Concentrated mineral P deposits have been the source of almost all new P entering the biosphere. However, this resource is often used inefficiently, raising concerns about both nutrient pollution and future access to fertilizers. One solution to both of these problems is to enhance our ability to capture and recycle P from waste streams. However, the efficacy of doing this has not been rigorously explored. Here, we examine the potential for recycling major P sources in the United States to supply the necessary P for domestic corn (maize) production. Using 2002 population and agricultural census data, we examine the distribution of three key recyclable P sources (human food waste, human excreta, and animal manure) and P demand from grain and silage corn across the country to determine the distance P would need to be transported from sources to replenish P removed from soils in harvested corn plants. We find that domestic recyclable P sources, predominantly from animal manures, could meet national corn production P demands with no additional fertilizer inputs. In fact, only 37% of U.S. sources of recyclable P would be required to meet all P demand from U.S. corn harvested annually. Seventy-four percent of corn P demand could be met by recyclable P sources in the same county. Surplus recyclable P sources within-counties would then need to travel on average 302 km to meet the largest demand in and around the center of the 'Corn Belt' region where ~50% of national corn P demand is located. We find that distances between recyclable sources and crop demands are surprisingly short for most of the country, and that this recycling potential is mostly related to manure. This information can help direct where recycling efforts should be most-effectively directed.

Environmental health impacts of feeding crops to farmed fish.

Half of the seafood consumed globally now comes from aquaculture, or farmed seafood. Aquaculture therefore plays an increasingly important role in the global food system, the environment, and human health. Traditionally, aquaculture feed has contained high levels of wild fish, which is unsustainable for ocean ecosystems as demand grows. The aquaculture industry is shifting to crop-based feed ingredients, such as soy, to replace wild fish as a feed source and allow for continued industry growth. This shift fundamentally links seafood production to terrestrial agriculture, and multidisciplinary research is needed to understand the ecological and environmental health implications. We provide basic estimates of the agricultural resource use associated with producing the top five crops used in commercial aquaculture feed. Aquaculture's environmental footprint may now include nutrient and pesticide runoff from industrial crop production, and depending on where and how feed crops are produced, could be indirectly linked to associated negative health outcomes. We summarize key environmental health research on health effects associated with exposure to air, water, and soil contaminated by industrial crop production. Our review also finds that changes in the nutritional content of farmed seafood products due to altered feed composition could impact human nutrition. Based on our literature reviews and estimates of resource use, we present a conceptual framework describing the potential links between increasing use of crop-based ingredients in aquaculture and human health. Additional data and geographic sourcing information for crop-based ingredients are needed to fully assess the environmental health implications of this trend. This is especially critical in the context of a food system that is using both aquatic and terrestrial resources at unsustainable rates.

Climate variation explains a third of global crop yield variability.

Many studies have examined the role of mean climate change in agriculture, but an understanding of the influence of inter-annual climate variations on crop yields in different regions remains elusive. We use detailed crop statistics time series for ~13,500 political units to examine how recent climate variability led to variations in maize, rice, wheat and soybean crop yields worldwide. While some areas show no significant influence of climate variability, in substantial areas of the global breadbaskets, >60% of the yield variability can be explained by climate variability. Globally, climate variability accounts for roughly a third (~32-39%) of the observed yield variability. Our study uniquely illustrates spatial patterns in the relationship between climate variability and crop yield variability, highlighting where variations in temperature, precipitation or their interaction explain yield variability. We discuss key drivers for the observed variations to target further research and policy interventions geared towards buffering future crop production from climate variability.

Leverage points for improving global food security and the environment.

Achieving sustainable global food security is one of humanity's contemporary challenges. Here we present an analysis identifying key "global leverage points" that offer the best opportunities to improve both global food security and environmental sustainability. We find that a relatively small set of places and actions could provide enough new calories to meet the basic needs for more than 3 billion people, address many environmental impacts with global consequences, and focus food waste reduction on the commodities with the greatest impact on food security. These leverage points in the global food system can help guide how nongovernmental organizations, foundations, governments, citizens' groups, and businesses prioritize actions.

Land-use legacies are important determinants of lake eutrophication in the anthropocene.

BACKGROUND: A hallmark of the latter half of the 20(th) century is the widespread, rapid intensification of a variety of anthropogenically-driven environmental changes--a "Great Acceleration." While there is evidence of a Great Acceleration in a variety of factors known to be linked to water quality degradation, such as conversion of land to agriculture and intensification of fertilizer use, it is not known whether there has been a similar acceleration of freshwater eutrophication. METHODOLOGY/PRINCIPAL FINDINGS: Using quantitative reconstructions of diatom-inferred total phosphorus (DI-TP) as a proxy for lake trophic state, we synthesized results from 67 paleolimnological studies from across Europe and North America to evaluate whether most lakes showed a pattern of eutrophication with time and whether this trend was accelerated after 1945 CE, indicative of a Great Acceleration. We found that European lakes have experienced widespread increases in DI-TP over the 20(th) century and that 33% of these lakes show patterns consistent with a post-1945 CE Great Acceleration. In North America, the proportion of lakes that increased in DI-TP over time is much lower and only 9% exhibited a Great Acceleration of eutrophication. CONCLUSIONS/SIGNIFICANCE: The longer and more widespread history of anthropogenic influence in Europe, the leading cause for the relatively pervasive freshwater eutrophication, provides an important cautionary tale; our current path of intensive agriculture around the world may lead to an acceleration of eutrophication in downstream lakes that could take centuries from which to recover.