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Rapid demographic ageing substantially affects socioeconomic development 1-4 and presents considerable challenges for food security and agricultural sustainability 5-8 , which have so far not been well understood. Here, by using data from more than 15,000 rural households with crops but no livestock across China, we show that rural population ageing reduced farm size by 4% through transferring cropland ownership and land abandonment (approximately 4 million hectares) in 2019, taking the population age structure in 1990 as a benchmark. These changes led to a reduction of agricultural inputs, including chemical fertilizers, manure and machinery, which decreased agricultural output and labour productivity by 5% and 4%, respectively, further lowering farmers' income by 15%. Meanwhile, fertilizer loss increased by 3%, resulting in higher pollutant emissions to the environment. In new farming models, such as cooperative farming, farms tend to be larger and operated by younger farmers, who have a higher average education level, hence improving agricultural management. By encouraging the transition to new farming models, the negative consequences of ageing can be reversed. Agricultural input, farm size and farmer's income would grow by approximately 14%, 20% and 26%, respectively, and fertilizer loss would reduce by 4% in 2100 compared with that in 2020. This suggests that management of rural ageing will contribute to a comprehensive transformation of smallholder farming to sustainable agriculture in China., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)

China's agriculture is dominated by smallholder farms, which have become major sources of negative environmental impacts including eutrophication, formation of haze, soil acidification and greenhouse gas emissions. To mitigate these environmental impacts, new farming models including family farming, cooperation farming and industrial farming have emerged in recent years. However, whether these new farming practices would improve the economic and environmental performance as compared to the current smallholder farming has yet to be verified on ground level. In this paper, by using pilot farming cases within the watershed of Tai Lake, we found that alternative farming models produced 7% more crop yield, while using 8% less fertilizer, leading to a 28% decrease in pollutant emission per hectare. These alternative farming models have a 17% higher fertilizer use efficiency and 50% higher profit per hectare. Compared to smallholder farming, these alternative farming practices invest 27% more resources into agricultural facilities, including advanced machinery, and have a younger, better educated labor force as a consequence of a larger farm size and more specialization. These input changes substantially increase fertilizer use efficiency and reduce agricultural pollution. Policy arrangements to support and facilitate the uptake of these farming models will further promote the green development and sustainable intensification of agricultural production., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Producing more food with less pollution and greenhouse gas emissions is a grand challenge for the 21st century. Strategies to successfully promote win‐win outcomes for both food security and environmental health are not easy to identify. Here we comprehensively assess an ecological rice‐animal co‐culture system (RAC) (e.g., rice‐fish, rice‐duck, and rice‐crayfish) through a global meta‐analysis and identify the potential benefits of global promotion. Compared to traditional monoculture of rice or animal production, the RAC can not only reduce the demand for agricultural land areas, but also increase rice yields (+4%) as well as nitrogen use efficiency of rice (+6%). At the same time, RAC reduces nitrogen losses (−16% runoff and −13% leaching) and methane emissions (−11%), except for rice‐fish coculture systems, which are likely to increase methane emissions (+29%). Furthermore, RAC increases the net income of farmers through reducing cost of fertilizer and pesticide input and achieving higher outputs with more marketable products. According to the development stage of different countries, promotion of RAC will thus realize multiple benefits and aid sustainable intensification. Plain Language Summary: How to feed the growing world population with less pollution is a grand challenge for the 21st century. Rice‐animal co‐culture systems present an ecological integrated farming approach to tackle the challenge. Through a global consensus by synthesizing evidence from existing literature, we found that rice‐animal co‐culture systems could produce more diverse food types and nutrient sources, enhance resource use efficiency and reduce methane emissions, while increasing farmers' income. Global promotion of rice‐animal coculture system has the potential to benefit sustainable development goals. Key Points: Rice‐animal co‐culture systems could produce more diverse food with higher rice yield and extra animal proteinGlobal promotion of rice‐animal co‐culture will reduce nitrogen loss and methane emissions from rice paddiesGlobal promotion of rice‐animal co‐culture will increase income of producers by 152–171 billion US dollars annually [ABSTRACT FROM AUTHOR]

The fast economic development of southwest China has resulted in significant increases in the concentrations of reactive nitrogen (Nr) in the atmosphere. In this study, an urban (Chengdu, CD), suburban (Shifang, SF) and agriculture (Yanting, YT) – dominated location in the Sichuan Province, southwest China, were selected to investigate the atmospheric composition of Nr, their concentrations and deposition rates. We measured Nr concentrations in precipitation (NH 4 + , NO 3 − and organic N (DON)), the gas phase (NH 3 and NO 2 ), and the aerosol particles (PM 2.5 ), and calculated their fluxes over a two year period (2014–2016). Total annual N deposition rates were 49.2, 44.7 and 19.8 kg N ha −1 yr −1 at CD, SF and YT, respectively. Ammonia concentrations were larger at the urban and suburban sites than the agricultural site (12.2, 14.9, and 4.9 μg N m −3 at CD, SF and YT, respectively). This is consistent with the multitude of larger sources of NH 3 , including city garbage, livestock and traffic, in the urban and suburban areas. Monthly NO 2 concentrations were lower in warmer compared to the colder months, but seasonal differences were insignificant. Daily PM 2.5 concentrations ranged from 7.7 to 236.0, 5.0–210.4 and 4.2–128.4 μg m −3 at CD, SF and YT, respectively, and showed significant correlations with fine particulate NH 4 + and NO 3 − concentrations. Ratios of reduced to oxidized N were in the range of 1.6–2.7. This implies that the control of reduced Nr especially in urban environments is needed to improve local air quality. [ABSTRACT FROM AUTHOR]

To feed an increasingly affluent population, the nitrogen input into global food production systems is currently two times the safe planetary boundary leading to adverse impacts on the local and global environments. The nitrogen footprint is an important index to understand the impact of human activities on the environment, however, it is rarely applied at a watershed scale. By using the C oupled H uman A nd N atural S ystem (CHANS) model, it was found that the total nitrogen input to the Lake Tai watershed has increased from 141.1 Gg N yr−1 in 1995 to 244.3 Gg N yr−1 in 2010, and then decreased again to 201.2 Gg N yr−1 in 2015. The study findings are consistent with the change in the total nitrogen concentration observed in Lake Tai. While the per capita nitrogen footprint remained stable at around 30 kg N yr−1 before 2010, a substantial decrease to approximately 25 and 20 kg N yr−1 in 2010 and 2015, respectively, has occurred. Dominant sources of nitrogen emissions contributing to the nitrogen footprint gradually have changed from agricultural production to wastewater and nitrogen oxides emissions from fossil fuel combustion. A reduction of the nitrogen footprint is beneficial for effective nitrogen pollution control strategies and better wastewater treatment techniques should be prioritized for future policymaking. • The nitrogen footprint has been reduced in the Lake Tai watershed. • The nitrogen footprint can link water pollution and human activities. • Urban areas have become new hotspots of the nitrogen footprint for Lake Tai. • Optimization of the nitrogen footprint of urban areas can achieve sustainable development in the watershed. [ABSTRACT FROM AUTHOR]