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Urban landscapes are high phosphorus (P) consumption areas and consequently generate substantial P-containing urban solid waste (domestic kitchen wastes, animal bones, and municipal sludge), due to large population. However, urbanization can also trap P through cultivated land loss and urban solid waste disposal. Trapped urban P is an overlooked and inaccessible P stock. Here, we studied how urbanization contributes to trapped urban P and how it affects the P cycle. We take China as a case study. Our results showed that China generated a total of 13 (±0.9) Tg urban trapped P between 1992–2019. This amounts to 6 (±0.5) % of the total consumed P and 9 (±0.6) % of the chemical fertilizer P used in China over that period. The loss of cultivated land accounted for 15% of the trapped urban P, and half of this was concentrated in three provinces: Shandong, Henan, and Hebei. This is primarily since nearly one-third of the newly expanded urban areas are located within these provinces. The remaining 85% of trapped urban P was associated with urban solid waste disposal. Our findings call for more actions to preserve fertile cultivated land and promote P recovery from urban solid waste through sound waste classification and recycling systems to minimize P trapped in urban areas.

The sustainable development of livestock production faces challenges due to substantial emissions of ammonia and nitrous oxide, contributing to global warming and ecosystem acidification. Over the past four decades, the global spotlight on reducing livestock ammonia emissions, notably within Europe, has resulted in the heightened accumulation of ammonium ions in manure. Remarkably, the repercussions of ammonium accumulation in manure have been relatively overlooked, notwithstanding the potential conversion of accumulated ammonium into nitrous oxide through microbial processes. Here, we delved into the microbial mechanisms responsible for this phenomenon, utilizing 15N labeling and metagenomic sequencing, and assessed its global implications. Our analysis reveals that ammonium accumulation, driven by upstream ammonia mitigation in manure management, can reduce nitrous oxide emissions, due to bacterial denitrifiers’ constraints in carbon acquisition. A global assessment suggests that augmenting the accumulation of ammonium in manure by implementing ammonia abatement can unlock substantial benefits in nitrous oxide mitigation.

Reactive nitrogen (N) is a requisite nutrient for agricultural production, but results in greenhouse gas and air and water pollution. The environmental and economic impacts of N fertilizer use in China are particularly relevant, as China consumes the largest amount of N fertilizer in the world to meet its soaring food demand. Here, we use an agro-economic land system model (MAgPIE) in combination with a difference-in-differences econometric model to provide a forward-looking assessment of China’s fertilizer policies in terms of removing fertilizer manufacturing subsidies and implementing measures to improve agricultural nutrient management efficiency. Our model results indicate that enhancing soil N uptake efficiency and manure recycled to soil alongside fertilizer subsidy removal can largely reduce N fertilizer use and N losses and abate N pollution in the short and long term, while food security remains largely unaffected. Enhancing soil N uptake efficiency appears to be decisive to achieving China’s national strategic target of zero growth in N fertilizer use. This study also finds that improving agricultural nutrient management efficiency contributes to higher land productivity and less cropland expansion, with substantial benefits for the environment and food security.

There is an urgent need for countries to transition their national food and land-use systems toward food and nutritional security, climate stability, and environmental integrity. How can countries satisfy their demands while jointly delivering the required transformative change to achieve global sustainability targets? Here, we present a collaborative approach developed with the FABLE—Food, Agriculture, Biodiversity, Land, and Energy—Consortium to reconcile both global and national elements for developing national food and land-use system pathways. This approach includes three key features: (1) global targets, (2) country-driven multi-objective pathways, and (3) multiple iterations of pathway refinement informed by both national and international impacts. This approach strengthens policy coherence and highlights where greater national and international ambition is needed to achieve global goals (e.g., the SDGs). We discuss how this could be used to support future climate and biodiversity negotiations and what further developments would be needed.

Reducing ammonia (NH3) volatilization from croplands while satisfying the food demand is strategically required to mitigate haze pollution. However, the global pattern of NH3volatilization remains uncertain, primarily because of the episodic nature of NH3volatilization rates and the high variation of fertilization practices. Here, we improve a global estimate of crop-specific NH3emissions at a high spatial resolution using an updated data-driven model with a survey-based dataset of the fertilization scheme. Our estimate of the globally averaged volatilization rate (12.6% ± 2.1%) is in line with previous data-driven studies (13.7 ± 3.1%) but results in one-quarter lower emissions than process-based models (16.5 ± 3.1%). The associated global emissions are estimated at 14.4 ± 2.3 Tg N, with more than 50% of the total stemming from three stable crops or 12.2% of global harvested areas. Nearly three-quarters of global cropland-NH3emissions could be reduced by improving fertilization schemes (right rate, right type, and right placement). A small proportion (20%) of global harvested areas, primarily located in China, India, and Pakistan, accounts for 64% of abatement potentials. Our findings provide a critical reference guide for the future abatement strategy design when considering locations and crop types.

ABSTRACTPig production systems in China are shifting from small to industrial scale. Significant variation in housing ammonia (NH3) emissions can exist due to differences in diet, housing design, and management practices. However, there is a knowledge gap regarding the impacts of farm-scale in China, which may be critical in identifying hotspots and mitigation targets. Here, continuous in-situNH3concentration measurements were made at pig farms of different scales for sows and fattening pigs over periods of 3–6 days during two different seasons (summer vs. winter). For the sow farms, NH3emission rates were greater at the small farm (summer: 0.52 g pig−1hr−1; winter: 0.21 g pig−1hr−1) than at the large farm (summer: 0.34 g pig−1hr−1; winter: 0.12 g pig−1hr−1). For the fattening pig farms, NH3emission rates were greater at the large farm (summer: 0.22 g pig−1hr−1; winter: 0.16 g pig−1hr−1) than at the small farm (summer: 0.19 g pig−1hr−1; winter: 0.07 g pig−1hr−1). Regardless of farm scale, the NH3emission rates measured in summer were greater than those in winter; the NH3emission rates were greater in the daytime than at the nighttime; a positive relationship (R2 = 0.06–0.68) was established between temperature and NH3emission rate, whereas a negative relationship (R2 = 0.10–0.47) was found between relative humidity and NH3emission rate. The effect of farm-scale on indoor NH3concentration could mostly be explained by the differences in ventilation rates between farms. The diurnal variation in NH3concentration could be partly explained by ventilation rate (R2 = 0.48–0.78) in the small traditional farms and by emission rate (R2 = 0.26–0.85) in the large industrial farms, except for the large fattening pig farm in summer. Overall, mitigation of NH3emissions from sow farms should be a top priority in the North China Plain.Implications: The present study firstly examined the farm-scale effect of ammonia emissions in the North China Plain. Of all farms, the sow farm was identified as the greatest source of ammonia emission. Regardless of farm scale, ammonia emission rates were observed to be higher in summer. Ammonia concentrations were mostly higher in the large industrial farms partly due to lower ventilation rates than in the small traditional farms.

China’s fertilization practices contribute greatly to the global biogeochemical nitrogen (N) and phosphorus (P) flows, which have exceeded the safe-operating space. Here, we quantified the potentials of improved nutrient management in the food chain and spatial planning of livestock farms on nutrient use efficiency and losses in China, using a nutrient flow model and detailed information on >2300 counties. Annual fertilizer use could be reduced by 26 Tg N and 6.4 Tg P following improved nutrient management. This reduction N and P fertilizer use would contribute 30% and 80% of the required global reduction, needed to keep the biogeochemical N and P flows within the planetary boundary. However, there are various barriers to make this happen. A major barrier is the transportation cost due to the uneven distributions of crop land, livestock, and people within the country. The amounts of N and P in wastes and residues are larger than the N and P demand of the crops grown in 30% and 50% of the counties, respectively. We argue that a drastic increase in the recycling and utilization of N and P from wastes and residues can only happen following relocation of livestock farms to areas with sufficient cropland.

This study analyzed ammonia reduction potential and related costs and benefits of several ammonia emission reduction technologies applicable for dairy production from cattle in China. Specifically, these included diet manipulation, manure acidification, manure/slurry covers, and solid manure compaction. Ammonia emissions for China were estimated using the GAINS and NUFER models, while mitigation potentials of technologies were determined from laboratory studies. Ammonia reduction potentials from dairy production in China ranged from 0.8 to 222 Gg NH3year–1for the selected technologies. Implementation costs ranged from a savings of US$15 kg–1NH3abated to an expenditure of US$45 kg–1NH3abated, while the total implementation costs varied from a savings of US$1.5 billion in 2015 to an expenditure of a similar size. The best NH3reduction technology was manure acidification, while the most cost-effective option was diet optimization with lower crude protein input. For most abatement options, material costs were the critical element of overall costs. The fertilizer value of manure could partly offset the implementation cost of the options tested. Furthermore, benefits due to avoided health damage, as a result of reducing NH3emissions, could make all abatement options (except for manure compaction) profitable on the scale of a national economy.

Chinese surface waters are severely polluted by nutrients. This study addresses three challenges in nutrient modeling for rivers in China: (1) difficulties in transferring modeling results across biophysical and administrative scales, (2) poor representation of the locations of point sources, and (3) limited incorporation of the direct discharge of manure to rivers. The objective of this study is, therefore, to quantify inputs of nitrogen (N) and phosphorus (P) to Chinese rivers from different sources at multiple scales. We developed a novel multi-scale modeling approach including a detailed, state-of-the-art representation of point sources of nutrients in rivers. The model results show that the river pollution and source attributions differ among spatial scales. Point sources accounted for 75% of the total dissolved phosphorus (TDP) inputs to rivers in China in 2012, and diffuse sources accounted for 72% of the total dissolved nitrogen (TDN) inputs. One-third of the sub-basins accounted for more than half of the pollution. Downscaling to the smallest scale (polygons) reveals that 14% and 9% of the area contribute to more than half of the calculated TDN and TDP pollution, respectively. Sources of pollution vary considerably among and within counties. Clearly, multi-scale modeling may help to develop effective policies for water pollution.

Developing sustainable food systems is essential, especially for emerging economies, where food systems are changing rapidly and affect the environment and natural resources. We explored possible future pathways for a sustainable food system in China, using multiple environmental indicators linked to eight of the Sustainable Development Goals (SDGs). Forecasts for 2030 in a business as usual scenario (BAU) indicate increases in animal food consumption as well as increased shortages of the land available and the water needed to produce the required food in China. Associated greenhouse gas emissions and nitrogen and phosphorus losses could become 10–42% of global emissions in 2010. We developed three main pathways besides BAU [produce more and better food (PMB), consume and waste less food (CWL), and import more food (IMF)] and analyzed their impacts and contributions to achieving one or more of the eight SDGs. Under these scenarios, the demand for land and water and the emissions of GHG and nutrients may decrease by 7–55% compared to BAU, depending on the pathway followed. A combination of PMB and CWL was most effective, while IMF externalizes impacts to countries exporting to China. Modestly increasing feed or food imports in a selective manner could ease the pressure on natural resources. Our modeling framework allows us to analyze the effects of changes in food production–consumption systems in an integrated manner, and the results can be linked to the eight SDGs. Despite formidable technological, social, educational, and structural barriers that need to be overcome, our study indicates that the ambitious targets of China’s new agricultural and environmental strategy appear to be achievable.

Nitrogen (N) supports food production, but its excess causes water pollution. We lack an understanding of the boundary of N for water quality while considering complex relationships between N inputs and in-stream N concentrations. Our knowledge is limited to regional reduction targets to secure food production. Here, we aim to derive a spatially explicit boundary of N inputs to rivers for surface water quality using a bottom-up approach and to explore ways to meet the derived N boundary while considering the associated impacts on both surface water quality and food production in China. We modified a multiscale nutrient modeling system simulating around 6.5 Tg of N inputs to rivers that are allowed for whole of China in 2012. Maximum allowed N inputs to rivers are higher for intensive food production regions and lower for highly urbanized regions. When fertilizer and manure use is reduced, 45–76% of the streams could meet the N water quality threshold under different scenarios. A comparison of “water quality first” and “food production first” scenarios indicates that trade-offs between water quality and food production exist in 2–8% of the streams, which may put 7–28% of crop production at stake. Our insights could support region-specific policies for improving water quality.

Nitrous oxide (N2O) is a potent greenhouse gas with a global warming potential 265–298 times greater than carbon dioxide (CO2) and causes destruction of stratospheric ozone. In soil, N2O is produced through the process of incomplete microbial denitrification or as a by-product of nitrification. Agricultural soils are the main source of N2O emissions globally. Total N2O emissions from dairy grazed farm systems can be dominated by large emissions within a small area (hotspots). Typically, N2O hotspots are areas with high stocking density, high excretal inputs (resulting in high soil N), and situations when soil water filled pore space is elevated. Different pasture grazing systems can be used on dairy farms, including year-round low input dairy systems and higher input systems with some animal confinement component. Potential N2O hotspot areas can be categorized into the following: areas of manure accumulation, storage, and spreading; areas of high stocking intensity leading to soil compaction and high inputs of urine and dung; cultivation and grazing of forage crops; and landscape features including topography, riparian areas, and soil property effects. High input systems can lead to a greater potential for N2O emission hotspots. To demonstrate the effect of hotspot zones on the calculation of total farm N2O emissions, a model was developed and used to assess the N2O emissions from a New Zealand case-study farm. Emission factor (EF3) values for cow urine in the gateway and water-trough areas were measured on the case-study farm and were both found to be about five times that of the rest of the paddock. Using these values for the total farm emissions calculation, it was found that gateways could be significant hotspots for N2O emission with 3.2% of the farm area contributing 9.4% of the total farm N2O emissions. Knowledge of the significance of hotspot zones would enable more accurate calculation of total farm emissions and more efficient targeting of N2O mitigation strategies. There is a paucity of studies which specifically examine hotspots of N2O emissions from farm-scale features and the full magnitude of the emissions from possible hotspot areas and their contributions to the total farm emissions require further investigation.

Animal production systems provide nutritious food for humans, income and survivability for numerous smallholder farms and transform residues to valuable products. However, animal production is implicated in human health issues (diet-related diseases, zoonosis, antimicrobial resistance) and environmental burdens (ammonia and greenhouse gas emissions, eutrophication of surface waters, biodiversity loss). This paper reviews changes in global animal production and associated nitrogen (N) and phosphorus (P) flows over the past 50 years, during which time total animal production roughly tripled. Cattle still dominate the world in terms of animal biomass, but the number and total production of pigs and poultry have increased faster. Animal production systems are highly diverse and respond to changes in markets. Specialised systems have become more dominant, especially in developed and rapidly developing countries. The annual production of N and P in manure is similar to the amounts of N and P in synthetic fertiliser produced annually, but manure nutrients are often not recycled effectively and used efficiently by plants. Nutrient losses greatly depend on the system, management and regulations. Nitrogen and P use efficiency (NUE and PUE respectively) at the animal level is in the range 5–45%, depending on animal category, feeding and management. NUE of mixed crop-animal systems may range from 5% to 65% depending on NUE at the animal level, and the utilisation of manure nitrogen and new nitrogen inputs. Potentially, values for PUE are higher than those for NUE. Solutions for improving NUE and PUE in animal production are based on a coherent set of activities in the whole chain of ‘feed production–animal production–manure management’. A high efficiency at the system level is achieved through combination of high NUE and PUE at the animal level and effective recycling and utilisation of manure N and P in crop production. Specific regional regulations (low-emission manure storage and application, proper application limits and timing) greatly contribute to high efficiency at a system level.

Eutrophication is a serious problem in Chinese rivers and seas, largely caused by increased nitrogen (N) and phosphorus (P) losses from agriculture. Chinese agriculture is known to be nutrient inefficient. Previous studies showed that fertiliser use can be reduced while increasing yields in the so-called Double High Agriculture (DHA) program. We simulated the effects of improved nutrient management on N and P export by rivers in China in 2050 and the associated coastal eutrophication using the Global Nutrient Export from WaterSheds 2 (NEWS 2) model. Four scenarios were developed: (1) improved practice (IP), assuming an approximate 20% decrease in synthetic fertiliser use and a 15% increase in crop yields relative to a reference scenario; (2) integrated soil-crop systems management (ISSM), assuming a 30% decrease in synthetic fertilisers and a 30% increase in crop yields; (3) IP-MR, with assumptions as for the IP scenario as well as efficient manure recycling (MR); and (4) ISSM-MR, with assumptions as for the ISSM scenario in addition to efficient MR. The results indicate that reducing inputs of synthetic fertilisers alone (IP and ISSM scenarios) may reduce river export of N and P by <15%. The scenarios also accounting for improved manure management (MR) are more effective, and reduce N and P inputs to rivers by 10–35%.

Animal-derived food production accounts for one-third of the global anthropogenic greenhouse gas (GHG) emissions. Diet followed in China is ranked as low-carbon emitting (i.e.0.21 t CO2-eq per capita in 2018, ranking at 145thout of 168 countries) due to the low average animal-derived food consumption rate, and preferential consumption of animal-derived foods with lower-GHG emissions (i.e.pork and eggs vs beef and milk). However, the projected increase in GHG emissions from livestock production poses great challenges for achieving China’s “Carbon Neutrality” Pledge. We propose that the livestock sector may achieve “Climate Neutrality” with net-zero warming around 2050 by implementing healthy diet and mitigation strategies to control enteric methane emissions.

Eutrophication refers to the nutrient enrichment, leading to blooms of algae. Such blooms in lakes can happen throughout the year because of the changes in nutrient and hydrological cycles. Nutrient export to lakes from rivers is the main cause of eutrophication problems. Seasonal trends in nitrogen (N) export by rivers to lakes are still not well understood. The objective of this study is, therefore, to better understand the seasonal trends in river export of dissolved inorganic N (DIN) to lakes of the Hai He Basin. To this end, we selected Guanting and Baiyangdian as representative lakes, whose drainage areas include various cropping systems. We developed a seasonal version of the Model to Assess River Inputs of Nutrients to lAkes (MARINA‐Lakes) model for Guanting and Baiyangdian while assessing N flows from the land to the lakes. The model accounts for the seasonality in human activities (e.g., cropping systems and fertilizer practices), climate, and hydrology. The effective seasons are winter (December–February), spring (March–May), summer (June–August), and fall (September–November). The model results for the year 2012 indicate that river export of DIN was highest in winter and lowest in summer. Point sources accounted for over 50% of DIN exports to Guanting and Baiyangdian across seasons. Avoiding direct discharges of animal manure (point source) in winter is needed to reduce future lake pollution. We argue that effective lake pollution control requires accounting for seasonal N cycles. Our study can support effective nutrient management and environmental policies. Blooms of algae in lakes can happen throughout the year because of the changes in nutrient and hydrological cycles. Nutrient export to lakes from rivers is an important cause of eutrophication problems. The objective of this study is to better understand the seasonal trends in river export of dissolved inorganic N (DIN) to two lakes of the Hai He Basin. We developed a seasonal version of the Model to Assess River Inputs of Nutrients to lAkes (MARINA‐Lakes) model for Guanting and Baiyangdian while assessing N flows from the land to the lakes. The model accounts for the seasonality in human activities (e.g., cropping systems and fertilizer practices), climate, and hydrology. The effective seasons are winter (December–February), spring (March–May), summer (June–August), and fall (September–November). The model results for the year 2012 indicate highest DIN exports in winter and lowest in summer. Point sources accounted for over 50% of DIN exports to Guanting and Baiyangdian across seasons. Avoiding direct discharges of animal manure (point source) in winter is needed to reduce future lake pollution. Our study can support effective nutrient management and environmental policy assessments. River export of nitrogen to the lakes was highest in winter and lowest in summerPoint sources contribute over 50% of nitrogen across seasonsEffective lake pollution control requires accounting for seasonal nitrogen cycles River export of nitrogen to the lakes was highest in winter and lowest in summer Point sources contribute over 50% of nitrogen across seasons Effective lake pollution control requires accounting for seasonal nitrogen cycles

Global development has been heavily reliant on the overexploitation of natural resources since the Industrial Revolution. With the extensive use of fossil fuels, deforestation, and other forms of land-use change, anthropogenic activities have contributed to the ever-increasing concentrations of greenhouse gases (GHGs) in the atmosphere, causing global climate change. In response to the worsening global climate change, achieving carbon neutrality by 2050 is the most pressing task on the planet. To this end, it is of utmost importance and a significant challenge to reform the current production systems to reduce GHG emissions and promote the capture of CO2from the atmosphere. Herein, we review innovative technologies that offer solutions achieving carbon (C) neutrality and sustainable development, including those for renewable energy production, food system transformation, waste valorization, C sink conservation, and C-negative manufacturing. The wealth of knowledge disseminated in this review could inspire the global community and drive the further development of innovative technologies to mitigate climate change and sustainably support human activities.

The COVID-19 pandemic is worsening food shortages in food deficit countries, such as China, which rely on import for domestic food consumption. We argue that fundamental revolution in China’s livestock system can meet about 50% of its consumption of livestock products and thereby reduce the country’s reliance on imports. Three food system revolutions that can greatly reduce China’s reliance on imports are technically and economically feasible, and generate high eco-system benefits: (1) organic or inorganic based microbial feed protein production to substitute imported feed protein, (2) vegetation greening and fodder production through grassland restoration to reduce import of ruminant animal products, and (3) insect protein based fish-plant production and offshore marine restoration to replace red meat consumption and increase recycling of manure. Together these revolutions can accelerate progress towards multiple Sustainable Development Goals in exporting countries.