Marine aquaculture can deliver 40% lower carbon footprints than freshwater aquaculture based on feed, energy and biogeochemical cycles.

Freshwater aquaculture is an increasingly important source of blue foods but produces substantial methane and nitrous oxide emissions. Marine aquaculture, also known as mariculture, is a smaller sector with a large growth potential, but its climate impacts are challenging to accurately quantify. Here we assess the greenhouse gas emissions from mariculture's aquatic environment in global potentially suitable areas at 10 km resolution on the basis of marine biogeochemical cycles, greenhouse gas measurements from research cruises and satellite-observed net primary productivity. Mariculture's aquatic emissions intensities are estimated to be 1-6 g CH4 kg-1 carcass weight and 0.05-0.2 g N2O kg-1 carcass weight, >98% and >80% lower than freshwater systems. Using a life-cycle assessment approach, we show that mariculture's carbon footprints are ~40% lower than those of freshwater aquaculture based on feed, energy use and the aquatic environment emissions. Adoption of mariculture alongside freshwater aquaculture production could offer considerable climate benefits to meet future dietary protein and nutritional needs.

Climate-adaptive crop distribution can feed food demand, improve water scarcity, and reduce greenhouse gas emissions.

Optimizing crop distribution stands as a pivotal approach to climate change adaption, enhancing crop production sustainability, and has been recognized for its immense potential in ensuring food security while minimizing environmental impacts. Here, we developed a climate-adaptive framework to optimize the distribution of staple crops (i.e., wheat, maize, and rice) to meet the multi-dimensional needs of crop production in China. The framework considers the feasibility of the multiple cropping systems (harvesting more than once on a cropland a year) and adopts a multi-dimensional approach, incorporating goals related to crop production, water consumption, and greenhouse gas (GHG) emissions. By optimizing, the total irrigated area of three crops would decrease by 7.7 % accompanied by a substantial 69.8 % increase in rain-fed areas compared to the baseline in 2010. This optimized strategy resulted in a notable 10.0 % reduction in total GHG emissions and a 13.1 % decrease in irrigation water consumption while maintaining consistent crop production levels. In 2030, maintaining the existing crop distribution and relying solely on yield growth would lead to a significant maize production shortfall of 27.0 %, highlighting a looming challenge. To address this concern, strategic adjustments were made by reducing irrigated areas for wheat, rice, and maize by 2.3 %, 12.8 %, and 6.1 %, respectively, while simultaneously augmenting rain-fed areas for wheat and maize by 120.2 % and 55.9 %, respectively. These modifications ensure that production demands for all three crops are met, while yielding a 6.9 % reduction in GHG emissions and a 15.1 % reduction in irrigation water consumption. This optimization strategy offers a promising solution to alleviate severe water scarcity issues and secure a sustainable agricultural future, effectively adapting to evolving crop production demands in China.

Promoting sustainable smallholder farming via multistakeholder collaboration.

Transforming smallholder farms is critical to global food security and environmental sustainability. The science and technology backyard (STB) platform has proved to be a viable approach in China. However, STB has traditionally focused on empowering smallholder farmers by transferring knowledge, and wide-scale adoption of more sustainable practices and technologies remains a challenge. Here, we report on a long-term project focused on technology scale-up for smallholder farmers by expanding and upgrading the original STB platform (STB 2.0). We created a formalized and standardized process by which to engage and collaborate with farmers, including integrating their feedback via equal dialogues in the process of designing and promoting technologies. Based on 288 site-year of field trials in three regions in the North China Plain over 5 y, we find that technologies cocreated through this process were more easily accepted by farmers and increased their crop yields and nitrogen factor productivity by 7.2% and 28.1% in wheat production and by 11.4% and 27.0% in maize production, respectively. In promoting these technologies more broadly, we created a "one-stop" multistakeholder program involving local government agencies, enterprises, universities, and farmers. The program was shown to be much more effective than the traditional extension methods applied at the STB, yielding substantial environmental and economic benefits. Our study contributes an important case study for technology scale-up for smallholder agriculture. The STB 2.0 platform being explored emphasizes equal dialogue with farmers, multistakeholder collaboration, and long-term investment. These lessons may provide value for the global smallholder research and practitioners.

Sustainable Blue Foods from Rice-Animal Coculture Systems.

Global interest grows in blue foods as part of sustainable diets, but little is known about the potential and environmental performance of blue foods from rice-animal coculture systems. Here, we compiled a large experimental database and conducted a comprehensive life cycle assessment to estimate the impacts of scaling up rice-fish and rice-crayfish systems in China. We find that a large amount of protein can be produced from the coculture systems, equivalent to ∼20% of freshwater aquaculture and ∼70% of marine wild capture projected in 2030. Because of the ecological benefits created by the symbiotic relationships, cocultured fish and crayfish are estimated to be carbon-negative (-9.8 and -4.7 kg of CO2e per 100 g of protein, respectively). When promoted at scale to displace red meat, they can save up to ∼98 million tons of greenhouse gases and up to ∼13 million hectares of farmland, equivalent to ∼44% of China's total rice acreage. These results suggest that rice-animal coculture systems can be an important source of blue foods and contribute to a sustainable dietary shift, while reducing the environmental footprints of rice production. To harvest these benefits, robust policy supports are required to guide the sustainable development of coculture systems and promote healthy and sustainable dietary change.