Integrated carbon and nitrogen management brings climate, health, and ecosystem benefits

The study, published in Science, was supported by IIASA through the development of future scenarios, including the quantification of both the costs of emission reductions and the benefits of avoided environmental and health damages. Drawing on a synthesis of extensive field experiments, the researchers identified mitigation measures tailored to China’s unique conditions.

The team modeled four future scenarios: Business-as-Usual, Carbon-Only Reduction, Nitrogen-Only Reduction, and Combined Carbon-Nitrogen Management. Their findings show that the integrated approach could reduce China’s carbon emissions by 91% and nitrogen emissions by 74% by 2060, advancing the country’s ability to meet its environmental targets.

“This integrated approach offers a powerful pathway to sustainable development,” says Professor Baojing Gu, main author and lead researcher at Zhejiang University’s College of Environmental and Resource Sciences. “China’s rapid urbanization, industrialization, and intensive agriculture have led to excessive emissions, resulting in air pollution, acid rain, water eutrophication, and greenhouse effects.”

Policies have historically addressed carbon and nitrogen separately, leaving the benefits of a joint approach largely untapped – until now. The study tracks carbon and nitrogen flows in China from 1980 to 2020 across multiple socioeconomic sectors, including agriculture, industry, energy, and waste. Over those four decades, nitrogen losses to air and water increased 2.3 times, while carbon emissions surged 6.5 times.

The analysis also reveals a growing imbalance: as nitrogen emissions were partially controlled after 2000, carbon emissions continued rising. By 2020, the carbon-to-nitrogen (C/N) emission ratio had nearly tripled to 119, up from a steady range of 35–44 in earlier decades.

The study’s cost-benefit analysis highlights the strong economic case for integrated carbon and nitrogen management. While the combined approach would cost an estimated $424 billion to implement by 2060, this is nearly 40% less than tackling carbon and nitrogen separately. In return, the investment could generate up to $1.8 trillion in benefits – including improved public health, better ecosystem services, and climate gains – more than four times the total cost.

“This research demonstrates that protecting our environment doesn’t come cheap,” says Wilfried Winiwarter, study coauthor and a senior research scholar in the Pollution Management Research Group of the IIASA Energy, Climate, and Environment Program. “Coordinated strategies that tap into co-benefits are far more cost-effective than tackling impacts in isolation. As shown in this study for China, integrated scenarios help shape practical and efficient policies.”

The study highlights that integrated carbon and nitrogen strategies are key to aligning environmental and economic goals, and calls for tailored, region-specific solutions, including nature-based approaches.

Winiwarter also notes that the work is now being extended beyond China to the European Union, as part of a Marie Skłodowska-Curie fellowship led by Xiuming Zhang, study coauthor and a researcher in the IIASA Energy, Climate, and Environment Program, with the aim of applying the approach globally. He emphasized that the GAINS model plays a key role in this effort by providing crucial data for scenario development, while also being enhanced through the new insights generated by the study.

Reference:
Gu, B., Xu, X., Zhang, X., Winiwarter, W., Zhang, S., Vitousek, P., de Vries, W., Chen, T., Zou, Y., Zhan, J. (2025). Integrated carbon and nitrogen management for cost-effective environmental policies in China Science DOI: 10.1126/science.ads4105