the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 08 Feb 2024
Opinion: Understanding the impacts of agriculture and food systems on atmospheric chemistry is instrumental to achieving multiple Sustainable Development Goals
Abstract. Agriculture and food systems play important roles shaping atmospheric chemistry and air quality, most dominantly via the release of reactive nitrogen (Nr) compounds, but also via agricultural burning, energy use, and cropland and pastureland expansion. In this opinion, we first succinctly review our current understanding of agricultural and food-system emissions of Nr and other atmospherically relevant compounds, their fates and impacts on air quality, human health and terrestrial ecosystems, and how such emissions can be potentially mitigated through better cropland management, livestock management and whole food-system transformation. With that, we highlight important knowledge gaps that warrant more extensive research, and argue that we scientists need to provide a more detailed, process-based understanding of the impacts of agriculture and food systems on atmospheric chemistry, especially as the importance of emissions from other fossil fuel-intensive sectors is fading in the face of regulatory measures worldwide. Such knowledge is necessary to guide food-system transformation in technologically feasible, economically viable, socially inclusive, and environmentally responsible manners, and essential to help society achieve multiple Sustainable Development Goals (SDGs), especially to ensure food security for the people, protect human and ecosystem health, improve farmers’ livelihood, and ultimately help communities achieve socioeconomic and environmental sustainability.
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CC1: 'Comment on egusphere-2024-293', Lei Liu, 18 Mar 2024
This opinion reviews agricultural and food system emissions of Nr and other atmospherically relevant compounds, their fates and impacts on air quality, human health, and terrestrial ecosystems, and how such emissions can be potentially mitigated through better cropland management, livestock management, and whole food-system transformation. In general, this paper is well-organized and written. I have minor comments to strengthen the paper before it can be published in ACP.
First, I am missing the impact of N deposition on the oceanic N cycle and ecosystems, which I think is a very important part. Food-driven N deposition poses a significant part of human N input to oceans. See refs: Liu et al., Modeling global oceanic nitrogen deposition from food systems and its mitigation potential by reducing overuse of fertilizers, https://doi.org/10.1073/pnas.2221459120; Jickells et al., A re-evaluation of the magnitude and impacts of anthropogenic nitrogen inputs on the ocean. Global Biogeochem. Cycl. 31, 289–305 (2017).
Second, I suggest the authors split the agricultural NH3 emissions into crop and livestock emissions, and confirm all numbers in Table 2 (whether it is total agricultural NH3 emissions or just part of them) since I have seen a huge gap between different studies (26-60 Tg N yr-1). There are also recent studies reporting global NH3 emissions which should be cited properly. See refs: Liu et al., Exploring global changes in agricultural ammonia emissions and their contribution to nitrogen deposition since 1980 https://doi.org/10.1073/pnas.2121998119; Yang et al., Improved global agricultural crop- and animal-specific ammonia emissions during 1961–2018, https://doi.org/10.1016/j.agee.2022.108289
Third, are there any social-economic drivers for changes in food emissions? For instance, when we talked about NH3, it’s usually controlled by increasing population and food production (N fertilizer, livestock). NH3 changes are mainly affected by temperature and fertilizer applications. I hope to see some additional discussions on long-term changes and their social-economic drivers. How the urbanization affect emissions and pollution? (see refs: L. Liu. 2023 Nature, https://doi.org/10.1038/d41586-023-02753-9; Deng et al. 2024 Nature communications, https://doi.org/10.1038/s41467-023-44685-y).
Fourth, I would like to see some discussion on how climate change/extreme weather affects food emissions and production, which I think is an essential part of future efforts on maintaining food production. Please see refs: Liu et al, China’s response to extreme weather events must be long term, https://doi.org/10.1038/s43016-023-00892-w; Lesk, C. et al. Nat. Rev. Earth Environ. 3, 872–889 (2022).
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Citation: https://doi.org/10.5194/egusphere-2024-293-CC1 -
RC1: 'Comment on egusphere-2024-293', Anonymous Referee #1, 12 Apr 2024
The authors have put together a commanding review of the impacts of agriculture on the atmosphere. As such it will be a useful contribution to literature, but I recommend that the following comments be taken into consideration to further strengthen the work:
1. The causal linkages from the source and activity emitting pollutants to the fundamental governing chemistry and impacts can be strongly and sequentially highlighted. The manuscript, as it stands, focuses on the magnitude of contributions, but the basic processes influencing emissions and the chemistry pathways need to be explicitly mentioned. This is also true for the discussion of impacts - while there is extensive discussion of the magnitude of impacts, the biochemical pathways that enable such impacts are minimally discussed. This is important for a non-expert to readily understand the complexity and non-linearities in atmospheric chemistry
2. Comparisons to typical sectors (power generation/industry/transportation) should be provided. Agriculture and food systems are typically unregulated but often have comparable if not outsized impacts on air pollution.Â
3. The manuscript has briefly mentioned the need for life-cycle lens (para 75) to characterize the challenges with food systems. The recent literature and many conflicting evidence (as in the case of food miles) should be summarized and better highlighted.Â
4. Sections 2.3.1-2.3.4: There is a lot of useful information here, but it may help with readability if the contents were structured in a similar blocks of information. Section 2.3.4, for example, has a lot of discussion of how to model the impacts but the content does not follow the thought indicated in the title.
 5. A lot of the challenges in food systems are dietary choices (either personal choices or as shaped by larger environmental, economic, social structures). The discussion of these choices and impacts must be better highlighted. There is some discussion in Section 3.3. but it must include choices driven by diets (plant v/s animal rich), nutrition (triple burden of malnutrition), access - and of course food loss and waste as nicely discussed by the authors.Â
Overall, the authors should consider being succinct as there is overlap in messaging across the manuscript.Â
Citation: https://doi.org/10.5194/egusphere-2024-293-RC1 -
RC2: 'Comment on egusphere-2024-293', Anonymous Referee #2, 01 May 2024
The authors have made a good effort to collect information about sources and effects of nitrogen related to the agriculture and food system. Although there is wide variety of issues that has been dealt with, the overall causal link between are mostly lacking. Especially for new readers in the field, these causal links could be better explained for a better understanding of the issues.
The authors mention knowledge gaps in their introduction. I suppose that most of these knowledge gaps are listed in the closing section. However, if these are indeed the knowledge gaps, they are rather general without sometimes a clear link to the earlier sections. Furthermore, it needs to be clear that these knowledge gaps are most likely not general (global), but rather regional. This because most of the knowledge gaps are already addressed in different regions of the world. In that case these are rather information gaps that knowledge gaps (for which additional research is needed). I would suggest to make clear what is already done and where, so others can take notice and learn from it.
What furthermore is missing (I think), is the notice that the linkage between the agriculture/food systems and the SDG's is not only through the atmospheric pathway, but also (and sometimes maybe even more) through the aquatic pathway. I would suggest to, at least, mention this and, when possible, to give an indication of the relative contributions from these two pathways. This to provide some more context to the reader.
Citation: https://doi.org/10.5194/egusphere-2024-293-RC2 -
AC1: 'Comment on egusphere-2024-293', Amos Tai, 31 Aug 2024
We would like to thank the reviewers for the thoughtful and insightful comments for this Opinion article. The manuscript has been revised accordingly, and our point-by-point responses are provided here as an attached PDF file. For the reviewers' and editor's convenience, the revised manuscript is also linked here:
https://gocuhk-my.sharepoint.com/:b:/g/personal/amostai_cuhk_edu_hk/ETF3HuVbNPFAr4FmNELrDGUBa2jzwWn2aZJjFiBi996GYQ?e=JMG9dk
We also thank the editor for the time and effort handling this manuscript.
Status: closed
-
CC1: 'Comment on egusphere-2024-293', Lei Liu, 18 Mar 2024
This opinion reviews agricultural and food system emissions of Nr and other atmospherically relevant compounds, their fates and impacts on air quality, human health, and terrestrial ecosystems, and how such emissions can be potentially mitigated through better cropland management, livestock management, and whole food-system transformation. In general, this paper is well-organized and written. I have minor comments to strengthen the paper before it can be published in ACP.
First, I am missing the impact of N deposition on the oceanic N cycle and ecosystems, which I think is a very important part. Food-driven N deposition poses a significant part of human N input to oceans. See refs: Liu et al., Modeling global oceanic nitrogen deposition from food systems and its mitigation potential by reducing overuse of fertilizers, https://doi.org/10.1073/pnas.2221459120; Jickells et al., A re-evaluation of the magnitude and impacts of anthropogenic nitrogen inputs on the ocean. Global Biogeochem. Cycl. 31, 289–305 (2017).
Second, I suggest the authors split the agricultural NH3 emissions into crop and livestock emissions, and confirm all numbers in Table 2 (whether it is total agricultural NH3 emissions or just part of them) since I have seen a huge gap between different studies (26-60 Tg N yr-1). There are also recent studies reporting global NH3 emissions which should be cited properly. See refs: Liu et al., Exploring global changes in agricultural ammonia emissions and their contribution to nitrogen deposition since 1980 https://doi.org/10.1073/pnas.2121998119; Yang et al., Improved global agricultural crop- and animal-specific ammonia emissions during 1961–2018, https://doi.org/10.1016/j.agee.2022.108289
Third, are there any social-economic drivers for changes in food emissions? For instance, when we talked about NH3, it’s usually controlled by increasing population and food production (N fertilizer, livestock). NH3 changes are mainly affected by temperature and fertilizer applications. I hope to see some additional discussions on long-term changes and their social-economic drivers. How the urbanization affect emissions and pollution? (see refs: L. Liu. 2023 Nature, https://doi.org/10.1038/d41586-023-02753-9; Deng et al. 2024 Nature communications, https://doi.org/10.1038/s41467-023-44685-y).
Fourth, I would like to see some discussion on how climate change/extreme weather affects food emissions and production, which I think is an essential part of future efforts on maintaining food production. Please see refs: Liu et al, China’s response to extreme weather events must be long term, https://doi.org/10.1038/s43016-023-00892-w; Lesk, C. et al. Nat. Rev. Earth Environ. 3, 872–889 (2022).
Â
Â
Citation: https://doi.org/10.5194/egusphere-2024-293-CC1 -
RC1: 'Comment on egusphere-2024-293', Anonymous Referee #1, 12 Apr 2024
The authors have put together a commanding review of the impacts of agriculture on the atmosphere. As such it will be a useful contribution to literature, but I recommend that the following comments be taken into consideration to further strengthen the work:
1. The causal linkages from the source and activity emitting pollutants to the fundamental governing chemistry and impacts can be strongly and sequentially highlighted. The manuscript, as it stands, focuses on the magnitude of contributions, but the basic processes influencing emissions and the chemistry pathways need to be explicitly mentioned. This is also true for the discussion of impacts - while there is extensive discussion of the magnitude of impacts, the biochemical pathways that enable such impacts are minimally discussed. This is important for a non-expert to readily understand the complexity and non-linearities in atmospheric chemistry
2. Comparisons to typical sectors (power generation/industry/transportation) should be provided. Agriculture and food systems are typically unregulated but often have comparable if not outsized impacts on air pollution.Â
3. The manuscript has briefly mentioned the need for life-cycle lens (para 75) to characterize the challenges with food systems. The recent literature and many conflicting evidence (as in the case of food miles) should be summarized and better highlighted.Â
4. Sections 2.3.1-2.3.4: There is a lot of useful information here, but it may help with readability if the contents were structured in a similar blocks of information. Section 2.3.4, for example, has a lot of discussion of how to model the impacts but the content does not follow the thought indicated in the title.
 5. A lot of the challenges in food systems are dietary choices (either personal choices or as shaped by larger environmental, economic, social structures). The discussion of these choices and impacts must be better highlighted. There is some discussion in Section 3.3. but it must include choices driven by diets (plant v/s animal rich), nutrition (triple burden of malnutrition), access - and of course food loss and waste as nicely discussed by the authors.Â
Overall, the authors should consider being succinct as there is overlap in messaging across the manuscript.Â
Citation: https://doi.org/10.5194/egusphere-2024-293-RC1 -
RC2: 'Comment on egusphere-2024-293', Anonymous Referee #2, 01 May 2024
The authors have made a good effort to collect information about sources and effects of nitrogen related to the agriculture and food system. Although there is wide variety of issues that has been dealt with, the overall causal link between are mostly lacking. Especially for new readers in the field, these causal links could be better explained for a better understanding of the issues.
The authors mention knowledge gaps in their introduction. I suppose that most of these knowledge gaps are listed in the closing section. However, if these are indeed the knowledge gaps, they are rather general without sometimes a clear link to the earlier sections. Furthermore, it needs to be clear that these knowledge gaps are most likely not general (global), but rather regional. This because most of the knowledge gaps are already addressed in different regions of the world. In that case these are rather information gaps that knowledge gaps (for which additional research is needed). I would suggest to make clear what is already done and where, so others can take notice and learn from it.
What furthermore is missing (I think), is the notice that the linkage between the agriculture/food systems and the SDG's is not only through the atmospheric pathway, but also (and sometimes maybe even more) through the aquatic pathway. I would suggest to, at least, mention this and, when possible, to give an indication of the relative contributions from these two pathways. This to provide some more context to the reader.
Citation: https://doi.org/10.5194/egusphere-2024-293-RC2 -
AC1: 'Comment on egusphere-2024-293', Amos Tai, 31 Aug 2024
We would like to thank the reviewers for the thoughtful and insightful comments for this Opinion article. The manuscript has been revised accordingly, and our point-by-point responses are provided here as an attached PDF file. For the reviewers' and editor's convenience, the revised manuscript is also linked here:
https://gocuhk-my.sharepoint.com/:b:/g/personal/amostai_cuhk_edu_hk/ETF3HuVbNPFAr4FmNELrDGUBa2jzwWn2aZJjFiBi996GYQ?e=JMG9dk
We also thank the editor for the time and effort handling this manuscript.
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