Spatially explicit estimates of N<sub>2</sub>O emissions from croplands suggest climate mitigation opportunities from improved fertilizer management

Gerber, James; Carlson, Kimberly M.; Makowski, David; Mueller, Nathaniel D.; Cortázar-Atauri, Iñaki García de; Havlík, Petr; Herrero, Mario; Launay, Marie; O’Connell, Christine; Smith, Pete; West, Paul

doi:10.1111/gcb.13341

Cited by 126 publications

(120 citation statements)

References 44 publications

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“…Bouwman's estimate for manure nitrogen applied to cropland is higher than our estimate, mainly due to the consideration of more refined manure management in different livestock production systems from our study. Gerber et al (2016) and Carlson et al (2017) suggested that only 7.4-7.8 Tg N yr −1 was applied to cropland, which is lower than our estimate. One big difference between our study and Gerber et al (2016) and Carlson et al (2017) is that we include the managed manure lost through leaching.…”

Section: Comparison With Previous Studiescontrasting

confidence: 86%

Global manure nitrogen production and application in cropland during 1860–2014: a 5 arcmin gridded global dataset for Earth system modeling

Zhang

Tian

Lü

et al. 2017

Earth Syst. Sci. Data

158

125

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Abstract. Given the important role of nitrogen input from livestock systems in terrestrial nutrient cycles and the atmospheric chemical composition, it is vital to have a robust estimation of the magnitude and spatiotemporal variation in manure nitrogen production and its application to cropland across the globe. In this study, we used the dataset from the Global Livestock Impact Mapping System (GLIMS) in conjunction with country-specific annual livestock populations to reconstruct the manure nitrogen production during 1860-2014. The estimated manure nitrogen production increased from 21.4 Tg N yr −1 in 1860 to 131.0 Tg N yr −1 in 2014 with a significant annual increasing trend (0.7 Tg N yr −1 , p < 0.01). Changes in manure nitrogen production exhibited high spatial variability and concentrated in several hotspots (e.g., Western Europe, India, northeastern China, and southeastern Australia) across the globe over the study period. In the 1860s, the northern midlatitude region was the largest manure producer, accounting for ∼ 52 % of the global total, while low-latitude regions became the largest share (∼ 48 %) in the most recent 5 years (2010)(2011)(2012)(2013)(2014). Among all the continents, Asia accounted for over one-fourth of the global manure production during 1860-2014. Cattle dominated the manure nitrogen production and contributed ∼ 44 % of the total manure nitrogen production in 2014, followed by goats, sheep, swine, and chickens. The manure nitrogen application to cropland accounts for less than one-fifth of the total manure nitrogen production over the study period. The 5 arcmin gridded global dataset of manure nitrogen production generated from this study could be used as an input for global or regional land surface and ecosystem models to evaluate the impacts of manure nitrogen on key biogeochemical processes and water quality. To ensure food security and environmental sustainability, it is necessary to implement proper manure management practices on cropland across the globe. Datasets are available at https://doi.org/10.1594/PANGAEA.871980 .

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Section: Comparison With Previous Studiescontrasting

confidence: 86%

Global manure nitrogen production and application in cropland during 1860–2014: a 5 arcmin gridded global dataset for Earth system modeling

Zhang

Tian

Lü

et al. 2017

Earth Syst. Sci. Data

158

125

View full text Add to dashboard Cite

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“…The timing of these processes, and that of peak stream flow, corresponds to the dominant modes of ambient N 2 O variability observed in this region (Griffis et al, 2017). Finally, we find that emissions decrease relative to the a priori estimate in the western USA and Canada (in both the standard and SVD inversions), where natural soil emissions may be too high in the CLMCN-N 2 O inventory (Saikawa et al, 2014) used here, and where recent work argues that direct agricultural emissions are overestimated using a standard linear emission model (Gerber et al, 2016).…”

Section: North Americasupporting

confidence: 45%

“…Saikawa et al (2014) (International Fertilizer Association, 2016); it is possible that direct on-field N 2 O emissions here are underestimated with N inputs exceeding crop demands (Shcherbak et al, 2014). Indeed, a recent bottom-up estimate derives a direct emission response for China that is 42 % larger than the global average (Gerber et al, 2016). Over northern Asia our results point to an overestimate of natural soil emissions (as this is the dominant regional source in the model); a similar overestimate was inferred by Saikawa et al (2014).…”

Section: Asiamentioning

confidence: 99%

“…These sources are all subject to large uncertainties. For example, by assuming a linear flux response to fertilizer application, one can either under-or overestimate emissions depending on the application rate (Shcherbak et al, 2014;Gerber et al, 2016). Recent work also suggests that the indirect N 2 O flux could be 2.6-9 times larger than is presently accounted for in bottom-up estimates (Griffis et al, 2013;Turner et al, 2015b), which would imply an underestimate of the agricultural contribution to the overall N 2 O budget.…”

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confidence: 99%

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Top-down constraints on global N<sub>2</sub>O emissions at optimal resolution: application of a new dimension reduction technique

et al. 2018

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Abstract. We present top-down constraints on global monthly N 2 O emissions for 2011 from a multi-inversion approach and an ensemble of surface observations. The inversions employ the GEOS-Chem adjoint and an array of aggregation strategies to test how well current observations can constrain the spatial distribution of global N 2 O emissions. The strategies include (1) a standard 4D-Var inversion at native model resolution (4 • × 5 • ), (2) an inversion for six continental and three ocean regions, and (3) a fast 4D-Var inversion based on a novel dimension reduction technique employing randomized singular value decomposition (SVD). The optimized global flux ranges from 15.9 Tg N yr −1 (SVDbased inversion) to 17.5-17.7 Tg N yr −1 (continental-scale, standard 4D-Var inversions), with the former better capturing the extratropical N 2 O background measured during the HIAPER Pole-to-Pole Observations (HIPPO) airborne campaigns. We find that the tropics provide a greater contribution to the global N 2 O flux than is predicted by the prior bottomup inventories, likely due to underestimated agricultural and oceanic emissions. We infer an overestimate of natural soil emissions in the extratropics and find that predicted emissions are seasonally biased in northern midlatitudes. Here, optimized fluxes exhibit a springtime peak consistent with the timing of spring fertilizer and manure application, soil thawing, and elevated soil moisture. Finally, the inversions reveal a major emission underestimate in the US Corn Belt in the bottom-up inventory used here. We extensively test the impact of initial conditions on the analysis and recommend formally optimizing the initial N 2 O distribution to avoid biasing the inferred fluxes. We find that the SVD-based approach provides a powerful framework for deriving emission information from N 2 O observations: by defining the optimal resolution of the solution based on the information content of the inversion, it provides spatial information that is lost when aggregating to political or geographic regions, while also providing more temporal information than a standard 4D-Var inversion.

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“…Currently available mitigation options based on improved efficiencies and best farming practices such as improved nutrition and health management of ruminant livestock (Gerber et al, 2013), reduction of water use in paddy rice (Yan, Akiyama, Yagi, & Akimoto, 2009) and more efficient use of nitrogen fertilizers (Gerber et al, 2016) could be the entry points. Meeting the 2°C goal will require widespread uptake of such existing options.…”

Section: Resultsmentioning

confidence: 99%

National contributions to climate change mitigation from agriculture: allocating a global target

2018

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Globally, agriculture and related land use change contributed about 17% of the world's anthropogenic GHG emissions in 2010 (8.4 GtCO 2 e yr −1 ), making GHG mitigation in the agriculture sector critical to meeting the Paris Agreement's 2°C goal. This article proposes a range of country-level targets for mitigation of agricultural emissions by allocating a global target according to five approaches to effort-sharing for climate change mitigation: responsibility, capability, equality, responsibility-capability-need and equal cumulative per capita emissions. Allocating mitigation targets according to responsibility for total historical emissions or capability to mitigate assigned large targets for agricultural emission reductions to North America, Europe and China. Targets based on responsibility for historical agricultural emissions resulted in a relatively even distribution of targets among countries and regions. Meanwhile, targets based on equal future agricultural emissions per capita or equal per capita cumulative emissions assigned very large mitigation targets to countries with large agricultural economies, while allowing some densely populated countries to increase agricultural emissions. There is no single 'correct' framework for allocating a global mitigation goal. Instead, using these approaches as a set provides a transparent, scientific basis for countries to inform and help assess the significance of their commitments to reducing emissions from the agriculture sector.

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Spatially explicit estimates of N₂O emissions from croplands suggest climate mitigation opportunities from improved fertilizer management

Cited by 126 publications

References 44 publications

Global manure nitrogen production and application in cropland during 1860–2014: a 5 arcmin gridded global dataset for Earth system modeling

Global manure nitrogen production and application in cropland during 1860–2014: a 5 arcmin gridded global dataset for Earth system modeling

Top-down constraints on global N<sub>2</sub>O emissions at optimal resolution: application of a new dimension reduction technique

National contributions to climate change mitigation from agriculture: allocating a global target

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Spatially explicit estimates of N2O emissions from croplands suggest climate mitigation opportunities from improved fertilizer management

Cited by 126 publications

References 44 publications

Global manure nitrogen production and application in cropland during 1860–2014: a 5 arcmin gridded global dataset for Earth system modeling

Global manure nitrogen production and application in cropland during 1860–2014: a 5 arcmin gridded global dataset for Earth system modeling

Top-down constraints on global N&lt;sub&gt;2&lt;/sub&gt;O emissions at optimal resolution: application of a new dimension reduction technique

National contributions to climate change mitigation from agriculture: allocating a global target

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Resources

About

Spatially explicit estimates of N₂O emissions from croplands suggest climate mitigation opportunities from improved fertilizer management

Global manure nitrogen production and application in cropland during 1860–2014: a 5 arcmin gridded global dataset for Earth system modeling

Global manure nitrogen production and application in cropland during 1860–2014: a 5 arcmin gridded global dataset for Earth system modeling

Top-down constraints on global N<sub>2</sub>O emissions at optimal resolution: application of a new dimension reduction technique