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1. Predicting the spatial variation in cost-efficiency for agricultural greenhouse gas mitigation programs in the U.S.

   https://doi.org/10.1186/s13021-024-00252-6  

   Cameron-Harp, Micah V. ; Hendricks, Nathan P. ; Potter, Nicholas A. ( February 2024 , Carbon Balance and Management)

   Two major factors that determine the efficiency of programs designed to mitigate greenhouse gases by encouraging voluntary changes in U.S. agricultural land management are the effect of land use changes on producers’ profitability and the net sequestration those changes create. In this work, we investigate how the interaction of these factors produces spatial heterogeneity in the cost-efficiency of voluntary programs incentivizing tillage reduction and cover-cropping practices. We map county-level predicted rates of adoption for each practice with the greenhouse gas mitigation or carbon sequestration benefits expected from their use. Then, we use these bivariate maps to describe how the cost efficiency of agricultural mitigation efforts is likely to vary spatially in the United States.

   Our results suggest the combination of high adoption rates and large reductions in net emissions make reduced tillage programs most cost efficient in the Chesapeake Bay watershed or the Upper Mississippi and Lower Missouri sub-basins of the Mississippi River. For programs aiming to reduce net emissions by incentivizing cover-cropping, we expect cost-efficiency to be greatest in the areas near the main stem of the Mississippi River within its Middle and Lower sections.

   Many voluntary agricultural conservation programs offer the same incentives across the United States. Yet spatial variation in profitability and efficacy of conservation practices suggest that these uniform approaches are not cost-effective. Spatial targeting of voluntary agricultural conservation programs has the potential to increase the cost-efficiency of these programs due to regional heterogeneity in the profitability and greenhouse gas mitigation benefits of agricultural land management practices across the continental United States. We illustrate how predicted rates of adoption and greenhouse gas sequestration might be used to target regions where efforts to incentivize cover-cropping and reductions in tillage are most likely to be cost -effective.

    

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2. Evaluating Cropland N 2 O Emissions and Fertilizer Plant Greenhouse Gas Emissions With Airborne Observations

   https://doi.org/10.1029/2020JD032815  

   Gvakharia, A. ; Kort, E. A. ; Smith, M. L. ; Conley, S. ( August 2020 , Journal of Geophysical Research: Atmospheres)

   Agricultural activity is a significant source of greenhouse gas emissions. The fertilizer production process emits N₂O, CO₂, and CH₄, and fertilized croplands emit N₂O. We present continuous airborne observations of these trace gases in the Lower Mississippi River Basin to quantify emissions from both fertilizer plants and croplands during the early growing season. Observed hourly emission rates from two fertilizer plants are compared with reported inventory values, showing agreement for N₂O and CO₂emissions but large underestimation in reported CH₄emissions by up to a factor of 100. These CH₄emissions are consistent with loss rates of 0.6–1.2%. We quantify regional emission fluxes (100 km) of N₂O using the airborne mass balance technique, a first application for N₂O, and explore linkages to controlling processes. Finally, we demonstrate the ability to use airborne measurements to distinguish N₂O emission differences between neighboring fields, determining we can distinguish different emission behaviors of regions on the order of 2.5 km²with emissions differences of approximately 0.026μmol m⁻²s⁻¹. This suggests airborne approaches such as outlined here could be used to evaluate the impact of different agricultural practices at critical field‐size spatial scales.

    

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3. The Wasatch Environmental Observatory: A mountain to urban research network in the semi‐arid western US

   https://doi.org/10.1002/hyp.14352  

   Follstad Shah, Jennifer J. ; Bares, Ryan ; Bowen, Brenda B. ; Bowen, Gabriel J. ; Bowling, David R. ; Eiriksson, David P. ; Fasoli, Benjamin ; Fiorella, Richard P. ; Hallar, Anna Gannet ; Hinners, Sarah J. ; et al ( September 2021 , Hydrological Processes)

   The 2085 km²Jordan River Basin, and its seven sub‐catchments draining the Central Wasatch Range immediately east of Salt Lake City, UT, are home to an array of hydrologic, atmospheric, climatic and chemical research infrastructure that collectively forms the Wasatch Environmental Observatory (WEO). WEO is geographically nested within a wildland to urban land‐use gradient and built upon a strong foundation of over a century of discharge and climate records. A 2200 m gradient in elevation results in variable precipitation, temperature and vegetation patterns. Soil and subsurface structure reflect systematic variation in geology from granitic, intrusive to mixed sedimentary clastic across headwater catchments, all draining to the alluvial or colluvial sediments of the former Lake Bonneville. Winter snowfall and spring snowmelt control annual hydroclimate, rapid population growth dominates geographic change in lower elevations and urban gas and particle emissions contribute to episodes of severe air pollution in this closed‐basin. Long‐term hydroclimate observations across this diverse landscape provide the foundation for an expanding network of infrastructure in both montane and urban landscapes. Current infrastructure supports both basic and applied research in atmospheric chemistry, biogeochemistry, climate, ecology, hydrology, meteorology, resource management and urban redesign that is augmented through strong partnerships with cooperating agencies. These features allow WEO to serve as a unique natural laboratory for addressing research questions facing seasonally snow‐covered, semi‐arid regions in a rapidly changing world and an excellent facility for providing student education and research training.

    

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4. US climate policy yields water quality cobenefits in the Mississippi Basin and Gulf of Mexico

   https://doi.org/10.1073/pnas.2302087120  

   Zuidema, Shan ; Liu, Jing ; Chepeliev, Maksym G. ; Johnson, David R. ; Baldos, Uris Lantz ; Frolking, Steve ; Kucharik, Christopher J. ; Wollheim, Wilfred M. ; Hertel, Thomas W. ( October 2023 , Proceedings of the National Academy of Sciences)

   We utilize a coupled economy–agroecology–hydrology modeling framework to capture the cascading impacts of climate change mitigation policy on agriculture and the resulting water quality cobenefits. We analyze a policy that assigns a range of United States government’s social cost of carbon estimates ($51, $76, and $152/ton of CO₂-equivalents) to fossil fuel–based CO₂emissions. This policy raises energy costs and, importantly for agriculture, boosts the price of nitrogen fertilizer production. At the highest carbon price, US carbon emissions are reduced by about 50%, and nitrogen fertilizer prices rise by about 90%, leading to an approximate 15% reduction in fertilizer applications for corn production across the Mississippi River Basin. Corn and soybean production declines by about 7%, increasing crop prices by 6%, while nitrate leaching declines by about 10%. Simulated nitrate export to the Gulf of Mexico decreases by 8%, ultimately shrinking the average midsummer area of the Gulf of Mexico hypoxic area by 3% and hypoxic volume by 4%. We also consider the additional benefits of restored wetlands to mitigate nitrogen loading to reduce hypoxia in the Gulf of Mexico and find a targeted wetland restoration scenario approximately doubles the effect of a low to moderate social cost of carbon. Wetland restoration alone exhibited spillover effects that increased nitrate leaching in other parts of the basin which were mitigated with the inclusion of the carbon policy. We conclude that a national climate policy aimed at reducing greenhouse gas emissions in the United States would have important water quality cobenefits.

    

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5. Reduced Lower Mississippi River Discharge During the Medieval Era

   https://doi.org/10.1029/2020GL091182  

   Wiman, Charlotte ; Hamilton, Brynnydd ; Dee, Sylvia G. ; Muñoz, Samuel E. ( February 2021 , Geophysical Research Letters)

   Changes in climate are expected to influence discharge of the lower Mississippi River, but projections disagree on whether discharge will increase or decrease over the coming century. Using a reconstructed median peak annual flow for the past 1,500 years based on geomorphic scaling laws, we show that discharge on the lower Mississippi River decreased during the Medieval era (c. 1000–1200 CE)—a period of regionally warm and dry conditions that serves as a partial analog for projected warming. These changes in discharge inferred from channel morphology track discharge simulated in the Community Earth System Model Last Millennium Ensemble. Simulations show that decreased Medieval era discharge is driven primarily by regionally enhanced evapotranspiration. Our findings are consistent with 21st century projections of decreased discharge on the lower Mississippi River under moderate greenhouse forcing scenarios, and demonstrate consistency between reconstructed and simulated discharge over the last millennium.

    

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