School of Water, Energy and Environment (SWEE)

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Browsing School of Water, Energy and Environment (SWEE) by Publisher "American Geophysical Union (AGU) - Wiley"

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    How much food can we grow in urban areas? Food production and crop yields of urban agriculture: a meta-analysis
    (American Geophysical Union (AGU) - Wiley, 2022-08-23) Payen, Florian Thomas; Evans, Daniel L.; Falagán, Natalia; Hardman, Charlotte A.; Kourmpetli, Sofia; Liu, Lingxuan; Marshall, Rachel; Mead, Bethan R.; Davies, Jessica A. C.
    Urban agriculture can contribute to food security, food system resilience and sustainability at the city level. Whilst studies have examined urban agricultural productivity, we lack systemic knowledge of how agricultural productivity of urban systems compares to conventional agriculture and how productivity varies for different urban spaces (e.g., allotments vs. rooftops vs. indoor farming) and growing systems (e.g., hydroponics vs. soil-based agriculture). Here, we present a global meta-analysis that seeks to quantify crop yields of urban agriculture for a broad range of crops and explore differences in yields for distinct urban spaces and growing systems. We found 200 studies reporting urban crop yields, from which 2,062 observations were extracted. ‘Lettuces and chicories’ were the most studied urban grown crops. We observed high agronomic suitability of urban areas, with urban agricultural yields on par with or greater than global average conventional agricultural yields. ‘Cucumbers and gherkins’ were the category of crops for which differences in yields between urban and conventional agriculture were the greatest (17 kg m-2 cycle-1 vs. 3.8 kg m-2 cycle-1). Some urban spaces and growing systems also had a significant effect on specific crop yields (e.g., tomato yields in hydroponic systems were significantly greater than tomato yields in soil-based systems). This analysis provides a more robust, globally-relevant evidence base on the productivity of urban agriculture that can be used in future research and practice relating to urban agriculture, especially in scaling-up studies aiming to estimate the self-sufficiency of cities and towns and their potential to meet local food demand.
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    Optimizing the isoprene emission model MEGAN with satellite and ground-based observational constraints
    (American Geophysical Union (AGU) - Wiley, 2023-02-02) DiMaria, Christian A.; Jones, Dylan B. A.; Worden, Helen; Bloom, A. Anthony; Bowman, Kevin; Stavrakou, Trissevgeni; Miyazaki, Kazuyuki; Worden, John; Guenther, Alex; Sarkar, Chinmoy; Seco, Roger; Park, Jeong-Hoo; Tota, Julio; Gomes Alves, Eliane; Ferracci, Valerio
    Isoprene is a hydrocarbon emitted in large quantities by terrestrial vegetation. It is a precursor to several air quality and climate pollutants including ozone. Emission rates vary with plant species and environmental conditions. This variability can be modeled using the Model of Emissions of Gases and Aerosols from Nature (MEGAN). MEGAN parameterizes isoprene emission rates as a vegetation-specific standard rate which is modulated by scaling factors that depend on meteorological and environmental driving variables. Recent experiments have identified large uncertainties in the MEGAN temperature response parameterization, while the emission rates under standard conditions are poorly constrained in some regions due to a lack of representative measurements and uncertainties in landcover. In this study, we use Bayesian model-data fusion to optimize the MEGAN temperature response and standard emission rates using satellite- and ground-based observational constraints. Optimization of the standard emission rate with satellite constraints reduced model biases but was highly sensitive to model input errors and drought stress and was found to be inconsistent with ground-based constraints at an Amazonian field site, reflecting large uncertainties in the satellite-based emissions. Optimization of the temperature response with ground-based constraints increased the temperature sensitivity of the model by a factor of five at an Amazonian field site but had no impact at a UK field site, demonstrating significant ecosystem-dependent variability of the isoprene emission temperature sensitivity. Ground-based measurements of isoprene across a wide range of ecosystems will be key for obtaining an accurate representation of isoprene emission temperature sensitivity in global biogeochemical models.