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  • IOP Publishing  (9)
  • 2020-2024  (9)
  • 1
    Online Resource
    Online Resource
    Greenhouse gas balance in global pasturelands and rangelands
    IOP Publishing ; 2020
    In:  Environmental Research Letters Vol. 15, No. 10 ( 2020-10-01), p. 104006-
    Details
    In: Environmental Research Letters, IOP Publishing, Vol. 15, No. 10 ( 2020-10-01), p. 104006-
    Abstract: Grassland ecosystems play an essential role in climate regulation through carbon (C) storage in plant and soil. But, anthropogenic practices such as livestock grazing, grazing related excreta nitrogen (N) deposition, and manure/fertilizer N application have the potential to reduce the effectiveness of grassland C sink through increased nitrous oxide (N 2 O) and methane (CH 4 ) emissions. Although the effect of anthropogenic activities on net greenhouse gas (GHG) fluxes in grassland ecosystems have been investigated at local to regional scales, estimates of net GHG balance at the global scale remains uncertain. With the data-model framework integrating empirical estimates of livestock CH 4 emissions with process-based modeling estimates of land CO 2 , N 2 O and CH 4 fluxes, we examined the overall global warming potential (GWP) of grassland ecosystems during 1961–2010. We then quantified the grassland-specific and regional variations to identify hotspots of GHG fluxes. Our results show that, over a 100-year time horizon, grassland ecosystems sequestered a cumulative total of 113.9 Pg CO 2 -eq in plant and soil, but then released 91.9 Pg CO 2 -eq to the atmosphere, offsetting 81% of the net CO 2 sink. We also found large grassland-specific variations in net GHG fluxes, with pasturelands acting as a small GHG source of 1.52 ± 143 Tg CO 2 -eq yr −1 (mean ± 1.0 s.d.) and rangelands a strong GHG sink (−442 ± 266 Tg CO 2 -eq yr −1 ) during 1961–2010. Regionally, Europe acted as a GHG source of 23 ± 10 Tg CO 2 -eq yr −1 , while other regions (i.e. Africa, Southern Asia) were strong GHG sinks during 2001–2010. Our study highlights the importance of considering regional and grassland-specific differences in GHG fluxes for guiding future management and climate mitigation strategies in global grasslands.
    Type of Medium: Online Resource
    ISSN: 1748-9326
    URL: Article
    DOI: 10.1088/1748-9326/abaa79
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2020
    detail.hit.zdb_id: 2255379-4
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  • 2
    Online Resource
    Online Resource
    Four decades of nitrous oxide emission from Chinese aquaculture underscores the urgency and opportunity for climate change mitigation
    IOP Publishing ; 2021
    In:  Environmental Research Letters Vol. 16, No. 11 ( 2021-11-01), p. 114038-
    Details
    In: Environmental Research Letters, IOP Publishing, Vol. 16, No. 11 ( 2021-11-01), p. 114038-
    Abstract: As the fastest growing food production sector in the world, aquaculture may become an important source of nitrous oxide (N 2 O)—a potent greenhouse gas and the dominant source of ozone-depleting substances in the stratosphere. China is the largest aquaculture producer globally; however, the magnitude of N 2 O emission from Chinese aquaculture systems (CASs) has not yet been extensively investigated. Here, we quantified N 2 O emission from the CASs since the Reform and Opening-up (1979–2019) at the species-, provincial-, and national-levels using annual aquaculture production data, based on nitrogen (N) levels in feed type, feed amount, feed conversion ratio, and emission factor (EF). Our estimate indicates that over the past 41 years, N 2 O emission from CASs has increased approximately 25 times from 0.67 ± 0.04 GgN in 1979 to 16.69 ± 0.31 GgN in 2019. Freshwater fish farming, primarily in two provinces, namely, Guangdong and Hubei, where intensive freshwater fish farming has been adopted in the past decades, accounted for approximately 89% of this emission increase. We also calculated the EF for each species, ranging from 0.79 ± 0.23 g N 2 O kg −1 animal to 2.41 ± 0.14 g N 2 O kg −1 animal. The results of this study suggest that selecting low-EF species and improving feed use efficiency can help reduce aquaculture N 2 O emission for building a climate-resilient sustainable aquaculture.
    Type of Medium: Online Resource
    ISSN: 1748-9326
    URL: Article
    DOI: 10.1088/1748-9326/ac3177
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2021
    detail.hit.zdb_id: 2255379-4
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  • 3
    Online Resource
    Online Resource
    Increasing sensitivity of terrestrial nitrous oxide emissions to precipitation variations
    IOP Publishing ; 2022
    In:  Environmental Research: Climate Vol. 1, No. 2 ( 2022-12-01), p. 025010-
    Details
    In: Environmental Research: Climate, IOP Publishing, Vol. 1, No. 2 ( 2022-12-01), p. 025010-
    Abstract: Nitrous oxide (N 2 O), a major greenhouse gas and ozone-depleting agent, is generated over land mostly from two key biochemical processes—nitrification and denitrification. Nitrifying and denitrifying N 2 O production occurs preferably under alternative oxic and anoxic conditions, which are closely linked with variations in water filled soil pores, and thus indirectly with precipitation. We show here that the interannual anomalies in the annual growth rate of the global land N 2 O emissions are significantly ( P 〈 0.001) correlated with precipitation anomalies, with an overall sensitivity ( α PRE , changes of land N 2 O emission variations per precipitation anomalies) of 2.50 ± 0.98 Tg N 2 O–N per 100 mm of precipitation across the global land (1998–2016). The sensitivity ( α PRE ) and precipitation-driven N 2 O anomalies increased during 1998–2016, partly due to increased nitrogen inputs to agricultural lands and enhanced precipitation anomalies. Spatially, we find that the α PRE increases with aridity. We predict a larger α PRE under future climate conditions (with radiative forcing levels of 4.5, 7.0 and 8.5 Wm −2 ) by the year 2100 if nitrogen fertilization follows the present practice.
    Type of Medium: Online Resource
    ISSN: 2752-5295
    URL: Article
    DOI: 10.1088/2752-5295/aca2d1
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 3144322-9
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  • 4
    Online Resource
    Online Resource
    Riverine nitrogen footprint of agriculture in the Mississippi–Atchafalaya River Basin: do we trade water quality for crop production?
    IOP Publishing ; 2023
    In:  Environmental Research Letters Vol. 18, No. 11 ( 2023-11-01), p. 114043-
    Details
    In: Environmental Research Letters, IOP Publishing, Vol. 18, No. 11 ( 2023-11-01), p. 114043-
    Abstract: Increasing food and biofuel demands have led to the cascading effects from cropland expansions, raised fertilizer use, to increased riverine nitrogen (N) loads. However, little is known about the current trade-off between riverine N pollution and crop production due to the lack of predictive understanding of ecological processes across the land-aquatic continuum. Here, we propose a riverine N footprint (RNF) concept to quantify how N loads change along with per unit crop production gain. Using data synthesis and a well-calibrated hydro-ecological model, we find that the RNF within the Mississippi–Atchafalaya River Basin peaked at 1.95 g N kg −1 grain during the 1990s, and then shifted from an increasing to a decreasing trend, reaching 0.65 g N kg −1 grain in the 2010s. This implies decoupled responses of crop production and N loads to key agricultural activities approximately after 2000, but this pattern varies considerably among sub-basins. Our study highlights the importance of developing a food–energy–water nexus indicator to examine the region-specific trade-offs between crop production and land-to-aquatic N loads for achieving nutrient mitigation goals while sustaining economic gains.
    Type of Medium: Online Resource
    ISSN: 1748-9326
    URL: Article
    DOI: 10.1088/1748-9326/ad0128
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2023
    detail.hit.zdb_id: 2255379-4
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  • 5
    Online Resource
    Online Resource
    Pronounced and unavoidable impacts of low-end global warming on northern high-latitude land ecosystems
    IOP Publishing ; 2020
    In:  Environmental Research Letters Vol. 15, No. 4 ( 2020-04-01), p. 044006-
    Details
    In: Environmental Research Letters, IOP Publishing, Vol. 15, No. 4 ( 2020-04-01), p. 044006-
    Abstract: Arctic ecosystems are particularly vulnerable to climate change because of Arctic amplification. Here, we assessed the climatic impacts of low-end, 1.5 °C, and 2.0 °C global temperature increases above pre-industrial levels, on the warming of terrestrial ecosystems in northern high latitudes (NHL, above 60 °N including pan-Arctic tundra and boreal forests) under the framework of the Inter-Sectoral Impact Model Intercomparison Project phase 2b protocol. We analyzed the simulated changes of net primary productivity, vegetation biomass, and soil carbon stocks of eight ecosystem models that were forced by the projections of four global climate models and two atmospheric greenhouse gas pathways (RCP2.6 and RCP6.0). Our results showed that considerable impacts on ecosystem carbon budgets, particularly primary productivity and vegetation biomass, are very likely to occur in the NHL areas. The models agreed on increases in primary productivity and biomass accumulation, despite considerable inter-model and inter-scenario differences in the magnitudes of the responses. The inter-model variability highlighted the inadequacies of the present models, which fail to consider important components such as permafrost and wildfire. The simulated impacts were attributable primarily to the rapid temperature increases in the NHL and the greater sensitivity of northern vegetation to warming, which contrasted with the less pronounced responses of soil carbon stocks. The simulated increases of vegetation biomass by 30–60 Pg C in this century have implications for climate policy such as the Paris Agreement. Comparison between the results at two warming levels showed the effectiveness of emission reductions in ameliorating the impacts and revealed unavoidable impacts for which adaptation options are urgently needed in the NHL ecosystems.
    Type of Medium: Online Resource
    ISSN: 1748-9326
    URL: Article
    DOI: 10.1088/1748-9326/ab702b
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2020
    detail.hit.zdb_id: 2255379-4
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  • 6
    Online Resource
    Online Resource
    The NASA Carbon Monitoring System Phase 2 synthesis: scope, findings, gaps and recommended next steps
    IOP Publishing ; 2022
    In:  Environmental Research Letters Vol. 17, No. 6 ( 2022-06-01), p. 063010-
    Details
    In: Environmental Research Letters, IOP Publishing, Vol. 17, No. 6 ( 2022-06-01), p. 063010-
    Abstract: Underlying policy efforts to address global climate change is the scientific need to develop the methods to accurately measure and model carbon stocks and fluxes across the wide range of spatial and temporal scales in the Earth system. Initiated in 2010, the NASA Carbon Monitoring System is one of the most ambitious relevant science initiatives to date, exploiting the satellite remote sensing resources, computational capabilities, scientific knowledge, airborne science capabilities, and end-to-end system expertise that are major strengths of the NASA Earth Science program. Here we provide a synthesis of ‘Phase 2’ activities (2011–2019), encompassing 79 projects, 482 publications, and 136 data products. Our synthesis addresses four key questions: What has been attempted? What major results have been obtained? What major gaps and uncertainties remain? and What are the recommended next steps? Through this review, we take stock of what has been accomplished and identify future priorities toward meeting the nation’s needs for carbon monitoring reporting and verification.
    Type of Medium: Online Resource
    ISSN: 1748-9326
    URL: Article
    DOI: 10.1088/1748-9326/ac7407
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 2255379-4
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  • 7
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    Online Resource
    Climate change-induced greening on the Tibetan Plateau modulated by mountainous characteristics
    IOP Publishing ; 2021
    In:  Environmental Research Letters Vol. 16, No. 6 ( 2021-06-01), p. 064064-
    Details
    In: Environmental Research Letters, IOP Publishing, Vol. 16, No. 6 ( 2021-06-01), p. 064064-
    Abstract: Global terrestrial vegetation is greening, particularly in mountain areas, providing strong feedbacks to a series of ecosystem processes. This greening has been primarily attributed to climate change. However, the spatial variability and magnitude of such greening do not synchronize with those of climate change in mountain areas. By integrating two data sets of satellite-derived normalized difference vegetation index (NDVI) values, which are indicators of vegetation greenness, in the period 1982–2015 across the Tibetan Plateau (TP), we test the hypothesis that climate-change-induced greening is regulated by terrain, baseline climate and soil properties. We find a widespread greening trend over 91% of the TP vegetated areas, with an average greening rate (i.e. increase in NDVI) of 0.011 per decade. The linear mixed-effects model suggests that climate change alone can explain only 26% of the variation in the observed greening. Additionally, 58% of the variability can be explained by the combination of the mountainous characteristics of terrain, baseline climate and soil properties, and 32% of this variability was explained by terrain. Path analysis identified the interconnections of climate change, terrain, baseline climate and soil in determining greening. Our results demonstrate the important role of mountainous effects in greening in response to climate change.
    Type of Medium: Online Resource
    ISSN: 1748-9326
    URL: Article
    DOI: 10.1088/1748-9326/abfeeb
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2021
    detail.hit.zdb_id: 2255379-4
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  • 8
    Online Resource
    Online Resource
    Five years of variability in the global carbon cycle: comparing an estimate from the Orbiting Carbon Observatory-2 and process-based models
    IOP Publishing ; 2021
    In:  Environmental Research Letters Vol. 16, No. 5 ( 2021-05-01), p. 054041-
    Details
    In: Environmental Research Letters, IOP Publishing, Vol. 16, No. 5 ( 2021-05-01), p. 054041-
    Abstract: Year-to-year variability in CO 2 fluxes can yield insight into climate-carbon cycle relationships, a fundamental yet uncertain aspect of the terrestrial carbon cycle. In this study, we use global observations from NASA’s Orbiting Carbon Observatory-2 (OCO-2) satellite for years 2015–2019 and a geostatistical inverse model to evaluate 5 years of interannual variability (IAV) in CO 2 fluxes and its relationships with environmental drivers. OCO-2 launched in late 2014, and we specifically evaluate IAV during the time period when OCO-2 observations are available. We then compare inferences from OCO-2 with state-of-the-art process-based models (terrestrial biosphere model, TBMs). Results from OCO-2 suggest that the tropical grasslands biome (including grasslands, savanna, and agricultural lands within the tropics) makes contributions to global IAV during the 5 year study period that are comparable to tropical forests, a result that differs from a majority of TBMs. Furthermore, existing studies disagree on the environmental variables that drive IAV during this time period, and the analysis using OCO-2 suggests that both temperature and precipitation make comparable contributions. TBMs, by contrast, tend to estimate larger IAV during this time and usually estimate larger relative contributions from the extra-tropics. With that said, TBMs show little consensus on both the magnitude and the contributions of different regions to IAV. We further find that TBMs show a wide range of responses on the relationships of CO 2 fluxes with annual anomalies in temperature and precipitation, and these relationships across most of the TBMs have a larger magnitude than inferred from OCO-2. Overall, the findings of this study highlight large uncertainties in process-based estimates of IAV during recent years and provide an avenue for evaluating these processes against inferences from OCO-2.
    Type of Medium: Online Resource
    ISSN: 1748-9326
    URL: Article
    DOI: 10.1088/1748-9326/abfac1
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2021
    detail.hit.zdb_id: 2255379-4
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  • 9
    Online Resource
    Online Resource
    Impacts of tillage practices on soil carbon stocks in the US corn-soybean cropping system during 1998 to 2016
    IOP Publishing ; 2020
    In:  Environmental Research Letters Vol. 15, No. 1 ( 2020-01-01), p. 014008-
    Details
    In: Environmental Research Letters, IOP Publishing, Vol. 15, No. 1 ( 2020-01-01), p. 014008-
    Abstract: Tillage alters the thermal and wetness conditions in soil, which facilitates soil organic matter oxidation and water transportation, leading to rapid depletion of soil carbon (C). Little is known about tillage intensity change (TIC) and its impacts in the US corn-soybean rotation system over the past two decades. Using time-series tillage maps developed from a private survey and a process-based land ecosystem model, here we examined how tillage intensity has changed across the nation and affected soil organic carbon (SOC) storage from 1998 to 2016. Results derived from the combination of tillage survey data and cropland distribution maps show that total corn-soybean area consistently increased from 62.3 Mha in 1998 to 66.8 Mha in 2008 and to 73.1 Mha in 2016, among which the acreage under no-till system increased from 16.9 Mha in 1998 to 28.9 Mha in 2008, while conservation and conventional tillage decreased by 3.8 and 3.9 Mha, respectively. The extent of no-till practice in corn-soybean lands shrank by 2.6 Mha from 2008 to 2016, while conservation and conventional tillage increased by 2.8 and 6.1 Mha in the same period. Modeling simulations reveal that historical tillage practices led to a soil C loss of 10.3 (spring till only) to 15.2 (tilled in both spring and fall) Tg C yr −1 in the study area from 1998 to 2016. In addition, reduced tillage intensity in corn-soybean cropland contributed to SOC accumulation at 1.0 Tg C yr −1 (1.6 g C m −2 yr −1 ) from 1998 to 2008, but the SOC gain was offset by SOC reduction at 2.4 Tg C yr −1 (3.4 g C m −2 yr −1 ) from increased tillage intensity during the period 2008–2016. For both periods, TIC-induced hydrological C loss accounted for 15% of the SOC change, while the rest was attributed to gaseous-C loss.
    Type of Medium: Online Resource
    ISSN: 1748-9326
    URL: Article
    DOI: 10.1088/1748-9326/ab6393
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2020
    detail.hit.zdb_id: 2255379-4
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