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Methane (CH 4 ) emissions from tropical wetlands contribute 60%-80% of global natural wetland CH 4 emissions. Decreased wetland CH 4 emissions can act as a negative feedback mechanism for future climate warming and vice versa. The impact of the El Niño-Southern Oscillation (ENSO) on CH 4 emissions from wetlands remains poorly quantified at both regional and global scales, and El Niño events are expected to become more severe based on climate models' projections. We use a process-based model of global wetland CH 4 emissions to investigate the impacts of the ENSO on CH 4 emissions in tropical wetlands for the period from 1950 to 2012. The results show that CH 4 emissions from tropical wetlands respond strongly to repeated ENSO events, with negative anomalies occurring during El Niño periods and with positive anomalies occurring during La Niña periods. An approximately 8-month time lag was detected between tropical wetland CH 4 emissions and ENSO events, which was caused by the combined time lag effects of ENSO events on precipitation and temperature over tropical wetlands. The ENSO can explain 49% of interannual variations for tropical wetland CH 4 emissions. Furthermore, relative to neutral years, changes in temperature have much stronger effects on tropical wetland CH 4 emissions than the changes in precipitation during ENSO periods. The occurrence of several El Niño events contributed to a lower decadal mean growth rate in atmospheric CH 4 concentrations throughout the 1980s and 1990s and to stable atmospheric CH 4 concentrations from 1999 to 2006, resulting in negative feedback to global warming., (© 2017 John Wiley & Sons Ltd.)

Human demand for livestock products has increased rapidly during the past few decades largely due to dietary transition and population growth, with significant impact on climate and the environment. The contribution of ruminant livestock to greenhouse gas (GHG) emissions has been investigated extensively at various scales from regional to global, but the long-term trend, regional variation and drivers of methane (CH 4 ) emission remain unclear. In this study, we use Intergovernmental Panel on Climate Change (IPCC) Tier II guidelines to quantify the evolution of CH 4 emissions from ruminant livestock during 1890-2014. We estimate that total CH 4 emissions in 2014 was 97.1 million tonnes (MT) CH 4 or 2.72 Gigatonnes (Gt) CO 2 -eq (1 MT = 10 12 g, 1 Gt = 10 15 g) from ruminant livestock, which accounted for 47%-54% of all non-CO 2 GHG emissions from the agricultural sector. Our estimate shows that CH 4 emissions from the ruminant livestock had increased by 332% (73.6 MT CH 4 or 2.06 Gt CO 2 -eq) since the 1890s. Our results further indicate that livestock sector in drylands had 36% higher emission intensity (CH 4 emissions/km 2 ) compared to that in nondrylands in 2014, due to the combined effect of higher rate of increase in livestock population and low feed quality. We also find that the contribution of developing regions (Africa, Asia and Latin America) to the total CH 4 emissions had increased from 51.7% in the 1890s to 72.5% in the 2010s. These changes were driven by increases in livestock numbers (LU units) by up to 121% in developing regions, but decreases in livestock numbers and emission intensity (emission/km 2 ) by up to 47% and 32%, respectively, in developed regions. Our results indicate that future increases in livestock production would likely contribute to higher CH 4 emissions, unless effective strategies to mitigate GHG emissions in livestock system are implemented., (© 2017 John Wiley & Sons Ltd.)

Large amounts of organic carbon are stored in Arctic permafrost environments, and microbial activity can potentially mineralize this carbon into methane, a potent greenhouse gas. In this study, we assessed the methane budget, the bacterial methane oxidation (MOX) and the underlying environmental controls of arctic lake systems, which represent substantial sources of methane. Five lake systems located on Samoylov Island (Lena Delta, Siberia) and the connected river sites were analyzed using radiotracers to estimate the MOX rates, and molecular biology methods to characterize the abundance and the community composition of methane-oxidizing bacteria (MOB). In contrast to the river, the lake systems had high variation in the methane concentrations, the abundance and composition of the MOB communities, and consequently, the MOX rates. The highest methane concentrations and the highest MOX rates were detected in the lake outlets and in a lake complex in a flood plain area. Though, in all aquatic systems, we detected both, Type I and II MOB, in lake systems, we observed a higher diversity including MOB, typical of the soil environments. The inoculation of soil MOB into the aquatic systems, resulting from permafrost thawing, might be an additional factor controlling the MOB community composition and potentially methanotrophic capacity., (© FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

This study explores the relationship between greenhouse gases (GHGs) and particulate emissions and quality of life. The aim is to understand how emissions affect quality of life globally—across countries, regions, and the global population. Statistical methods were used to examine the impact of various emissions' indicators on different aspects of quality of life. The study highlights the urgent need for climate change action and encourages policymakers to take strategic steps. Climate change adversely affects numerous aspects of daily life, leading to significant consequences that must be addressed through policy changes and global governance recommendations. Key findings include that higher CO2 and methane emissions and air pollution negatively impact quality of life. CO2 emissions are positively associated with electricity while air pollution is positively associated with GDP and negatively with unemployment. Air pollution has an adverse effect on all three aspects of the children's welfare dimension of quality of life. These results provide timely and convincing insights for policy- and decision-making aimed at mitigating the impact of emissions on quality of life. [ABSTRACT FROM AUTHOR]

Simple Summary: This review highlights the benefits of using valuable alternative feeds such as crop residues, silage, grasses, hay, browse, plant leaves, shrubs, and agro-industrial by-products in small ruminants' diets. Alternative feeds can significantly improve the productivity and reduce carbon footprints and GHG fluxes of small ruminant farms, making them both environmentally friendly and cost-effective. Additionally, these alternative feeds possess antioxidant, antimicrobial, and antiseptic properties that can enhance the quality of the meat and milk produced. Small ruminants, such as sheep (Ovisaries) and goats (Capra hircus), contribute to approximately 475 million metric tons of carbon dioxide equivalent (MtCO2e) greenhouse gas (GHG) emissions, accounting for approximately 6.5% of the global emissions in the agriculture sector. Crop residues, silage, grasses, hay, browse, plant leaves, shrubs, agro-industrial by-products, poultry litter, and other alternative feed sources are frequently utilized for small ruminant production. The use of these valuable alternative feeds can significantly improve animal productivity and reduce carbon footprints and GHG fluxes, making it both environmentally friendly and cost-effective. Additionally, these alternative feeds possess antioxidant, antimicrobial, and antiseptic properties that can enhance the quality of the meat and milk produced. By impacting the bacteria involved in ruminal biohydrogenation, alternative feeds can reduce methane emissions and contribute to a decrease in the carbon footprint. Overall, the use of alternative feed sources for small ruminants generally improves their apparent nutrient digestibility and productivity, and has an impact on the production of greenhouse gases, especially methane. Finally, this review recommends evaluating the economic analysis of reducing methane emissions in small ruminants by utilizing different feed sources and feeding techniques. [ABSTRACT FROM AUTHOR]

To achieve the goal in the Paris Agreement of limiting mean global temperature rise to 1.5 ​°C, total anthropogenic radiative forcing (RF) should be reduced from current 2.7 to around 1.9 ​W ​m−2. A newly developed RF-based climate footprint (RFCF) indicator, which quantifies the additional contribution to RF associated with current and historical emissions, can support transparent alignment with climate stabilization targets by assessing the profile of RF over time. Nevertheless, RFCF applications to date have been based on parameters and equations from IPCC 5th Assessment Report (AR). Considering the latest updates in the IPCC 6th AR, we applied the RFCF approach for the first time in a case study involving the Australian agricultural sector. We compared the RF, RFCF and annual changes in RFCF of CH4, N2O and CO2 using both models. All the results of RF as well as RFCF calculated using the latest model were slightly lower than those obtained using the former model. The agricultural sector's contribution to RF had plateaued in recent years and is projected to reach the point of net zero increase in 2022 (IPCC 6th AR model) or 2023 (IPCC 5th AR model). Considering the latest updates in emission lifetime, radiative efficiency and indirect effects based on the background concentration (1750–2019), the assessments based on IPCC 6th AR model provide more reliable results. However, a dynamic model is required to reflect the additional RF for the pulse emission based on the relevant climate background in the same year. The RF-based footprint approach can support national greenhouse gas emission reduction policy targets, especially for sectors with substantial biogenic methane emissions.

Small ruminants, such as sheep (Ovisaries) and goats (Capra hircus), contribute to approximately 475 million metric tons of carbon dioxide equivalent (MtCO2e) greenhouse gas (GHG) emissions, accounting for approximately 6.5% of the global emissions in the agriculture sector. Crop residues, silage, grasses, hay, browse, plant leaves, shrubs, agro-industrial by-products, poultry litter, and other alternative feed sources are frequently utilized for small ruminant production. The use of these valuable alternative feeds can significantly improve animal productivity and reduce carbon footprints and GHG fluxes, making it both environmentally friendly and cost-effective. Additionally, these alternative feeds possess antioxidant, antimicrobial, and antiseptic properties that can enhance the quality of the meat and milk produced. By impacting the bacteria involved in ruminal biohydrogenation, alternative feeds can reduce methane emissions and contribute to a decrease in the carbon footprint. Overall, the use of alternative feed sources for small ruminants generally improves their apparent nutrient digestibility and productivity, and has an impact on the production of greenhouse gases, especially methane. Finally, this review recommends evaluating the economic analysis of reducing methane emissions in small ruminants by utilizing different feed sources and feeding techniques.

Livestock production in developing countries faces several difficulties such as a general shortage of feed resources, regional availability, and quality. Climate change further exacerbates these problems, leading to a massive reduction in ruminant productivity. Therefore, there is a need for the use of adaptable and resilient forage plants that can also contribute to reducing greenhouse gases. The Moringa oleifera tree is well known as an agroforestry tree and has adapted to growing in harsh conditions. It produces a high amount of biomass in a short period and contains high levels of nutrients and biologically active components. All parts of the Moringa tree are valuable and have multiple benefits and applications. Therefore, Moringa oleifera has great potential and can be used as a forage crop, storing carbon dioxide (CO2) and improving ruminant performance and the livelihoods of farmers in the tropics. This article aimed to present the results and findings of studies related to the use of Moringa in ruminant feed (cattle, sheep, and goats) and its contribution to climate protection. Several studies highlighted that M. oleifera can be used as green fodder either individually or in combination with other crops or concentrate feeds to improve the performance of ruminants, such as the growth rate, milk yield, and milk constituents, without negatively impacting animal health. This improvement in performance could be attributed to the favorable nutrient content in M. oleifera, delivering proteins in conjunction with bioactive compounds such as alkaloids, flavonoids, phenolics, glucosinolates, carotenoids, sterols, saponins, phenolic acids, tannins, and isothiocyanates. Furthermore, it has been shown that this plant can be produced in high yields and thus might be an excellent carbon dioxide sink to absorb and utilize carbon dioxide, reducing the anthropogenic load of carbon dioxide in the atmosphere. In addition, feeding cattle and other ruminants with M. oleifera leaves or seeds significantly decreases ruminal methane emissions, which could contribute to adapting to climate-friendly farming. Thus, the use of Moringa can make a sustainable contribution to strengthening animal production, especially in countries with limited feed resources.

Lakes represent an important source of atmospheric methane (CH4); however, there are few studies on which lake-dwelling invasive aquatic plants generate CH4. Therefore, in this study, CH4 emissions were measured using a floating chamber and gas chromatography in a subtropical lake in China. We considered four community zones of invasive plants (Eichhornia crassipes), emergent vegetation (Zizania latifolia), floating-plant (Trapa natans) and open-water zones. The results indicate that the flux of CH4 emissions varied between −5.38 and 102.68 mg m−2 h−1. The higher emission values were attributed to lake eutrophication. Moreover, the flux of CH4 emissions in the invasive plant zone was 140–220% higher than that in the open-water and the floating-plant zones. However, there was no significant difference in CH4 emissions between the invasive plant and the emergent vegetation zones. This may be due to a higher production of plants, as well as the rapid reproductive rate of the invasive plants. Finally, CH4 emissions were positively associated with the air and water temperature; however, the emissions were also negatively associated with water depth. Our results suggest that invasive plants enhance freshwater CH4 emissions, thus contributing to global warming. [ABSTRACT FROM AUTHOR]

Simple Summary: Concerns about greenhouse gas (GHG) emissions from livestock and dairy farms, as well as their connection to global warming and climate change, have grown among the general public worldwide in recent years. To evaluate these emissions, there is a need to use reliable methods. Enteric methane (CH4) and other greenhouse gas emissions from ruminants can be mitigated in numerous ways. The objectives of this review were to examine currently available knowledge about methane evaluation and mitigation strategies, and food supplements. We wanted to present a critical view and raise visions of what is known and unknown about GHG reduction and control. Agriculture produces greenhouse gases. Methane is a result of manure degradation and microbial fermentation in the rumen. Reduced CH4 emissions will slow climate change and reduce greenhouse gas concentrations. This review compiled studies to evaluate the best ways to decrease methane emissions. Longer rumination times reduce methane emissions and milk methane. Other studies have not found this. Increasing propionate and reducing acetate and butyrate in the rumen can reduce hydrogen equivalents that would otherwise be transferred to methanogenesis. Diet can reduce methane emissions. Grain lowers rumen pH, increases propionate production, and decreases CH4 yield. Methane generation per unit of energy-corrected milk yield reduces with a higher-energy diet. Bioactive bromoform discovered in the red seaweed Asparagopsis taxiformis reduces livestock intestinal methane output by inhibiting its production. Essential oils, tannins, saponins, and flavonoids are anti-methanogenic. While it is true that plant extracts can assist in reducing methane emissions, it is crucial to remember to source and produce plants in a sustainable manner. Minimal lipid supplementation can reduce methane output by 20%, increasing energy density and animal productivity. Selecting low- CH4 cows may lower GHG emissions. These findings can lead to additional research to completely understand the impacts of methanogenesis suppression on rumen fermentation and post-absorptive metabolism, which could improve animal productivity and efficiency. [ABSTRACT FROM AUTHOR]

The possible consequences of decisions of the 26th Conference of the Parties to the UN Framework Convention on Climate Change (Glasgow, 2021) for the world energy and anthropogenic climate changes are investigated. A group of scenarios of the anthropogenic impact on the global climate system is proposed including the implementation of Glasgow solutions in the field of decarbonization of the world economy, reduction of methane emissions, and reforestation. It is shown that there is a technical potential for implementing the Glasgow decisions, but the desired pace of reformation of the world energy and the entire economy is unprecedented on a historical scale. Using the global carbon cycle and climate models developed at MPEI, the changes in the chemical composition, the thermal radiative balance of the Earth's atmosphere, and the global average air temperature for each of the scenarios are calculated. It is shown that the implementation of the entire range of measures proposed in Glasgow for reducing the anthropogenic impact on the planetary climate system can limit the warming to within 1.5°C of the pre-industrial level, but there are serious doubts about the practical implementation of the proposed program of decarbonization of the world economy. [ABSTRACT FROM AUTHOR]

Diesel-fueled ships have long been considered to contribute a marginal fraction of the global methane (CH4) emission budget compared to liquified natural gas (LNG)-fueled ships. Here, based on real-world measurements, we find that a specific yet-overlooked group of diesel-fueled ships–the old small fishing vessels (OSFVs)–is associated with high levels of CH4 emissions. The emission factors of CH4 from OSFVs is on average 5.2 ± 6.4 g CH4 per 1 kg fuel consumed, approaching EFCH4 of LNG-fueled ships (5.3–30.1 g/kg) and being at least six times EFCH4 of other types of diesel-fueled ships (0.0–0.9 g/kg). We estimate that CH4 emissions from OSFVs in China amount to 570–2,240 t per year, which is comparable to the total CH4 emission from all LNG-fueled ships worldwide. Our results thus call for revision of the global CH4 emission inventory for shipping.

Lakes represent an important source of atmospheric methane (CH4); however, there are few studies on which lake-dwelling invasive aquatic plants generate CH4. Therefore, in this study, CH4 emissions were measured using a floating chamber and gas chromatography in a subtropical lake in China. We considered four community zones of invasive plants (Eichhornia crassipes), emergent vegetation (Zizania latifolia), floating-plant (Trapa natans) and open-water zones. The results indicate that the flux of CH4 emissions varied between −5.38 and 102.68 mg m−2 h−1. The higher emission values were attributed to lake eutrophication. Moreover, the flux of CH4 emissions in the invasive plant zone was 140–220% higher than that in the open-water and the floating-plant zones. However, there was no significant difference in CH4 emissions between the invasive plant and the emergent vegetation zones. This may be due to a higher production of plants, as well as the rapid reproductive rate of the invasive plants. Finally, CH4 emissions were positively associated with the air and water temperature; however, the emissions were also negatively associated with water depth. Our results suggest that invasive plants enhance freshwater CH4 emissions, thus contributing to global warming.

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Abstract The livestock sector is the largest source of anthropogenic methane emissions and is projected to increase in the future with the increased demand for livestock products. Here, we compare livestock methane emissions and emission intensities, defined by the amount of methane emitted per unit of animal proteins, estimated by different methodologies, and identify mitigation potentials in different regions of the world based on possible future projections. We show that emission intensity decreased for most livestock categories globally during 2000–2018, due to an increasing protein‐production efficiency, and the IPCC Tier 2 method should be used for capturing the temporal changes in the emission intensities. We further show that efforts on the demand‐side to promote balanced, healthy, and environmentally sustainable diets in most countries will not be sufficient to mitigate livestock methane emissions without parallel efforts to improve production efficiency. The latter efforts have much greater mitigating effects than demand‐side efforts, and hence should be prioritized in a few developing countries that contribute most of the mitigation potential.

Researchers believe that greenhouse gas emissions (GHG) from livestock are an emerging problem. Beef cattle is one of the most emission-intensive sectors, which is responsible for 54% of total GHGs from livestock. This study has two purposes. First, we quantify the environmental loading of U.S. beef sector by calculating emission levels over the period 1970- 2014. Following Intergovernmental Panel on Climate Change (IPCC) guideline, we identify three sources of emissions, including enteric fermentation, manure management, and manure left on pastures. Second, we provide an understanding of consumption-environmental connection related to the beef industry. We used Tire 1 method calculations in this study. This method will provide the basic information for establishing policies to mitigate climate change. We encourage to use Tire 2 method in future studies. It is also recommended to see the impact of changing geographical locations of cattle farm to the regions that have lower emission factors in future studies. It t is concluded that providing information to the public regarding livestock and climate change relationship would be beneficial. Media attention is needed to convey this message to the public that eating more meat is environmentally detrimental, and we need to change our diet to confine GHG emissions. This knowledge might help develop schemes to avoid the catastrophic climate change consequences in the future

Methane is an important greenhouse gas. Prediction of its long-term effect on climate changes requires understanding of the sources of its release into the atmosphere. The present work aimed to review the most widely used modern methods for measuring microbial production and emission of methane in soils, and to assess their applicability to various microbial ecosystems. A classification of methods for measuring methane production in microbial soil ecosystems is proposed, based on the basic physical and mathematical approaches to data processing for each method. Under laboratory conditions, methane production is determined by soil samples incubation and layered mass balance methods, which makes it possible to investigate the methanogenic potential of a microbial community for subsequent simulation of microbial processes; these methods, however, cannot be directly extrapolated to natural ecosystems. To determine methane production in field experiments, gradient methods are used, as well as a deep soil chamber technique developed for wetlands. Methods for measuring methane emission are described, as well as their advantages and limitations. While traditional chamber techniques are simple and therefore widely used, their implementation is limited by such factors as changes in environmental conditions caused by using the chamber, small spatial scales, and difficulties in chamber installation in some ecosystems. More recently developed micrometeorological methods are free of these limitations and provide for proper estimations of gas emissions from ecosystems even if these emissions are heterogeneous in space and time. To estimate emissions from such specific objects as landfills and livestock complexes or at large scales (regional or even global), the inverse modeling method is used. [ABSTRACT FROM AUTHOR]

Geologic hydrocarbon seepage is considered to be the dominant natural source of atmospheric methane in terrestrial and shallowwater areas; in deep-water areas, in contrast, hydrocarbon seepage is expected to have no atmospheric impact because the gas is typically consumed throughout the water column. Here, we present evidence for a sudden expulsion of a reservoir-size quantity of methane from a deep-water seep during the Pliocene, resulting from natural reservoir overpressure. Combining three-dimensional seismic data, borehole data and fluid-flow modeling, we estimate that 18-27 of the 23-31 Tg of methane released at the seafloor could have reached the atmosphere over 39-241 days. This emission is ~10% and ~28% of present-day, annual natural and petroleum- industry methane emissions, respectively. While no such ultraseepage events have been documented in modern times and their frequency is unknown, seismic data suggest they were not rare in the past and may potentially occur at present in critically pressurized reservoirs. This neglected phenomenon can influence decadal changes in atmospheric methane. [ABSTRACT FROM AUTHOR]

Carbon dioxide emission and greenhouse gas emissions are considered core issue in the world that influence agricultural production and also cause climate change. The present study seeks to investigate the linkage of methane emissions, nitrous oxide emissions, carbon dioxide emission, and greenhouse gas emissions with agricultural gross domestic product in China. The long-term association was checked by using an autoregressive distributed lag (ARDL) bounds testing approach, fully modified least squares method, and canonical cointegrating regression analysis. The results from long-run analysis exposed that carbon dioxide emission and greenhouse gas emissions have positive coefficients that demonstrate the long-run linkage with the agricultural gross domestic product having p values of 0.5709 and 0.3751, respectively. Similarly, results also revealed that agricultural methane emissions and agricultural nitrous oxide emissions have a negative association with the agricultural gross domestic product having p values of 0.1737 and 0.0559. China is a huge emitter of CO2 emission and greenhouse gas emissions. Possible conservative policies are required to form the Chinese government to tackle this challenge to decrease CO2 emission in order to increase agricultural production. [ABSTRACT FROM AUTHOR]

Tropical peatlands are vital ecosystems that play an important role in global carbon storage and cycles. Current estimates of greenhouse gases from these peatlands are uncertain as emissions vary with environmental conditions. This study provides the first comprehensive analysis of managed and natural tropical peatland GHG fluxes: heterotrophic (i.e. soil respiration without roots), total CO2 respiration rates, CH4 and N2O fluxes. The study documents studies that measure GHG fluxes from the soil (n = 372) from various land uses, groundwater levels and environmental conditions. We found that total soil respiration was larger in managed peat ecosystems (median = 52.3 Mg CO2 ha−1 year−1) than in natural forest (median = 35.9 Mg CO2 ha−1 year−1). Groundwater level had a stronger effect on soil CO2 emission than land use. Every 100 mm drop of groundwater level caused an increase of 5.1 and 3.7 Mg CO2 ha−1 year−1 for plantation and cropping land use, respectively. Where groundwater is deep (≥0.5 m), heterotrophic respiration constituted 84% of the total emissions. N2O emissions were significantly larger at deeper groundwater levels, where every drop in 100 mm of groundwater level resulted in an exponential emission increase (exp(0.7) kg N ha−1 year−1). Deeper groundwater levels induced high N2O emissions, which constitute about 15% of total GHG emissions. CH4 emissions were large where groundwater is shallow; however, they were substantially smaller than other GHG emissions. When compared to temperate and boreal peatland soils, tropical peatlands had, on average, double the CO2 emissions. Surprisingly, the CO2 emission rates in tropical peatlands were in the same magnitude as tropical mineral soils. This comprehensive analysis provides a great understanding of the GHG dynamics within tropical peat soils that can be used as a guide for policymakers to create suitable programmes to manage the sustainability of peatlands effectively. [ABSTRACT FROM AUTHOR]

The contribution of aquaculture to the total greenhouse gas (GHG) emission from agriculture is small. However, it is a major concern as aquaculture is one of the fastest growing agricultural activities. Life cycle analysis (LCA) indicates that formulated feed is the major contributor to GHG emission from aquaculture. Depending on the boundaries set for the LCA, the contribution from feed to GHG emission varies between 24 and 93%. Therefore, insight in the mechanisms of GHG emission is important. Carbon dioxide (CO2) is the major contributor to global warming, but other gases, of which nitrous oxide (N2O) and methane (CH4) are the most important gases, are responsible for close to 30% of global warming. All water bodies release GHG, and the difference in emission between a natural water body and an aquaculture pond should be considered. Generating more in-depth insight in GHG emissions from aquaculture production systems in function of farm system design and operation is needed to develop strategies to reduce emissions from aquaculture farms. Ecological intensification by growing fish/shrimp within the carrying capacity of the pond, or using renewable energy such as solar power for farm operation, and using more efficient equipment, can help to reduce GHG emissions. The nutritious pond concept is providing nutrient inputs to ponds, aiming for a metabolic waste/faeces composition resulting from feeding that is easily degradable by microbiota and hence stimulates the natural food web of the pond. A dual-purpose feed is formulated that feed the fish directly and indirectly, as feed and natural food, respectively. The concept aims to reach the maximum production potential within the carrying capacity of the pond and might even be able to increase the carrying capacity through the efficient biogeochemical cycling of nutrients. The fact that in semi-intensive tilapia ponds fed nutritious pond feed, the protein contained in harvested fish was more than 70% of the protein fed, shows the nutrient utilization efficiency is high. How nutritious pond farming will influence GHG emissions from ponds needs further investigation. [ABSTRACT FROM AUTHOR]

• CH 4 and CO 2 fluxes from two wetlands in northeast China are presented. • Most variations of CH 4 were distributed at time scales of several days to some months. • Soil temperature and thaw depth imposed alternated influences on CH 4 at the peatland. • Soil temperature and plant productivity influenced CH 4 emissions at the marsh. • Both wetlands were carbon sinks while the marsh had a net positive radiative forcing. Quantifying net CO 2 exchange (NEE) and CH 4 emissions of northern wetlands and their responses to biophysical controls are central to understanding the role of wetlands in global climate change. This study presents two growing seasons of observations of CO 2 and CH 4 fluxes by eddy covariance technique from a permafrost peatland and an inundated marsh in northeast China. Wavelet analysis was used to explore the temporal multi-scale variations of NEE and CH 4 fluxes and their biophysical controls. NEE showed prominent variations at the diel and the seasonal scales. However, most CH 4 variance was distributed at time scales longer than one day. At the permafrost peatland wavelet analysis revealed strong spectral coherency and alternating coherence between soil temperature and CH 4 fluxes during the spring and summer seasons and between thaw depth and CH 4 fluxes in the late growing season, with the suggestion of an as yet unknown coherence at longer timescales than could be resolved with just growing season records. At the marsh, soil temperature and CH 4 flux showed strong spectral coherency throughout the growing seasons and gross ecosystem production (GEP) additionally imposed its influence on CH 4 mainly during the most active part of the growing season. The growing season average CH 4 emission from the peatland (0.7 g C CH 4 m−2) was quite small and was negligible compared to its growing season NEE (−74.2 g C CO 2). In contrast, the growing season CH 4 emission from the marsh (average 31.1 g C CH 4 m−2) was considerably higher and accounted for about 16.2 % of its NEE (−191.7 g C CO 2 m−2). Although the two wetlands were net carbon sinks during the growing seasons and the permafrost peatland had a negative radiative forcing (i.e., cooling effect), the high CH 4 emissions from the marsh resulted in a net positive radiative forcing (i.e., warming effect). To understand the function of northern wetlands in the global carbon cycle, continuous field observations of these greenhouse gases are vital. [ABSTRACT FROM AUTHOR]

The main objective of this study was to compare the effect of supplementing beef cattle with Desmanthus virgatus cv. JCU2, D. bicornutus cv. JCU4, D. leptophyllus cv. JCU7 and lucerne on in vivo methane (CH4) emissions measured by open-circuit respiration chambers (OC) or the GreenFeed emission monitoring (GEM) system. Experiment 1 employed OC and utilized sixteen yearling Brangus steers fed a basal diet of Rhodes grass (Chloris gayana) hay in four treatments—the three Desmanthus cultivars and lucerne (Medicago sativa) at 30% dry matter intake (DMI). Polyethylene glycol (PEG) was added to the diets to neutralize tannin binding and explore the effect on CH4 emissions. Experiment 2 employed GEM and utilized forty-eight animals allocated to four treatments including a basal diet of Rhodes grass hay plus the three Desmanthus cultivars in equal proportions at 0%, 15%, 30% and 45% DMI. Lucerne was added to equilibrate crude protein content in all treatments. Experiment 1 showed no difference in CH4 emissions between the Desmanthus cultivars, between Desmanthus and lucerne or between Desmanthus and the basal diet. Experiment 2 showed an increase in CH4 emissions in the three levels containing Desmanthus. It is concluded that on high-quality diets, Desmanthus does not reduce CH4 emissions.

Abstract Rice (Oryza sativa L.) paddies contribute approximately 7–17% to total global methane (CH 4) emissions and are considered an important source of human-induced climate change. However, the interactive effects of rice roots and soil microbes on CH 4 emissions in paddy fields are not clearly understood. We conducted two field experiments over three years. Soil CH 4 fluxes and cumulative CH 4 emissions, rice root traits, and microbial communities and activities in soil were measured using three mid-season japonica rice cultivars (Wuyujing 3, Zhendao 88, and Huaidao 5) that have the same growth durations and similar aboveground traits before heading. The CH 4 emissions during the mid-growing period (from panicle initiation to heading) contributed 39.0–49.7% of the total emissions during the entire growing season and differed significantly among the rice cultivars. The root morphological and physiological traits (i.e. root dry weight, root length, root oxidation activity, and root radial oxygen loss) were negatively correlated with CH 4 fluxes. Compared to the zero-N control, application rates of N fertilizer at 54 and 108 kg ha−1 increased root biomass of cultivar Zhendao 88 by 10.1% and 17.3%, respectively, leading to corresponding decreases in CH 4 emissions by 12.7% and 22.9%. The root exudates (malic acid, succinic acid, and citric acid) promoted the abundance and activity of methanotrophs, which was the primary factors underlying the low CH 4 emissions in the paddy fields. Our findings suggested that stronger root systems, higher oxygen delivered by roots available for methanotrophs and suitable root exudates interacted in the rhizosphere, established a favourable habitat for microbial populations, and reduced CH 4 emissions in paddy fields. Highlights • CH 4 emissions during the mid-growing period contribute mainly to the differences among rice cultivars. • Root traits, rather than aboveground traits, regulate CH 4 emissions. • Malic, succinic and citric acids promote CH 4 oxidation and reduce CH 4 emissions. [ABSTRACT FROM AUTHOR]

Researchers believe that greenhouse gas emissions (GHG) from livestock are an emerging problem. Beef cattle is one of the most emission-intensive sectors, which is responsible for 54% of total GHGs from livestock. This study has two purposes. First, we quantify the environmental loading of U.S. beef sector by calculating emission levels over the period 1970-2014. Following Intergovernmental Panel on Climate Change (IPCC) guideline, we identify three sources of emissions, including enteric fermentation, manure management, and manure left on pastures. Second, we provide an understanding of consumption-environmental connection related to the beef industry. We used Tire 1 method calculations in this study. This method will provide the basic information for establishing policies to mitigate climate change. We encourage to use Tire 2 method in future studies. It is also recommended to see the impact of changing geographical locations of cattle farm to the regions that have lower emission factors in future studies. It t is concluded that providing information to the public regarding livestock and climate change relationship would be beneficial. Media attention is needed to convey this message to the public that eating more meat is environmentally detrimental, and we need to change our diet to confine GHG emissions. This knowledge might help develop schemes to avoid the catastrophic climate change consequences in the future. [ABSTRACT FROM AUTHOR]

As an important source of atmospheric methane, methane emissions from coastal wetlands are affected by many factors. However, the methane emission process and interrelated coupling mechanisms in coastal wetland soils of a variety of environments remain unclear owing to complex interactions between intensified anthropogenic activities and climate change in recent years. In this study, we investigated methane cycling processes and the response mechanisms of environmental and microbial factors in soils at different depths under four typical coastal wetland vegetation types of the Yellow River Delta, China, using laboratory culture and molecular biology techniques. Our results show that methane generation pathways differed among the different soil layers, and that the methane emission process has a special response to soil N compounds (NO 3 −, NH 4 +). We found that nitrogen can indirectly affect methane emission by impacting key physicochemical properties (pH, oxidation reduction potential, etc.) and some functional communities (mcrA , ANME-2d, sulfate-reducing bacteria (SRB), narG , nosZ II). Methane production processes in shallow soils compete closely with sulfate reduction processes, while methane emissions facilitated in deeper soils due to denitrification processes. We believe that our results provide a reference for future research and wetland management practices that seek to mitigate the global greenhouse effect and climate change. [Display omitted] • Soil nitrogen has an important driving role in wetland methane emissions. • Sulfur and nitrogen cycles are differently coupled to methane emission processes in shallow versus deep soils. • Coastal wetland vegetation mainly affects soil methane emission through soil water content and soil salinity. • Vegetation increases methane production pathways and methane emissions. [ABSTRACT FROM AUTHOR]