Tg CO2e Research Articles

Soil greenhouse gas fluxes partially reduce the net gains in carbon sequestration in mangroves of the Brazilian Amazon

There is interest in assessing the potential climate mitigation benefit of coastal wetlands based on the balance between their greenhouse gas (GHG) emissions and carbon sequestration. Here we investigated soil GHG fluxes (CO2 and CH4) on mangroves of the Brazilian Amazon coast, and across common land use impacts including shrimp farms and a pasture. We found greater methane fluxes near the Amazon River mouth (1439 to 3312 μg C m−2 h−1), which on average are equivalent to 37% of mangrove C sequestration in the region. Soil CO2 fluxes were predominant in mangrove forests to the East of the Amazon Delta. Land use change shifted mangroves from C sinks (mean sequestration of 12.2 ± 1.4 Mg CO2e ha−1 yr-1) to net GHG sources (mean loss of 8.0 ± 3.3 Mg CO2e ha−1 yr−1). Our data suggests that mangrove forests in the Amazon can aid decreasing the net annual emissions in the Brazilian forest sector in 9.7 ± 0.8 Tg CO2e yr−1 through forest conservation and avoided deforestation.

The potential climate benefits of seaweed farming in temperate waters

Seaweed farming is widely promoted as an approach to mitigating climate change despite limited data on carbon removal pathways and uncertainty around benefits and risks at operational scales. We explored the feasibility of climate change mitigation from seaweed farming by constructing five scenarios spanning a range of industry development in coastal British Columbia, Canada, a temperate region identified as highly suitable for seaweed farming. Depending on growth rates and the fate of farmed seaweed, our scenarios sequestered or avoided between 0.20 and 8.2 Tg CO2e year−1, equivalent to 0.3% and 13% of annual greenhouse gas emissions in BC, respectively. Realisation of climate benefits required seaweed-based products to replace existing, more emissions-intensive products, as marine sequestration was relatively inefficient. Such products were also key to reducing the monetary cost of climate benefits, with product values exceeding production costs in only one of the scenarios we examined. However, model estimates have large uncertainties dominated by seaweed production and emissions avoided, making these key priorities for future research. Our results show that seaweed farming could make an economically feasible contribute to Canada’s climate goals if markets for value-added seaweed based products are developed. Moreover, our model demonstrates the possibility for farmers, regulators, and researchers to accurately quantify the climate benefits of seaweed farming in their regional contexts.

Biochar technology cannot offset land carbon emissions in Guangdong province, China

As a highly developed region, Guangdong province has substantial industrial emissions. Its subtropical monsoon climate, characterized by abundant hydrothermal conditions, contributes to a substantial biomass potential. The adoption of potential biomass-based carbon dioxide removal (CDR) technologies, such as biochar, presents an opportunity to mitigate emissions and work towards carbon neutrality in the future. However, the current state of the land carbon balance and the CDR potential of biochar in Guangdong province remains unclear. We first calculated the land carbon balance based on inventory data. Then we estimated the CDR potential of biochar derived from agricultural residues, forestry residues, and bioenergy crops cultivated on marginal lands in Guangdong province using life cycle analysis (LCA). Results show that Guangdong province has not yet achieved carbon neutrality, with a net emission (carbon emissions remaining after offsetting by carbon sinks) of 925.63 Tg CO2e (CO2 equivalent, 1Tg = 106 t) in 2021. Emissions from energy consumption account for the highest proportion, contributing 83.8% of total emissions. In the highest biomass utilization scenario, the maximum CDR potential of biochar derived from all biomass types reaches 84.30 Tg CO2e yr-1, which could offset 9.11% of net carbon emissions in Guangdong province. Our findings provide crucial guidance for setting emission reduction targets and implementing effective mitigation strategies in Guangdong province under temperature warming.Graphical

The Realistic Potential of Soil Carbon Sequestration in U.S. Croplands for Climate Mitigation

AbstractExisting estimates of the climate mitigation potential from cropland carbon sequestration (C‐sequestration) are limited because they tend to assume constant rates of soil organic carbon change over all available cropland area, use relatively coarse land delineations, and often fail to adequately consider the agronomic and socioeconomic dimensions of agricultural land use. This results in an inflated estimate of the C‐sequestration potential. We address this gap by defining a more appropriate land base for cover cropping in the United States for C‐sequestration purposes: stable croplands in annual production systems that can integrate cover cropping without irrigation. Our baseline estimate of this suitable stable cropland area is 32% of current U.S. cropland extent. Even an alternative, less restrictive definition of stability results in a large reduction in area (44% of current U.S. croplands). Focusing cover crop implementation to this constrained land base would increase durability of associated C‐sequestration and limit soil carbon loss from land conversion to qualify for carbon‐specific incentives. Applying spatially‐variable C‐sequestration rates from the literature to our baseline area yields a technical potential of 19.4 Tg CO2e yr−1 annually, about one‐fifth of previous estimates. We also find the cost of realizing about half (10 Tg CO2e yr−1) of this potential could exceed 100 USD Mg CO2e−1, an order of magnitude higher than previously thought. While our economic analyses suggest that financial incentives are necessary for large‐scale adoption of cover cropping in the U.S., they also imply any C‐sequestration realized under such incentives is likely to be additional.

The inclusion of Amazon mangroves in Brazil’s REDD+ program

The Legal Amazon of Brazil holds vast mangrove forests, but a lack of awareness of their value has prevented their inclusion into results-based payments established by the United Nations Framework Convention on Climate Change. Based on an inventory from over 190 forest plots in Amazon mangroves, we estimate total ecosystem carbon stocks of 468 ± 67 Megagrams (Mg) ha−1; which are significantly higher than Brazilian upland biomes currently included into national carbon offset financing. Conversion of mangroves results in potential emissions of 1228 Mg CO2e ha−1, which are 3-fold higher than land use emissions from conversion of the Amazon rainforest. Our work provides the foundation for the inclusion of mangroves in Brazil’s intended Nationally Determined Contribution, and here we show that halting mangrove deforestation in the Legal Amazon would generate avoided emissions of 0.9 ± 0.3 Teragrams (Tg) CO2e yr−1; which is equivalent to the annual carbon accumulation in 82,400 ha of secondary forests.

Silvopasture offers climate change mitigation and profit potential for farmers in the eastern United States

Silvopasture—integrating trees, forage, and grazing livestock on the same piece of land—is increasingly popular, given its potential to store carbon (C) and improve farmers’ livelihoods. We examined the C and economic implications of adding different silvopastoral systems to existing pastures in historically forested areas of the eastern United States (U.S.). We assessed nine distinct systems, varying by species and product (timber, nuts, and fodder for livestock), for two market scenarios: one based on current demand and one that assumes increased demand for products from silvopasture systems. For each system, we assessed C storage (biomass) and economics (internal rates of return (IRR) with and without C payments). We find that silvopasture in the eastern U.S. could expand by 5.6–25.3 million hectares under base case and full adoption scenarios (equaling a 6% increase in the global footprint of silvopasture), and could capture up to 4.9 or 25.6 Tg CO2e yr.−1, respectively. Expansion of silvopasture in these scenarios would come largely from demand for fodder as a supplemental feed, as well as specialty timber products. Per ha mitigation potential varied widely (0.5–6.5 tCO2e ha−1 yr.−1), due to species differences in C accumulation rates. Economics differed too, with some systems offering short break-even timelines (e.g., 7–9 years for fodder systems), and others costing more up front but having greater long-term returns (e.g., Chestnut). Furthermore, while some systems are profitable without any price on C (e.g., fodder-based silvopasture offers 6–14% 10-year IRRs without a price on C), higher payments for C would likely be necessary to unleash broad investment in timber and nut-based silvopasture. Our analysis included planting, maintenance, and harvest costs and tree product revenue. Future work is needed to fully incorporate additional considerations, like loss of grazing use during establishment, shade-induced effects on forage production, and livestock productivity. Furthermore, specific economic, ecological, site- and operation-level considerations are critical to evaluate the appropriateness of silvopasture systems for a given setting. This analysis suggests that across the eastern U.S., silvopasture could offer both climate change mitigation and enhanced profitability for farmers, with notable differences in the system-specific magnitude of opportunity.

Characteristics and reduction assessment of GHG emissions from crop residue open burning in China under the targets of carbon peak and carbon neutrality

Driven by the goal of carbon peak and carbon neutrality, greenhouse gas (GHG) emissions from the crop residue open burning (CROB) in China cannot be ignored. In this study, we have established a high-resolution (0.05° × 0.05°) GHG emissions inventory (including CO2, CH4, and N2O) of CROB from 2012 to 2021 in China based on the VIIRS data and official statistics. To improve the results accuracy, we compared the two commonly used bases for grid allocation, fire counts (FC) and fire radiative power (FRP), in the construction of high-resolution inventory. In 2012, GHG emissions are overestimated by 599 t CO2e per grid on average in 24,577 grids, and underestimated by 1096 t CO2e per grid on average in 13,546 grids based on FC compared to FRP. Then, we characterized the spatial and temporal distribution of GHG emissions from CROB by using the FRP-based method. From 2012 to 2021, total GHG emissions from CROB in China have decreased by 31.2 %, of which the East and South-Central China contributed 22.51 and 9.12 Tg CO2e of GHG reductions, while the Northeast China contributed 10.73 Tg CO2e of GHG growth, respectively. In addition, GHG emissions from CROB on the time scale are mainly concentrated in April, June, and October, with variations between years and regions influenced by the policy, climate, and farmers' perceptions. Finally, we assessed the GHG emission reductions from CROB under different scenarios in the future. By 2060, GHG emissions would be significantly reduced by 57.3 %–77.9 % compared to 2021 under effective control measures. We believe the results will be of great significance for GHG policy formulation and emission reduction potential assessment.

Global hotspots of salt marsh change and carbon emissions

Salt marshes provide ecosystem services such as carbon sequestration1, coastal protection2, sea-level-rise (SLR) adaptation3 and recreation4. SLR5, storm events6, drainage7 and mangrove encroachment8 are known drivers of salt marsh loss. However, the global magnitude and location of changes in salt marsh extent remains uncertain. Here we conduct a global and systematic change analysis of Landsat satellite imagery from the years 2000–2019 to quantify the loss, gain and recovery of salt marsh ecosystems and then estimate the impact of these changes on blue carbon stocks. We show a net salt marsh loss globally, equivalent to an area double the size of Singapore (719 km2), with a loss rate of 0.28% year−1 from 2000 to 2019. Net global losses resulted in 16.3 (0.4–33.2, 90% confidence interval) Tg CO2e year−1 emissions from 2000 to 2019 and a 0.045 (−0.14–0.115) Tg CO2e year−1 reduction of carbon burial. Russia and the USA accounted for 64% of salt marsh losses, driven by hurricanes and coastal erosion. Our findings highlight the vulnerability of salt marsh systems to climatic changes such as SLR and intensification of storms and cyclones.

Storing More Carbon by Improving Forest Management in the Acadian Forest of New England, USA

The capacity of forests to store carbon, combined with time-tested approaches to managing forests, make forests a useful tool for atmospheric carbon mitigation. The primary goals of this study are to determine the amount of unrealized mitigation available from Improved Forest Management (IFM) in the Acadian Forest of New England in the northeastern U.S., and to demonstrate how this mitigation can feasibly be attained. This study used the Forest Vegetation Simulator (FVS) to model the impacts of IFM practices articulated by the New England Forestry Foundation on carbon storage in the Acadian Forest. Our results, together with empirical data from well-managed forests, show that if the modeled improved management is employed on privately owned timberland across the Acadian Forest of New England, carbon storage could be increased by 488 Tg CO2e. Our financial modeling shows that IFM could be funded in this region by combining income from carbon markets with the philanthropic funding of conservation easements, timber revenues, and capital investments from private investors who prioritize social and economic goals alongside financial returns. This study adds to the body of evidence from around the world that the potential for managed forests to contribute to climate change mitigation has not been fully realized.

Four pathways towards carbon neutrality by controlling net greenhouse gas emissions in Chinese cropland

Decreasing greenhouse gas (GHG) emissions and enhancing soil carbon (C) sequestration in cropland are necessary to achieve carbon neutrality at national scale. However, feasible pathways to mitigate net GHG emissions in Chinese cropland while ensuring food security remain poorly defined. Here, we establish a comprehensive assessment framework and propose four mitigation pathways. In the baseline scenario, GHG emissions are projected to be 439.9–443.5 Tg CO2e after 2030. Through simultaneously implementing the four pathways of recycling organic waste, improving nitrogen (N) use efficiency, optimizing water management and strictly controlling N input/surplus, cropland GHG emissions are projected to decline from 433.5 Tg CO2e in 2020 to 389.7 Tg CO2e (-11.4%) in 2030 and 338.3 Tg CO2e (-23.7%) in 2060. The accumulated quantity of soil C sequestered would increase by 33.9% from 2021 to 2060. Considering both GHG emission reduction and increment of soil C stocks, the net GHG reduction rate would be 37.4% and 41.2% in 2030 and 2060, respectively. These pathways help transition crop production to a low-carbon and high-efficiency pattern while maintaining or increasing crop yield. As the first attempt, our study provides a scientific reference for approaches to accelerate GHG mitigation and soil C sequestration in Chinese cropland. This type of integrated assessment has potential to support policy-making in developing countries aimed at finding an equitable balance between crop production and environmental benefits.

Evaluation of Vietnam air emissions and the impacts of revised power development plan (PDP7 rev) on spatial changes in the thermal power sector

Emission reduction in the thermal power sector is highly prioritized by the Vietnam government to combat climate change and air pollution. This study developed an updated 2019 Vietnam emission inventory (base-year) using a bottom-up approach and the future emission projections up to 2030 to evaluate the potential emission changes due to regulatory measures from the Power Development Plan 7 Revision (PDP 7 rev). Results show that emission contributions from coal-fired thermal power plants (TPP) to total emissions (i.e., SO2, NOx, PM10, and PM2.5) ranged from 67.8% to 97.0% in 2019, and the annual emissions of global warming potential are expected to increase more than double (i.e., 335.8 Tg CO2e) due to the increased coal-fired TPPs between 2019 and 2030. A gradual reduction in NOx is anticipated from 2025, resulting from the scheduled installation of selective catalytic reduction systems, which would trigger a shift of NOx hotspots from Northern Midland to North Central in 2030. Overall, the study illustrated that even though NOx emissions are expected to decrease in 2030 due to effective pollution controls, carbon emissions would still escalate due to the intensive use of coal-fired TPPs. It poses a challenge to Vietnam's future carbon neutrality process.

Livestock Use on Public Lands in the Western USA Exacerbates Climate Change: Implications for Climate Change Mitigation and Adaptation

Public lands of the USA can play an important role in addressing the climate crisis. About 85% of public lands in the western USA are grazed by domestic livestock, and they influence climate change in three profound ways: (1) they are significant sources of greenhouse gases through enteric fermentation and manure deposition; (2) they defoliate native plants, trample vegetation and soils, and accelerate the spread of exotic species resulting in a shift in landscape function from carbon sinks to sources of greenhouse gases; and (3) they exacerbate the effects of climate change on ecosystems by creating warmer and drier conditions. On public lands one cow-calf pair grazing for one month (an “animal unit month” or “AUM”) produces 875 kg CO2e through enteric fermentation and manure deposition with a social carbon cost of nearly $36 per AUM. Over 14 million AUMs of cattle graze public lands of the western USA each year resulting in greenhouse gas emissions of 12.4 Tg CO2e year−1. The social costs of carbon are > $500 million year−1 or approximately 26 times greater than annual grazing fees collected by managing federal agencies. These emissions and social costs do not include the likely greater ecosystems costs from grazing impacts and associated livestock management activities that reduce biodiversity, carbon stocks and rates of carbon sequestration. Cessation of grazing would decrease greenhouse gas emissions, improve soil and water resources, and would enhance/sustain native species biodiversity thus representing an important and cost-effective adaptive approach to climate change.

Life-cycle greenhouse gas emissions and the associated carbon-peak strategies for PS, PVC, and ABS plastics in China

The plastic industry is a high carbon emission industry in China. Previous studies mainly focused on the flows and stocks of polystyrene (PS), polyvinyl chloride (PVC), and acrylonitrile-butadiene-styrene (ABS) plastics. However, there is limited detailed information on the GHG emissions of PS, PVC, and ABS in China and the key paths of carbon peak in 2030. Therefore, we established the GHG accounting model of PS, PVC, and ABS based on dynamic material flow analysis and life cycle assessment, and further analyzed the carbon peak path and strategy in 2030. The results show that the main source of GHG is the production and manufacturing stages. Notably, the key paths of GHG emissions are the manufacturing process of PS STP&C and foam plastics, PVC film and STP&C, and ABS STP&C. Moreover, the cumulative GHG emissions of these plastics reached 230.34, 677.43, 143.12 Tg CO2e in 2007-2017, respectively. From 2007 to 2017, the trends of GHG emissions from the PS, PVC, and ABS had their characteristics. PVC had the largest GHG emissions. Different from PVC and ABS, GHG emissions from PS showed a trend of slow rise and then slow decline in this period. According to the current trend, the life-cycle GHG emissions of PS, PVC, and ABS would not reach the carbon peak in 2030. Under some mitigation strategies, the carbon peak would be achieved before 2030. This study clarifies the main sources of life-cycle GHG emissions of these plastics, and reveals the path and strategy of carbon peak in 2030.

Blue carbon as a natural climate solution

Blue carbon ecosystems (BCEs), including mangrove forests, seagrass meadows and tidal marshes, store carbon and provide co-benefits such as coastal protection and fisheries enhancement. Blue carbon sequestration has therefore been suggested as a natural climate solution. In this Review, we examine the potential for BCEs to act as carbon sinks and the opportunities to protect or restore ecosystems for this function. Globally, BCEs are calculated to store >30,000 Tg C across ~185 million ha, with their conservation potentially avoiding emissions of 304 (141–466) Tg carbon dioxide equivalent (CO2e) per year. Potential BCE restoration has been estimated in the range of 0.2–3.2 million ha for tidal marshes, 8.3–25.4 million ha for seagrasses and 9–13 million ha for mangroves, which could draw down an additional 841 (621–1,064) Tg CO2e per year by 2030, collectively amounting to ~3% of global emissions (based on 2019 and 2020 global annual fossil fuel emissions). Mangrove protection and/or restoration could provide the greatest carbon-related benefits, but better understanding of other BCEs is needed. BCE destruction is unlikely to stop fully, and not all losses can be restored. However, engineering and planning for coastal protection offer opportunities for protection and restoration, especially through valuing co-benefits. BCE prioritization is potentially a cost-effective and scalable natural climate solution, but there are still barriers to overcome before blue carbon project adoption will become widespread.

Long-term trajectories of the C footprint of N fertilization in Mediterranean agriculture (Spain, 1860–2018)

Synthetic nitrogen (N) fertilization has helped boost agricultural yields, but it is also responsible for direct and indirect greenhouse gas (GHG) emissions. Fertilizer-related emissions are also promoted by irrigation and manure application, which has increased with livestock industrialization. Spanish agriculture provides a paradigmatic example of high industrialization under two different climates (temperate and Mediterranean) and two contrasting water management regimes (rainfed and irrigated). In this study, we estimated the historical evolution of the C footprint of N fertilization (including all the life cycle GHG emissions related to N fertilization) in Spanish agriculture from 1860 to 2018 at the province level (50 provinces) for 122 crops, using climate-specific N2O emission factors (EFs) adjusted to the type of water management and the N source (synthetic fertilizer, animal manure, crop residues and soil N mineralization) and considering changes in the industrial efficiency of N fertilizer production. Overall, N-related GHG emissions increased ∼12-fold, up to 10–14 Tg CO2e yr−1 in the 2010s, with much higher growth in Mediterranean than in temperate areas. Direct N2O EFs of N fertilizers doubled due to the expansion of irrigation, synthetic fertilizers and liquid manure, associated with livestock industrialization. Synthetic N production dominated the emissions balance (55%–60% of GHGe in the 21st century). Large energy efficiency gains of industrial fertilizer production were largely offset by the changes in the fertilizer mix. Downstream N2O emissions associated with NH3 volatilization and NO3 − leaching increased tenfold. The yield-scaled carbon footprint of N use in Spanish agriculture increased fourfold, from 4 and 5 Mg CO2e Mg N−1 to 16–18 Mg CO2e Mg N−1. Therefore, the results reported herein indicate that increased productivity could not offset the growth in manufacture and soil emissions related to N use, suggesting that mitigation efforts should not only aim to increase N use efficiency but also consider water management, fertilizer type and fertilizer manufacture as key drivers of emissions.

Spatial patterns of net greenhouse gas balance and intensity in Chinese orchard system.

Fruit production has been expanding due to the pursuit of healthier lifestyles in China. Determining the greenhouse gas (GHG) emissions status of the orchard system could contribute to adopting appropriate measures to alleviate climate change pressure from the growing fruit production. In this study, the net GHG balance and GHG intensity (GHGI) in the Chinese fruit production were estimated at the regional level using a meta-analysis based on databases compiled from relevant publications during 2000-2019, including soil nitrous oxide (N2O) and methane (CH4) emissions or uptake, upstream carbon dioxide (CO2) emissions related to farm practices, and the change of soil organic carbon (SOC) storage from the life cycle perspective. Results showed that the net GHG balance and GHGI varied among six regions, with ranges of 6.4±0.3 to 10.0±0.6Mg CO2e ha-1yr-1, and 2.2±0.2 to 3.0±0.2kg CO2e kg-1, respectively. Synthetic nitrogen (N) fertilization was the largest source of overall GHG emissions from fruit production throughout China, accounting for 46% and ranging from 43% to 55% in the six fruit production regions. Fertilizer-induced N2O emissions were responsible for 22-31% of the total GHG emissions, and the N2O-N emission factor was identified as 0.7%. Also, power use for irrigation contributed a non-negligible 17% to the emissions on a national level, yet with large regional variations. In addition, fruit production in North, Northeast, Central, and East, and South China have relatively lower GHGIs than in Northwest and Southwest China. The estimated total GHG emissions from the Chinese fruit production were 102 Tg CO2e, with the contribution of SOC change to a decrease by 11% for the year 2018. Our results highlight an urgency to lower fruit production-related carbon emissions by extending optimized N fertilization and irrigation modes in China's orchard system.

Consequences of terminating mangrove’s protection in Brazil

The Brazilian government agenda for downgrading and degazettement of protected ecosystems has seen an unprecedented move with the revocation of the mangrove’s protection act in the country. As the second largest country in mangrove extent, with over 11,000 km2 of forests that have been conserved for decades, mangroves may now be open for unsustainable economic development. Shrimp aquaculture and urban development are likely the highest threats to mangrove forests in Brazil. When built over mangrove land, shrimp ponds release greenhouse gases at a rate up to 10-fold larger than cattle pasture conversion on dryland forests. In a scenario of low rates of mangrove loss of 0.1% per year (2-fold current rates), emissions from land use would be close to 1.6 Tg CO2e per year, which is equivalent to 0.01% of emissions from deforestation in the Amazon over an area 1500 times smaller. Urban development and removal of mangroves to human infrastructure also have strong negative effects on pollutant retention, which could further decrease water quality and increase coastal vulnerability near urban centers. The loss of mangroves have also expected negative effects on food provision, which allied to other key ecosystem services provided by mangroves, will be key to a sustainable ocean under a changing climate during the next century.

Estimate of Hydrofluorocarbon Emissions for 2012–16 in the Yangtze River Delta, China

Hydrofluorocarbons (HFCs) have been widely used in China as substitutes for ozone-depleting substances, the production and use of which are being phased out under the Montreal Protocol. China is a major consumer of HFCs around the world, with its HFC emissions in CO2-equivalent contributing to about 18% of the global emissions for the period 2012–16. Three methods are widely used to estimate the emissions of HFCs—namely, the bottom-up method, top-down method and tracer ratio method. In this study, the tracer ratio method was adopted to estimate HFC emissions in the Yangtze River Delta (YRD), using CO as a tracer. The YRD region might make a significant contribution to Chinese totals owing to its rapid economic growth. Weekly flask measurements for ten HFCs (HFC-23, HFC-32, HFC-125, HFC-134a, HFC-143a, HFC-152a, HFC-227ea, HFC-236fa, HFC-245fa and HFC-365mfc) were conducted at Lin’an Regional Background Station in the YRD over the period 2012–16, and the HFC emissions were 2.4±1.4 Gg yr−1 for HFC-23, 2.8±1.2 Gg yr−1 for HFC-32, 2.2±1.2 Gg yr−1 for HFC-125, 4.8±4.8 Gg yr−1 for HFC-134a, 0.9±0.6 Gg yr−1 for HFC-152a, 0.3±0.3 Gg yr−1 for HFC-227ea and 0.3±0.2 Gg yr−1 for HFC-245fa. The YRD total HFC emissions reached 53 Tg CO2-e yr−1, contributing 34% of the national total. The per capita HFC CO2-equivalent emissions rate was 240 Tg yr−1, while the values of per unit area emissions and per million GDP emissions reached 150 Mg km−2 yr−1 and 3500 kg yr−1 (million CNY GDP)−1, which were much higher than national or global levels.

Global warming impacts of nitrogen use in agriculture: an assessment for India since 1960

ABSTRACT Global warming impacts of N use in Indian agriculture since 1960 was estimated for 20- and 100-year time scales using equation-based empirical method. During 2014, total Warming in terms of global temperature change potential (GTP) for a 20-year time scale (GTP20) was assessed as 217.31 ± 17.74 Tg CO2e, and for a 100-year time scale (GTP100) was 217.78 ± 17.78 Tg CO2e. N2O contributed 90% and 99%of the GTP20 and GTP100, respectively. Total cooling impacts were 94.86 ± 7.75 and 50.36 ± 4.11 Tg CO2e on GTP20 and GTP100, respectively. Aerosols of NH3 and NOx, NOx-induced O3 and CH4 alteration, and N-induced C sequestration contributed 41, 6 and 51%, respectively, to GTP20, however, N-induced C sequestration contributed about 99% to GTP100. Net warming impacts were 122.45 ± 10.00 and 167.42 ± 13.67 Tg CO2e on GTP20 and GTP100, respectively. Net warming impacts were lowered by 10% and 1% compared to total warming, and 37% and 23% compared to warming caused by N2O alone, for GTP20 and GTP100, respectively. Usually, to estimate the global warming impacts of N use in agriculture, the warming effects of only N2O emission are considered. However, both warming and cooling impacts should be considered to capture the net impacts of N use in agriculture on climate change.

Blue carbon of Mexico, carbon stocks and fluxes: a systematic review.

Mexico has more than 750,000 ha of mangroves and more than 400,000 ha of seagrasses. However, approximately 200,000 ha of mangroves and an unknown area of seagrass have been lost due to coastal development associated with urban, industrial and tourist purposes. In 2018, the approved reforms to the General Law on Climate Change (LGCC) aligned the Mexican law with the international objectives established in the 2nd Article of the Paris Agreement. This action proves Mexico’s commitment to contributing to the global target of stabilizing the greenhouse gas emissions concentration in the planet. Thus, restoring and conserving mangrove and seagrass habitats could contribute to fulfilling this commitment. Therefore, as a first step in establishing a mitigation and adaptation plan against climate change with respect to conservation and restoration actions of these ecosystems, we evaluated Mexican blue carbon ecosystems through a systematic review of the carbon stock using the standardized method of Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). We used the data from 126 eligible studies for both ecosystems (n = 1220). The results indicated that information is missing at the regional level. However, the average above and below ground organic carbon stocks from mangroves in Mexico is 113.6 ± 5.5 (95% CI [99.3–118.4]) Mg Corg ha−1 and 385.1 ± 22 (95% CI [344.5–431.9]) Mg Corg ha−1, respectively. The variability in the Corg stocks for both blue carbon ecosystems in Mexico is related to variations in climate, hydrology and geomorphology observed along the country’s coasts in addition to the size and number of plots evaluated with respect to the spatial cover. The highest values for mangroves were related to humid climate conditions, although in the case of seagrasses, they were related to low levels of hydrodynamic stress. Based on the official extent of mangrove and seagrass area in Mexico, we estimate a total carbon stock of 237.7 Tg Corg from mangroves and 48.1 Tg Corg from seagrasses. However, mangroves and seagrasses are still being lost due to land use change despite Mexican laws meant to incorporate environmental compensation. Such losses are largely due to loopholes in the legal framework that dilute the laws’ effectiveness and thus ability to protect the ecosystem. The estimated emissions from land use change under a conservative approach in mangroves of Mexico were approximately 24 Tg CO2e in the last 20 years. Therefore, the incorporation of blue carbon into the carbon market as a viable source of supplemental finance for mangrove and seagrass protection is an attractive win-win opportunity.