Net Carbon Sink Research Articles

Research on the Impact of Rural Population Structure Changes on the Net Carbon Sink of Agricultural Production-Take Huan County in the Loess Hilly Region of China as an Example

People are the fundamental purpose and driving force of agricultural development. The changes in population structure can directly affect social and economic development of rural areas and the entire process of agricultural production. This paper takes Huan County in the Loess Hilly Region of China as the evaluation object, the townships as the evaluation unit, the change of rural population structure as the key point, and the agricultural production as the mediating factor, to study the mechanism of agricultural net carbon sinks. The results show: 1) From 2009 to 2018, the number of rural labor force in Huan County was seriously lost, the quality of the labor force was steadily improved, and the age of the labor force was increased. The number of agricultural employees dropped from 72.6 to 49.4%. The number of people with high school education or above increased from 9.7 to 15.1%. Those over working age who participated in the labor force rose from 5.2 to 8.3%. 2) The Loess Hilly Region in the northwest of Huan County was “grain-trending,” and the River Valley and Plain Area in the southeast was “grain-removing.” The input structure index both increased first and then decreased. and the Loess Hilly Region was more dependent on the fertilizer. 3) The rural population structure affects the agricultural net carbon sink by affecting the planting structure index and the input structure index. The rural population quantity and quality structure have a significant positive effect on the agricultural net carbon sink, while the population age structure has a significant negative effect on the agricultural net carbon sink. 4) From the mediating effect, the loss of population can cause fluctuations in the agricultural net carbon sink. The improvement of population quality will promote the growth of the agricultural net carbon sink, and the aging of the population will cause the decline of the agricultural net carbon sink. 5) The return of the labor force, the improvement of labor force quality, the improvement of production methods, technological innovation, and skill training are the main ways to increase agricultural net carbon sinks and reduce emissions. This paper can lay a solid foundation for realizing the overall emission reduction target of agricultural production in the Loess Hilly Region.

Effect of stockpiling time on donor-peat hydrophysical properties: Implications for peatland restoration

Northern peatlands are an important global climate regulator storing approximately one-third of the global carbon pool, however the degradation of these ecosystems from land-use change can switch peatlands to persistent and long-term sources of atmospheric carbon dioxide. Active restoration is often required to return degraded peatlands to a net carbon sink. The peat-block restoration technique, where intact peat blocks are extracted from a donor peatland and transferred to restore peatlands where the remnant peat is non-existent, contaminated, and/or undergoes seasonal flooding is increasingly being adopted as a peatland restoration technique given the carbon sequestration that can occur immediately post-restoration. However, donor peat blocks often need to be temporarily stockpiled during the restoration process due to logistical constraints. The dewatering of the peat blocks during this stockpiling period may alter hydrophysical peat properties that sustain critical peatland ecohydrological functionality and ultimately affect peatland restoration success. Yet, the hydrophysical evolution of stockpiled peat blocks remains unknown. Here, we examine how peat block stockpiling time (3, 7, 11, and 14 months and a reference site) impacts peat hydrophysical properties and sphagnum moss photosynthesis, both of which are critical for peatland restoration success. Stockpiling peat differentially impacted the hydrophysical properties between the shallower and deeper peats, where little to no impact from stockpiling was observed in the shallower peats, regardless of stockpiling time. Rather, as stockpiling time increased, there was a marked decrease in macroporosity (pores >75 μm) and mobile porosity (drainable porosity at approximately −100 hpa) at depths below 20 cm but the water conducting matrix porosity (defined as mobile porosity minus macroporosity) was not significantly different than the reference samples. However, stockpiling created inhospitable conditions for sphagnum mosses., as chlorophyll fluorescence ratio was below 0.3, indicating little to no photosynthesis of the stockpiled peat during summertime drought conditions. Taken together, we suggest limiting stockpiling time as much as possible would be advantageous for using the stockpiled peat blocks for the peat-block restoration technique or other restoration efforts, such as floating mat creation.

Renewable butadiene: A case for hybrid processing via bio- and chemo-catalysis

1,3-butadiene (butadiene) is a by-product produced during naphtha steam cracking, predominantly used in tyre manufacturing. Recently, steam crackers have converted to using more cost effective, lighter feedstocks such as shale gas, yielding less butadiene. The potential shortfall, coupled with concerns around increasing greenhouse gas emissions, provides a unique opportunity for renewable production. This study investigated the techno-economics and greenhouse gas emissions associated with renewable butadiene production routes within the context of a China located pulp mill. A hybrid bio-catalytic route, utilising black liquor, was compared against two chemo-catalytic routes using forestry residues and pulpwood. The hybrid bio-catalytic route uses a novel aerobic gas fermentation platform, employing heat integrated supercritical water gasification and aerobic gas fermentation to produce acetaldehyde, followed by chemo-catalytic upgrading (Acet-BD). The two chemo-catalytic routes catalytically upgrade biomass derived syngas; where one route (Eth-BD) passes through an ethanol intermediate, and the other (Syn-BD) utilises a series of commercialised catalytic technologies with propene as an intermediate. The hybrid bio/chemo-catalytic route, Acet-BD, was the only route profitable using the nominal techno-economic inputs, producing a Net Present Value of $2.8 million and Minimum Selling Price of $1367 tn−1. In contrast, the two chemo-catalytic routes produced Minimum Selling Prices of $1954 tn−1 (Eth-BD) and $2196 tn−1 (Syn-BD), demonstrating the competitiveness of this novel platform. Sensitivity analyses highlighted the equipment capital as the main contributor to increased Minimum Selling Price for all cases, and the Acet-BD route presented a 19% probability of achieving a positive net present value. Moreover, owed to the low process emissions and sequestration of biogenic carbon, all routes produced net negative emissions within a cradle-to-gate framework. As such, renewable butadiene production has potential as a net carbon sink for pulp mill residues conventionally destined for energy recovery.

Quantifying Carbon Cycle Extremes and Attributing Their Causes Under Climate and Land Use and Land Cover Change From 1850 to 2300

AbstractThe increasing atmospheric carbon dioxide (CO2) mole fraction affects global climate through radiative (trapping longwave radiation) and physiological effects (reduction of plant transpiration). We use the simulations of the Community Earth System Model (CESM1‐BGC) forced with Representative Concentration Pathway 8.5 to investigate climate‐vegetation feedbacks from 1850 to the year 2300. Human‐induced land use and land cover change (LULCC), through biogeochemical and biogeophysical processes, alter the climate and modify photosynthetic activity. The changing characteristics of extreme anomalies in photosynthesis, referred to as carbon cycle extremes, increase the uncertainty of terrestrial ecosystems to act as a net carbon sink. However, the role of LULCC in altering carbon cycle extremes under business‐as‐usual (continuously rising) CO2 emissions is unknown. Here we show that LULCC magnifies the intensity, frequency, and extent of carbon cycle extremes, resulting in a net reduction in expected photosynthetic activity in the future. We found that large temporally contiguous negative carbon cycle extremes are due to a persistent decrease in soil moisture, which is triggered by declines in precipitation. With LULCC and global warming, vegetation exhibits increased vulnerability to hot and dry environmental conditions, increasing the frequency of fire events and resulting in considerable losses in photosynthetic activity. While most regions show strengthening of negative carbon cycle extremes, a few locations show a weakening effect driven by declining vegetation cover or benign climate conditions for photosynthesis. Increasing hot, dry, and fire‐driven carbon cycle extremes are essential for improving carbon cycle modeling and estimation of ecosystem responses to LULCC and rising CO2 mole fractions. Moreover, large aberrations in vegetation productivity represent potential and growing threats to human lives, wildlife, and food security.

Comment on “Seaweed ecosystems may not mitigate CO2 emissions” by Gallagher et al. (2022)

Abstract The role of animal (and plant) respiration in assessing the true carbon sequestration potential of a system is vital to acknowledge, and addressed in Gallagher et al. (2022). However, within this article, there is confusion around the respiration of kelp once exported to open waters from kelp ecosystems but respired before sequestration. From their consideration of a closed kelp ecosystem (but with import of phytoplankton and export of kelp), respiration of phytoplankton transported into the system is correctly considered in their net respiration figures (but not the fixation of carbon dioxide by the phytoplankton outside the system, again correct for a closed system). However, the respiration of kelp exported from the closed system is also considered as part of the kelp community respiration. A closed system must remove this respiration of exported kelp from calculations. Alternatively, an open system must consider also the carbon fixation by phytoplankton. The outcome of redefining open and closed systems is that the systems examined in Gallagher et al. (2022) will be net sinks of carbon, although, as yet, the magnitude of this sink is poorly quantified.

The response of soil-atmosphere greenhouse gas exchange to changing plant litter inputs in terrestrial forest ecosystems

Various global change factors (e.g. elevated CO2 concentrations, nitrogen deposition, etc.) can alter the amount of litterfall in terrestrial forests, which could subsequently lead to changes in the physical, chemical, and biological properties of forest soils. Yet, there is hitherto a lack of consensus on the role of litter in governing the soil-atmosphere exchange of greenhouse gases (GHGs) in forest ecosystems, which can significantly affect the overall climatic cooling impacts of forests as a net carbon sink. In this study, we carried out a meta-analysis of over 250 field observations to determine the response of soil GHG fluxes to in situ litter manipulation in global forests. Our results showed that overall, litter addition enhanced soil CO2 emissions from terrestrial forests by 26%, while litter removal reduced soil CO2 emissions from these forests by 26%. The negative response of soil CO2 emissions to litter removal was stronger in the tropical forests (−33%) than in the subtropical (−27%) and temperate (−21%) forests, and was significantly correlated with mean annual temperature and precipitation. Moreover, litter removal was observed to enhance soil CH4 uptake in tropical (+24%) and temperate (+9%) forests, but not in subtropical forests. Litter removal reduced N2O emissions from forest soils by 20% on average, with this negative effect increasing with mean annual precipitation. The duration of litter removal experiment was negatively correlated with the response of soil CO2 emissions but had no influence on the response of soil CH4 and N2O fluxes. We found that plant litter supply could alter soil GHG fluxes in forests by modulating the microclimate as well as the labile and recalcitrant soil carbon pools. Our findings highlighted the importance of considering the effects of changing plant litter inputs on soil-atmosphere GHG fluxes in terrestrial forests and their spatio-temporal variability in biogeochemical models.

Technological advancement expands carbon storage in harvested wood products in Maine, USA

Harvested wood products (HWPs) in-use, disposed to landfill, and the charcoal created by biomass fuel burning substantially store carbon and potentially mitigate the greenhouse gas effect. To quantify the HWPs carbon storage, we developed a carbon accounting framework, which has the ability to incorporate the influence of technological advancement on HWPs carbon storage. Through applying this framework together with the wood harvesting data of Maine, USA during the period of 1901–2019, we concluded that the current HWPs carbon pool size is 52 Tg C, which is 11% of the carbon stored in the entire forestry sector and wood products of Maine, USA. Technological advancement potentially increases the HWPs carbon storage by as much as 44% to 75 Tg C. In addition, the average net annual carbon sink can be increased from 0.44 Tg C to 0.63 Tg C. Production of innovative wood products with long service lives plays the most important role in expanding the HWPs carbon pool; however, the higher processing efficiency and recycling rate are less important.

Field-based tree mortality constraint reduces estimates of model-projected forest carbon sinks

Considerable uncertainty and debate exist in projecting the future capacity of forests to sequester atmospheric CO2. Here we estimate spatially explicit patterns of biomass loss by tree mortality (LOSS) from largely unmanaged forest plots to constrain projected (2015–2099) net primary productivity (NPP), heterotrophic respiration (HR) and net carbon sink in six dynamic global vegetation models (DGVMs) across continents. This approach relies on a strong relationship among LOSS, NPP, and HR at continental or biome scales. The DGVMs overestimated historical LOSS, particularly in tropical regions and eastern North America by as much as 5 Mg ha−1 y−1. The modeled spread of DGVM-projected NPP and HR uncertainties was substantially reduced in tropical regions after incorporating the field-based mortality constraint. The observation-constrained models show a decrease in the tropical forest carbon sink by the end of the century, particularly across South America (from 2 to 1.4 PgC y−1), and an increase in the sink in North America (from 0.8 to 1.1 PgC y−1). These results highlight the feasibility of using forest demographic data to empirically constrain forest carbon sink projections and the potential overestimation of projected tropical forest carbon sinks.

Controls on carbon dioxide and methane fluxes from a low-center polygonal peatland in the Mackenzie River Delta, Northwest Territories

Growing season surface–atmosphere exchange of carbon dioxide and methane were quantified at Fish Island, a wetland site in the lower northeast Mackenzie River Delta, Northwest Territories, Canada. The terrain consists of low-center polygonal tundra and is subject to infrequent flooding in high water years. Carbon dioxide and methane fluxes were continuously measured using eddy covariance and the relevance of different environmental controls were identified using neural networks. Net daily carbon dioxide uptake peaked in mid-July before gradually decreasing and transitioning to net daily emissions by September. Variations in light level and temperature were the main controls over diurnal net carbon dioxide uptake, whereas thaw depth and phenology were the main seasonal controls. Methane emissions measured at Fish Island were higher than comparable studies on river delta sites in the Arctic and were influenced by the interaction of a large number of factors including thaw and water table depth, soil temperatures, and net radiation. Spikes in methane emissions were associated with strong winds and turbulence. The Fish Island tundra was a net sink for carbon during the growing season and methane emissions only slightly reduced the overall sink strength.

Permafrost Active Layer Microbes From Ny Ålesund, Svalbard (79°N) Show Autotrophic and Heterotrophic Metabolisms With Diverse Carbon-Degrading Enzymes.

The active layer of permafrost in Ny Ålesund, Svalbard (79°N) around the Bayelva River in the Leirhaugen glacier moraine is measured as a small net carbon sink at the brink of becoming a carbon source. In many permafrost-dominating ecosystems, microbes in the active layers have been shown to drive organic matter degradation and greenhouse gas production, creating positive feedback on climate change. However, the microbial metabolisms linking the environmental geochemical processes and the populations that perform them have not been fully characterized. In this paper, we present geochemical, enzymatic, and isotopic data paired with 10 Pseudomonas sp. cultures and metagenomic libraries of two active layer soil cores (BPF1 and BPF2) from Ny Ålesund, Svalbard, (79°N). Relative to BPF1, BPF2 had statistically higher C/N ratios (15 ± 1 for BPF1 vs. 29 ± 10 for BPF2; n = 30, p < 10–5), statistically lower organic carbon (2% ± 0.6% for BPF1 vs. 1.6% ± 0.4% for BPF2, p < 0.02), statistically lower nitrogen (0.1% ± 0.03% for BPF1 vs. 0.07% ± 0.02% for BPF2, p < 10–6). The d13C values for inorganic carbon did not correlate with those of organic carbon in BPF2, suggesting lower heterotrophic respiration. An increase in the δ13C of inorganic carbon with depth either reflects an autotrophic signal or mixing between a heterotrophic source at the surface and a lithotrophic source at depth. Potential enzyme activity of xylosidase and N-acetyl-β-D-glucosaminidase increases twofold at 15°C, relative to 25°C, indicating cold adaptation in the cultures and bulk soil. Potential enzyme activity of leucine aminopeptidase across soils and cultures was two orders of magnitude higher than other tested enzymes, implying that organisms use leucine as a nitrogen and carbon source in this nutrient-limited environment. Besides demonstrating large variability in carbon compositions of permafrost active layer soils only ∼84 m apart, results suggest that the Svalbard active layer microbes are often limited by organic carbon or nitrogen availability and have adaptations to the current environment, and metabolic flexibility to adapt to the warming climate.

Operational assessment tool for forest carbon dynamics for the United States: a new spatially explicit approach linking the LUCAS and CBM-CFS3 models

BackgroundQuantifying the carbon balance of forested ecosystems has been the subject of intense study involving the development of numerous methodological approaches. Forest inventories, processes-based biogeochemical models, and inversion methods have all been used to estimate the contribution of U.S. forests to the global terrestrial carbon sink. However, estimates have ranged widely, largely based on the approach used, and no single system is appropriate for operational carbon quantification and forecasting. We present estimates obtained using a new spatially explicit modeling framework utilizing a “gain–loss” approach, by linking the LUCAS model of land-use and land-cover change with the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3).ResultsWe estimated forest ecosystems in the conterminous United States stored 52.0 Pg C across all pools. Between 2001 and 2020, carbon storage increased by 2.4 Pg C at an annualized rate of 126 Tg C year−1. Our results broadly agree with other studies using a variety of other methods to estimate the forest carbon sink. Climate variability and change was the primary driver of annual variability in the size of the net carbon sink, while land-use and land-cover change and disturbance were the primary drivers of the magnitude, reducing annual sink strength by 39%. Projections of carbon change under climate scenarios for the western U.S. find diverging estimates of carbon balance depending on the scenario. Under a moderate emissions scenario we estimated a 38% increase in the net sink of carbon, while under a high emissions scenario we estimated a reversal from a net sink to net source.ConclusionsThe new approach provides a fully coupled modeling framework capable of producing spatially explicit estimates of carbon stocks and fluxes under a range of historical and/or future socioeconomic, climate, and land management futures.

Carbon dynamics and sequestration by urban mangrove forests of Dar es Salaam, Tanzania

This study intended to 1) determine spatial and temporal changes of mangrove forests, 2) identify drivers of mangrove deforestation and forest degradation, 3) determine historical carbon storage, sequestration and deforestation emissions by mangrove forests, and 4) determine whether mangrove forests are a source or sink of CO2 in Dar es Salaam, Tanzania. Mangrove forests have decreased from 4,813 hectares in 1986 to 1961 hectares in 2016. The following were prominent drivers of deforestation in descending order: clearing mangrove forests for salt pans; hotel construction; settlement; and charcoal making. Tree removals for firewood and building poles were also prominent drivers of mangrove forest degradation. Similarly, carbon stored in mangrove forests has decreased from 1,131,055 tonnes CO2e in 1986 to 460,835 tonnes CO2e in 2016. Sequestration of CO2 by mangrove forests is estimated at 133,516 (1986-1995); 106,110 (1995-2006) and 69,616 (2006-2016) tonnes CO2e year-1. Conversely, mangrove deforestation has resulted in emissions of about 27,400, 16,500 and 24,000 tonnes CO2e year-1 in 1986-1995, 1995- 2006 and 2006-2016, respectively. Urban mangrove forests play an important environmental role in mitigating climate change and amelioration of local weather through the large carbon stocks they store and sequester. Mangrove forests in the study area remain a net carbon sink, however, the sink role played by mangrove forests in the study area is decreasing rapidly. The declining spatial and temporal trends of urban mangrove forest cover has resulted in a systematic decrease in the total carbon stored and sequestered by mangrove forests. In the absence of timely measures of preserving and rehabilitating degraded mangrove areas, the mangrove forests of Dar es Salaam may become the source of CO2. The study recommends effective urban land use planning and effective law enforcement to ensure a win-win situation through sustained ecosystem services offered by urban mangrove forests to support economic growth.

Pyrogenic carbon decomposition critical to resolving fire’s role in the Earth system

Recently identified post-fire carbon fluxes indicate that, to understand whether global fires represent a net carbon source or sink, one must consider both terrestrial carbon retention through pyrogenic carbon production and carbon losses via multiple pathways. Here these legacy source and sink pathways are quantified using a CMIP6 land surface model to estimate Earth’s fire carbon budget. Over the period 1901–2010, global pyrogenic carbon has driven an annual soil carbon accumulation of 337 TgC yr−1, offset by legacy carbon losses totalling −248 TgC yr−1. The residual of these values constrains the maximum annual pyrogenic carbon mineralization to 89 TgC yr−1 and the pyrogenic carbon mean residence time to 5,387 years, assuming a steady state. The residual is negative over forests and positive over grassland-savannahs (implying a potential sink), suggesting contrasting roles of vegetation in the fire carbon cycle. The paucity of observational constraints for representing pyrogenic carbon mineralization means that, without assuming a steady state, we are unable to determine the sign of the overall fire carbon balance. Constraining pyrogenic carbon mineralization rates, particularly over grassland-savannahs, is a critical research frontier that would enable a fuller understanding of fire’s role in the Earth system and inform attendant land use and conservation policy. Vegetation plays an important role in the aggregate carbon balance of fires, according to a 1901 to 2010 land surface model study that, assuming steady state, shows potentially greater pyrogenic carbon production than legacy losses at global scale, due mostly to grassland adaptations to fire.

Assessing the efficiency and sustainability of three eco-campus systems in Northwestern China using a comprehensive evaluation framework

Efforts have been made to alleviate plenty of various environmental issues and economic backwardness of elementary and secondary schools in rural China. In this paper, a multiple-perspective assessment framework was applied to evaluate the performance of three eco-campus systems. A set of emergy analysis, life cycle assessment, economic and social analysis indicators of the integrated framework were quantified and analyzed in detail. The results showed that the “Toilet-Biogas-Vegetables” mode (ESI=3.23) had the best sustainability in terms of comprehensive performance, followed by the “Grass-Goats&Toilet-Biogas-Fruits” mode (ESI=1.62) and the “Pigs&Toilet-Biogas-Vegetables” mode (ESI=0.82). In terms of environmental impact, the XDZS has the highest greenhouse gas emission reduction potential, reaching 26.44 ton in total. However, compared to common biogas integrated ecosystems, the three systems have some similarities in many aspects, such as appreciable resource recycling, net carbon sink, energy conservation, and economic feasibility. In this case, the combination of emergy synthesis, life cycle assessment, economic and social analysis provided a better insight into the comprehensive properties of rural campuses and thus could help us make a better environment for all the students and faculty.

Does Agricultural Mechanization Improve the Green Total Factor Productivity of China’s Planting Industry?

Agricultural mechanization is an important factor to improve the green total factor productivity of the planting industry, which is the key way to realize the sustainable development and high-quality development of agriculture. Based on the panel data of 30 provinces in China from 2001 to 2019, this paper uses the stochastic frontier analysis method of the output-oriented distance function to measure the green total factor productivity of China’s planting industry based on net carbon sinks, and empirically studies the impact of agricultural mechanization on the green total factor productivity in China’s planting industry. The main findings of this paper are as follows: (1) Agricultural mechanization can promote the planting green total factor productivity significantly, and this basic conclusion is still robust after using instrumental variables and sub sample regression. (2) The path of agricultural mechanization on planting green total factor productivity is mainly reflected in technology progress and spatial spillover, while the mechanisms of operation scale expansion, factor allocation optimization and technical efficiency change are not significant. (3) With the improvement in the mechanization level, the promotion effect of mechanization on planting GTFP will become clearer. Given these findings, the paper adds considerable value to the empirical literature and provides various policy and practical implications.

Significant winter CO2 uptake by saline lakes on the Qinghai-Tibet Plateau.

Direct measuring of CO2 flux remains challenging for global lakes. The traditional sampling and gas transfer models used to estimate lake CO2 fluxes are variable and uncertain, and ice-covered periods are often excluded from the annual carbon budget. Here, the first longtime (2013-2017) direct measurement of CO2 flux by eddy covariance system over the largest saline lake (Qinghai lake) in the Qinghai-Tibet Plateau (QTP) revealed that ice-covered period draws large amounts of CO2 from the atmosphere (-0.87±0.38g C m-2 d-1 ), a value more than twice the CO2 flux rate during the ice-free period (-0.41±0.35g C m-2 d-1 ). The total CO2 uptake by all saline lakes on the QTP was estimated to -10.28±1.65Tg C yr-1 , an equivalent to approximately one third of the net terrestrial ecosystems carbon sink in QTP. Our results indicate large sink for CO2 in winter is controlled by both seasonal hydrochemistry processes and lake ice absorption in saline lakes. This research also demonstrates decreasing CO2 uptake from the atmosphere by saline lakes on the QTP, which may turn carbon sinks to carbon sources with future warming.

Carbon footprints of the Indian AFOLU (Agriculture, Forestry, and Other Land Use) sector: a review

Stabilizing greenhouse gas (GHG) emissions from croplands as agricultural demand grows is a critical climate change mitigation strategy. Depending on management, the Agriculture, Forestry, and Other Land Use (AFOLU) sector can be both a source as well as a net sink for carbon. Currently, it contributes 25% of the global anthropogenic carbon emissions. Although India’s emissions from this sector are around 8% of the total national GHG emissions, it can contribute significantly to the country’s aspirations of reaching net-zero emissions by 2070. In this review, we explain the carbon footprints of the AFOLU sector in India, focusing on enteric fermentation, fertilizer and manure management, rice paddies, burning of crop residues, forest fires, shifting cultivation, and food wastage. Furthermore, using the standard autoregressive integrated moving average method, we project India’s AFOLU sector emission routes for 2070 under four scenarios: business as usual (BAU) and three emission reduction levels, viz., 10%, 20%, and 40% below BAU. The article focuses on how the AFOLU sector can be leveraged proactively to reach the net-zero emission goals. Increasing forest cover, agroforestry, and other tree-based land-use systems; improving soil health through soil management, better crop residue, and livestock feed management; emission avoidance from rice ecosystems; and reducing food waste are all important strategies for lowering India’s AFOLU sector carbon footprints.

Carbon emissions from land acquisitions in Laos

Large-scale land acquisitions repeatedly fall short of their acclaimed socioeconomic benefits and are associated with unintended social, economic, and ecological costs. In Laos, the government has started to question its own “Turning Land into Capital” policy, and reviews land acquisitions or concessions with regard to their socioeconomic impacts. Empirical investigations of environmental impacts of land concessions, however, remain underrepresented. We link the nation-wide concession development between 2001 and 2017 with associated land use changes and quantify related land use change-induced emissions. Results show that land acquisitions for agriculture, forestry, and mining affect mainly forests and land previously used for shifting cultivation and permanent agriculture; e.g., rice paddies. Consequently, land conversions caused by concessions resulted in net carbon emissions of 4.9 Mt CO₂e yr-1 on average in 2001–2017, which amounted to 34% of total emissions from land conversions. Even tree plantations that are meant to serve as net carbon sinks caused net emissions, but those data are the least robust. The relatively low carbon emission intensity of shifting cultivation compared to the high carbon emission intensity of concessions challenges the dominant narrative of shifting cultivation as a causal factor for forest degradation. Political means of fostering sustainable development include the reduction of land acquisitions because of their emissions intensity, and minimization of emissions and social conflict induced by granted concessions, for example, by allocating land with low carbon densities and obtaining consent of local land users.

Manila Clam and Mediterranean Mussel Aquaculture is Sustainable and a Net Carbon Sink

Manila Clam and Mediterranean Mussel Aquaculture is Sustainable and a Net Carbon Sink

Ecological restoration and rising CO2 enhance the carbon sink, counteracting climate change in northeastern China

The impact of climate change, rising CO2, land-use/land-cover change and land management on the carbon cycle in terrestrial ecosystems has been widely reported. However, only rarely have studies have been conducted to clarify the impact of climate change and rising CO2 on the carbon sink contributed by ecological restoration projects (ERPs). To better understand the impact of climate change and rising CO2 on ERPs, we took the Beijing–Tianjin Sand Source Control Project zone as an example to set up different scenarios to distinguish the confounding effects of these factors on the regional carbon budget based on a remote sensing data-driven model. Compared with business as usual, our results show that climate change caused a carbon loss of 78.97 Tg C. On the contrary, ERPs contributed a carbon sink of approximately 199.88 Tg C in forest and grassland. Furthermore, rising CO2 also contributed an additional carbon sink of 107.80 Tg C. This study distinguished the individual effects of different factors, and clarified the net carbon sink contributed by ERPs and rising CO2 and their significance for enhancing the regional carbon sink and reversing the adverse effects of climate change on the carbon sink. Furthermore, ERPs can sequester carbon more effectively and faster compared with rising atmospheric CO2 concentration.