Carbon

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A life cycle and product type based estimator for quantifying the carbon stored in wood products
(Springer Nature, 2023-01-23) Wei, Xinyuan; Zhao, Jianheng; Hayes, Daniel J.; Daigneault, Adam; Zhu, He
Background Timber harvesting and industrial wood processing laterally transfer the carbon stored in forest sectors to wood products creating a wood products carbon pool. The carbon stored in wood products is allocated to end-use wood products (e.g., paper, furniture), landfill, and charcoal. Wood products can store substantial amounts of carbon and contribute to the mitigation of greenhouse effects. Therefore, accurate accounts for the size of wood products carbon pools for different regions are essential to estimating the land-atmosphere carbon exchange by using the bottom-up approach of carbon stock change. Results To quantify the carbon stored in wood products, we developed a state-of-the-art estimator (Wood Products Carbon Storage Estimator, WPsCS Estimator) that includes the wood products disposal, recycling, and waste wood decomposition processes. The wood products carbon pool in this estimator has three subpools: (1) end-use wood products, (2) landfill, and (3) charcoal carbon. In addition, it has a user-friendly interface, which can be used to easily parameterize and calibrate an estimation. To evaluate its performance, we applied this estimator to account for the carbon stored in wood products made from the timber harvested in Maine, USA, and the carbon storage of wood products consumed in the United States. Conclusion The WPsCS Estimator can efficiently and easily quantify the carbon stored in harvested wood products for a given region over a specific period, which was demonstrated with two illustrative examples. In addition, WPsCS Estimator has a user-friendly interface, and all parameters can be easily modified.
China’s terrestrial ecosystem carbon balance during the 20th century: an analysis with a process-based biogeochemistry model
(Springer Nature, 2022-10-08) Lu, Yanyu; Huang, Yao; Zhuang, Qianlai; Sun, Wei; Chen, Shutao; Lu, Jun
Background: China’s terrestrial ecosystems play a pronounced role in the global carbon cycle. Here we combine spatially-explicit information on vegetation, soil, topography, climate and land use change with a process-based bio geochemistry model to quantify the responses of terrestrial carbon cycle in China during the 20th century. Results: At a century scale, China’s terrestrial ecosystems have acted as a carbon sink averaging at 96 Tg C yr−1, with large inter-annual and decadal variabilities. The regional sink has been enhanced due to the rising temperature and CO2 concentration, with a slight increase trend in carbon sink strength along with the enhanced net primary production in the century. The areas characterized by C source are simulated to extend in the west and north of the Hu Huanyong line, while the eastern and southern regions increase their area and intensity of C sink, particularly in the late 20th century. Forest ecosystems dominate the C sink in China and are responsible for about 64% of the total sink. On the century scale, the increase in carbon sinks in China’s terrestrial ecosystems is mainly contributed by rising CO2. Aforestation and reforestation promote an increase in terrestrial carbon uptake in China from 1950s. Although climate change has generally contributed to the increase of carbon sinks in terrestrial ecosystems in China, the positive effect of climate change has been diminishing in the last decades of the 20th century. Conclusion: This study focuses on the impacts of climate, CO2 and land use change on the carbon cycle, and presents the potential trends of terrestrial ecosystem carbon balance in China at a century scale. While a slight increase in carbon sink strength benefits from the enhanced vegetation carbon uptake in China’s terrestrial ecosystems during the 20th century, the increase trend may diminish or even change to a decrease trend under future climate change.
Comprehensive evidence implies a higher social cost of CO2
(Springer Nature, 2022-09-01) Rennert, Kevin; Errickson, Frank; Prest, Brian C.; Rennels, Lisa; Newell, Richard G.; Pizer, William; Kingdon, Cora; Wingenroth, Jordan; Cooke, Roger; Parthum, Bryan; Smith, David; Cromar, Kevin; Diaz, Delavane; Moore, Frances C.; Müller, Ulrich K.; Plevin, Richard J.; Raftery, Adrian E.; Ševčíková, Hana; Sheets, Hannah; Stock, James H.; Tan, Tammy; Watson, Mark; Wong, Tony E.; Anthoff, David
The social cost of carbon dioxide (SC-CO2) measures the monetized value of the damages to society caused by an incremental metric tonne of CO2 emissions and is a key metric informing climate policy. Used by governments and other decision-makers in benefit–cost analysis for over a decade, SC-CO2 estimates draw on climate science, economics, demography and other disciplines. However, a 2017 report by the US National Academies of Sciences, Engineering, and Medicine (NASEM) highlighted that current SC-CO2 estimates no longer reflect the latest research. The report provided a series of recommendations for improving the scientific basis, transparency and uncertainty characterization of SC-CO2 estimates. Here we show that improved probabilistic socioeconomic projections, climate models, damage functions, and discounting methods that collectively reflect theoretically consistent valuation of risk, substantially increase estimates of the SC-CO2. Our preferred mean SC-CO2 estimate is $185 per tonne of CO2 ($44–$413 per tCO2: 5%–95% range, 2020 US dollars) at a near-term risk-free discount rate of 2%, a value 3.6 times higher than the US government’s current value of $51 per tCO2. Our estimates incorporate updated scientific understanding throughout all components of SC-CO2 estimation in the new open-source Greenhouse Gas Impact Value Estimator (GIVE) model, in a manner fully responsive to the near-term NASEM recommendations. Our higher SC-CO2 values, compared with estimates currently used in policy evaluation, substantially increase the estimated benefits of greenhouse gas mitigation and thereby increase the expected net benefits of more stringent climate policies.
Conservation Agriculture and Soil Organic Carbon: Principles, Processes, Practices and Policy Options
(MDPI, 2023-02-22) Francaviglia, Rosa; Almagro, María; Vicente-Vicente, José Luis
Intensive agriculture causes land degradation and other environmental problems, such as pollution, soil erosion, fertility loss, biodiversity decline, and greenhouse gas (GHG) emissions, which exacerbate climate change. Sustainable agricultural practices, such as reduced tillage, growing cover crops, and implementing crop residue retention measures, have been proposed as cost-effective solutions that can address land degradation, food security, and climate change mitigation and adaptation by enhancing soil organic carbon (SOC) sequestration in soils and its associated co-benefits. In this regard, extensive research has demonstrated that conservation agriculture (CA) improves soil physical, chemical, and biological properties that are crucial for maintaining soil health and increasing agroecosystem resilience to global change. However, despite the research that has been undertaken to implement the three principles of CA (minimum mechanical soil disturbance, permanent soil organic cover with crop residues and/or cover crops, and crop diversification) worldwide, there are still many technical and socio-economic barriers that restrict their adoption. In this review, we gather current knowledge on the potential agronomic, environmental, and socio-economic benefits and drawbacks of implementing CA principles and present the current agro-environmental policy frameworks. Research needs are identified, and more stringent policy measures are urgently encouraged to achieve climate change mitigation targets.
Effects of forest degradation classification on the uncertainty of aboveground carbon estimates in the Amazon
(Springer Nature, 2023-02-14) Rangel Pinagé, Ekena ; Keller, Michael; Peck, Christopher P.; Longo, Marcos; Duffy, Paul; Csillik, Ovidiu
Background Tropical forests are critical for the global carbon budget, yet they have been threatened by deforestation and forest degradation by fire, selective logging, and fragmentation. Existing uncertainties on land cover classification and in biomass estimates hinder accurate attribution of carbon emissions to specific forest classes. In this study, we used textural metrics derived from PlanetScope images to implement a probabilistic classification framework to identify intact, logged and burned forests in three Amazonian sites. We also estimated biomass for these forest classes using airborne lidar and compared biomass uncertainties using the lidar-derived estimates only to biomass uncertainties considering the forest degradation classification as well. Results Our classification approach reached overall accuracy of 0.86, with accuracy at individual sites varying from 0.69 to 0.93. Logged forests showed variable biomass changes, while burned forests showed an average carbon loss of 35%. We found that including uncertainty in forest degradation classification significantly increased uncertainty and decreased estimates of mean carbon density in two of the three test sites. Conclusions Our findings indicate that the attribution of biomass changes to forest degradation classes needs to account for the uncertainty in forest degradation classification. By combining very high-resolution images with lidar data, we could attribute carbon stock changes to specific pathways of forest degradation. This approach also allows quantifying uncertainties of carbon emissions associated with forest degradation through logging and fire. Both the attribution and uncertainty quantification provide critical information for national greenhouse gas inventories.
Hydroclimatic vulnerability of peat carbon in the central Congo Basin
(Springer Nature, 2022-11-02) Garcin, Yannick; Schefuß, Enno; Dargie, Greta C.; Hawthorne, Donna; Lawson, Ian T.; Sebag, David; Biddulph, George E.; Crezee, Bart; Bocko, Yannick E.; Ifo, Suspense A.; Wenina, Y. Emmanuel Mampouya; Mbemba, Mackline; Ewango, Borneille E. N.; Emba, Ovide; Bola, Pierre; Tabi, Joseph Kanyama; Tyrrell, Genevieve; Young, Dylan M.; Gassier, Ghislain; Girkin, Nicholas T.; Vane, Christopher H.; Adatte, Thierry; Baird, Andy J.; Boom, Arnoud; Gulliver, Pauline; Morris, Paul J.; Page, Susan E.; Sjögersten, Sofie; Lewis, Simon
The forested swamps of the central Congo Basin store approximately 30 billion metric tonnes of carbon in peat. Little is known about the vulnerability of these carbon stocks. Here we investigate this vulnerability using peat cores from a large interfluvial basin in the Republic of the Congo and palaeoenvironmental methods. We find that peat accumulation began at least at 17,500 calibrated years before present (cal. yr BP; taken as AD 1950). Our data show that the peat that accumulated between around 7,500 to around 2,000 cal. yr BP is much more decomposed compared with older and younger peat. Hydrogen isotopes of plant waxes indicate a drying trend, starting at approximately 5,000 cal. yr BP and culminating at approximately 2,000 cal. yr BP, coeval with a decline in dominant swamp forest taxa. The data imply that the drying climate probably resulted in a regional drop in the water table, which triggered peat decomposition, including the loss of peat carbon accumulated prior to the onset of the drier conditions. After approximately 2,000 cal. yr BP, our data show that the drying trend ceased, hydrologic conditions stabilized and peat accumulation resumed. This reversible accumulation–loss–accumulation pattern is consistent with other peat cores across the region, indicating that the carbon stocks of the central Congo peatlands may lie close to a climatically driven drought threshold. Further research should quantify the combination of peatland threshold behaviour and droughts driven by anthropogenic carbon emissions that may trigger this positive carbon cycle feedback in the Earth system.
Mineral-enriched biochar delivers enhanced nutrient recovery and carbon dioxide removal
(Springer Nature, 2022-03-18) Buss, Wolfram; Wurzer, Christian; Manning, David A. C.; Rohling, Eelco J.; Borevitz, Justin; Mašek, Ondřej
Biochar production via biomass pyrolysis with subsequent burial in soils provides a carbon dioxide removal technology that is ready for implementation, yet uptake requires acceleration; notably, through generation of cost reductions and co-benefits. Here we find that biomass enrichment (doping) with refined minerals, mineral by-products, or ground rocks reduces carbon loss during pyrolysis, lowering carbon dioxide removal costs by 17% to US$ 80–150 t−1 CO2, with 30% savings feasible at higher biomass costs. As a co-benefit, all three additives increase plant-available nutrient levels. Doping with potassium-bearing minerals can increase both potassium and phosphorus release. Mineral doping in biochar production therefore offers carbon dioxide removal at lower costs, while alleviating global phosphorus and potassium shortages. This makes it unique among carbon dioxide removal technologies.
On the use of Earth Observation to support estimates of national greenhouse gas emissions and sinks for the Global stocktake process: lessons learned from ESA-CCI RECCAP2
(Springer Nature, 2022-10-01) Bastos, Ana; Ciais, Phillippe; Sitch, Stephen; Aragão, Luiz O. C.; Chevallier, Frédéric; Fawcett, Dominic; Rosan, Thais M.; Saunois, Marielle; Günther, Dirk; Perugini, Lucia; Robert, Colas; Deng, Zhu; Pongratz, Julia; Ganzenmüller, Raphael; Fuchs, Richard; Winkler, Karina; Zaehle, Sönke; Albergel, Clément
The Global Stocktake (GST), implemented by the Paris Agreement, requires rapid developments in the capabilities to quantify annual greenhouse gas (GHG) emissions and removals consistently from the global to the national scale and improvements to national GHG inventories. In particular, new capabilities are needed for accurate attribution of sources and sinks and their trends to natural and anthropogenic processes. On the one hand, this is still a major challenge as national GHG inventories follow globally harmonized methodologies based on the guidelines established by the Intergovernmental Panel on Climate Change, but these can be implemented diferently for individual countries. Moreover, in many countries the capability to systematically produce detailed and annually updated GHG inventories is still lacking. On the other hand, spatially-explicit datasets quantifying sources and sinks of carbon dioxide, methane and nitrous oxide emissions from Earth Observations (EO) are still limited by many sources of uncertainty. While national GHG inventories follow diverse methodologies depending on the availability of activity data in the diferent countries, the proposed comparison with EO-based estimates can help improve our understanding of the comparability of the estimates published by the diferent countries. Indeed, EO networks and satellite platforms have seen a massive expansion in the past decade, now covering a wide range of essential climate variables and ofering high potential to improve the quantifcation of global and regional GHG budgets and advance process understanding. Yet, there is no EO data that quantifes greenhouse gas fuxes directly, rather there are observations of variables or proxies that can be transformed into fuxes using models. Here, we report results and lessons from the ESA-CCI RECCAP2 project, whose goal was to engage with National Inventory Agencies to improve understanding about the methods used by each community to estimate sources and sinks of GHGs and to evaluate the potential for satellite and in-situ EO to improve national GHG estimates. Based on this dialogue and recent studies, we discuss the potential of EO approaches to provide estimates of GHG budgets that can be compared with those of national GHG invento ries. We outline a roadmap for implementation of an EO carbon-monitoring program that can contribute to the Paris Agreement.
Optimizing Sampling Strategies for Near-Surface Soil Carbon Inventory: One Size Doesn’t Fit All
(MDPI, 2023-03-17) Bettigole, Charles; Hanle, Juliana; Kane, Daniel A.; Pagliaro, Zoe; Kolodney, Shaylan; Szuhay, Sylvana; Chandler, Miles; Hersh, Eli; Wood, Stephen A.; Basso, Bruno; Goodwin, Douglas Jeffrey; Hardy, Shane; Wolf, Zachary; Covey, Kristofer R.
Soils comprise the largest pool of terrestrial carbon yet have lost significant stocks due to human activity. Changes to land management in cropland and grazing systems present opportunities to sequester carbon in soils at large scales. Uncertainty in the magnitude of this potential impact is largely driven by the difficulties and costs associated with measuring near-surface (0–30 cm) soil carbon concentrations; a key component of soil carbon stock assessments. Many techniques exist to optimize sampling, yet few studies have compared these techniques at varying sample intensities. In this study, we performed ex-ante, high-intensity sampling for soil carbon concentrations at four farms in the eastern United States. We used post hoc Monte-Carlo bootstrapping to investigate the most efficient sampling approaches for soil carbon inventory: K-means stratification, Conditioned Latin Hypercube Sampling (cLHS), simple random, and regular grid. No two study sites displayed similar patterns across all sampling techniques, although cLHS and grid emerged as the most efficient sampling schemes across all sites and strata sizes. The number of strata chosen when using K-means stratification can have a significant impact on sample efficiency, and we caution future inventories from using small strata n, while avoiding even allocation of sample between strata. Our findings reinforce the need for adaptive sampling methodologies where initial site inventory can inform primary, robust inventory with site-specific sampling techniques.
Organic C Fractions in Topsoil under Different Management Systems in Northeastern Brazil
(MDPI, 2023-02-05) Gualberto, Adriano Venicius Santana; de Souza, Henrique; Sagrilo, Edvaldo; Araujo, Ademir Sergio Ferreira; Mendes, Lucas William; de Medeiros, Erika Valente; Pereira, Arthur Prudêncio de Araujo; da Costa, Diogo Paes; Vogado, Renato Falconeres; da Cunha, João Rodrigues; Teixeira, Marcos Lopes; Leite, Luiz Fernando Carvalho
The conversion from native forest to other land-use systems can decline the soil organic carbon (SOC) in tropical soils. However, conservationist management could mitigate SOC losses, promoting the functioning and stability of agricultural soils. This study aimed to address the influence of conversion from native forest to different land-use systems on SOC fractions in Northeastern Brazil. Topsoil soil samples were collected in areas under pasture (PAS), no-tillage (NT1 and NT2), eucalyptus (EUC), and native forests of Cerrado in Northeastern, Brazil. Total organic C, microbial biomass (MBC), particulate (POC), and mineral-occluded organic C (MOC), as well as fulvic acids (C-FA), humic acids (C-HA), and humin (C-HUM) fractions were accessed. The results showed that land conversion maintained similar levels of humic fractions and total organic carbon (TOC) stocks in the PAS, NT1, NT2, and EUC as compared to native Cerrado. Soils with the input of permanent and diverse fresh organic material, such as NT2, PAS, and EUC, presented high levels of MBC and POC, and the lowest C-FA:TOC and C-HA:TOC ratios. The land conversion to agricultural systems that include cropping rotations associated with pasture species such as Mombasa grass and eucalyptus prevents topsoil losses of active C compartments in the Cerrado of the Brazilian Northeast. It suggests that sustainable and conservationist management should be emphasized to maintain and improve the status of soil organic C.
Response of soil respiration to changes in soil temperature and water table level in drained and restored peatlands of the southeastern United States
(Springer Nature, 2022-11-19) Swails, E. E.; Ardón, M.; Krauss, K. W.; Peralta, A. L.; Emanual, R. E.; Helton, A. M.; Morse, J. L.; Gutenberg, L.; Cormier, N.; Shoch, D.; Settlemyer, S.; Soderholm, E.; Boutin, B. P.; Peoples, C.; Ward, S.
Background: Extensive drainage of peatlands in the southeastern United States coastal plain for the purposes of agriculture and timber harvesting has led to large releases of soil carbon as carbon dioxide (CO2) due to enhanced peat decomposition. Growth in mechanisms that provide fnancial incentives for reducing emissions from land use and land-use change could increase funding for hydrological restoration that reduces peat CO2 emissions from these ecosystems. Measuring soil respiration and physical drivers across a range of site characteristics and land use histories is valuable for understanding how CO2 emissions from peat decomposition may respond to raising water table levels. We combined measurements of total soil respiration, depth to water table from soil surface, and soil temperature from drained and restored peatlands at three locations in eastern North Carolina and one location in southeastern Virginia to investigate relationships among total soil respiration and physical drivers, and to develop models relating total soil respiration to parameters that can be easily measured and monitored in the feld. Results: Total soil respiration increased with deeper water tables and warmer soil temperatures in both drained and hydrologically restored peatlands. Variation in soil respiration was more strongly linked to soil temperature at drained (R2=0.57, p<0.0001) than restored sites (R2=0.28, p<0.0001). Conclusions: The results suggest that drainage amplifes the impact of warming temperatures on peat decomposi tion. Proxy measurements for estimation of CO2 emissions from peat decomposition represent a considerable cost reduction compared to direct soil fux measurements for land managers contemplating the potential climate impact of restoring drained peatland sites. Research can help to increase understanding of factors infuencing variation in soil respiration in addition to physical variables such as depth to water table and soil temperature.
Socio-economic factors infuencing the adoption of low carbon technologies under rice production systems in China
(Springer Nature, 2022-12-08) Chen, Zhong-Du; Chen, Fu
Background: Rice (Oryza sativa L.) production, such as farmers’ livelihood and the soil quality, has been identifed to be strong infuenced by climate change in China. However, the benefts of low carbon technologies (LCTs) are still debatable in rice production for farmers, which have been identifed to tackle agricultural challenges. The choice of potential LCTs relevant to the case study is based on a literature review of previous empirical studies. Thus, the objectives of the study were to (1) investigate the public perception and preferences of LCTs in rice production of China, and (2) analyze the infuences of the factors on farmer’s decision in adopting LCTs in rice production. There were 555 farmer surveys from eight representative rice production counties in HP province of southern China, both the Poisson estimators and multivariate probit (MVP) approach were applied in the study. Results: Our results show that water-saving irrigation, integrated pest management techniques and planting green manure crops in winter season were the three major LCTs adapted by farmers in rice production. The intensity and probability of LCTs adoptions were infuenced by the main factors including farmers’ education level, climate change awareness, machinery ownership, technical support and subsidies. There is a signifcant correlation among the LCTs, and the adoption of the technologies is interdependent, depicting either complementarities or substitutabilities between the practices. Conclusions: This study suggests that policies enhance the integration of LCTs would be central to farmers’ knowledge, environmental concerns, technical service and fnancial support in rice production systems in China.
Soil carbon sequestration benefits of active versus natural restoration vary with initial carbon content and soil layer
(Springer Nature, 2023-03-17) Tian, Dashuan; Xiang, Yangzou; Seabloom, Eric; Wang, Jinsong; Jia, Xiaoxu; Li, Tingting; Li, Zhaolei; Yang, Jian; Guo, Hongbo; Niu, Shuli
Reducing terrestrial carbon emissions is a big challenge for human societies. Ecosystem restoration is predominant to reverse land degradation and carbon loss. Though active restoration of croplands is assumed to increase carbon sequestration more than natural regeneration, it still lacks the robust paired comparisons between them. Here we performed a large-scale paired comparison of active versus natural restoration effects on soil carbon sequestration across China. We found that two restoration strategies consistently enhanced soil carbon relative to croplands, however, the benefits of active restoration versus natural regeneration were highly context-dependent. Active restoration only sequestered more carbon in carbon-poor soils but less carbon in carbon-rich soils than natural regeneration. Moreover, active restoration fixed greater carbon in topsoil but less carbon in subsoil. Overall, these findings highlight landscape context-dependent application of active restoration and natural regeneration, further guiding the efficient management of limited resources to maximize the restoration benefits of carbon sequestration.
Spatiotemporal variations in urban CO2 flux with land-use types in Seoul
(Springer Nature, 2022-05-03) Park, Chaerin; Jeong, Sujong; Park, Moon-Soo; Park, Hoonyoung; Yun, Jeongmin; Lee, Sang-Sam; Park, Sung-Hwa
Background Cities are a major source of atmospheric CO2; however, understanding the surface CO2 exchange processes that determine the net CO2 flux emitted from each city is challenging owing to the high heterogeneity of urban land use. Therefore, this study investigates the spatiotemporal variations of urban CO2 flux over the Seoul Capital Area, South Korea from 2017 to 2018, using CO2 flux measurements at nine sites with different urban land-use types (baseline, residential, old town residential, commercial, and vegetation areas). Results Annual CO2 flux significantly varied from 1.09 kg C m− 2 year− 1 at the baseline site to 16.28 kg C m− 2 year− 1 at the old town residential site in the Seoul Capital Area. Monthly CO2 flux variations were closely correlated with the vegetation activity (r = − 0.61) at all sites; however, its correlation with building energy usage differed for each land-use type (r = 0.72 at residential sites and r = 0.34 at commercial sites). Diurnal CO2 flux variations were mostly correlated with traffic volume at all sites (r = 0.8); however, its correlation with the floating population was the opposite at residential (r = − 0.44) and commercial (r = 0.80) sites. Additionally, the hourly CO2 flux was highly related to temperature. At the vegetation site, as the temperature exceeded 24 ℃, the sensitivity of CO2 absorption to temperature increased 7.44-fold than that at the previous temperature. Conversely, the CO2 flux of non-vegetation sites increased when the temperature was less than or exceeded the 18 ℃ baseline, being three-times more sensitive to cold temperatures than hot ones. On average, non-vegetation urban sites emitted 0.45 g C m− 2 h− 1 of CO2 throughout the year, regardless of the temperature. Conclusions Our results demonstrated that most urban areas acted as CO2 emission sources in all time zones; however, the CO2 flux characteristics varied extensively based on urban land-use types, even within cities. Therefore, multiple observations from various land-use types are essential for identifying the comprehensive CO2 cycle of each city to develop effective urban CO2 reduction policies.
Sub-continental-scale carbon stocks of individual trees in African drylands
(Springer Nature, 2023-03-01) Tucker, Compton; Brandt, Martin; Hiernaux, Pierre; Kariyaa, Ankit; Rasmussen, Kjeld; Small, Jennifer; Igel, Christian; Reiner, Florian; Melocik, Katherine; Meyer, Jesse; Sinno, Scott; Romero, Eric; Glennie, Erin; Fitts, Yasmin; Morin, August; Pinzon, Jorge; McClain, Devin; Morin, Paul; Porter, Claire; Loeffler, Shane; Kergoat, Laurent; Issoufou, Bil-Assaour; Savadogo, Patrice; Wigneron, Jean-Pierre; Poulter, Benjamin; Cliais, Phillippe; Kaufmann, Robert; Myneni, Ranga; Saatchi, Sassan; Fensholt, Rasmus
The distribution of dryland trees and their density, cover, size, mass and carbon content are not well known at sub-continental to continental scales. This information is important for ecological protection, carbon accounting, climate mitigation and restoration efforts of dryland ecosystems. We assessed more than 9.9 billion trees derived from more than 300,000 satellite images, covering semi-arid sub-Saharan Africa north of the Equator. We attributed wood, foliage and root carbon to every tree in the 0–1,000 mm year−1 rainfall zone by coupling field data, machine learning, satellite data and high-performance computing. Average carbon stocks of individual trees ranged from 0.54 Mg C ha−1 and 63 kg C tree−1 in the arid zone to 3.7 Mg C ha−1 and 98 kg tree−1 in the sub-humid zone. Overall, we estimated the total carbon for our study area to be 0.84 (±19.8%) Pg C. Comparisons with 14 previous TRENDY numerical simulation studies for our area found that the density and carbon stocks of scattered trees have been underestimated by three models and overestimated by 11 models, respectively. This benchmarking can help understand the carbon cycle and address concerns about land degradation. We make available a linked database of wood mass, foliage mass, root mass and carbon stock of each tree for scientists, policymakers, dryland-restoration practitioners and farmers, who can use it to estimate farmland tree carbon stocks from tablets or laptops.
The impact of human and livestock respiration on CO2 emissions from 14 global cities
(Springer Nature, 2022-11-03) Cai, Qixiang; Zeng, Ning; Zhao, Fang; Han, Pengfei; Liu, Xiaohui; Chen, Jingwen
Background: The CO2 released by humans and livestock through digestion and decomposition is an important part of the urban carbon cycle, but is rarely considered in studies of city carbon budgets since its annual magnitude is usually much lower than that of fossil fuel emissions within the boundaries of cities. However, human and livestock respiration may be substantial compared to fossil fuel emissions in areas with high population density such as Manhattan or Beijing. High-resolution datasets of CO2 released from respiration also have rarely been reported on a global scale or in cities globally. Here, we estimate the CO2 released by human and livestock respiration at global and city scales and then compare it with the carbon emissions inventory from fossil fuels in 14 cities worldwide. Results: The results show that the total magnitude of human and livestock respiration emissions is 38.2% of the fossil fuel emissions in Sao Paulo, highest amongst the 14 cities considered here. The proportion is larger than 10% in cities of Delhi, Cape Town and Tokyo. In other cities, it is relatively small with a proportion around 5%. In addition, almost 90% of respiratory carbon comes from urban areas in most of the cities, while up to one-third comes from suburban areas in Beijing on account of the siginificant livestock production. Conclusion: The results suggest that the respiration of human and livestock represents a significant CO2 source in some cities and is nonnegligible for city carbon budget analysis and carbon monitoring.

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