Carbon-isotope records of the Early Jurassic (Toarcian) oceanic anoxic event from the Valdorbia (Umbria–Marche Apennines) and Monte Mangart (Julian Alps) sections: palaeoceanographic and stratigraphic implications

The Toarcian oceanic anoxic event ( ca 183 Ma) coincides with a global perturbation marked by enhanced organic carbon burial and a general decrease in calcium carbonate production, probably triggered by changes in the composition of marine plankton and elevated carbon dioxide levels in the atmosphere. This study is based on high-resolution sampling of two stratigraphic successions, located in Valdorbia (Umbria–Marche Apennines) and Monte Mangart (Julian Alps), Italy, which represent expressions of the Toarcian oceanic anoxic event in deep-water pelagic sediments. These successions are characterized by the occurrence of black shales showing relatively low total organic carbon concentrations (compared with coeval strata in Northern Europe), generally < 2%, and low hydrogen indices. On this basis, they are similar to other Toarcian black shales described from the Tethyan region. The positive and negative carbon-isotope records from the two localities permit a high-resolution correlation such that ammonite biostratigraphy information from Valdorbia can be transferred to those parts of the Monte Mangart section that lack these fossils. Spectral analyses of δ¹³C_org values and of CaCO₃ percentages from the sedimentary records of both the Valdorbia and Monte Mangart sections reveal a strong cyclic pattern, best interpreted as an eccentricity signal which hence implies a duration of ca 500 kyr for the negative carbon-isotope excursion. Based on the carbon-isotope curves obtained, the high-resolution correlation between the Italian successions and a section in Yorkshire (Northern Europe) confirms the supposition that the apparent mismatch between the dating of the Toarcian oceanic anoxic event in the Boreal and Tethyan realms is an artefact of biostratigraphy.     

Sediment organic matter source estimation and ecological classification in the semi-enclosed Batan Bay Estuary,Philippines

The large organic matter flow in tropical coastal areas is recognized as an important process in the global carbon(C)cycle.However,the nature of organic matter flow in semi-enclosed tropical estuaries remains unclear due to the various environmental processes(tidal change,river flow,waves from the sea,and internal circulation)and organic matter sources therein.Thus,sediment organic matter(SOM)sources,and their distribution pattern,are key to understanding ecosystem material flow.Our research in the Batan Bay Estuary,Philippines,a semi-enclosed estuary under large mangrove deforestation,was conducted to determine ecosystem properties through analysis of C and nitrogen stable isotope ratios and environmental factors.First,we determined that mangrove litter,microphytobenthos,and phytoplankton are the main SOM sources in the Batan Bay Estuary.Second,the estuary was classified into three ecological zones(the Bay zone,Back-barrier zone,and River zone).In addition,we estimated SOM source ratios using the Stable Isotope Analysis in R package and determined different organic matter sources in different zone.The high ratios of mangrove litter as SOM indicate that a large amount of terrestrial plant organic matter remains despite the heavy mangrove deforestation that has occurred since the 1980s,and that the Back-barrier zone consists of a different type of ecosystem that promotes accumulation of C from mangrove litter and microphytobenthos.     

The Geochemical Significance of Deep-water Coral and Their Food Source

Deep-sea corals live in the dark cold-water environments, the food of which that provides them with energy and nutrition is a key ecological and biogeochemical problem. Currently, the most common understanding is that their food mainly comes from organic matter produced by and deposited from surface seawater. However, more and more studies have found that they can also obtain food supply through symbiosis with a variety of chemosynthetic autotrophs and heterotrophs. Carbon and nitrogen isotopes have been used to trace and reveal the food sources of deep-sea corals. They also have been successfully used to reconstruct the phytoplankton community structure and the changes of nitrate isotopes in surface seawater in the past, thus providing valuable biogeochemical data for paleoceanographic study. However, due to the widespread existence of symbiosis with chemosynthetic autotrophs, further studies are needed to assess the reliability of organic carbon and nitrogen isotopes of deep-sea corals to reflect changes in the surface seawater. The deep-sea gorgonian coral, like those gorgonian forests recently found in the South China Sea, is relatively new and insufficiently studied in the field of deep-sea corals. Thus, basic biochemical and paleoceanographic researches on the South China Sea deep-water gorgonians will provide profound and novel insights to understanding the cold-water coral system.     

Near‐surface hydraulic conductivity of northern hemisphere glaciers

The hydrology of near‐surface glacier ice remains a neglected aspect of glacier hydrology despite its role in modulating meltwater delivery to downstream environments. To elucidate the hydrological characteristics of this near‐surface glacial weathering crust, we describe the design and operation of a capacitance‐based piezometer that enables rapid, economical deployment across multiple sites and provides an accurate, high‐resolution record of near‐surface water‐level fluctuations. Piezometers were employed at 10 northern hemisphere glaciers, and through the application of standard bail–recharge techniques, we derive hydraulic conductivity (K) values from 0.003 to 3.519 m day^?1, with a mean of 0.185 ± 0.019 m day^?1. These results are comparable to those obtained in other discrete studies of glacier near‐surface ice, and for firn, and indicate that the weathering crust represents a hydrologically inefficient aquifer. Hydraulic conductivity correlated positively with water table height but negatively with altitude and cumulative short‐wave radiation since the last synoptic period of either negative air temperatures or turbulent energy flux dominance. The large range of K observed suggests complex interactions between meteorological influences and differences arising from variability in ice structure and crystallography. Our data demonstrate a greater complexity of near‐surface ice hydrology than hitherto appreciated and support the notion that the weathering crust can regulate the supraglacial discharge response to melt production. The conductivities reported here, coupled with typical supraglacial channel spacing, suggest that meltwater can be retained within the weathering crust for at least several days. Not only does this have implications for the accuracy of predictive meltwater run‐off models, but we also argue for biogeochemical processes and transfers that are strongly conditioned by water residence time and the efficacy of the cascade of sediments, impurities, microbes, and nutrients to downstream ecosystems. Because continued atmospheric warming will incur rising snowline elevations and glacier thinning, the supraglacial hydrological system may assume greater importance in many mountainous regions, and consequently, detailing weathering crust hydraulics represents a research priority because the flow path it represents remains poorly constrained.     

Assessing protected area’s carbon stocks and ecological structure at regional-scale using GEDI lidar

Protected areas (PAs) serve as a critical strategy for protecting natural resources, conserving biodiversity, and mitigating climate change. While there is a critical need to guide area-based conservation efforts, a systematic assessment of PA effectiveness for storing carbon stocks has not been possible due to the lack of globally consistent forest biomass data. In this study, we present a new methodology utilizing forest structural information and aboveground biomass density (AGBD) obtained from the Global Ecosystem Dynamics Investigation (GEDI) mission. We compare PAs with similar, unprotected forests obtained through statistical matching to assess differences in carbon storage and forest structure. We also assess matching outcomes for a robust and minimally biased way to quantify PA efficacy. We find that all analyzed PAs in Tanzania possess higher biomass densities than their unprotected counterfactuals (24.4% higher on average). This is also true for other forest structure metrics, including tree height, canopy cover, and plant area index (PAI). We also find that community-governed PAs are the most effective category of PAs at preserving forest structure and AGBD – often outperforming those managed by international or national entities. In addition, PAs designated under more than one entity perform better than the PAs with a single designation, especially those with multiple international designations. Finally, our findings suggest that smaller PAs may be more effective for conservation, depending on levels of connectivity. Taken together, these findings support the designation of PAs as an effective means for forest management with considerable potential to protect forest ecosystems and achieve long-term climate goals.     

海洋浮游动物粪便通量

海洋浮游动物粪便颗粒的沉降被认为是碳从海洋表层向海底输送的主要途径之一，对研究碳通量和水层－底栖耦合具有重要意义。综述了有关浮游动物粪便的形态、产生率、分解速度和沉降速度的研究，以及近年来沉积物捕捉器样品的研究。虽然通过粪便产生率和沉降速度估计出的粪便通量很大，但是沉积物中粪便颗粒造成的碳通量所占比例不大。因此，对其它沉积途径的研究不容忽视。     

Finding Common Ground: A Critique of Subsumption Theory and Its Application to Small-Scale Forest Carbon Offsetting in Uganda

Carbon markets as a policy tool to mitigate emissions of greenhouse gases continue to be controversial, especially in developing countries. It is thus refreshing that Carton and Andersson (2017 Carton, W., and E. Andersson. 2017. Where forest carbon meets its maker: Forestry-based offsetting as the subsumption of nature. Society &; Natural Resources 30 (7):829–43.[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]) undertook a field investigation of a transnational forest carbon offset project in Uganda. However, I am concerned that assumptions of structural Marxism that underwrite subsumption theory may have led the authors to see the project as inherently conflict ridden and exploitative and to neglect actual benefits. Their presentation of the project’s local impact jarred with my own empirical research into this project, undertaken in 2009, as well as more recent news accounts. While my field effort preceded the authors’ by 6 years, I attribute our different interpretations largely to theoretical and methodological differences. Evidence I present below suggests considerable alignment between the interests of transnational carbon markets and Ugandan smallholder farmers. Additional fieldwork might be able to resolve these differences in interpretation.     

Defining deep decarbonization pathways for Switzerland: an economic evaluation

This article simulates deep decarbonization pathways for a small open economy that lacks the usual avenues for large CO₂ reductions – heavy industry and power generation. A computable general equilibrium model is used to assess the energy and economic impacts of the transition to only one ton of CO₂ emissions per capita in 2050. This represents a 76% reduction with respect to 1990 levels, while the population is expected to be 46% larger and GPD to increase by 90%. The article discusses several options and scenarios that are compatible with this emissions target and compares them with a reference scenario that extrapolates already-decided climate and energy policy instruments. We show that the ambitious target is attainable at moderate welfare costs, even if it needs very high carbon prices, and that these costs are lower when either CO₂ can be captured and sequestered or electricity consumption can be taxed sufficiently to stabilize it.

Policy relevance

In the context of COP 21, all countries must propose intended contributions that involve deep decarbonization of their economy over the next decades. This article defines and analyses such pathways for Switzerland, taking into consideration the existing energy demand and supply and also already-defined climate policies. It draws several scenarios that are compatible with a target of 1 ton of CO₂ emissions per capita in 2050. This objective is very challenging, especially with the nuclear phase out decided after the disaster in Fukushima and the political decision to balance electricity trade. Nevertheless, it is possible to design several feasible pathways that are based on different options. The economic cost is significant but affordable for the Swiss economy. The insights are relevant not only for Switzerland, but also for other industrialized countries when defining their INDCs.     

Effectiveness of pilot carbon emissions trading systems in China

China is in the process of establishing a national emissions trading system (ETS). Evaluating the implementation effectiveness of the seven pilot ETSs in China is critical for designing this national system. This study administered a questionnaire survey to assess the behaviour of enterprises covered by the seven ETS pilots from the perspective of: the strictness of compliance measures; rules for monitoring, reporting and verification (MRV); the mitigation pressure felt by enterprises; and actual mitigation and trading activities. The results show that the pilot MRV and compliance rules have not yet been fully implemented. The main factors involved are the lack of compulsory force of the regulations and the lack of policy awareness within the affected enterprises. Most enterprises have a shortage of free allowances and thus believe that the ETSs have increased their production costs. Most enterprises have already established mitigation targets. Some of the covered enterprises are aware of their own internal emission reduction costs and most of these have used this as an important reference in trading. Many enterprises have accounted for carbon prices in their long-term investment. The proportion of enterprises that have participated in trading is fairly high; however, reluctance to sell is quite pervasive in the market, and enterprises are mostly motivated to trade simply in order to achieve compliance. Few enterprises are willing to manage their allowances in a market-oriented manner. Different free allowance allocation methods directly affect the pathways enterprises take to control emissions.

Key policy insights

• In the national ETS, the compulsory force of ETS provisions should be strengthened.

• A reasonable level of free allowance shortage should be ensured to promote emission reduction by enterprises.

• Sufficient information should be provided to guide enterprises in their allowance management to activate the market.

• To promote the implementation of mitigation technologies by enterprises, actual output-based allocation methods should be used.

• The government should use market adjustment mechanisms, such as a price floor and ceiling, to ensure that carbon prices are reasonable and stable, so as to guide long-term low carbon investment.

     

中国森林乔木林碳储量及其固碳潜力预测

加强对我国森林碳储量和固碳潜力的研究,是制定中国增汇减排政策的重要依据,对我国国际气候谈判和全面了解森林碳汇潜力具有重要作用。利用我国第七次和第八次森林资源清查中各优势树种的面积和蓄积量数据,采用IPCC材积源生物量法（volume-biomass method),估算了我国森林（乔木林）碳储量和碳密度及其分布,分析我国不同省份天然乔木林和人工乔木林碳储量龄组结构特征;建立分区域、分起源主要优势树种的单位面积蓄积-林龄Logistic生长方程,结合我国森林2020年和2030年面积蓄积增长目标,预测我国乔木林2010—2050年间碳汇潜力。结果表明：第八次清查期间中国乔木林总碳储量为6135.68 Tg,碳密度为37.28 Mg/hm ²;天然乔木林和人工乔木林的碳储量分别为5246.07 Tg和889.61 Tg,分别占总碳储量的85.50%和14.50%。到2050年,中国乔木林和新造林的总碳储量和平均碳密度将分别达到11125.76 Tg和52.52 Mg/hm ²,与2010年相比分别增加81%和41%。分析结果表明中国乔木林有很大的碳汇潜力,将在应对和减缓全球气候变化中发挥重要作用。