Asset-Based Adaptation Project Promotes Tree and Shrub Diversity and Above-Ground Carbon Stocks in Smallholder Agroforestry Systems in Western Kenya

Agroforestry has potential to address the adverse effects of climate change through carbon sequestration, increasing biodiversity and improving adaptive capacity and resilience among smallholder farmers. However, this potential is context specific and insufficiently quantified in smallholder faming systems, partly because of inherent variability of smallholder farms. Our study aimed to determine the tree/shrub diversity and carbon stocks in different agroforestry systems within smallholder farms in two 100 km2 sites, the so-called lower and middle Nyando sites, in western Kenya. In both, context-specific agroforestry adoption had been promoted among households of four community associations through an asset-based community development (ABCD) approach. Their farms were assessed and compared with those of relevant comparison samples. Trees and shrubs were inventoried on a total of 106 farms, and their formations classified in five major agroforestry practices: hedgerows, multipurpose trees on farm (MPT), riparian buffers, woodlots, and boundary planting. To assess above-ground biomass (AGB) of individual trees/shrubs, diameter at breast height measurements were taken. Strong regional differences were considered in data analysis and presentation. Altogether, 3,353 and 6,346 trees/shrubs were inventoried in the lower and middle Nyando sites, respectively. AGB was significantly higher in middle than in lower Nyando. Woodlots had the highest amount of AGB carbon stock, while MPT had the highest diversity of tree/shrub species in all the groups. Conversely, boundary planting had the highest number of trees/shrubs inventoried and hence was the most common agroforestry practice across all the samples in both regions. Dominant AGB contributor species were Grevillea robusta (37.8%) in middle, and Eurphobia tirucalli (16.5%) in lower Nyando. This study provides empirical evidence that asset-based and community-driven selection and implementation of both tree/shrub species and agroforestry practices can contribute positively to species and practice diversity, which are associated with AGB carbon stock levels and wider agro-ecosystem diversity. This study hence provides benchmark information that is relevant for SDG goal 15 on “life on land,” and various specific targets, and can inform sustainable establishment of carbon sink facilities by supporting smallholders to uptake contextually suitable and economically sensible agroforestry practices in an overall effort to foster and support sustainable development.

Microbial Mediation of Carbon, Nitrogen and Sulfur Cycles During Solid Waste Decomposition

Landfills is a unique “terrestrial ecosystem” and serves as a significant carbon sink. Microorganism convert biodegradable substances in municipal solid waste (MSW) to CH4, CO2 and microbial biomass, consisting of the carbon cycling in landfills. Meanwhile, microbial mediated N and S cycles affect carbon cycling. How microbial community structure and function respond to C, N, and S cycling during solid waste decomposition, however are not well characterized. Here we show the response of bacterial and archaeal community structure and functions to C, N, and S cycling during solid waste decomposition in a long-term (265 days) operation laboratory-scale bioreactor through 16S rRNA based pyrosequencing and metagenomics analysis. Bacterial and archaeal community composition varied during solid waste decomposition. Aerobic respiration was the main pathway for CO2 emission, while anaerobic C fixation was the main pathway in carbon fixation. Methanogenesis and denitrification increased during solid waste decomposition, suggesting increasing CH4 and N2O emission. In contract, fermentation decreased along solid waste decomposition. Interestingly, Clostridiales were abundant and showed potential for several pathways in C, N, and S cycling. Archaea were involved in many pathways of C and N cycles. There is a shift between bacteria and archaea involvement in N2 fixation along solid waste decomposition that bacteria Clostridiales and Bacteroidales were initial dominant and then Methanosarcinales increased and became dominant in methanogenic phase. These results provide extensive microbial mediation of C, N, and S cycling profiles during solid waste decomposition.

A review of exotic earthworm observations in the Canadian boreal forest and taiga zones

In the last decades, concerns have emerged that boreal forests could convert from a carbon sink to a carbon source, thus accentuating climate change. Although forest fire is generally mentioned as the main factor that could cause the boreal forest to transition to a carbon source, other factors, such as exotic earthworm activity, could also play an important role. Invasive exotic earthworms can also affect nutrient cycling, biodiversity and forest dynamics. In this context, a better knowledge of the distribution of exotic earthworms can help understand the likely changes in the ecosystems that they have colonized. Here we report the results of an exhaustive literature review of the presence of exotic earthworms in the Canadian boreal forest and taiga zones. We identified 230 sectors containing 14 earthworm species (11 exotic, 2 native and 1 putative native) in 6 provinces and 3 territories across Canada’s boreal forest and taiga zone. We also report 23 as-yet unpublished observations from the province of Quebec. We note the presence of earthworms in environments (acid soils, harsh climate) that were historically considered inadequate for their survival. This suggests that the portion of Canada’s boreal forests suitable for their presence or colonization is larger than what was previously believed. This study represents the first compilation of exotic earthworm presence in this large northern area. Factors that could affect their distribution and potential effects on boreal ecosystems are also discussed. Globally, several earthworm species seem to be overcoming the previously assumed limitation by temperature and pH.

Opportunities and risks of the climate policy in Russia

The climate agenda involves significant economic dimension and component. This is precipitated, on the one hand, by the climate change impact on the economy and its implications for economic development that necessitate costs for planning and implementing adaptation measures, and, on the other hand, by the imperatives of structural and technological modernization of the economy to strengthen its competitiveness and sustainability of socio-economic development including reduction of industrial greenhouse gases (GHG) emissions and increasing the ecosystems’ carbon sink capacity. The above implies harmonization of ecological, climatic, socio-economic, and technological characteristics to produce an effective national low GHG emissions socio-economic development strategy required by the Paris Climate Agreement. This in turn calls for comprehensive assessment of the impact produced by new low-carbon technologies on economic dynamics using the framework of macrostructural calculations and scenarios of economic development of Russia with different volumes of funding invested in decarbonization. It is argued that the most efficient is a group of so-called moderate scenarios that provide for both GHG reduction and economic growth rates above the global average. More ambitious scenarios involve risks of slowing GDP growth given weighty additional investment which constrains the dynamics of household consumption. The key role of the Russian ecosystems capacity to absorb and sequester carbon in implementation of the low GHG emissions socio-economic development strategy is substantiated and the imperative for the complex of measures to improve the efficiency of land use and forestry resources (LULUCF), primarily the quality of R&D and the national monitoring system development, is emphasized.

Venus’ light slab hinders its development of planetary-scale subduction and habitability

Terrestrial planets Venus and Earth have similar sizes, masses, and bulk compositions, but only Earth developed planetary-scale plate tectonics. Plate tectonics generates weatherable fresh rocks and transfers surface carbon back to Earth’s interior, which provides a long-term climate feedback, serving as a thermostat to keep Earth a habitable planet. Yet Venus shares a few common features with early Earth, such as stagnant-lid tectonics and the possible early development of a liquid ocean. Given all these similarities with early Earth, why would Venus fail to develop global-scale plate tectonics? In this study, we explore solutions to this problem by examining Venus’ slab densities under hypothesized subduction-zone conditions. Our petrologic simulations show that eclogite facies may be reached at greater depths on Venus than on Earth, and Venus’ slab densities are consistently lower than Earth’s. We suggest that the lack of sufficient density contrast between the high-pressure metamorphosed slab and mantle rocks may have impeded self-sustaining subduction. Although plume-induced crustal downwelling exists on Venus, the dipping of Venus’ crustal rocks to mantle depth fails to transition into subduction tectonics. As a consequence, the supply of fresh silicate rocks to the surface has been limited. This missing carbon sink eventually diverged the evolution of Venus’ surface environment from that of Earth.

An Empirical Study on the Growth of Agricultural Green Total Factor Productivity in the Huanghuai River Economic Zone by Big Data Computing

Facing the new form and situation of the Huaihe Economic Zone, it is of great significance to analyze the sources of growth and the intrinsic mechanism of the green total factor productivity of its economic-ecological system, to grasp the spatial and temporal characteristics of green total factor productivity, and to study the influence of each factor on green total factor productivity to achieve sustainable economic development in the Huaihe Economic Zone. Based on the clarification of economic growth theory, green economy theory, carbon cycle theory, and green total factor productivity theory, this paper identifies and discusses the limitation that the existing research literature often ignores the endogenous role of carbon sinks when measuring green total factor productivity. Then, the green total factor productivity of Huaihe Economic Zone based on carbon cycle from 2004 to 2017 is measured using the superefficient nonradial SBM model. Combined with the GML productivity index, it is decomposed into technical progress and technical efficiency and analyzed in comparison with the green total factor productivity without considering ecological purification capacity (carbon sink) from the perspective of time and space. Finally, the spatial Durbin model is used to analyze the effects of seven variables, including the level of economic development, environmental regulation, R&D level, and openness to the outside world, on green total factor productivity in the Huaihe Economic Zone, and to analyze the direct and indirect effects of each variable on green total factor productivity. TFP based on expected output carbon sink and GDP overall outperforms TFP based on expected output GDP only, mainly because the growth of technical efficiency is underestimated when carbon sink is not considered. Technical efficiency and technological progress are equally important for the growth of TFP in an eco-economic perspective. It is of great practical significance for both the comprehensive understanding of the green total factor productivity level and the improvement path of the ecosystem and the coordinated and sustainable development of the Huaihe Economic Zone.