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The African continent is facing one of the driest periods in the past three decades as well as continued deforestation. These disturbances threaten vegetation carbon (C) stocks and highlight the need for improved capabilities of monitoring large-scale aboveground carbon stock dynamics. Here we use a satellite dataset based on vegetation optical depth derived from low-frequency passive microwaves (L-VOD) to quantify annual aboveground biomass-carbon changes in sub-Saharan Africa between 2010 and 2016. L-VOD is shown not to saturate over densely vegetated areas. The overall net change in drylands (53% of the land area) was -0.05 petagrams of C per year (Pg C yr-1) associated with drying trends, and a net change of -0.02 Pg C yr-1 was observed in humid areas. These trends reflect a high inter-annual variability with a very dry year in 2015 (net change, -0.69 Pg C) with about half of the gross losses occurring in drylands. This study demonstrates, first, the applicability of L-VOD to monitor the dynamics of carbon loss and gain due to weather variations, and second, the importance of the highly dynamic and vulnerable carbon pool of dryland savannahs for the global carbon balance, despite the relatively low carbon stock per unit area.

This paper focuses on the potential use of insurance as a climate change adaptation mechanism in agriculture. We analyse the attractiveness of a climate risk insurance scheme and the choices farmers face between adaptation via farm management practices and purchase of crop insurance in the market. A choice experiment is used to reveal Danish farmers preferences regarding an insurance contract where adoption of land management practices to improve soil sustainability is conditional for obtaining insurance cover in the market. Results indicate that in general arable farmers and farmers with low soil quality who have experienced crop damages in the past are more likely to purchase such conditional insurance. Farmers with good quality soils, who perceive that they have already adapted their practices to climatic risks and who have not experienced losses due to adverse climatic events in the past are less willing to purchase insurance. The paper contributes to the limited knowledge on preferences for climate risk related insurance in agricultural systems in general, and in Europe in particular. © 2019 The paper was prepared under EU Framework 7 project “Ecological Function and Biodiversity Indicators in European soils” (ECOFINDERS grant no. 264465 ). Furthermore, the paper has benefited from support from the PREAR project (No 652615) granted under the FACCE SURPLUS ERA-NET Cofund and funded by the Danish Innovation Fund .

The oleaginous alga Chlorella protothecoides accumulates lipid in its biomass when grown in nitrogen-restricted conditions. To assess the relationship between nitrogen provision and lipid accumulation and to determine the contribution of photosynthesis in mixotrophic growth, C. protothecoides was grown in mixo- and heterotrophic nitrogen-limited continuous flow cultures. Lipid content increased with decreasing C/N, while biomass yield on glucose was not affected. Continuous production of high lipid levels (57% of biomass) was possible at high C/N (87-94). However, the lipid production rate (2.48 g L(-1) d(-1)) was higher at D=0.84 d(-1) with C/N 37 than at D=0.44 d(-1) and C/N 87 even though the lipid content of the biomass was lower (38%). Photosynthesis contributed to biomass and lipid production in mixotrophic conditions, resulting in 13-38% reduction in CO2 production compared with heterotrophic cultures, demonstrating that photo- and heterotrophic growth occurred simultaneously in the same population.

International climate negotiations have stressed the importance of considering emissions from forest degradation under the planned REDD+ (Reducing Emissions from Deforestation and forest Degradation + enhancing forest carbon stocks) mechanism. However, most research, pilot-REDD+ projects and carbon certification agencies have focused on deforestation and there appears to be a gap in knowledge on complex mosaic landscapes containing degraded forests, smallholder agriculture, agroforestry and plantations. In this paper we therefore review current research on how avoided forest degradation may affect emissions of greenhouse gases (GHG) and expected co-benefits in terms of biodiversity and livelihoods. There are still high uncertainties in measuring and monitoring emissions of carbon and other GHG from mosaic landscapes with forest degradation since most research has focused on binary analyses of forest vs. deforested land. Studies on the impacts of forest degradation on biodiversity contain mixed results and there is little empirical evidence on the influence of REDD+ on local livelihoods and tenure security, partly due to the lack of actual payment schemes. Governance structures are also more complex in landscapes with degraded forests as there are often multiple owners and types of rights to land and trees. Recent technological advances in remote sensing have improved estimation of carbon stock changes but establishment of historic reference levels is still challenged by the availability of sensor systems and ground measurements during the reference period. The inclusion of forest degradation in REDD+ calls for a range of new research efforts to enhance our knowledge of how to assess the impacts of avoided forest degradation. A first step will be to ensure that complex mosaic landscapes can be recognised under REDD+ on their own merits.

Abstract This study evaluates the potential to produce phosphorus (P)-rich fertilizer substrates with high plant availability as well as carbon (C)-rich biochar with soil enhancement properties in a single slow-pyrolysis plant. Campaign-based production or co-production of soil enhancers and fertilizer substrates may increase the potential societal value of slow pyrolysis plants. The assessment focus on conventional slow pyrolysis operated at 600 °C to produce biochar from various substrates as well as two options for post-process char treatments—char oxidation at 550 °C and char steam gasification at 800 °C, as a potential way to improve substrate fertilizer value. Four P-rich biomass residues including municipal sewage sludge (SS), biogas fiber (BF), cattle manure (CM), and poultry manure (PM) as well as two C-rich biomasses: wood chips (WC) and wheat straw (WS), were tested. Production yields of biochar and ash from char oxidation and steam gasification were compared and the materials were characterized to be used as soil enhancers and P-fertilizers through direct analysis and soil incubation studies with two different agricultural soils. All thermal treatments increased the concentration of the plant nutrients P, potassium and magnesium in the resulting biochar and ashes compared to the dry biomass. At the same time, concentrations of nitrogen and sulfur were reduced. The dry biomasses generally increased the amount of available P in the soils to a greater extent than biochar or ashes at an application rate of 80 mg P/kg soil. The P-rich biochar and ash made from BF, CM and PM had higher P fertilizer values than those made from SS. In terms of thermal processes, pyrolysis with subsequent char steam gasification was found to be the best option for high P availability in both soils, except for operation on SS where the oxidized char gave the best results. The C-rich biochars made from wood and wheat straw both showed potential for improving soil properties including soil organic matter (SOM) content, cation exchange capacity (CEC) and water holding capacity (WHC). The study shows that campaign operation of slow pyrolysis with the option for char steam gasification is a viable option for producing fertilizer substrates with high levels of plant available P as well as biochar with substantial soil enhancing properties on a single plant. In addition, results also indicate that direct co-pyrolysis of P-rich substrates—especially BF and CM, with any of the two tested C-rich substrates—without subsequent char treatment may be a sufficiently well integrated option for combined soil fertility and soil P fertilization management. Graphic Abstract