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2022-08-02Zeitschriftenartikel
Dealing with the COVID-19 pandemic: an opportunity to reflect on sustainability research
(Integrative Forschungsinstitute) Nölting, Benjamin; König, Bettina; Zimmermann, Anne B.; Di Giulio, Antonietta; Schäfer, Martina; Schneider, Flurina
The COVID-19 pandemic has jolted societies out of normality, possibly creating new conditions for sustainability transformations. What does this mean for sustainability research? Because of the scope of the crisis, researchers have been heavily involved: not only have they had to speed up the pace of scientific production to provide urgently needed COVID-19 knowledge, but they have also been affected citizens. For sustainability science, this calls for an experience-based reflection on the positionality and orientation of research aiming to support sustainability transformations. Twenty sustainability researchers discussed their sustainability research on COVID-19 in three workshops based on the following questions: How does the pandemic—and the measures taken to deal with it—affect sustainable development? What can we learn from the pandemic from the perspective of societal transformation? The present discussion paper emerged from this multidisciplinary exchange among sustainability researchers, considering five topics: impacts of the COVID-19 crisis on sustainability transformations; learning for sustainability transformations; the role of solidarity; governance and political steering; and the role of science in society. Our discussions led to a meta-level reflection on what sustainability research can learn from research on COVID-19 regarding topics and disciplinary angles, time dimensions, the role of researchers, and how adequate preparation for both crises and long-term transformations requires interdisciplinary interaction.
2022-11-30Zeitschriftenartikel
Graphene-on-gold surface plasmon resonance sensors resilient to high-temperature annealing
(Mathematisch-Naturwissenschaftliche Fakultät) Jungnickel, Robert; Mirabella, Francesca; Stockmann, Jörg Manfred; Radnik, Joerg; Balasubramanian, Kannan
Gold films coated with a graphene sheet are being widely used as sensors for the detection of label-free binding interactions using surface plasmon resonance (SPR). During the preparation of such sensors, it is often essential to subject the sensor chips to a high-temperature treatment in order to ensure a clean graphene surface. However, sensor chips used currently, which often use chromium as an adhesion promoter, cannot be subjected to temperatures above 250 °C, because under such conditions, chromium is found to reorganize and diffuse to the surface, where it is easily oxidized, impairing the quality of SPR spectra. Here we present an optimized preparation strategy involving a three-cycle tempering coupled with chromium (oxide) etching, which allows the graphene-coated SPR chips to be annealed up to 500 °C with little deterioration of the surface morphology. In addition, the treatment delivers a surface that shows a clear enhancement in spectral response together with a good refractive index sensitivity. We demonstrate the applicability of our sensors by studying the kinetics of avidin–biotin binding at different pH repeatedly on the same chip. The possibility to anneal can be exploited to recover the original surface after sensing trials, which allowed us to reuse the sensor for at least six cycles of biomolecule adsorption.
2022-09-02Zeitschriftenartikel
Discussion on: “Programmable money: next generation blockchain-based conditional payments” by Ingo Weber and Mark Staples
(Wirtschaftswissenschaftliche Fakultät) Burda, Michael
My comment on Weber and Staples (Digit Financ, https://doi.org/10.1007/s42521-022-00064-8 [Titel anhand dieser DOI in Citavi-Projekt übernehmen] , 2022) elaborates an economic perspective of their “programmable money” proposal. While claims issued and tendered for goods and services resemble money, a number of issues must be resolved before this innovation is feasible as money in analog trade or digital finance. These include secondary tradability, permissioned access, standardization and transparency. Programmable money is an important step towards the implementation of contingent commodities in the sense of Arrow and Debreu (Econometrica, 22(3):265–290, 1954) and Debreu (1959).
2024Buch
El pensamiento literario
(Sprach- und literaturwissenschaftliche Fakultät) Kamecke, Gernot
2024Buch
Human Enhancements und Patentrecht
(Juristische Fakultät) Vetter, Sven
Ist das Patentrecht wirklich »wertneutral« oder gar »ethisch blind«? Die Praxis des Patentrechts wird von einem ungebrochenen Fortschrittsoptimismus getragen. Das hohe Maß an Technik- und Innovationsgläubigkeit lässt traditionell wenig Raum für eine tiefergehende Reflexion außerrechtlicher Wirkdimensionen des Patentsystems. Es stellt sich jedoch die Frage, ob Innovationsförderung ohne ein Mindestmaß an gesellschaftlicher Innovationsverantwortung überhaupt ein sinnvolles Ziel sein kann. Ein so facettenreiches Forschungsthema wie »Human Enhancements« eignet sich hervorragend dazu, um die Funktionen und Wirkungen des Patentschutzes zu veranschaulichen. An die Stelle eines allgemeinen Verweises auf »ethisch umstrittene Forschungsfelder« treten konkrete Beispiele. Die gewonnenen Erkenntnisse können wiederum in den interdisziplinären Gesamtdiskurs einfließen, der die biotechnische Selbstgestaltung des Menschen als Teil und Folge der modernen Gesellschaft und ihrer Charakteristika betrachtet. Die Arbeit wurde mit dem Innovationspreis 2023 der Humboldt-Universität zu Berlin und als beste Dissertation im Zivilrecht mit dem Promotionspreis 2023 der Juristischen Fakultät der Humboldt-Universität zu Berlin ausgezeichnet.
2017-10-04Zeitschriftenartikel
High resolution remote sensing for reducing uncertainties in urban forest carbon offset life cycle assessments
(Mathematisch-Naturwissenschaftliche Fakultät) Tigges, Jan; Lakes, Tobia
Background Urban forests reduce greenhouse gas emissions by storing and sequestering considerable amounts of carbon. However, few studies have considered the local scale of urban forests to effectively evaluate their potential long-term carbon offset. The lack of precise, consistent and up-to-date forest details is challenging for long-term prognoses. Therefore, this review aims to identify uncertainties in urban forest carbon offset assessment and discuss the extent to which such uncertainties can be reduced by recent progress in high resolution remote sensing. We do this by performing an extensive literature review and a case study combining remote sensing and life cycle assessment of urban forest carbon offset in Berlin, Germany. Main text Recent progress in high resolution remote sensing and methods is adequate for delivering more precise details on the urban tree canopy, individual tree metrics, species, and age structures compared to conventional land use/cover class approaches. These area-wide consistent details can update life cycle inventories for more precise future prognoses. Additional improvements in classification accuracy can be achieved by a higher number of features derived from remote sensing data of increasing resolution, but first studies on this subject indicated that a smart selection of features already provides sufficient data that avoids redundancies and enables more efficient data processing. Our case study from Berlin could use remotely sensed individual tree species as consistent inventory of a life cycle assessment. However, a lack of growth, mortality and planting data forced us to make assumptions, therefore creating uncertainty in the long-term prognoses. Regarding temporal changes and reliable long-term estimates, more attention is required to detect changes of gradual growth, pruning and abrupt changes in tree planting and mortality. As such, precise long-term urban ecological monitoring using high resolution remote sensing should be intensified, especially due to increasing climate change effects. This is important for calibrating and validating recent prognoses of urban forest carbon offset, which have so far scarcely addressed longer timeframes. Additionally, higher resolution remote sensing of urban forest carbon estimates can improve upscaling approaches, which should be extended to reach a more precise global estimate for the first time. Conclusions Urban forest carbon offset can be made more relevant by making more standardized assessments available for science and professional practitioners, and the increasing availability of high resolution remote sensing data and the progress in data processing allows for precisely that.
2015-06-01Zeitschriftenartikel
Effects of ankle–foot braces on medial gastrocnemius morphometrics and gait in children with cerebral palsy
(Kultur-, Sozial- und Bildungswissenschaftliche Fakultät) Hösl, Matthias; Böhm, Harald; Arampatzis, Adamantios; Döderlein, Leonhard
Purpose In children with cerebral palsy (CP), braces are used to counteract progressive joint and muscle contracture and improve function. We examined the effects of positional ankle–foot braces on contracture of the medial gastrocnemius (MG) and gait in children with CP while referencing to typically developing children. Methods Seventeen independently ambulant children with CP and calf muscle contracture (age 10.4 ± 3.0y) and 17 untreated typically developing peers (age 9.5 ± 2.6y) participated. Children with CP were analysed before and 16 ± 4 weeks after ankle–foot bracing. MG muscle belly length and thickness, tendon and fascicle length, as well as their extensibility were captured by 2D ultrasound and 3D motion capturing during passive, manually applied stretches. In addition, 3D gait analysis was conducted. Results Prior to bracing, the MG muscle–tendon unit in children with CP was 22 % less extensible. At matched amounts of muscle–tendon unit stretch, the muscle belly and fascicles in CP were 7 % and 14 % shorter while the tendon was 11 % longer. Spastic fascicles displayed 32 % less extensibility than controls. Brace wear increased passive dorsiflexion primarily with the knees flexed. During gait, children walked faster and foot lift in swing improved. MG muscle belly and tendon length showed little change, but fascicles further shortened (−11 %) and muscle thickness (−8 %) decreased. Conclusions Use of ankle–foot braces improves function but may lead to a loss of sarcomeres in series, which could explain the shortened fascicles. To potentially induce gastrocnemius muscle growth, braces may also need to extend the knee or complementary training may be necessary to offset the immobilizing effects of braces.
2016-04-29Zeitschriftenartikel
Small-scale variability of particulate matter and perception of air quality in an inner-city recreational area in Aachen, Germany
(Mathematisch-Naturwissenschaftliche Fakultät) Paas, Bastian; Schmidt, Teresa; Markova, Stanimira; Maras, Isabell; Ziefle, Martina; Schneider, Christoph
Spatial micro-scale variability of particle mass concentrations is an important criterion for urban air quality assessment. In this study we present results from detailed spatio-temporal measurements in the urban roughness layer along with a survey to determine perceptions of citizens regarding air quality in an inner city park in Aachen, Germany. Particles were sampled with two different approaches in February, May, July and September 2014 using an optical particle counter at six fixed measurement locations, representing different degrees of outdoor particle exposure that can be experienced by a pedestrian walking in an intra-urban recreational area. A simulation of aerosol emissions induced by road traffic was conducted using the German reference dispersion model Austal2000. The mobile measurements revealed unexpected details in the distribution of urban particles with highest mean concentrations of PM(1;10) inside the green area 100 m away from bus routes (arithmetic mean: 22.5 μg m−3 and 18.9 μg m−3; geometric mean: 9.3 μg m−3 and 6.5 μg m−3), whereas measurement sites in close proximity to traffic lines showed far lower mean values (arithmetic mean: 7.5 μg m−3 and 8.7 μg m−3; geometric mean: 5.8 μg m−3 and 6.5 μg m−3). Concerning simulation results, motor traffic is still proved to be an important aerosol source in the area, although the corresponding concentrations declined rapidly as the distances to the line sources increased. Further analysis leads to the assumption that particularly coarse particles were emitted through diffuse sources e.g. on the ability of surfaces to release particles by resuspension which were dominantly apparent in measured PM(1;10) and PM(0.25;10) data. The contribution of diffuse particle sources and urban background transport to local PM(0.25;10) concentrations inside the green area were quantified to be up to 17.9 μg m−3. The analysis of perception related experiments demonstrate that particle concentrations in form of PM(0.25;10) were inconsistent with park user opinions regarding perception of air quality. At least in investigated concentration magnitudes there proved to be no connection between user assessment and physical values at all.
2017-09-19Zeitschriftenartikel
Uncertainties in demonstrating environmental benefits of payments for ecosystem services
(Mathematisch-Naturwissenschaftliche Fakultät) Lima, Letícia Santos de; Krueger, Tobias; García-Marquez, Jaime
Payments for Ecosystem Services (PES) have become the flagship of conservation organizations in recent years. However, PES schemes are as much criticized as they are acclaimed in the literature. Researchers have pointed that many PES schemes, particularly water-related ones, are based on unreliable assumptions and lack strong causal links between land use and ecosystem services. Evidence of outcomes is hardly demonstrated. This uncertainty in PES schemes arises not only from practical difficulties, but from the complexity of the human-environment systems (HES), and the limits of current knowledge about HES. Many scientists and practitioners have proposed that more research is needed to improve the scientific basis of PES. Here we argue that this research should be complemented with a deeper understanding of the uncertainties involved in PES, an explicit treatment of these in the whole process of PES negotiation, design and monitoring, and clear uncertainty communication among the actors involved. Neglecting uncertainties could lead to unfounded expectations and poor assessments of PES outcomes. If recognizing and accounting for uncertainties are to threaten the success of PES, then uncertainty can be seen as an opportunity to open up the dialogue to alternative ways of achieving the desired conservation goals.
2017-09-28Zeitschriftenartikel
Decoupled systems on trial: Eliminating bottlenecks to improve aquaponic processes
(Lebenswissenschaftliche Fakultät) Monsees, Hendrik; Kloas, Werner; Wuertz, Sven
In classical aquaponics (coupled aquaponic systems, 1-loop systems) the production of fish in recirculating aquaculture systems (RAS) and plants in hydroponics are combined in a single loop, entailing systemic compromises on the optimal production parameters (e.g. pH). Recently presented decoupled aquaponics (2-loop systems) have been awarded for eliminating major bottlenecks. In a pilot study, production in an innovative decoupled aquaponic system was compared with a coupled system and, as a control, a conventional RAS, assessing growth parameters of fish (FCR, SGR) and plants over an experimental period of 5 months. Soluble nutrients (NO3--N, NO2--N, NH4+-N, PO43-, K+, Ca2+, Mg2+, SO42-, Cl2- and Fe2+), elemental composition of plants, fish and sludge (N, P, K, Ca, Mg, Na, C), abiotic factors (temperature, pH, oxygen, and conductivity), fertilizer and water consumption were determined. Fruit yield was 36% higher in decoupled aquaponics and pH and fertilizer management was more effective, whereas fish production was comparable in both systems. The results of this pilot study clearly illustrate the main advantages of decoupled, two-loop aquaponics and demonstrate how bottlenecks commonly encountered in coupled aquaponics can be managed to promote application in aquaculture.
2017-01-18Zeitschriftenartikel
Potential of aquacultural sludge treatment for aquaponics: evaluation of nutrient mobilization under aerobic and anaerobic conditions
(Lebenswissenschaftliche Fakultät) Monsees, Hendrik; Keitel, Jonas; Paul, Maurice; Kloas, Werner; Wuertz, Sven
In recirculating aquaculture systems (RAS), mechanical removal of suspended solids by clarifiers or drum filters provides an organic mixture rich in nutrients. Still, in most traditional RAS, this sludge is discharged directly or following dewatering. Here, the potential recycling of nutrients from sludge is assessed, comparing aerobic and anaerobic mobilization of nutrients experimentally, ultimately aiming at an application in aquaponic systems. Nutrient mobilization processes were studied, monitoring soluble nutrients photometrically in the treatment tanks (NO3--N, NO2--N, total ammonia nitrogen, soluble reactive phosphorus [SRP], K+, Mg2+ and Fe2+), the nutrient composition of the sludge (total phosphorus, Fe, Mn, Al, S, Mg, Ca) by inductively coupled plasma optical emission spectrometry, as well as C:N ratio, total solids (TS) and total suspended solids (TSS). Aerobic treatment (aerated, AT) resulted in a 3.2-fold increase in mean (±SD) SRP from 9.4 (± 0.7) to 29.7 (± 2.1) mg l-1, most likely owing to a decrease in pH. In contrast, in the anaerobic treatment (unaerated, UT), SRP remained unchanged between 9.4 (± 0.7) and 9.3 (± 0.4) mg l-1. Both treatments resulted in increased K+ concentrations from 28.1 (± 1.5) to 36.8 (± 2.3) mg l-1 in AT and to 32.2 (± 2.3) mg l-1 in UT. AT revealed best mobilization of P and K+ without major losses of NO3--N. Thus, aerobic treatment of water-sludge mixture has a high potential for significant improvements of nutrient recycling in aquaponics.
2018-01-12Zeitschriftenartikel
Cognitive control moderates parenting stress effects on children's diurnal cortisol
(Lebenswissenschaftliche Fakultät) Raffington, Laurel; Schmiedek, Florian; Heim, Christine; Shing, Yee Lee
This study investigated associations between parenting stress in parents and self-reported stress in children with children's diurnal cortisol secretion and whether these associations are moderated by known stress-regulating capacities, namely child cognitive control. Salivary cortisol concentrations were assessed from awakening to evening on two weekend days from 53 6-to-7-year-old children. Children completed a cognitive control task and a self-report stress questionnaire with an experimenter, while parents completed a parenting stress inventory. Hierarchical, linear mixed effects models revealed that higher parenting stress was associated with overall reduced cortisol secretion in children, and this effect was moderated by cognitive control. Specifically, parenting stress was associated with reduced diurnal cortisol levels in children with lower cognitive control ability and not in children with higher cognitive control ability. There were no effects of self-reported stress in children on their cortisol secretion, presumably because 6-to-7-year-old children cannot yet self-report on stress experiences. Our results suggest that higher cognitive control skills may buffer the effects of parenting stress in parents on their children’s stress regulation in middle childhood. This could indicate that training cognitive control skills in early life could be a target to prevent stress-related disorders.
2018-01-09Zeitschriftenartikel
The Biosphere Under Potential Paris Outcomes
(Mathematisch-Naturwissenschaftliche Fakultät) Ostberg, Sebastian; Boysen, Lena; Schaphoff, Sibyll; Lucht, Wolfgang; Gerten, Dieter
Rapid economic and population growth over the last centuries have started to push the Earth out of its Holocene state into the Anthropocene. In this new era, ecosystems across the globe face mounting dual pressure from human land use change (LUC) and climate change (CC). With the Paris Agreement, the international community has committed to holding global warming below 2°C above preindustrial levels, yet current pledges by countries to reduce greenhouse gas emissions appear insufficient to achieve that goal. At the same time, the sustainable development goals strive to reduce inequalities between countries and provide sufficient food, feed, and clean energy to a growing world population likely to reach more than 9 billion by 2050. Here, we present a macro-scale analysis of the projected impacts of both CC and LUC on the terrestrial biosphere over the 21st century using the Representative Concentration Pathways (RCPs) to illustrate possible trajectories following the Paris Agreement. We find that CC may cause major impacts in landscapes covering between 16% and 65% of the global ice-free land surface by the end of the century, depending on the success or failure of achieving the Paris goal. Accounting for LUC impacts in addition, this number increases to 38%–80%. Thus, CC will likely replace LUC as the major driver of ecosystem change unless global warming can be limited to well below 2°C. We also find a substantial risk that impacts of agricultural expansion may offset some of the benefits of ambitious climate protection for ecosystems.
2017-11-16Zeitschriftenartikel
Mesocosm experiments identifying hotspots of groundwater upwelling in a water column by fibre optic distributed temperature sensing
(Mathematisch-Naturwissenschaftliche Fakultät) Marruedo Arricibita, Amaya Irene; Krause, Stefan; Gomez-Velez, Jesus; Hannah, David M.; Lewandowski, Jörg
Lacustrine groundwater discharge (LGD) can substantially impact ecosystem characteristics and functions. Fibre optic distributed temperature sensing (FO-DTS) has been successfully used to locate groundwater discharge into lakes and rivers at the sediment–water interface, but locating groundwater discharge would be easier if it could be detected from the more accessible water surface. So far, it is not clear if how and under which conditions the LGD signal propagates through the water column to the water surface–atmosphere interface, and what perturbations and signal losses occur along this pathway. In the present study, LGD was simulated in a mesocosm experiment. Under winter conditions, water with temperatures of 14 to 16 °C was discharged at the bottom of a 10 × 2.8-m mesocosm. Water within this mesocosm ranged from 4.0 to 7.4 °C. Four layers (20, 40, 60, and 80 cm above the sediment) of the 82 cm deep mesocosm were equipped with FO-DTS for tracing thermal patterns in the mesocosm. Aims are (a) to test whether the positive buoyancy of relatively warm groundwater imported by LGD into shallow water bodies allows detection of LGD at the lake's water surface–atmosphere interface by FO-DTS, (b) to analyse the propagation of the temperature signal from the sediment-water interface through the water column, and (c) to learn more about detectability of the signal under different discharge rates and weather conditions. The experiments supported the benchmarking of scale dependencies and robustness of FO-DTS applications for measuring upwelling into aquatic environments and revealed that weather conditions can have important impacts on the detection of upwelling at water surface–atmosphere interfaces at larger scales.
2017-03-16Zeitschriftenartikel
Encountering a bait is necessary but insufficient to explain individual variability in vulnerability to angling in two freshwater benthivorous fish in the wild
(Lebenswissenschaftliche Fakultät) Monk, Christopher Thomas; Arlinghaus, Robert
Fish personality traits, such as swimming activity, or personality related emergent behavioural properties, such as the degree of space use shown by an individual fish, should affect encounter rates between individual fish and fishing gear. Increased encounters should in turn drive vulnerability to capture by passively operated gears. However, empirical evidence documenting a relationship between activity-based behaviours and vulnerability to capture by passive fishing gear in the wild is limited. Using whole-lake acoustic telemetry, we first documented significant repeatabilities over several months in a suite of encounter rate-associated behaviours (swimming distance, activity space size, time on baited feeding sites, switching frequency among baited feeding sites, distance to the lake bottom) in two recreationally important benthivorous cyprinid species, the common carp (Cyprinus carpio) and tench (Tinca tinca). We then experimentally targeted both species using stationary angling on baited feeding sites. Individual fish regularly visited the angling sites, documenting that the fishes encountered the angling baits. When attempting to explain individual variation in vulnerability as a function of repeatable behavioural traits, we found no evidence of a significant relationship among various encounter-based behaviours and vulnerability to angling for both species. There was also no evidence for size selection or for energetically less conditioned fish to be more vulnerable. The data cumulatively suggest that fine-scale behaviours after encountering a bait (e.g., frequency of bait intake) may be ultimately decisive for determining vulnerability to angling in benthivorous fish. Based on our work, fishing-induced selection on encounter-based behaviours in recreational angling for benthivorous fish in the wild appears unlikely.
2024-09-24Zeitschriftenartikel
JLT-Gespräch: Die Praxis der Literaturtheorie
(Kultur-, Sozial- und Bildungswissenschaftliche Fakultät) Geulen, Eva; Martus, Steffen; Spoerhase, Carlos
JLT Talks offers a new format for discussing current topics in the field of literary theory. It was inspired by the focus of this special issue, which foregrounds the practice of literary theory. Although the amount of praxeological work has increased in recent years, there are only a few studies that deal specifically with literary theory. The participants in the discussion – Eva Geulen, Steffen Martus, and Carlos Spoerhase – explore the challenges facing a practical analysis of literary theory. They discuss what it might mean to move from the concept of theory to the concept of theorizing, and where the expected advantages and possible deficits of a praxeological approach and reconstruction of theorizing might lie. One focus is put on the questions of how theorizing can be conceptualized, which indicators are to be assumed, to what extent it differs from other practices in literary studies, and which forms and norms of theorizing should be analysed praxeologically. The discussion outlines a spectrum of theorizing practices, ranging from the establishment and implementation of ›grand theories‹ and the theoretical reflection of conceptual foundations to smaller-scale practices, such as abstraction and generalization. In addition, the analytical view of the activities and claims associated with ›theory‹ is distinguished from literary theorists’ self-reflection (self-understanding). Various features are discussed which indicate practices of theorizing, including abstracting, generalizing, explaining and disciplining scientific exchange. In addition, the discussants consider to what extent there are different ›degrees‹ of theorizing, and emphasize the need to distinguish between theory as a result and theory as an activity or process. As proposed, theorizing can be understood as an activity that shapes processes of literary research as a whole and is determined by the subject matter. It becomes clear that practices of theorizing should not be viewed in isolation, but rather in their interplay with other practices, especially practices of interpretation. Further questions that are addressed include the following: What do ›grand theories‹ with general explanatory claims such as deconstruction or systems theory achieve, and to what extent have they changed literary studies? How can theorizing be better conveyed in university teaching? The ›standard‹ approach – reading theoretical texts, deriving methodological consequences from them, and applying them to literary texts – is considered to be inadequate. Instead, in teaching, stronger emphasis should be put on theorizing as an intellectual and collaborative activity. This could be achieved by integrating practices of trial and error into the teaching of theory. The advantage of a theoretical orientation, in the sense of abstraction as well as the generalization of problems and statements, is undisputed, especially with regard to communication and exchange with the international academic community: a common theoretical basis seems to promote international exchange, while facilitating interdisciplinarity. Nevertheless, the question arises as to whether there is a certain ›level of theory‹ that guarantees international and interdisciplinary connectivity. What costs are associated with a specific level of generalization? To what extent is the development of abstract ›grand theories‹ driven by a striving for symbolic capital? Finally, the notorious question of the material required for a comprehensive praxeological analysis of theorizing is addressed.
2018-05-15Zeitschriftenartikel
Landsat phenological metrics and their relation to aboveground carbon in the Brazilian Savanna
(Mathematisch-Naturwissenschaftliche Fakultät) Schwieder, Marcel; Leitão, P. J.; Pinto, J. R. R.; Teixeira, A. M. C.; Pedroni, F.; Sanchez, M.; Bustamante, M. M.; Hostert, Patrick
Background The quantification and spatially explicit mapping of carbon stocks in terrestrial ecosystems is important to better understand the global carbon cycle and to monitor and report change processes, especially in the context of international policy mechanisms such as REDD+ or the implementation of Nationally Determined Contributions (NDCs) and the UN Sustainable Development Goals (SDGs). Especially in heterogeneous ecosystems, such as Savannas, accurate carbon quantifications are still lacking, where highly variable vegetation densities occur and a strong seasonality hinders consistent data acquisition. In order to account for these challenges we analyzed the potential of land surface phenological metrics derived from gap-filled 8-day Landsat time series for carbon mapping. We selected three areas located in different subregions in the central Brazil region, which is a prominent example of a Savanna with significant carbon stocks that has been undergoing extensive land cover conversions. Here phenological metrics from the season 2014/2015 were combined with aboveground carbon field samples of cerrado sensu stricto vegetation using Random Forest regression models to map the regional carbon distribution and to analyze the relation between phenological metrics and aboveground carbon. Results The gap filling approach enabled to accurately approximate the original Landsat ETM+ and OLI EVI values and the subsequent derivation of annual phenological metrics. Random Forest model performances varied between the three study areas with RMSE values of 1.64 t/ha (mean relative RMSE 30%), 2.35 t/ha (46%) and 2.18 t/ha (45%). Comparable relationships between remote sensing based land surface phenological metrics and aboveground carbon were observed in all study areas. Aboveground carbon distributions could be mapped and revealed comprehensible spatial patterns. Conclusion Phenological metrics were derived from 8-day Landsat time series with a spatial resolution that is sufficient to capture gradual changes in carbon stocks of heterogeneous Savanna ecosystems. These metrics revealed the relationship between aboveground carbon and the phenology of the observed vegetation. Our results suggest that metrics relating to the seasonal minimum and maximum values were the most influential variables and bear potential to improve spatially explicit mapping approaches in heterogeneous ecosystems, where both spatial and temporal resolutions are critical.
2018-02Zeitschriftenartikel
Livelihood and climate trade-offs in Kenyan peri-urban vegetable production
(Lebenswissenschaftliche Fakultät) Kurgat, Barnabas; Stöber, Silke; Mwonga, Samuel; Lotze-Campen, Hermann; Rosenstock, Todd
Trade-offs between livelihood and environmental outcomes due to agricultural intensification in sub-Saharan Africa are uncertain. The present study measured yield, economic performance and nitrous oxide (N2O) emissions in African indigenous vegetable (AIV) production to investigate the optimal nutrient management strategies. In order to achieve this, an on-farm experiment with four treatments – (1) 40 kg N/ha diammonium phosphate (DAP), (2) 10 t/ha cattle manure, (3) 20 kg N/ha DAP and 5 t/ha cattle manure and (4) a no-N input control – was performed for two seasons. Yields and N2O emissions were directly measured with subsampling and static chambers/gas chromatography, respectively. Economic outcomes were estimated from semi-structured interviews (N = 12). Trade-offs were quantified by calculating N2O emissions intensity (N2OI) and N2O emissions economic intensity (N2OEI). The results indicate that, DAP alone resulted at least 14% greater yields, gross margin and returns to labour in absolute terms but had the highest emissions (p = 0.003). Productivity-climate trade-offs, expressed as N2OI, were statistically similar for DAP and mixed treatments. However, N2OEI was minimized under mixed management (p = 0.0004) while maintaining productivity and gross margins. We therefore conclude that soil fertility management strategies that mix inorganic and organic source present a pathway to sustainable intensification in AIV production. Future studies of GHG emissions in crop production need to consider not only productivity but economic performance when considering trade-offs.
2018-07-19Zeitschriftenartikel
Drivers of sustainable intensification in Kenyan rural and peri-urban vegetable production
(Lebenswissenschaftliche Fakultät) Kurgat, Barnabas; Ngenoh, Evans; Bett, Hillary K.; Stöber, Silke; Mwonga, Samuel; Lotze-Campen, Hermann; Rosenstock, Todd
Sustainable intensification promotes environmentally sound and productive agriculture. However, use of sustainable intensification practices (SIPs) is low in many sub-Sharan African countries. This study examined the adoption of SIPs in Kenyan rural and peri-urban vegetable production to understand the scale of and underlying factors in the use of SIPs. A multistage sampling technique was employed to randomly select 685 rural and peri-urban vegetable farm households. Household data was then collected and anaylsed for four practices namely improved irrigation, integrated soil fertility, organic manure and crop diversification using a pre-tested structured questionnaire. A multivariate probit model was run to model simultaneous interdependent adoption decisions. Adoption of organic manure and African indigenous vegetables (AIV) diversification was high in both rural and peri-urban areas. However, adoption of improved irrigation systems and integrated soil fertility management was low, and even significantly lower in rural areas than in peri-urban areas (p < 0.041). Similarly, adoption intensity of SIPs was lower in rural areas than in peri-urban areas. Furthermore, the findings also show complementarities and substitutabilities between SIPs. Market integration, the farm location and household income were the major factors heavily influencing the adoption of most SIPs. Policies and programmes that seek to build household financial capital base and integrate farm households into effective and efficient vegetable markets need to be formulated and implemented in order to enhance adoption of SIPs in AIV production.
2018-06-13Zeitschriftenartikel
Is Bhutan destined for 100% organic? Assessing the economy-wide effects of a large-scale conversion policy
(Lebenswissenschaftliche Fakultät) Feuerbacher, Arndt; Luckmann, Jonas; Boysen, Ole; Zikeli, Sabine; Grethe, Harald
Organic agriculture (OA) is considered a strategy to make agriculture more sustainable. Bhutan has embraced the ambitious goal of becoming the world’s first 100% organic nation. By analysing recent on-farm data in Bhutan, we found organic crop yields on average to be 24% lower than conventional yields. Based on these yield gaps, we assess the effects of the 100% organic conversion policy by employing an economy-wide computable general equilibrium (CGE) model with detailed representation of Bhutan’s agricultural sector incorporating agroecological zones, crop nutrients, and field operations. Despite a low dependency on agrochemicals from the onset of this initiative, we find a considerable reduction in Bhutan’s GDP, substantial welfare losses, particularly for non-agricultural households, and adverse impacts on food security. The yield gap is the main driver for a strong decline in domestic agricultural production, which is largely compensated by increased food imports, resulting in a weakening of the country’s cereal self-sufficiency. Current organic by default farming practices in Bhutan are still underdeveloped and do not apply the systems approach of organic farming as defined in the IFOAM organic farming standards. This is reflected in the strong decline of nitrogen (N) availability to crops in our simulation and bears potential for increased yields in OA. Improvement of soil-fertility practices, e.g., the adoption of N-fixing crops, improved animal husbandry systems with increased provision of animal manure and access to markets with price premium for organic products could help to lower the economic cost of the large-scale conversion.

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