21st Century Challenges in Arable Farming - Essays on the Agricultural Land Market and Drone Adoption in Germany

This cumulative thesis addresses two key challenges facing modern arable farming in Germany in the 21st century. The first challenge considered is the agricultural land market. The ongoing reduction in the limited production factor of land and the sharp price increases on the purchase and rental market for agricultural land are leading to an ongoing social, political and scientific debate about causes, effects and the need for political intervention. The scarcity of land requires an increase in productivity from a sectoral perspective and an increase in the profitability of the land under cultivation from a business management perspective. Additionally, sustainability and resource efficiency are playing a considerably increasing role in arable farming. By adopting precision agriculture technologies, farmers can increase farm productivity by improving yields while reducing input use and external environmental impacts. Therefore, the adoption of precision agriculture technologies is considered an important goal and current challenge in arable farming. Drones are one of the newest technologies belonging to precision agriculture, and many potential applications are promised due to their multifunctionality. Nevertheless, so far drones are less used in arable farming than expected and very little is known about the adoption process of drones. The adoption of precision agriculture technologies, and in this case specifically the case of drones, is therefore considered as the second key challenge in arable farming in the cumulative thesis. The first paper studies the status quo regarding price drivers on European farmland rental markets according to current literature and offers primary survey results of German farmers’ perceptions regarding those identified price drivers. Results show that "policy/CAP", "bioenergy", "climate change" as well as "market prices/competition" are identified by the primary literature as central price drivers on the European farmland rental markets and that the surveyed German farmers perceive these four price drivers differently from the literature regarding their relevance. The second paper studies the effect of restricted tendering in farmland auctions as a widely used policy intervention tool on the agricultural land market utilizing Propensity Score Matching (PSM) and auction theory. It is demonstrated that restricted tendering in land market auctions reduces the average number of bidders but does not fulfill the ultimate purpose of lower prices for structurally disadvantaged groups of bidders, as it leads to higher purchase prices on average. In the third paper, key factors influencing the adoption of drones are studied with a modified trans-theoretical model of adoption (TTMA). The focus of this fundamental research is mainly on sociodemographic farm and farmer characteristics. Results show that, among other factors, farmers' age, gender, and technology literacy, as well as farm size, influence the adoption process of drones in arable farming. The fourth paper extends the scope of research towards the latent factors influencing the adoption process of drones in arable farming based on an extended Technology Acceptance Model (TAM). It is shown that both raising farmers' awareness of farm-specific applications of drones and confidence in using a drone can increase farmers' intention to use a drone. The results are primarily of interest to agricultural policymakers who are involved in the active debate on agricultural land market interventions as well as those who wish to politically promote the dissemination of PAT. Furthermore, the results are of interest to farmers, (potential) buyers in the farmland market and agricultural expansion services. Developers and providers of drones and farm equipment that integrates drone technology could also benefit from this research. Each of the papers contributes to its particular body of literature and shows potential directions for future research.2021-09-1

Quantification of transport across the boundary of the lower stratospheric vortex during Arctic winter 2002/2003

Strong perturbations of the Arctic stratosphere during the winter 2002/2003 by planetary waves led to enhanced stretching and folding of the vortex. On two occasions the vortex in the lower stratosphere split into two secondary vortices that re-merged after some days. As a result of these strong disturbances the role of transport in and out of the vortex was stronger than usual. An advection and mixing simulation with the Chemical Lagrangian Model of the Stratosphere (CLaMS) utilising a suite of inert tracers tagging the original position of the air masses has been carried out. The results show a variety of synoptic and small scale features in the vicinity of the vortex boundary, especially long filaments peeling off the vortex edge and being slowly mixed into the mid latitude environment. The vortex folding events, followed by re-merging of different parts of the vortex led to strong filamentation of the vortex interior. During January, February, and March 2003 flights of the Russian high-altitude aircraft Geophysica were performed in order to probe the vortex, filaments and in one case the merging zone between the secondary vortices. Comparisons between CLaMS results and observations obtained from the Geophysica flights show in general good agreement. Several areas affected by both transport and strong mixing could be identified, allowing explanation of many of the structures observed during the flights. Furthermore, the CLaMS simulations allow for a quantification of the air mass exchange between mid latitudes and the vortex interior. The simulation suggests that after the formation of the vortex was completed, its interior remaind relatively undisturbed. Only during the two re-merging events were substantial amounts of extra-vortex air transported into the polar vortex. When in March the vortex starts weakening additional influence from lower latitudes becomes apparent in the model results. In the lower stratosphere export of vortex air leads only to a fraction of about 5% polar air in mid latitudes by the end of March. An upper limit for the contribution of ozone depleted vortex air on mid-latitude ozone loss is derived, indicating that the maximum final impact of dilution is on the order of 50%

Monthly resolved modelled oceanic emissions of carbonyl sulfide and carbon disulfide for the period 2000–2019

Carbonyl sulfide (OCS) is the most abundant, long-lived sulphur gas in the atmosphere and a major supplier of sulfur to the stratospheric sulfate aerosol layer. The short-lived gas carbon disulfide (CS2) is oxidized to OCS and constitutes a major indirect source to the atmospheric OCS budget. The atmospheric budget of OCS is not well constrained due to a large missing source needed to compensate for substantial evidence that was provided for significantly higher sinks. Oceanic emissions are associated with major uncertainties. Here we provide a first, monthly resolved ocean emission inventory of both gases for the period 2000–2019 (available at https://doi.org/10.5281/zenodo.4297010) (Lennartz et al., 2020a). Emissions are calculated with a numerical box model (resolution 2.8° × 2.8° at equator, T42 grid) for the surface mixed layer. We find that interannual variability in OCS emissions is smaller than seasonal variability, and is mainly driven by variations in chromophoric dissolved organic matter (CDOM), which influences both photochemical and light-independent production. A comparison with a global database of more than 2500 measurements reveals overall good agreement. Emissions of CS2 constitute a larger sulfur source to the atmosphere than OCS, and equally show interannual variability connected to variability of CDOM. The emission estimate of CS2 is associated with higher uncertainties, as process understanding of the marine cycling of CS2 is incomplete. We encourage the use of the data provided here as input for atmospheric modelling studies to further assess the atmospheric OCS budget and the role of OCS in climate

Dark Production: A Significant Source of Oceanic COS

Carbonyl sulfide (COS) in air and dissolved in seawater was determined during a cruise in August 1999 in the Sargasso Sea in the northwest Atlantic Ocean. Dissolved concentrations at the sea surface displayed only a weak diel cycle with a mean of 8.6 ± 2.8 pmol dm−3 owing to low abundance of photochemical precursors and high temperatures causing rapid hydrolysis. Depth profiles measured over the oceanic mixed layer revealed significant vertical gradients of COS concentration with higher values at the surface, suggesting that the rate of photochemical production at the surface exceeds the rate of vertical mixing. The mean atmospheric mixing ratio was 486 ± 40 ppt, and calculated sea-air fluxes ranged from 0.03 to 0.8 g COS km−2 d−1. COS dark production, estimated from the predawn COS concentration at the surface and the hydrolysis constant, contributed significantly to the total amount of COS produced. A strong temperature dependence of the COS dark production rate q was found by comparing previously published values. The data further indicate an approximately first-order relationship between q and chromophoric dissolved organic matter (CDOM) absorbance at 350 nm, a350, which is used as a proxy for the CDOM content of the water but is likely to covary with other parameters, such as biological activity, that could also affect COS dark production. Together with known functions for COS hydrolysis and solubility, the parameterization of dark production as a function of temperature and a350 allows for the prediction of COS concentrations and saturation ratios as a function of physical and optical seawater properties in the absence of photoproduction. This is used to estimate a lower limit of 0.056 Tg COS yr−1 to the annual COS flux from the ocean to the atmosphere

Atmospheric Abundances, Trends and Emissions of CFC-216ba, CFC-216ca and HCFC-225ca

The first observations of the feedstocks, CFC-216ba (1,2-dichlorohexafluoropropane) and CFC-216ca (1,3-dichlorohexafluoropropane), as well as the CFC substitute HCFC-225ca (3,3-dichloro-1,1,1,2,2-pentafluoropropane), are reported in air samples collected between 1978 and 2012 at Cape Grim, Tasmania. Present day (2012) mixing ratios are 37.8 ± 0.08 ppq (parts per quadrillion; 1015) and 20.2 ± 0.3 ppq for CFC-216ba and CFC-216ca, respectively. The abundance of CFC-216ba has been approximately constant for the past 20 years, whilst that of CFC-216ca is increasing, at a current rate of 0.2 ppq/year. Upper tropospheric air samples collected in 2013 suggest a further continuation of this trend. Inferred annual emissions peaked 421 at 0.18 Gg/year (CFC-216ba) and 0.05 Gg/year (CFC-216ca) in the mid-1980s and then decreased sharply as expected from the Montreal Protocol phase-out schedule for CFCs. The atmospheric trend of CFC-216ca and CFC-216ba translates into continuing emissions of around 0.01 Gg/year in 2011, indicating that significant banks still exist or that they are still being used. HCFC-225ca was not detected in air samples collected before 1992. The highest mixing ratio of 52 ± 1 ppq was observed in 2001. Increasing annual emissions were found in the 1990s (i.e., when HCFC-225ca was being introduced as a replacement for CFCs). Emissions peaked around 1999 at about 1.51 Gg/year. In accordance with the Montreal Protocol, restrictions on HCFC consumption and the short lifetime of HCFC-225ca, mixing ratios declined after 2001 to 23.3 ± 0.7 ppq by 2012

GMOs Across the Atlantic

GMOs Across the AtlanticSacrificing Precaution in the Name of Free Trade?Kofi Annan once said “[…] that arguing against globalisation is like arguing against the laws of gravity”. The world has evolved into a place of omnipresent interconnectivity where people are linked across borders by economic, political, friendly and family ties. Although risks have likewise become globalised in the process, risk management still largely constitutes a national issue. While transnational food scandals as the BSE crisis in 1997 or the horse meat scandal of 2013 have shaken consumers within and beyond the European Union (EU), Member States (MS) nonetheless continue to insist on their sovereignty to approach and handle uncertain risks by themselves. There are a variety of levels related to dealing with uncertain risks that are affected by this controversy. Amongst them are science as in risk assessment, law as in risk regulation and politics as in risk management and the overall coordinating risk governance processes. As neither science or law nor politics are able to provide fully sound and satisfying solutions for coping with uncertain risks, controversy and heated debate remains even long after a political decision has been made on a case. It is striking how all these disciplines attempt to appropriately respond to uncertainty, while they do actually add more complexity and differing opinions. There consequently is no solid ground for policy-makers to base their final decisions on and justify the particular regulation or acceptance of risks. It remains an issue how politics can effectively work in light of uncertainty. This is especially important when considering the effects of globalisation. Through international trade and the flow of goods through the world economy, products associated with uncertain risk cross national borders on a daily basis and need to be regulated. The ongoing negotiations on a free trade agreement between the European Union and the United States of America have highlighted the difficulties regarding this process. If successfully concluded, supposedly by the end of 2014, the Transatlantic Trade and Investment Partnership (TTIP) would constitute the largest free trade zone worldwide and both the EU and the US would benefit tremendously. However, negotiations have not gone so smoothly due to prevailing disagreement over the rules that should apply for the TTIP. With regards to food safety, the EU and the US have already had difficulties in the past to agree on a common denominator. Related differences and incompatibilities become evident in the debate on food safety. Although consumer protection is a highlyranked principle for both parties, there is little agreement on what requires strict protective measures and what should be regulated only mildly. In the past and recently, problematic issues for the EU have included US exports of genetically modified crops into the EU as well as meat imports from American hormone-treated or -fed animals and chicken meat that was treated with chlorine. On the part of the US, concerns have mostly been about EU lactic-acid washed meat, raw milk cheese and dairy imports into the States. Both parties have according precautionary measures in place, but request each other to drop the various bans and ease regulatory practices and processes on other products

Heterogeneous chlorine activation on stratospheric aerosols and clouds in the Arctic polar vortex

Chlorine activation in the Arctic is investigated by examining different parameterizations for uptake coefficients on stratospheric aerosols, high-resolution in-situ measurements and vortex-wide satellite observations. The parameterizations for heterogeneous chemistry on liquid aerosols are most sensitive to temperature with the reaction rates doubling for every 1 K increase in temperature. However, differences between the currently available parameterizations are negligible. For Nitric Acid Trihydrate particles (NAT) the major factors of uncertainty are the number density of nucleated particles and different parameterizations for heterogeneous chemistry. These two factors induce an uncertainty that covers several orders of magnitude on the reaction rate. Nonetheless, since predicted reaction rates on liquid aerosols always exceed those on NAT, the overall uncertainty for chlorine activation is small. In-situ observations of ClO<sub>x</sub> from Arctic winters in 2005 and 2010 are used to evaluate the heterogeneous chemistry parameterizations. The conditions for these measurements proved to be very different between those two winters with HCl being the limiting reacting partner for the 2005 measurements and ClONO<sub>2</sub> for the 2010 measurements. Modeled levels of chlorine activation are in very good agreement with the in-situ observations and the surface area provided by Polar Stratospheric Clouds (PSCs) has only a limited impact on modeled chlorine activation. This indicates that the parameterizations give a good representation of the processes in the atmosphere. Back-trajectories started on the location of the observations in 2005 indicate temperatures on the threshold for PSC formation, hence the surface area is mainly provided by the background aerosol. Still, the model shows additional chlorine activation during this time-frame, providing cautionary evidence for chlorine activation even in the absence of PSCs. Vortex-averaged satellite observations by the MLS instrument also show no definite connection between chlorine activation and PSC formation. The inter -and intra-annual variability of vortex-average HCl and HNO<sub>3</sub> based on MLS observations is examined for the Arctic winters 2004/2005 to 2010/2011. These observations show that removal of HCl and HNO<sub>3</sub> from the gas-phase are not correlated. HNO<sub>3</sub> loss exhibits great inter-annual variability depending on prevailing temperatures while HCl loss is continuous through December without considerable inter- or intra-annual variability. Only the recovery of HCl in late winter depends on the level of denitrification. Hence, the occurrence of HNO<sub>3</sub> containing PSC particles does not seem to have a significant effect on the speed of initial chlorine activation on a vortex-wide scale

Infrared limb emission measurements of aerosol in the troposphere and stratosphere

Altitude-resolved aerosol detection in the upper troposphere and lower stratosphere (UTLS) is a challenging task for remote sensing instruments. Infrared limb emission measurements provide vertically resolved global measurements at day- and nighttime in the UTLS. For high-spectral-resolution infrared limb instruments we present here a new method to detect aerosol and separate between ice and non-ice particles. The method is based on an improved aerosol–cloud index that identifies infrared limb emission spectra affected by non-ice aerosol or ice clouds. For the discrimination between non-ice aerosol and ice clouds we employed brightness temperature difference correlations. The discrimination thresholds for this method were derived from radiative transfer simulations (including scattering) and Michelson Interferometer for Passive Atmospheric Sounding (MIPAS)/Envisat measurements obtained in 2011. We demonstrate the value of this approach for observations of volcanic ash and sulfate aerosol originating from the Grímsvötn (Iceland, 64° N), Puyehue–Cordón Caulle (Chile, 40° S), and Nabro (Eritrea, 13° N) eruptions in May and June 2011 by comparing the MIPAS volcanic aerosol detections with Atmospheric Infrared Sounder (AIRS) volcanic ash and SO2 measurements