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2023-03-08Zeitschriftenartikel
On Two Coupled Degenerate Parabolic Equations Motivated by Thermodynamics
(Mathematisch-Naturwissenschaftliche Fakultät) Mielke, Alexander
We discuss a system of two coupled parabolic equations that have degenerate diffusion constants depending on the energy-like variable. The dissipation of the velocity-like variable is fed as a source term into the energy equation leading to conservation of the total energy. The motivation of studying this system comes from Prandtl’s and Kolmogorov’s one- and two-equation models for turbulence, where the energy-like variable is the mean turbulent kinetic energy. Because of the degeneracies, there are solutions with time-dependent support like in the porous medium equation, which is contained in our system as a special case. The motion of the free boundary may be driven by either self-diffusion of the energy-like variable or by dissipation of the velocity-like variable. The crossover of these two phenomena is exemplified for the associated planar traveling fronts. We provide existence of suitably defined weak and very weak solutions. After providing a thermodynamically motivated gradient structure, we also establish convergence into steady state for bounded domains and provide a conjecture on the asymptotically self-similar behavior of the solutions in Rdfor large times.
2023-05-16Zeitschriftenartikel
Balanced-Viscosity Solutions to Infinite-Dimensional Multi-Rate Systems
(Mathematisch-Naturwissenschaftliche Fakultät) Mielke, Alexander; Rossi, Riccarda
We consider generalized gradient systems with rate-independent and rate-dependent dissipation potentials. We provide a general framework for performing a vanishing-viscosity limit leading to the notion of parametrized and true Balanced-Viscosity solutions that include a precise description of the jump behavior developing in this limit. Distinguishing an elastic variable u having a viscous damping with relaxation time εαand an internal variable z with relaxation time εwe obtain different limits for the three cases α∈(0,1), α=1and α>1. An application to a delamination problem shows that the theory is general enough to treat nontrivial models in continuum mechanics.
2022-06-22Zeitschriftenartikel
Political Theory of the Digital Constellation
(Kultur-, Sozial- und Bildungswissenschaftliche Fakultät) Berg, Sebastian; Staemmler, Daniel; Thiel, Thorsten
The introductory contribution to this special issue on “Political Theory of the Digital Constellation” addresses the conditions and possibilities of political theory’s engagement with digital developments. The motivation for this inquiry is the growing interest in questions of political theory arising from the digital transformation, as well as the acknowledgement that digitalisation not only changes politics, but conversely that politics also shapes digitalisation. The article identifies three pitfalls of previous engagement: The narrowing of the subject of “digitalisation” to the topic of the “internet” and, thereby, to the aspect of communication, the disregard for the technicality of the digital, and the insufficient recognition that (digital) technology is political. To avoid these pitfalls, the research perspective of the digital constellation is presented. The digital constellation serves as an epistemological guide that helps to structure theoretical reflection on the interrelationship between digitalisation and political questions. Ultimately, the outlines of the political theory in the digital constellation become clear in the fourteen contributions of the special volume, which are presented in conclusion.
2022-02-23Zeitschriftenartikel
Traveling Fronts in a Reaction–Diffusion Equation with a Memory Term
(Mathematisch-Naturwissenschaftliche Fakultät) Mielke, Alexander; Reichelt, Sina
Based on a recent work on traveling waves in spatially nonlocal reaction–diffusion equations, we investigate the existence of traveling fronts in reaction–diffusion equations with a memory term. We will explain how such memory terms can arise from reduction of reaction–diffusion systems if the diffusion constants of the other species can be neglected. In particular, we show that two-scale homogenization of spatially periodic systems can induce spatially homogeneous systems with temporal memory. The existence of fronts is proved using comparison principles as well as a reformulation trick involving an auxiliary speed that allows us to transform memory terms into spatially nonlocal terms. Deriving explicit bounds and monotonicity properties of the wave speed of the arising traveling front, we are able to establish the existence of true traveling fronts for the original problem with memory. Our results are supplemented by numerical simulations.
2023-12-07Zeitschriftenartikel
Time-domain modeling of interband transitions in plasmonic systems
(Mathematisch-Naturwissenschaftliche Fakultät) Pfeifer, Max; Huynh, Dan-Nha; Wegner, Gino; Intravaia, Francesco; Peschel, Ulf; Busch, Kurt
Efficient modeling of dispersive materials via time-domain simulations of the Maxwell equations relies on the technique of auxiliary differential equations. In this approach, a material’s frequency-dependent permittivity is represented via a sum of rational functions, e.g., Lorentz poles, and the associated free parameters are determined by fitting to experimental data. In the present work, we present a modified approach for plasmonic materials that requires considerably fewer fit parameters than traditional approaches. Specifically, we consider the underlying microscopic theory and, in the frequency domain, separate the hydrodynamic contributions of the quasi-free electrons in partially filled bands from the interband transitions. As an illustration, we apply our approach to gold and demonstrate how to treat the interband transitions within the effective model via connecting to the underlying electronic band structure, thereby assigning physical meaning to the remaining fit parameters. Finally, we show how to utilize this approach within the technique of auxiliary differential equations. Our approach can be extended to other plasmonic materials and leads to efficient time-domain simulations of plasmonic structures for frequency ranges where interband transitions have to be considered.
2023-06-10Zeitschriftenartikel
Field path optimization to reduce headland and turning maneuvers at regional scales: automated detection of cultivation direction in the state of Brandenburg, Germany
(Lebenswissenschaftliche Fakultät) Donat, Marco; Geistert, Jonas; Grahmann, Kathrin; Bellingrath-Kimura, Sonoko D.
Path planning for optimized field-work pattern is an important task within precision farming. The decision on a particular direction and path to cultivate and manage the field is complex and can significantly affect working time, energy consumption, soil compaction and yield. This study proposed a new method for automated detection of the current cultivation direction of several thousands of agricultural fields and compared the current cultivation direction with an optimized cultivation direction generated from a path planning algorithm. Airborne imagery from 2019 was analyzed using a modified Gabor filter. The identification takes place on a sub-plot level and can therefore detect small-scale differences in cultivation direction within fields. The method for identification of current cultivation direction had a high success rate of 87.5%. Fields with a high potential to save turning maneuvers and to reduce the area of headland were identified. From 3410 fields, a total of 58162 turning maneuvers and 507 ha headland were saved. This corresponds to 14.1% of all turning maneuvers and 7.6% of the total headland area for all analyzed fields in Brandenburg. A high optimization potential was demonstrated for field paths when efficient processing directions are taken into account. The method can be extended to the analysis of satellite imagery and thus offers the possibility of identifying current cultivation directions with a high spatial and temporal resolution. In future, this knowledge can be embedded within decision support systems for real-time optimization of field machinery path planning to support sustainable cropping practices.
2023-11-14Zeitschriftenartikel
Farmers’ behavioural determinants of on-farm biodiversity management in Europe: a systematic review
Klebl, Fabian; Feindt, Peter H.; Piorr, Annette
Agricultural intensification and landscape homogenisation are major drivers of biodiversity loss in European agricultural landscapes. Improvements require changes in farming practices, but empirical evidence on farmers’ motivations underlying their on-farm biodiversity management remains fragmented. To date, there is no aggregated overview of behavioural determinants that influence European farmers’ decisions to implement biodiversity-friendly farming practices. This study aims to fill this knowledge gap by conducting a systematic literature review of 150 empirical studies published between 2000 and 2022. We identified 108 potential determinants of farmers’ behaviour, which were integrated into a multilevel framework. The results show that the farmers’ decisions are complex and often non-directional processes, shaped by numerous external (at a society, landscape, community, and farm level) and internal factors. These factors are embedded in regional and cultural contexts. However, the analysis of study sites indicates that the spatial coverage of scientific evidence on biodiversity-friendly farming measures is uneven across Europe. Given the diversity of local and socio-cultural conditions, there is a need for public policies, including the European Union’s Common Agricultural Policy, to address more specifically determinants encouraging biodiversity-friendly farm management. This entails reflecting culture-specific perspectives and incorporating experiential knowledge into multilevel policy design processes, as well as offering regionally adapted advice on measure implementation and biodiversity impacts.
2022-10-25Zeitschriftenartikel
Infected grasses as inoculum for Fusarium infestation and mycotoxin accumulation in wheat with and without irrigation
(Lebenswissenschaftliche Fakultät) Gerling, Marina; Petry, Laura; Barkusky, Dietmar; Büttner, Carmen; Müller, Marina E. H.
Grasses growing next to agricultural fields influence the Fusarium abundance, the species composition, and the mycotoxin accumulation of wheat plants, especially the field parts directly adjacent to grasses, are highly affected. Grasses are a more attractive and suitable habitat for Fusarium fungi compared to other arable weeds and occur at mostly every semi-natural landscape element (e.g., kettle holes, hedgerows, field-to-field-borders). In our study, we analyzed the ability of a highly Fusarium infected grass stripe ( F. graminearum , F. culmorum , F. sporotrichioides ) to infect an adjacent wheat field with these species. Results show that the primary inoculated Fusarium species were as well the dominant species isolated from the wheat field. Regarding transects originating from the grass stripe going into the field, the results demonstrate that wheat ears next to the infected grass stripe have a higher Fusarium abundance and furthermore show higher mycotoxin accumulation in the wheat kernels. This effect was highly promoted by irrigation. Therefore, grass stripes next to arable fields must be considered as reservoirs for fungal infections and as a source for a contamination with mycotoxins.
2023-03-17Zeitschriftenartikel
Upscaling agroforestry in the tropics through actor-networks: a comparative case study of cacao farming systems in two regions of Colombia
Rodríguez, Tatiana; Bonatti, Michelle; Löhr, Katharina; Bravo, Aura; Del Río, Martha; Lana, Marcos; Sieber, Stefan
Agroforestry systems (AFS) upscaling has the potential to integrate sustainability and resilience objectives into agriculture. However, this is a daunting task requiring multi-actor collaboration across public and private sectors at multiple governance levels, coupled with innovative approaches to jointly managing AFS knowledge. Understanding such multi-actor interactions from a network perspective may help to unravel how social structures, created by relational patterns enhance or hinder AFS upscaling. Our paper aims to comparatively explore the role of regional actor-networks on AFS upscaling for a selected farming system. By conducting semi-structured interviews, we collected information about the ties of 86 actors supporting cacao agroforestry systems (CAFS) across two regions of Colombia. We use social network analysis (SNA) to comparatively visualize and understand the general structure of these networks, find relational patterns between the diverse categories of actors involved, and identify a set of key players bridging the majority of the actors within these networks. We find highly centralized networks that connect multiple actors by a low number of mostly non-reciprocal ties. Within these networks, we identify a predominance of bridging ties over bonding ties, homophily patterns among research and education institutions, and heterophily configurations among farmer-based organizations. We also find that the composition of the sets of key actors and the platforms where they converge varies substantially from region to region due to decentralized agricultural policies and differing characteristics across regions. Our approach provides key entry points for promoting multi-actor coalitions that can effectively expand the benefits of AFS in tropical agricultural systems.
2023-04-13Zeitschriftenartikel
Conceptualizing Community-based Environmental Peacebuilding in Cesar, Colombia
Hachmann, Samyra; Löhr, Katharina; Morales-Muñoz, Héctor; Eufemia, Luca; Sieber, Stefan; Bonatti, Michelle
In conflict studies, environmental peacebuilding (EPB) has become an established concept to explain how environmental cooperation among opposing parties provides a platform for peacebuilding. EPB literature has been shaped predominantly by political science perspectives, initially with a focus on interstate conflicts, and ecological dynamics have received little attention to date. Building on the Social-Ecological Systems Framework (SESF), we develop a framework for community-based EPB and test it in post-conflict settings in the department of Cesar, Colombia. We use a qualitative mixed-methods approach, with 26 semi-structured interviews, six focus group discussions, and a World Café session with 30 participants. Our findings show that in six cases communities self-organize to access, conserve, and defend water and land resources while striving to achieve recognition of their civic rights by state actors. A central outcome of cooperation within and among communities is the (re)construction of collective and territorial identities and increased social cohesion. However, community-based EPB does not contribute to improving relations between communities and the private sector or the state, thus failing to strengthen actor relationships that are essential for Colombian peacebuilding. Despite limitations of this exploratory analysis, our approach proves fruitful for integrating ecological aspects in the understanding of EPB. To further develop the EPB concept, future research should look to other disciplines to diversify the understanding of key terms like resource value, cooperation, and peace.
2022-01-18Zeitschriftenartikel
Analyzing influencing factors to scale up agroforestry systems in Colombia: A comparative ex-ante assessment of cacao farming and cattle ranching in two regions
Rodríguez, Tatiana; Bonatti, Michelle; Löhr, Katharina; Lana, Marcos; Del Río, Martha; Sieber, Stefan
Agroforestry systems (AFS) are proved to enhance sustainable land management. Thus, there is increasing demand for effective ways to scale up AFS so that more people can benefit. Consequently, this study assesses the scaling-up potential of agroforestry systems (AFS) using cacao farming and cattle ranching in Caquetá and Cesar, Colombia, as examples. An ex-ante assessment using the ScalA tool is conducted through interviews with AFS experts from institutions promoting AFS. Using a comparative approach, results reveal that AFS have different scaling-up potential depending on the type of farming system and location characteristics. In our case, it is slightly higher for cacao farming than for cattle ranching in both regions and it is higher in Caquetá than in Cesar for both systems. Factors hindering the scaling-up potential for both regions are economic conditions at the local and regional levels since there is a lack of stable and differentiated markets to absorb AFS products. In contrast, the scaling-up potential in both regions is increased by the factors related to the capacity of the organizations that promote AFS and the attitudes of local communities toward them. The study generates information about factors that may hinder or foster AFS scaling-up, including not just the capacities and mechanisms to promote them but also the enabling conditions. This contributes to prioritizing AFS interventions and better allocating their resources to increase their chances of successful scaling-up.
2022-02-26Zeitschriftenartikel
Social learning as an underlying mechanism for sustainability in neglected communities: The Brazilian case of the Bucket Revolution project
(Lebenswissenschaftliche Fakultät) Bonatti, Michelle; Erismann, Carla; Askhabalieva, Ayna; Borba, Juliano; Pope, Kamila; Reynaldo, Renata; Eufemia, Luca; Turetta, Ana Paula; Sieber, Stefan
In neglected communities, waste and organic residues are not only a vector of several problems, like diseases and water pollution, but also a contributor to increasing forms of vulnerability and marginalization. At the same time, these communities also have presented innovative local initiatives and transformative learning about natural resources management that can be a vehicle for achieving more sustainable food systems. In the south of Brazil, community-based organic residue management has shown an extraordinary potential to improve food security and livelihoods for (≈1600) community members of a vulnerable urban territory. In this context, the overall objective of this article is (a) To better understand what Social Learning (SL) processes related to successful organic residues management in neglected communities exist and (b) To identify what knowledge systems are created in one empirical case. The study case is based on a communitarian waste management project, the Bucket Revolution Project (BRP). The analytical framework builds upon social learning theory and its triple-loop process focusing on four specific phenomena. The applied mixed-methods approach was made in four steps: 1. a focus group to investigate collective community issues; 2. semi-structured interviews to investigate specific and individual issues in the context of the BRP; 3. social media analysis to better understand the BRP narratives; and finally 4. participant observation in community and institutional meetings. Mainly using MaxQda software and coding indicators of SL, the data show that “Diversity of knowledge integration” is the most identified SL indicator in the interviews (52%). For BRP, identity development, community conditions improvement, and environment understanding are three key components of the knowledge system enhanced through an underlying process of social learning. Furthermore, the study also shows that there are endogenous and exogenous social learning processes at work.
2022-08-06Zeitschriftenartikel
Modelling cropland expansion and its drivers in Trans Nzoia County, Kenya
(Lebenswissenschaftliche Fakultät) Kipkulei, Harison Kiplagat; Bellingrath-Kimura, Sonoko Dorothea; Lana, Marcos; Ghazaryan, Gohar; Boitt, Mark; Sieber, Stefan
Population growth and increasing demand for agricultural production continue to drive global cropland expansions. These expansions lead to the overexploitation of fragile ecosystems, propagating land degradation, and the loss of natural diversity. This study aimed to identify the factors driving land use/land cover changes (LULCCs) and subsequent cropland expansion in Trans Nzoia County in Kenya. Landsat images were used to characterize the temporal LULCCs in 30 years and to derive cropland expansions using change detection. Logistic regression (LR), boosted regression trees (BRTs), and evidence belief functions (EBFs) were used to model the potential drivers of cropland expansion. The candidate variables included proximity and biophysical, climatic, and socioeconomic factors. The results showed that croplands replaced other natural land covers, expanding by 38% between 1990 and 2020. The expansion in croplands has been at the expense of forestland, wetland, and grassland losses, which declined in coverage by 33%, 71%, and 50%, respectively. All the models predicted elevation, proximity to rivers, and soil pH as the critical drivers of cropland expansion. Cropland expansions dominated areas bordering the Mt. Elgon forest and Cherangany hills ecosystems. The results further revealed that the logistic regression model achieved the highest accuracy, with an area under the curve (AUC) of 0.96. In contrast, EBF and the BRT models depicted AUC values of 0.86 and 0.77, respectively. The findings exemplify the relationships between different potential drivers of cropland expansion and contribute to developing appropriate strategies that balance food production and environmental conservation.
2022-10-21Zeitschriftenartikel
Assessment of Maize Yield Response to Agricultural Management Strategies Using the DSSAT–CERES-Maize Model in Trans Nzoia County in Kenya
(Lebenswissenschaftliche Fakultät) Kipkulei, Harison Kiplagat; Bellingrath-Kimura, Sonoko Dorothea; Lana, Marcos; Ghazaryan, Gohar; Baatz, Roland; Boitt, Mark; Chisanga, Charles B.; Rotich, Brian; Sieber, Stefan
Maize production in low-yielding regions is influenced by climate variability, poor soil fertility, suboptimal agronomic practices, and biotic influences, among other limitations. Therefore, the assessment of yields to various management practices is, among others, critical for advancing site-specific measures for production enhancement. In this study, we conducted a multiseason calibration and evaluation of the DSSAT–CERES-Maize model to assess the maize yield response of two common cultivars grown in Trans Nzoia County in Kenya under various agricultural strategies, such as sowing dates, nitrogen fertilization, and water management. We then applied the Mann–Kendall (MK), and Sen’s Slope Estimator (SSE) tests to establish the yield trends and magnitudes of the different strategies. The evaluated model simulated long-term yields (1984–2021) and characterized production under various weather regimes. The model performed well in simulating the growth and development of the two cultivars, as indicated by the model evaluation results. The RMSE for yield was 333 and 239 kg ha −1 for H614 and KH600-23A, respectively, representing a relative error (RRMSE) of 8.1 and 5.1%. The management strategies assessment demonstrated significant feedback on sowing dates, nitrogen fertilization, and cultivars on maize yield. The sowing date conducted in mid-February under fertilization of 100 kg of nitrogen per hectare proved to be the best strategy for enhancing grain yields in the region. Under the optimum sowing dates and fertilization rate, the average yield for cultivar KH600-23A was 7.1% higher than that for H614. The MK and SSE tests revealed a significant (p < 0.05) modest downwards trend in the yield of the H614 cultivar compared to the KH600-23A. The eastern part of Trans Nzoia County demonstrated a consistent downwards trend for the vital yield enhancement strategies. Medium to high nitrogen levels revealed positive yield trends for more extensive coverage of the study area. Based on the results, we recommend the adoption of the KH600-23A cultivar which showed stability in yields under optimum nitrogen levels. Furthermore, we recommend measures that improve soil quality and structure in the western and northern parts, given the negative model response on maize yield in these areas. Knowledge of yield enhancement strategies and their spatial responses is of utmost importance for precision agricultural initiatives and optimization of maize production in Trans Nzoia County.
2023-02-27Zeitschriftenartikel
Seasonal and diurnal patterns of littoral microhabitat use by fish in gravel pit lakes, with special reference to supplemented deadwood brush piles
(Lebenswissenschaftliche Fakultät) Maday, Andreas; Matern, Sven; Monk, Christopher T.; Klefoth, Thomas; Wolter, Christian; Arlinghaus, Robert
The habitat quality of the littoral zone is of key importance for almost all lentic fish species. In anthropogenically created gravel pit lakes, the littoral zone is often structurally homogenized with limited fish habitats. We supplemented deadwood brush piles in the littoral zone of eight gravel pit lakes and investigated the diurnal and seasonal use of this and other typical microhabitats by six dominant fish species. Shoreline habitats were sampled using point abundance electrofishing during day and night in all four seasons, and patterns of fish abundance were compared amongst unstructured littoral habitats, emerged macrophytes and brush piles. We caught a total of 14,458 specimens from 15 species in the gravel pit lakes. Complex shoreline structures were used by all fish species that we examined, especially during daytime, whilst the use of unstructured habitats was highest during night. The newly added brush piles constituted suitable microhabitats for selected fish species, perch ( Perca fluviatilis ), roach ( Rutilus rutilus ) and pike ( Esox lucius ), particularly during winter. Supplemented deadwood provides suitable fish habitat in gravel pit lakes and may to some degree compensate for the loss of submerged macrophytes in winter by offering refuge and foraging habitat for selected fish species.
2022-03-23Zeitschriftenartikel
Who Opts Out? The Customisation of Marriage in the German Matrimonial Property Regime
(Kultur-, Sozial- und Bildungswissenschaftliche Fakultät) Nutz, Theresa; Nelles, Anika; Lersch, Philipp M.
This study examines the prevalence of marital contracts across marriage cohorts (1990–2019) in Germany. We further investigate the characteristics of spouses who signed a marital contract. Using cross-sectional data from the German Family Panel (pairfam, 2018/19), we employ complementary log–log and multinomial logistic regression models to predict the prevalence and the type of marital contracts. The results show that 5% of all married couples opt out of the default matrimonial property regime by signing a contract in Germany. Differentiating between contract types, most couples either specify a separation of property (40%) or modify the default community of accrued gains (31%). We find an increase in the prevalence of marital contracts across marriage cohorts. The decision to opt out of the default is strongly positively associated with self-employment that often requires the customisation of asset ownership structures within marriage. Married individuals with prior divorce experiences are more likely to opt for the separation of property, indicating that the awareness of the economic consequences of divorce promotes the individualisation of marriage. Our results are in line with the cross-national trend towards customised marriages, although the trend in Germany is less pronounced than in other countries.
2022-08-12Zeitschriftenartikel
The Nexus between Methods and Power in Sociological Research
(Kultur-, Sozial- und Bildungswissenschaftliche Fakultät) Schmitz, Andreas; Hamann, Julian
This article develops an integrative perspective on the nexus between power and sociological research methods. By reflecting upon two of the most widely used methodological approaches in sociology – standardized survey research and qualitative interview research – we develop a comprehensive heuristic framework for examining the ways in which the use of sociological methods affects and intersects any social scientific practice: (1) the power effects that societies and institutional settings exert on methods and the use of methods, (2) power in the use and implementation of methods, and (3) the power effects that methods and the use of methods exert on societies and institutional settings.
2022-10-01Zeitschriftenartikel
Size-selective mortality fosters ontogenetic changes in collective risk-taking behaviour in zebrafish, Danio rerio
Roy, Tamal; Arlinghaus, Robert
Size-selective mortality is common in fish populations and can operate either in a positive size-selective fashion by harvesting larger-than-average fish or be negatively size-selective by harvesting smaller-than-average fish. Through various mechanisms (like genetic correlations among behaviour and life-history traits or direct selection on behaviour co-varying with growth rate or size-at-maturation), size-selection can result in evolutionary changes in behavioural traits. Theory suggests that both positive and negative size-selection without additional selection on behaviour favours boldness, while evolution of shyness is possible if the largest fish are harvested. Here we examined the impact of size-selective mortality on collective boldness across ontogeny using three experimental lines of zebrafish (Danio rerio) generated through positive (large-harvested), negative (small-harvested) and random (control line) size-selective mortality for five generations and then relaxed selection for 10 generations to examine evolutionarily fixed outcomes. We measured collective risk-taking during feeding (boldness) under simulated aerial predation threat, and across four contexts in presence/absence of a cichlid. Boldness decreased across ontogeny under aerial predation threat, and the small-harvested line was consistently bolder than controls. The large and small-harvested lines showed higher behavioural plasticity as larvae and developed personality earlier compared to the controls. The large-harvested line showed increased variability and plasticity in boldness throughout ontogeny. In the presence of a live predator, fish did not differ in boldness in three contexts compared to the controls, but the large-harvested line showed reduced behavioural plasticity across contexts than controls. Our results confirmed theory by demonstrating that size-selective harvesting evolutionarily alters collective boldness and its variability and plasticity.
2022-01-15Zeitschriftenartikel
Resource frontiers and agglomeration economies: The varied logics of transnational land-based investing in Southern and Eastern Africa
Abeygunawardane, Dilini; Kronenburg García, Angela; Sun, Zhanli; Müller, Daniel; Sitoe, Almeida; Meyfroidt, Patrick
Actor-level data on large-scale commercial agriculture in Sub-Saharan Africa are scarce. The peculiar choice of transnational investing in African land has, therefore, been subject to conjecture. Addressing this gap, we reconstructed the underlying logics of investment location choices in a Bayesian network, using firm- and actor-level interview and spatial data from 37 transnational agriculture and forestry investments across 121 sites in Mozambique, Zambia, Tanzania, and Ethiopia. We distinguish four investment locations across gradients of resource frontiers and agglomeration economies to derive the preferred locations of different investors with varied skillsets and market reach (i.e., track record). In contrast to newcomers, investors with extensive track records are more likely to expand the land use frontier, but they are also likely to survive the high transaction costs of the pre-commercial frontier. We highlight key comparative advantages of Southern and Eastern African frontiers and map the most probable categories of investment locations.
2023-10-30Zeitschriftenartikel
Charting the course of plant virology: innovations in diagnostics and beyond—reports from the DPG meeting
Krenz, Björn; Niehl, Annette; Büttner, Carmen
Plant viruses pose a significant threat to global agriculture, resulting in economic losses and threatening food security. High-throughput sequencing and molecular techniques are advancing our understanding of these viruses, allowing for their detection, characterization, and control. The 55th meeting of the DPG Working Group “Viruskrankheiten der Pflanzen” showcased these advancements, encouraging international collaboration and idea exchange to tackle plant virus challenges. The perspectives paper we present summarizes this conference’s findings, highlighting the potential of these technologies in revolutionizing plant virus research.

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