The Arctic is experiencing severe changes to its landscapes due to the thawing of permafrost influenced by the twofold increase of temperature across the Arctic due to global warming compared to the global average. This process, which affects the livelihoods of indigenous people, is also associated with the further release of greenhouse gases and also connected to ecological impacts on the arctic flora and fauna. These small-scale changes and disturbances to the land surface caused by permafrost thaw have been inadequately documented.

To better understand and monitor land surface changes, the project "UndercoverEisAgenten" is using a combination of local knowledge, satellite remote sensing, and data from unmanned aerial vehicles (UAVs) to study permafrost thaw impacts in Northwest Canada. The high-resolution UAV data will serve as a baseline for further analysis of optical and radar remote sensing time series data. The project aims to achieve two main goals: 1) to demonstrate the value of using unmanned aerial vehicle (UAV) data in remote regions of the global north, and 2) to involve young citizen scientists from schools in Canada and Germany in the process. By involving students in the project, the project aims to not only expand the use of remote sensing in these regions, but also provides educational opportunities for the participating students. By using UAVs and satellite imagery, the project aims to develop a comprehensive archive of observable surface features that indicate the degree of permafrost degradation. This will be accomplished through the use of automatic image enhancement techniques, as well as classical image processing approaches and machine learning-based classification methods. The data is being prepared to be shared and analyzed through a web-based crowd mapping application. The project aims to involve the students in independently acquiring data and developing their own scientific questions through the use of this application.

In September 2022, a first expedition was conducted in the Northwest Territories, Canada and UAV data was collected with the assistance of students from Moose Kerr School in Aklavik. The data consists of approximately 30,000 individual photos taken over an area of around 13 km². The expedition also provided an opportunity for the students to learn about the basics of data collection and the goals of the collaborative permafrost survey, which included the incorporation of local knowledge to address the questions of the local community.

By involving school students in the data acquisition, classification and evaluation process, the project also seeks to transfer knowledge and raise awareness about global warming, permafrost, and related regional and global challenges. Additionally, a connection through the shared research experience between students in Germany and Canada is established to enable the exchange of knowledge. The resulting scientific data will provide new insights into biophysical processes in Arctic regions and contribute to a better understanding of the state and change of permafrost in the Arctic. This project is funded by the German Federal Ministry of Education and Research and was initiated in 2021.

How to cite: Mueller, M. M., Thiel, C., Kaiser, S., Lenz, J., Langer, M., Lantuit, H., Marx, S., Fritz, O., and Zipf, A.: UndercoverEisAgenten - Monitoring Permafrost Thaw in the Arctic using Local Knowledge and UAVs, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-2698, https://doi.org/10.5194/egusphere-egu23-2698, 2023.

In the Tropics, disasters associated with natural hazards (intense convective rainfalls, floods, landslides) occur regularly. However, the general scarcity of reliable and accurate data collected on these events does not allow for a complete picture of their frequency and magnitude, thus hindering effective Disaster Risk Reduction (DRR). Such situation is observed in the Kivu region, in the eastern part of the DR Congo. Recurrent insecurity, long distances to travel, poor communication networks and the lack of financial resources to reach the affected areas are the main challenges faced by the Congolese Civil Protection in building a database that would allow for a better knowledge of these phenomena, in view of an appropriate disaster response and, in the long term, efficient DRR.

Based on this observation, a group of 20 citizen observers was set up to collect data on six different types of natural hazard disasters (floods, landslides, wind storms, hail storms, lightning, and earthquakes) using smartphone technology connected to an online platform. This new approach, based on citizen science, makes it possible to significantly improve the documenting and understanding of the spatial and temporal occurrence of these disasters that affect the provinces of North and South Kivu. Since the establishment of this network in December 2019, more than 700 events have been recorded.

If the data collected by this network of citizen observers constitute above all an unprecedented amount of information on the disasters occurring in such a tropical environment, they also allow for the compilation of a WebGIS and quarterly reports illustrated with maps and graphs, disseminated by Civil Protection to key DRR stakeholders active in the region, for a more tailored response, its planification, and, to some extent, the anticipation of such events. Scientists from universities and research centers in Bukavu and Goma are associated to that data collection and analysis. Moreover, citizen observers position themselves within their communities as key actors in raising awareness about disaster risks. However, although this type of approach has proven to be effective in the short term, the motivation on the long term of citizen observers, as volunteers, has been identified as a weakness to be addressed.

How to cite: Michellier, C., Mana Ngotuly, T., Maki Mateso, J.-C., Kambale Makundi, J., Bwishe, J.-M., Dewitte, O., and Kervyn, F.: Tracking natural hazard disasters in non-surveyed regions: the “citizen” observer network of the Kivu in DR Congo, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-15940, https://doi.org/10.5194/egusphere-egu23-15940, 2023.

The possibilities of citizen science-based approaches to environmental research and especially climate monitoring have recently expanded. This is among other things due to the availability of diverse measuring equipment at low costs, so that citizen science-based measuring missions can be implemented with a large number of participants. The advantages of high data density and spatial coverage are obvious. These advantages have been exploited for years by platforms such as www.awekas.at or www.weatherunderground.com and many others. With the help of mobile monitoring systems, the spatial coverage can now be extended even further. This means that the variability of climate values such as air temperature and relative humidity in cities can be investigated and more accurate forecasting models can be used.

A crucial aspect here is the reliability and comparability of the data collected with different devices. Therefore, we tested and compared within the EU project CityCLIM (www.cityclim.eu) different measurement equipment. Important characteristics of these devices are their low cost, ease of use and data access, data security and protection and the reliability of the measurement data. In the experiments presented here, 4 mobile systems were used: Meteotracker, senseBox, CHEAL5, PAM-AS520. All of these devices can determine air temperature, relative humidity, GPS-location and time and partly also particulate matter. In order to compare these systems, several measurement trips were made in the city of Leipzig in Saxony/Germany at different times of the year.

Surprisingly, there are considerable deviations between the devices in all measured values. This starts with the time and the GPS position. Here, there are sometimes shifts of several minutes and several metres. These errors could certainly be corrected with the help of calibration. However, this must also be practicable for the citizen scientist. In general, this example shows that quality control and backup of the data is necessary. In this sense, it is advantageous if there is a possibility to check the data live from the measurement operator or citizen. For this purpose, a direct upload of the data into the online portal/dashboard is very helpful. This direct data transfer also allows a simple and automated evaluation and storage of the large amounts of data.

Also the measurements of the air parameters show larger differences. Here, air flow at the sensor during the journey, protection from direct sunlight and the sensors used influence the measurement results. In any case, it is necessary to provide the users with detailed guidelines for the use of the sensors in order to increase the data quality. In summary, it turned out that the mobile measuring systems are suitable for citizen science-based climate observation with some limitations. Through the experiments, clear requirements for the devices could be worked out, which is helpful for the planning of future projects. The investigation of further devices and especially of quality control tools for the data are important next steps.

How to cite: Schmidt, F., Schütze, C., Ködel, U., Schütze, F., Liang, C., Schäfer, D., and Dietrich, P.: Comparison of Mobile Environmental Sensors for Citizen Science Based Climate Monitoring, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-12542, https://doi.org/10.5194/egusphere-egu23-12542, 2023.

Academia is more and more under the demand to create both scientific and societally relevant research with beneficial effects for society. There is a strong consensus that the engagement of non-academic actors in research activities is associated with greater societal relevance and usability of science for society. Involving non-academic actors within natural hazards and disaster risk research has seen a rise in popularity with the advent of participatory and transdisciplinary research approaches. Particularly in countries of the Global South, the participation, engagement, or involvement of non-academic actors in research on natural hazards and disaster risk is seen as promising strategy for solving data issues, raising awareness and generating knowledge. However, besides beneficial consequences, the participation, engagement, or involvement in scientific research may also have negative side-effects for non-academic actors (e.g., causing mistrust, anxiety, or research-fatigue). Against this background, the aim of the ImSE-R project is to assess how the participation, engagement, or involvement in scientific research on natural hazards and disaster risk may have consequences – ranging from intended impacts to unintended implications and negative side-effects for non-academic actors. This contribution presents the results of a systematic review of studies on hazards and disaster risk in the Himalayan region (2000-2022) to better understand how academic actors negotiate and manage research relationships with non-academic actors in the context of natural hazards and disaster risk research. The contribution derives insights on how non-academic actors were involved in natural hazard and disaster risk research activities (actively, passively); underlying motivations and goals of academic actors for involving non-academic actors in natural hazard and disaster risk research; and perceived impacts and implications of involving non-academic actors in research. The results of the review feed into the development of a conceptual framework on research impacts and implications in the context of natural hazard and disaster risk research.

How to cite: Posch, E.: Side-effects of doing research? Potential consequences of involving non-academic actors in natural hazard research, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-14528, https://doi.org/10.5194/egusphere-egu23-14528, 2023.

Roots are physical and chemical engineers of the subsurface that are sensitive to changes in climate, and whose power to reshape the subsurface differs with land cover. Roots create and destroy porosity through enmeshment of particles, lateral and vertical boring through regolith, and cleaving of rocks from parent material. Their ability to translocate water, exude sugars and acids, and take up solutes influences hydrologic connectivity, water residence times, carbon transport and transformation, microbial access to resources, and chemical equilibrium conditions. Analysis of land-cover datasets suggest that root depth distributions are changing globally, shallowing in agricultural environments and deepening with woody encroachment. Yet where, when, and how changes in root distributions alter water and carbon dynamics in the critical zone is not well known. Using data generated at environmental observatories across the U.S. Long-Term Ecological Research program, the Critical Zone Collaborative Network, National Ecological Observatory Network, and the Department of Energy Watershed Focus Areas in combination with the Pedogenic and Environmental Dataset (PEDS), we ask: How do roots shape regolith hydrology and carbon dynamics? 

A clear signal is emerging from grassland, forest, and agricultural sites across the U.S. that indicates changes in rooting dynamics have measurable and meaningful impacts on critical zone functions. Evidence shows that changes from forest to crop and back to forest impacts soil structure deep beneath the plow line in systematic ways. Losses of rooting abundance upon conversion of grasslands to agriculture affects the propensity of organic carbon to form and protect aggregates throughout the subsoil. Reduced fire frequency at tallgrass prairie sites in the Midwest have led to rapid woody expansion in recent decades. Where woody encroachment persists, coarse roots, smaller mean soil aggregate diameters, and more readily destabilized carbon pools proliferate. Encroachment of woody plants increases the infiltration of soil water rich in  CO₂ into deep rocks and enhances carbonate weathering as predicted by models. These woody plants rely on deeper water sources, draw soil moisture down to a greater degree at depth, and are likely responsible for reducing streamflow and changing the timing of groundwater contributions to the stream. At Rocky Mountains sites dominated by conifers and aspen, coarse- and fine-root abundances are elevated under aspen in the upper 75 cm of the soil profile compared to conifer sites. Elevated soil organic carbon, lower extractable organic carbon, lower C:N values and elevated enzyme activity indicate soil carbon under aspen is likely more stable as a result of more microbial processing. Finally, in a predominantly Douglas-fir forest in the Pacific Northwest, second-growth forests exhibit substantially fewer fine roots at depths <50 cm, which appears to exert control on nitrogen availability in this nutrient-limited system and thus potentially limits carbon stability as more extractable organic carbon is generated from second-growth forests at depth. Data from these sites demonstrate how alterations to rooting distributions change the physical structure and moisture status of soil, and may be linked to carbon stability as the proportion of fine and coarse roots dictate overall access to carbon pools.     

How to cite: Sullivan, P. L. and the SitS, FRES, and CZCN teams: How do roots restructure water and carbon dynamics in the critical zone?, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-4538, https://doi.org/10.5194/egusphere-egu23-4538, 2023.

In continental subsurface environments, biogeochemical reactions drive nutrient delivery, deep microbial life and mineral weathering, with crucial importance in the critical zone. Current models often simplify groundwater transport, using the residence time approach or hillslope models. However, increasing observations suggest that the nature, location and efficiency of reactions are strongly affected by groundwater 3D flow patterns, chemical gradients and subsurface heterogeneity. Here, we investigate how hydrological and geological structures control where and when biogeochemical reactions occur in the deep critical zone. For this purpose, our approach integrates long-term and widespread local observations in a catchment-scale framework and is based on data from two critical zone observatories of the French OZCAR national network. The first study took place in Guadeloupe (Obsera), where we integrated geophysical, hydrological and geochemical data in a reactive-hydrogeological model to simulate the 3D structure of groundwater flow paths and weathering. We found that the downstream evolution of the river chemistry is controlled by the pattern of hydrogeological circulations and by the depth of the weathering front. Furthermore, the calibrated 3D model allowed the delimitation of areas where weathering occurs and we showed that active weathering is restricted to catchment-areas where downward groundwater flows are deep. The second study focused on the dynamics of dissolved oxygen (DO) in a fractured aquifer at the Ploemeur catchment (Bretagne, France). Deep and intermittent inputs of DO in groundwater were observed, enabling the reaction of DO with dissolved Fe²⁺, in turn sustaining the development of deep microbial communities. In this study, we designed a simple model to simulate jointly the depth-distribution of DO and Fe²⁺ and to investigate the hydrological and geological factors controlling the DO depth-distribution. We found that the reducing capacity of the bedrock and the mean fluid transit time are the main parameters to explain and predict the depth of the oxic-anoxic transition in crystalline environments. In this presentation, we will provide new perspectives to observe and understand the origin of subsurface biogeochemical reactions and we will illustrate key processes that breakdown classical assumptions of reactive groundwater models.

How to cite: Bouchez, C., Osorio, I., Le Traon, C., and Le Borgne, T.: Groundwater flow patterns and subsurface heterogeneity drive critical zone geochemical reactions, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-12067, https://doi.org/10.5194/egusphere-egu23-12067, 2023.

The ecohydrology of the Urban Critical Zone is characterised by strong heterogeneity and the entangling of hydrological and human time scales (Sivapalan & Blöschl, 2015). This not only poses a challenge to field measurements and the transfer of insights to other urban systems, but consequently limits the development of universal theoretical approaches for urban systems. In this contribution, we propose an interdisciplinary methodology to approach this challenge. Following the school of Darwinian hydrology (Harman & Troch, 2014), we hypothesise that analog to the co-evolution of natural systems, the history of a city and its neighbourhoods is a strong control on current ecohydrological patterns and processes. Thus, we argue that field measurements must be complemented by research into the historical evolution of the urban area to provide a full description and explanation of any observations made. While we need to be careful to avoid a too deterministic or simplistic view of history, research into the historical evolution of an urban area can strengthen explanation of current urban ecohydrological behaviour and potentially enable knowledge transfer and prediction capabilities in “ungauged” cities with similar historical development, as well as to help guide measurement campaigns. Hence, we search for historical and environmental patterns that correlate to provide a testable explanation of current ecohydrological function of urban space. Similar to the "uniqueness of place" in hydrology, every society and city has a unique history that is shaped by the complex interaction among culture, environment, and political events (Berking & Löw, 2008). Thus, we want to formulate a framework for determining similarities in historical development at relevant temporal scales. This requires a strictly interdisciplinary approach, because the application of historical sciences and the interpretation of results is non-trivial and should not be attempted separately. 
 
We discuss our current progress in developing such an interdisciplinary framework in a case study of the city of Braunschweig, Germany. Braunschweig has 250,000 inhabitants, a medieval city centre with Gründerzeit–era neighbourhoods surrounding it. The former fortifications of the city have been converted into urban green spaces during the 18th century. The Oker river that surrounds the medieval city centre has been heavily modified. The built areas of the city centre show very little green space with few trees, especially compared to the surrounding neighbourhoods, where we find a multitude of street trees, smaller green spaces scattered throughout, and large parks adjacent to the built-up area. This works as an example of how the policy regarding green spaces has changed over time. In this heterogeneous environment, we hunt for urban ecohydrological units. In particular, we are interested in whether similar historical development is an indicator of similar ecohydrological function in an urban context.

References
Berking, H. & Löw, M. (2008). Die Eigenlogik der Städte, Campus Verlag, Frankfurt, Germany.
Harman, C. & Troch, P. (2014), Hydrology & Earth System Science, 18, 417–433.
Sivapalan, M. & Blöschl, G. (2015), Water Resources Research, 51, 6988–7022.

How to cite: Gillefalk, M., Neumann, F., Bücker, M., and Özgen-Xian, I.: Darwinian approaches for the Urban Critical Zone — A case study in the city of Braunschweig, Lower Saxony, Germany, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-7816, https://doi.org/10.5194/egusphere-egu23-7816, 2023.

Recent IPCC reports claim carbon neutrality as the key strategy for climate mitigation, therefore compensating greenhouse gases’ emissions by carbon (С) sequestration become the core of climate mitigation measures taken by cities. Developing urban green infrastructures is considered an efficient measure for C sequestration and climate mitigation in cities. However, most of these solutions consider C sequestration in aboveground biomass and ignore the role of urban soil-C stocks. Urban soils’ contribution to C balance in urban ecosystems remains overlooked so far, but gets increasingly important with ongoing climate change. Urban soils are exposed to direct and indirect anthropogenic influences, they are very heterogeneous and dynamic. This variability is driven by both environmental (e.g., vegetation, geomorphology, and parent material) and social (e.g., decisions on maintenance and management) factors. Traditional soil surveys focus on the environmental factor and barely ignore the social drivers, that might be appropriate for natural or agricultural areas, but can hardly be implemented to study soil C stocks in cities.  In the Netherlands, urban areas cover at least 15% of the territory and are projected to expand with more than 1000 km² by 2040, however urban soils remain overlooked and sustainable urban development strategies are not supported by soil data. this study we aimed to explore the effect of natural and social factors on the spatial variability in soil C on Wageningen – a middle-size university town in the Netherlands.

Wageningen is a perfect case study to investigate factors influencing spatial variability of urban soil C. A long history and unique landscape diversity create conditions for high spatial variation in soil-forming factors. Based on the parent materials, the residential blocks outside the center can be subdivided into strata dominated by sandy and clayey soils. Urban expansion and building up new residential blocks, public and private green areas coincided with development and management of urban soils. A random stratified soil survey (n=56) allowed capturing the effect of parent materials, land cover and land-use history. The effect of the social factor was studied by expert interviews with the owners of the green areas (key plots, n=10), where detailed soil survey was done. Expert interviews included information on soil management as well as personal questions. In result, typical ‘portraits’ of landowners/ green-keepers were developed and related to soil C-stocks assessment. It was concluded that land-cover and land-use history/ historical zoning distinguished spatial patterns in soil C at the city level, whereas at the local scale social factors dominated. Moreover, local spatial variability distinguished by differences in maintenance/ management practices (e.g., minimal management in a student house in comparison to an intensive maintenance with irrigation and adding composts in a high-price cottage) was comparable or even higher than total variance at the city level.  This is an important message for urban planners and landscape designers, claiming that the social factors and personal decisions shall not be ignored in climate-resilient strategies and practices to develop and maintain urban green infrastructures.

How to cite: Vasenev, S., Vlaming, M., Breeman, J., Romzaykina, O., and Stoorvogel, J.: Environmental and social drivers behind spatial variability of soil carbon in urban green infrastructures of Wageningen, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-11691, https://doi.org/10.5194/egusphere-egu23-11691, 2023.