Wildfire risk increases following non-fire disturbance events, but this relationship is not always linear or cumulative, and previous studies are not consistent in differentiating between disturbance loops versus cascades. Previous research on disturbance interactions and their influence on forest fires has primarily focused on fire-prone regions, such as North America, Australia, and Southern Europe. In contrast, less is known about these dynamics in Central Europe, where wildfire risk and hazard are increasing. In recent years, forest disturbances, particularly windthrow, insect outbreaks, and drought, have become more frequent in Central Europe. At the same time, climate change is influencing fire weather conditions that further intensify forest fire dynamics. Here, we synthesize findings from the recent literature on disturbance interactions in Central Europe with the aim to identify disturbance-driven processes that influence the regional fire regime. We propose a conceptual framework of interacting disturbances that can be used in wildfire risk assessments and beyond. In addition, we identify knowledge gaps and make suggestions for future research regarding disturbance interactions and their implications for wildfire activity. Our findings indicate that fire risk in the temperate forests of Central Europe is increasing and that non-fire disturbances and their interactions modify fuel properties that subsequently influence wildfire dynamics in multiple ways.

Glaciers on Kilimanjaro are unique indicators for climatic change in the tropical midtroposphere of Africa, but their disappearance seems imminent. A key unknown is their present ice thickness. Here, we present thickness maps for the Northern Ice Field (NIF) and Kersten Glacier (KG) with mean values of 26.6 and 9.3 m, respectively, in 2011. In absence of direct measurements on KG, multitemporal satellite information was exploited to infer past thickness values in areas that have become ice-free and therefore allow glacier-specific calibration. In these areas, KG is unrealistically thick in the existing consensus estimate of global glacier ice thickness.

In Europe, forest disturbances increased in scale and severity over the past 70 years producing large amounts of disturbed timber volume [1]. Projections show a further increase of natural disturbances in severity and frequency under a changing climate [2]. In addition, climate change also causes shifts in forest biome distribution due to changes in growing conditions [3] and disturbance patterns [4].As different disturbance types are interconnected and effects of these interactions have been identified [5], investigating them is especially relevant as they can cause amplification of disturbance effects.Current ground-based monitoring programs, such as national forest inventories, cannot provide comprehensive and continuous coverage of large areas over time. Therefore, remote sensing applications improve existing data gathering and availability of spatially explicit records for the monitoring of affected areas [6].For European forests, several different databases collect spatially explicit data on different types of forest disturbances, such as windthrow, fire, and pathogen or insect infections [1]. Across Europe, data from these databases indicate several hotspots, where disturbance interactions can be investigated.In this study, we investigate several different areas affected by natural disturbances along a gradient in Europe by combining climate data and data on drought occurrence to identify and assess spatio-temporal combinations of predisposing large-scale climate conditions preceding disturbance events. In addition to assessing current interactions between climate and natural disturbance occurrences, our goal is to relate those to projected climate change scenarios in order to investigate the impacts of disturbances on future forest ecosystems. References:[1] Patacca, M., Lindner, M., Lucas-Borja, M. E., Cordonnier, T., Fidej, G., Gardiner, B., Hauf, Y., Jasinevičius, G., Labonne, S., Linkevičius, E., Mahnken, M., Milanovic, S., Nabuurs, G.-J., Nagel, T. A., Nikinmaa, L., Panyatov, M., Bercak, R., Seidl, R., Ostrogović Sever, M. Z., Socha, J., Thom, D., Vuletic, D., Zudin, S., and Schelhaas, M.-J.: Significant increase in natural disturbance impacts on European forests since 1950, Global change biology, 29, 1359–1376, https://doi.org/10.1111/gcb.16531, 2023.[2] Machado Nunes Romeiro, J., Eid, T., Antón-Fernández, C., Kangas, A., and Trømborg, E.: Natural disturbances risks in European Boreal and Temperate forests and their links to climate change – A review of modelling approaches, Forest Ecology and Management, 509, 120071, https://doi.org/10.1016/j.foreco.2022.120071, 2022.[3] Kirschbaum, M. U. F.: Forest growth and species distribution in a changing climate, Tree physiology, 20, 309–322, https://doi.org/10.1093/treephys/20.5-6.309, 2000.[4] Altman, J., Fibich, P., Trotsiuk, V., and Altmanova, N.: Global pattern of forest disturbances and its shift under climate change, The Science of the total environment, 915, 170117, https://doi.org/10.1016/j.scitotenv.2024.170117, 2024.[5] Burton, P. J., Jentsch, A., and Walker, L. R.: The Ecology of Disturbance Interactions, BioScience, 70, 854–870, https://doi.org/10.1093/biosci/biaa088, 2020.[6] Gnilke, A. and Sanders, T. G. M.: Distinguishing Abrupt and Gradual Forest Disturbances With MODIS-Based Phenological Anomaly Series, Frontiers in plant science, 13, 863116, https://doi.org/10.3389/fpls.2022.863116, 2022.

Glaciers on Kilimanjaro are unique indicators for climatic changes in the tropical mid-troposphere of Africa. The history of severe glacier area loss raises concerns about an imminent future disappearance. Yet, the remaining ice volume is not well known. We reconstruct thickness maps for 2000 and 2011 for the Northern Icefield (NIF) and Kersten Glacier (KG) that are informed by ground-truth thickness measurements and multi-temporal satellite information. For 2011, we find mean thickness values of 26.6 and 9.3 m, respectively. The existing consensus estimate for global glacier ice thickness shows unrealistically thick values for KG in areas that are meanwhile ice-free.

The glaciers on Kilimanjaro are unique indicators for climatic changes in the tropical mid-troposphere of Africa. Glaciers in the tropics have shown a severe retreat since the Last Glacial Maximum and the glaciers on Mt. Kilimanjaro are no exception, with an 85% reduction in glacier area from 1912 to 2013. This history of severe glacier area loss raises concerns about an imminent future disappearance. Yet, the remaining ice volume is not well known.By combining state-of-the-art techniques from satellite remote sensing and glacier mass balance modelling with data assimilation, we inferred the  glacier ice thickness of two selected glaciers on Mt. Kilimanjaro. We reconstruct thickness maps for 2000 and 2011 for the Northern Icefield and Kersten Glacier and find mean thickness values of 26.6 and 9.3 m for 2011, respectively. Model validation was difficult for Kersten Glacier, as no ice thickness  measurements were available. Thus, the first attempt to use decadal retreat information, to infer past glacier ice thickness, which are used to do a glacier-specific calibration of the ice thickness reconstruction, was conducted by creating a generic margin thickness from glacier outlines and DEM differencing. This approach proved to be reasonable for Kersten Glacier, where a more common glacier type was assumed, but seemed to underestimate ice thickness at the Northern Icefield, because of the complex topography.The poster summarizes the results obtained from the thickness reconstructions and compares them to thickness maps from an existing global consensus estimate. In comparison to our results the consensus estimate shows unrealistically thick values for KG in areas that are meanwhile ice-free. A rough projection on glacier recession based on the generated thickness data agrees with other estimates pointing towards the disappearance of the glaciers between 2040 and 2060.