Impact of natural hazards on global ecosystems

Abstract

Natural hazards are a driver of ecological dynamics as they alter individual species, community structure and entire ecosystems. Their ecological impact can be highly variable over space and time: perceived by some species as disastrous but vital for the survival of others. The ability of a system to cope with such events is called ecological resilience and depends on biotic and abiotic factors, as well as the disturbance legacies. With global climate change, intensity, frequency, and spatial distribution of natural hazards will change. As a result, understanding the ecological resilience is crucial to analyse implications of future changes. So far, studies investigated mainly the impact of one natural hazard on specific species, regions, or ecosystem services but an approach to investigate global patterns is still missing. In this thesis, the impact modelling platform CLIMADA was used to assess the current impact of four natural hazards (tropical cyclones, river floods, wildfires, European winter storms) on ecoregions on a global scale. For each natural hazard type, distinct patterns of a hazard’s impact on ecoregions were found with large differences among and within ecological realms and biomes. Based on the current hazard-ecosystem interactions, the relative change of hazard activity over the next 60 years was quantified by comparing current and future hazard patterns. Results indicated global changes in hazard activity with new patterns of tropical cyclone activity and river flood events for most ecoregions. To identify the implications of changing hazard regimes for ecoregions, recovery times of experimental field studies were analysed and linked to local return periods of tropical cyclones. Differences between modelled return periods and measured recovery times were found between the analysed sites, but a global scientific link was difficult to prove because of differences in site and hazard characteristics. The knowledge about hazard-ecosystem interactions combined with the implications of recovery times yields great potential to investigate upcoming changes through climate change for specific regions. Lastly, the findings of this thesis were applied on a set of ecologically important areas. Here again, all regions experienced natural hazards to some extent so far, but future intensities and frequencies will change radically for some areas. Additionally, the statistical tests imply a link between hazard occurrence and ecological status which has great potential for further application.