Risks to Marine and Estuarine Ecosystems and Nature's Contributions to People under Extreme Events

Marine and estuarine ecosystems provide essential contributions to people, from coastal protection and biodiversity support to cultural and economic well-being. Due to the changing climate, these ecosystems are increasingly exposed to extreme storms, floods, droughts, and marine heatwaves, threatening not only the ecosystems themselves but also their contributions. To identify the direct impacts on ecosystem conditions that these extremes can have and their cascading impacts on the social-ecological system, impact webs have been developed with different actors. Impact webs are a conceptual modelling approach for assessing systemic risks that have been employed in diverse cases. However, the impact web methodology has not yet been applied to focus on ecosystem conditions and their cascading impacts on Nature’s Contributions to People. Using the Elbe estuary and its adjunct German Bight as a case study, nine ecosystems have been used as an analytical focus for the impact webs, corresponding to IUCN ecosystem functional groups and Natura 2000 habitats commonly found in the case study area. Actors contributing to the co-creation of the webs included ecologists, experts from federal and local agencies responsible for the management of these ecosystems, as well as actors representing local interests, like tourism.

This contribution to the World Biodiversity Forum presents the methodological approach to identify systemic ecosystem risks and discusses the direct and cascading impacts on ecosystem conditions and their contributions to people, considering the different biodiversity nexus elements. It pays particular attention to the similarities and differences of impacts across the different ecosystems in relation to extreme events. This is critical for identifying compound risks, e.g., when storm surges and river floods occur simultaneously. Compound risks have been found to accelerate the impact on ecosystems beyond the sum of the impacts in individual events.

Building on the various identified direct, compounding, and cascading impacts, entry points for the development of adaptation options, including nature-based solutions, to protect marine and estuarine ecosystems and their contributions to people will be presented and discussed.