This report presents a holistic assessment of risk from cumulative human pressures in a region of the outer Oslofjord including Ytre Hvaler and Færder national parks. The work comprises an evaluation of human sectors (e.g. fisheries, tourism, wastewater treatment) which, through their activities in the region, add pressures to the marine environment. The risk of negative impact on the marine ecosystem is evaluated based on how exposed ecosystem components are to the different pressures from the sectors, and what effect a pressure is expected to have. This provides a systematic assessment of information from multiple sources, which combined with expert judgment is used to give a weighting of pressures and present a holistic view of ecosystem risk. The primary goal is to provide a common ground for discussion about direct, negative impacts on the ecosystem as seen across sectors and management responsibilities.
The method used in this report has been utilized in several other marine ecosystem risk assessments, both in Norway and internationally, by ICES, OSPAR and through various research projects. It was developed in a former EU-project, Options for Delivering Ecosystem-based Marine Management (ODEMM), and is often called the “ODEMM-method” or (in Norway) the “CoastRisk-method” since it was also used in the CoastRisk project (2019-2024). An assessment of risk based on exposure and effect is considered more reasonable for evaluating pressures from activities already operating in an area, compared to the traditional evaluation of risk as probability × consequence. Accidental events (e.g. oil-spills) are not considered, and we have focused on activities generally occurring through a “normal year”, preferably the period 2022-2023 where data has been available.
Harvesting, contaminants, microplastics, abrasion and input of nutrients are the five main risk-contributing pressures, which in sum contribute to more than 70 % of the total risk score for the region evaluated. These pressures are considered to give a relatively wide exposure, are added frequently throughout the year, arise from multiple sectors and have chronic to acute effects on a range of ecosystem components. Shellfish, demersal fish, seagrass, soft-bottom fauna and early life stages of fish are the ecosystem components with the highest risk of cumulative, negative impacts.
A confidence assessment shows that there is generally high confidence that ecosystem components are exposed to harvesting and nutrients, but lower confidence for exposure to contaminants and microplastics. The two latter are considered to have a high persistence in the environment, which may give accumulated effects over time and is particularly important for sustainable management of this ecosystem. Demersal fish, seabirds, seagrass, marine mammals and hard-bottom fauna (corals) are the ecosystem components considered to have the lowest resilience in the region.
Our results show that cross-sectoral cooperation is a necessity to solve the environmental challenges in the Oslofjord. Risk from harvesting is associated with both recreational and commercial fishing, while risk from contaminants is associated with wastewater treatment, land-based industry, marine transportation (shipping) and (to a smaller extent) agriculture, coastal infrastructure and tourism & recreation. Risk from microplastics is associated with coastal infrastructure, wastewater treatment and to some extent from fishing activities and leisure boats, and risk from abrasion is associated with commercial fishing (bottom trawling) in addition to smaller contributions from a range of other sectors. Appendix 1 of the report provides a description of each sector and its activities in the region, which pressures the activities are associated with and why, and is meant to give an indication for how exposure has been scored for the respective sectors. Evaluation of exposure and effect is presented in figures in the report and Appendix 3, for full transparency and as a starting point for further discussions.