Mapping potential cumulative impacts of multiple anthropogenic stressors in Danish marine waters

NIVA Denmark is a regional office under the Norwegian Institute for Water Research (NIVA), an institution with over 50 years experience in applied aquatic science.  NIVA Denmark is focussed on applied research in aquatic ecosystems and evidence-based consultancy. Their key areas of research include eutrophication, hazardous substances, biodiversity and ecosystem health, as well as the implications of multiple human activities in aquatic environments. The organisation’s work is split between applied research and innovation and projects for government agencies, international organisations and industry.

Within NIVA Denmark, researchers were aiming to map the potential cumulative impacts of multiple anthropogenic activities and their resulting stressors on coastal and estuarine ecosystems in Danish waters of the North Sea - Baltic Sea transition zone, to assess differences in stressor contributions between the EU’s Marine Strategy Framework Directive (MSFD) and Water Framework Directive (WFD) and to determine the relative local importance of stressors along a gradient from inner fjords to offshore waters. In order to achieve this, they required access to datasets on both stressors and ecosystem components in Danish marine waters. The study was based primarily on publicly available datasets for both stressors and ecosystem components.

EMODnet Seabed Habitats' EUSeaMap 2016, was a key data source for defining benthic habitats in Danish waters. The original data contained 37 benthic habitat types, which the authors re-classified into eight broad-scale benthic habitat types for use in this study. This information was merged with datasets on estuaries and coastal waters, as well as data on other environmental factors such as oxygen deficit and oceanographic processes. This spatial analysis was then combined with calculation estimates of potential cumulative impacts, which were also made using open-source software. Eventually, these two components came together to create a spatial human impact model, revealing areas of highest potential impact and ranking stressors to identify those causing the highest degree of impact throughout the study area. The spatial distribution of ecosystem components and mapped stressors were summarised by calculating an ecosystem index and an unweighted stressor index. Throughout the study, the authors emphasized and demonstrated the benefits of open-source data and software in making their methodologies cost-effective.

The authors were able to conclude that the top ranked stressors for the entire study area were nutrient input and climate anomalies. They also determined that nutrients and physical modifications to a habitat had higher impacts within fjords or estuarine systems, and that fisheries, contaminants and noise pollution had higher impacts in offshore waters. These results showed an impaired status for the Danish marine environment and provide evidence-based information in support of ecosystem-based management, and the importance of considering all components of an ecosystem when establishing management measures and a greater need for co-ordination and harmonization while implementing the Marine Strategy Framework Directive and Water Framework Directive.