Identifying and addressing the anthropogenic drivers of global change in the North Sea: a systematic map

Marine ecosystems worldwide face extreme stress from human activities, with the North Sea being particularly affected and experiencing altered processes. To assess anthropogenic drivers for sustainable management, the Millenium Ecosystem Assessment (MEA) and the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) distinguished five main anthropogenic drivers: direct exploitation of fish and seafood, sea use change, human-driven climate change, pollution, and invasive alien species. However, evidence of the drivers' relevance and their potential effects on species and the environment over time remains scarce. This systematic map provides knowledge on the five main anthropogenic drivers in the North Sea from 1945 to 2020 and identifies potential knowledge gaps in terms of management implications.

To identify relevant articles we used our published systematic map protocol. We conducted systematic searches of academic and grey literature in English, German, and French in online databases (Web of Science, Scopus, PubMed, AquaDocs). The search followed a Population-Exposure-Comparison-Outcome framework and included the period January 1945 to December 2020. A total of 22,511 articles were deduplicated and screened by title and abstract, the remaining 5795 were screened full-text to provide a widely integrated evidence base. A set of 3356 articles were retained following eligibility criteria and were included in the final database. We extracted information on drivers in detail and their effects on study populations within different areas in the North Sea. Knowledge clusters and gaps were identified from the scientific effort and are synthesized narratively.

Out of the 3356 articles, the majority focused on pollution throughout the entire period of 75 years. Research interest has increased in climate change and biological invasion only in the most recent decades. We identified knowledge clusters in the southern North Sea, especially in ICES standard species areas 6 and 7, which has the most articles overall, mainly emphasizing pollution. Northern areas were in contrast studied the least. The effects of pollution were mainly linked to changes in chemical water properties and to contamination levels for benthos and fish. The other drivers were rather associated with changes in biomass or abundance, with a strong focus on fish and benthos populations. A key knowledge gap was on the effects of global change, herein defined as simultaneous assessment of all five drivers, at different organizational levels and therein on different populations.

This systematic map reveals substantial peer-reviewed evidence on the five main anthropogenic drivers in the North Sea. The map uncovers a strong increase in research interest regarding these drivers over the years, with a strong focus towards pollution and southern North Sea areas. Despite the increasing importance of climate change effects, this map highlights limited research effort on it. As ecosystem management nowadays strives for sustainable use of marine systems, it is more important than ever to understand linkages between drivers, potential cumulative effects and possible repercussions. The map revealed a strong knowledge gap regarding these linkages due to global change. On this basis, further systematic reviews can acknowledge these gaps, identifying the drivers' impacts and their quick evolvement to support management decision-making at various governance levels.