https://doi.org/10.5194/esd-2021-54 Preprint. Discussion started: 6 July 2021 c Author(s) 2021. CC BY 4.0 License. Human impacts and their interactions in the Baltic Sea region Marcus Reckermann1, Anders Omstedt2, Tarmo Soomere3,4, Juris Aigars5, Naveed Akhtar6, Magdalena Bełdowska7, Jacek Bełdowski8, Tom Cronin9, Michał Czub10, Margit Eero11, Kari Hyytiäinen12, Jukka- Pekka Jalkanen13, Anders Kiessling14, Erik Kjellström15, Karol Kuliński8, Xiaoli Guo Larsén9, Michelle 5 McCrackin16, H. E. Markus Meier17,18, Sonja Oberbeckmann19, Kevin Parnell3, Cristian Pons-Seres de Brauwer9, Anneli Poska20, 21, Jarkko Saarinen22,23, Beata Szymczycha8, Emma Undeman16, Anders Wörman24, Eduardo Zorita6 1International Baltic Earth Secretariat, Helmholtz-Zentrum Hereon, Max-Planck-Str. 1, 21502 Geesthacht, Germany. 10 2Departement of Marine Sciences, Box 461, 405 30 Göteborg, Sweden. 3Department of Cybernetics, School of Science, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn, Estonia 4Estonian Academy of Sciences, Kohtu 6, 10130 Tallinn, Estonia. 5Latvian Institute of Aquatic Ecology, Voleru iela 4, 1007, Rīga, Latvia. 6Institute of Coastal Systems – Analysis and Modeling, Helmholtz-Zentrum Hereon, Max-Planck-Str. 1, 21502 Geesthacht, 15 Germany. 7Institute of Oceanography, University of Gdansk, Pilsudskiego 46, 81-378 Gdynia, Poland. 8Institute of Oceanology, Polish Academy of Sciences, Marine Chemistry and Biochemistry Department, Powstańców Warszawy 55, 81-712 Sopot, Poland. 9DTU Wind Energy Department, Frederiksborgvej 399, Bygning 115, rum S40, 4000 Roskilde, Denmark. 20 10Institute of Oceanology, Polish Academy of Sciences, Marine Ecology Department, Powstańców Warszawy 55, 81-712 Sopot, Poland. 11Technical University of Denmark, National Institute of Aquatic Resources, Kemitorvet, Building 201, 2800 Kgs. Lyngby, Denmark. 12Department of Economics and Management, P.O. Box 27, 00014 University of Helsinki, Finland. 25 13Finnish Meteorological Institute, Erik Palménin aukio 1, 00560 Helsinki, Finland. 14Swedish University of Agricultural Sciences, Department of Animal Nutrition and Management; Aquaculture, Box 7024, 750 07 Uppsala, Sweden. 15Swedish Meteorological and Hydrological Institute, Rossby Centre, 601 76 Norrköping, Sweden. 16Baltic Sea Centre, Baltic Nest Institute, Stockholm University, 106 91 Stockholm, Sweden. 30 17Department of Physical Oceanography and Instrumentation, Leibniz Institute for Baltic Sea Research Warnemünde, Rostock, 18119, Germany. 18Research and Development Department, Swedish Meteorological and Hydrological Institute, Norrköping, 601 76, Sweden. 19Biological Oceanography, Environmental Microbiology, Leibniz-Institute for Baltic Sea Research, Seestrasse 15, 18119 Rostock, Germany. 35 20Department of Physical Geography and Ecosystem Science, Lund University, Sölvegatan 12, 223 62 Lund, Sweden. 21Department of Geology, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn Estonia. 22Geography Research Unit, P.O.Box 8000, 90014 University of Oulu, Oulu, Finland. 23School of Tourism and Hospitality, University of Johannesburg, Johannesburg, South Africa. 24KTH Royal Institute of Technology, 100 44 Stockholm, Sweden. 40 Correspondence to: Marcus Reckermann ([email protected]) 45 50 1 https://doi.org/10.5194/esd-2021-54 Preprint. Discussion started: 6 July 2021 c Author(s) 2021. CC BY 4.0 License. 55 Table of content 1. Introduction 2. The region 3. Terminology and the DPSIR matrix 4. The impact matrix of interrelations 60 5. Factors of regional change Natural 5.1. Climate change 5.2. Coastal processes 5.3. Hypoxia 65 5.4. Acidification 5.5. Submarine Groundwater Discharge 5.6. Marine ecosystems 5.7. Non-indigenous species 5.8. Land use and land cover 70 Human-induced 5.9. Agriculture and nutrient loads 5.10. Aquaculture 5.11. Fisheries 5.12. River regulations and restorations 75 5.13. Offshore wind farms 5.14. Shipping 5.15. Chemical contaminants 5.16. Unexploded and dumped warfare agents 5.17. Marine litter and microplastics 80 5.18. Tourism 5.19. Coastal management 6. Key messages and knowledge gaps 7. Summary and discussion 8. Conclusions 85 90 95 2 https://doi.org/10.5194/esd-2021-54 Preprint. Discussion started: 6 July 2021 c Author(s) 2021. CC BY 4.0 License. Abstract. Coastal environments, in particular heavily populated semi-enclosed marginal seas and coasts like the Baltic Sea region, are stongly affected by human activities. A multitude of human impacts, including climate change, affects the different compartments of the environment, and these effects interact with each other. As part of the Baltic Earth Assessment Reports (BEAR), we present an inventory and discussion of different human-induced 100 factors and processes affecting the environment of the Baltic Sea region, and their interrelations. Some are naturally occurring and modified by human activities (i.e. climate change, coastal processes, hypoxia, acidification, submarine groundwater discharges, marine ecosystems, non-indigenous species, land use and land cover), some are completely human-induced (i.e. agriculture, aquaculture, fisheries, river regulations, offshore wind farms, shipping, chemical contamination, dumped warfare agents, marine litter and microplastics, tourism, coastal management), and they are all interrelated to different degrees. 105 We present a general description and analysis of the state of knowledge on these interrelations. Our main insight is that climate change has an overarching, integrating impact on all of the other factors and can be interpreted as a background effect, which has different implications for the other factors. Impacts on the environment and the human sphere can be roughly allocated to anthropogenic drivers such as food production, energy production, transport, industry and economy. We conclude that a sound management and regulation of human activities must be implemented in order to use and keep the 110 environments and ecosystems of the Baltic Sea region sustainably in a good shape. This must balance the human needs, which exert tremendous pressures on the systems, as humans are the overwhelming driving force for almost all changes we see. The findings from this inventory of available information and analysis of the different factors and their interactions in the Baltic Sea region can largely be transferred to other comparable marginal and coastal seas in the world. 115 120 125 130 3 https://doi.org/10.5194/esd-2021-54 Preprint. Discussion started: 6 July 2021 c Author(s) 2021. CC BY 4.0 License. 135 1 Introduction Anthropogenic climate change has been regarded as a major driver for environmental changes since the industrial revolution. The IPCC has been the leading worldwide expert body to assess and document the currently available knowledge (Agrawala, 1998). Regional climate change assessment reports have taken the IPCC example to the regional scale, e.g. for the Baltic and North Seas (BACC Author Team, 2008, BACC II Author Team, 2015, Quante and Coljn, 2016). However, a multitude of 140 human-induced factors next to climate change affects the environments of coastal seas. For the Baltic Sea region, the following was concluded: „When addressing climate impacts on, for example, foresty, agriculture, urban complexes, and the marine environment in the Baltic Sea basin, a broad perspective is needed which consider not only climate change but also other significant factors such as changes in emissions, demographic and economic changes, and change in land use.“ (von Storch et al., 2015). Furthermore, it was stated that climate change effects “are not straightforward and are difficult to distinguish 145 from other human factors such as atmospheric deposition, forest and wetland management, eutrophication and hydrological alterations” (Humborg et al., 2015). In this paper, we examine a number of different human factors (see definition of terms below) affecting the coastal environment of the Baltic Sea region. We assess what is currently known about the impact of climate change on these factors and how they influence each other. In this respect, we define the coastal zone as the land areas, which have an impact on or are affected by the coastal sea, and the sea areas that are directly and substantially affected by the 150 land in their immediate neighborhood, or have an impact on the land. The Baltic Sea is a marginal sea that is strongly influenced by its coasts so that coastal issues can be examined here like under a magnifying glass. The notion that the state and function of physical and living environments depend on different interacting factors is old. Humboldt stated in 1807: “In this great chain of causes and effects, no single fact can be considered in isolation. The general equilibrium obtaining in the midst of these disturbances and apparent disorder is the result of an infinite number of mechanical 155 forces and chemical attractions which balance each other; and while each series of facts must be examined separately in order to recognize a specific law, the study of nature, which is the main problem of general physics, demands the gathering together of all the knowledge dealing with modifications of matter.” (Humboldt and Bonpland, 2009). This notion has since evolved into now generally accepted and used concepts, e.g. “ecosystem” (Tansley, 1935), “biosphere” and “biogeochemistry” (Lapo, 2001). 160 At least since the Neolithic Revolution, i.e. the transformation from a hunter-gatherer to a farmer subsistence, humans have shaped the earth´s surface,