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The ocean’s past may determine its future

The world’s oceans and seas have undergone enormous change over time and, in recent decades, the marine environment has deteriorated significantly in several ways. Reversing the trend and taking good care of our seas requires knowledge of how the marine environment has changed over time. And this has been confirmed by a new pilot study conducted by RISE and partners on behalf of the Swedish Agency for Marine and Water Management. 

Many recreational anglers maintain that considerably more fish were caught along Sweden’s coasts when they were younger, and there seems to be a general consensus that the sea has changed. For example, cod stocks in Kattegat have declined sharply over the past 25 years. But what constitutes natural change and how much is due to human impact? In order to create solutions for the management of truly sustainable seas, it is necessary to look further back in time.

– “To really understand the changes that have occurred, and thereby create common objectives, we need to have much longer time series,” says Sara Hornborg, Researcher at RISE and the person responsible for the pilot project on historical perspectives of the seas. “In this study, we employ a perspective that begins 10,000 years ago to try to create a picture of what the oceans looked like then and how they have changed over time.”

The project has studied how knowledge of the ocean’s past – more natural – ecosystems could be harnessed to strengthen what is referred to as ecosystem-based management. The assignment has been carried out on behalf of the Swedish Agency for Marine and Water Management in partnership with SGU (Geological Survey of Sweden) and the University of Gothenburg as well as international experts. In concrete terms, it has largely involved scouring literature and contacting various experts in order to get an overview of what types of data can be obtained to achieve a broader historical understanding of marine development. It turns out that using historical sources provides many advantages.

It is very difficult to describe this development in words alone

First time in Sweden

The Swedish Agency for Marine and Water Management is mandated by the government to ensure the conservation and sustainable use of seas, lakes and watercourses. This includes protecting endangered species and developing strategies for future fishing. It is now hoped that mapping historical marine data will serve as a better basis for decision-making.

– “This is the first time that a national agency in Sweden has taken a comprehensive approach to the issue of longer historical time series,” says Ingela Isaksson, Investigator at the Swedish Agency for Marine and Water Management.

According to Isaksson, fishing, in particular, is an area for which there is a great need to look further back in time in order to get an accurate and fair view of what a functioning ecosystem looks like:

– “Today we use data that goes back a maximum of 35 years, but at that point the stocks were already heavily depleted. With reliable historical data, we are able to adapt decisions concerning quantities that should be allowed to be fished.”

Aims to increase awareness

One challenge when it comes to understanding marine development is that much of what happens below the surface is hidden from human observation. In order to shed light on how the marine environment looked during different time periods, an illustrator was commissioned to create pictures from the source material. One example is how the Swedish west coast may have looked around 10,000 years ago when the first settlements were established. Another example is how the seabed may have looked before bottom trawling began in Kattegat, based on unique historical data.

– “It is very difficult to describe this development in words alone,” says Sara Hornborg at RISE. “Much of this project is about increasing awareness of changes in the sea, and these illustrations are a great help.”

The next step will involve the ways in which authorities and agencies can utilise the identified data, based on what needs exist and how different data sources can be used.

– “The UN has designated the 2020s as the decade of marine research for sustainable development. This means it’s important to increase awareness about our seas and oceans and what they were like in the past in order to gain acceptance and engage in dialogue regarding measures that may need to be implemented to ensure more sustainable use of our seas. We must have a scientific basis for the management of our seas, and historical data play an important role in this,” says Ingela Isaksson. 

Download the report here

Sara Hornborg

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Sara Hornborg


+46 10 516 66 96

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