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The effects of climate change are already visible in Finland. Milder winters and heavy rainfall are more commonplace, and the sea no longer completely freezes over. Even small changes arising from global warming have significant consequences that threaten the entire ecosystem. As the Baltic Sea is one of the world’s most sensitive and polluted seas, climate change is especially harmful to its ecosystem.

Voimakas aalto törmää sileään kalliopohjaan. Kuvattu aallon alta merenpohjalta.

Climate change affects ecosystems

Climate change affects the entire planet’s ecosystem and it changes the living conditions in the sensitive Baltic Sea. Humans, animals, plants, and other organisms are all connected in an ecosystem. What happens to one species will affect many different organisms.Nothing and no one is safe from the climate crisis. 

The visible consequences of climate change include rising sea levels, overly warm air and seawater, and extreme weather phenomena such as prolonged periods of heatwaves, rainfall, or storms.  

Up here in the north, climate change is reflected in heavier rainfall, milder and less snowy winters, and the fact that the sea no longer completely freezes over.  

Regenerative farming mitigates climate change

Heavier rainfall will cause even more nutrients to leach from the land into the Baltic Sea, thereby fuelling eutrophication. Significant methane emissions have been measured in shallow, eutrophicated coastal waters, and these emissions will further accelerate climate change. 

Seas worldwide have acted as carbon sinks, countering climate change. However, disturbing the ecological balance of the Baltic Sea may turn the sea into a source of climate emissions.

As regenerative farming sequesters carbon, it can mitigate climate change and reduce agricultural nutrient leaching. On the Carbon Action platform, BSAG works with farmers, researchers, and companies that are forerunners in regenerative agriculture. 

Lähikuva kaurasta, joka kasvaa pellolla.
Regenerative farming can sequester carbon, support biodiversity and improve soil health. It enables farmers to mitigate climate change and help the Baltic Sea.

Warmer air and seawater fuels eutrophication 

As the Baltic Sea is one of the most polluted seas in the world, the effects of climate change could be particularly damaging for the sea and its inhabitants.   

If there is no snow and the sea and rivers don’t freeze, there won’t be any spring floods either. Instead, freshwater will drain from the land into the sea all year round. 

The longer the soil and sea remain unfrozen, the more time there will be for running water to wash soil, organic matter, and nutrients into the sea. 

As the amount of organic matter in the sea increases, the seawater becomes darker and cloudier yearly. As the nutrient load rises, eutrophication and blue-green algae will also increase.The growth of blue-green algae promotes eutrophication, which fuels a cycle of eutrophication.  

Decreasing salinity and a changing ecosystem

The Baltic Sea is a naturally low-saline sea classified as brackish water. As more freshwater enters the sea through rainfall, its salinity further decreases.  

The Baltic Sea’s salinity has so far been maintained by salt, that is, [pulses of salty ocean water] that sporadically come through the Straits of Denmark. However, climate change may affect these pulses in unexpected ways. At worst, it will further reduce their frequency.

Many Baltic Sea species are already doing poorly due to the low salinity of the water. If the sea’s salinity continues to decrease, species that need saltwater may disappear while freshwater species will increase. 

Kuva on otettu merenalaisen jään alta, lähellä pintaa. Jäässä on ilmakuplia.
The Baltic Sea no longer completely freezes over in winter, affecting its ecosystems on many levels.


Maintaining the sea’s salinity level is essential, as Baltic Sea species have adapted to living in its distinctive brackish waters.

Invasive species are appearing on the shores of the Baltic Sea

Rising temperatures are also bringing new species to the coasts of the Baltic Sea – species that don’t belong to the native population and may have no natural enemies.

For example, previously unknown bird species may come to nest in the archipelago or coastal areas of the Baltic Sea.

Other new arrivals include raccoon dogs, which are already disturbing nesting birds, and the ramanas rose, which has spread into the wild from private gardens and is now overrunning formerly sandy beaches.

Tree cover is also changing. In Finland, the coniferous forest zone is moving towards Lapland due to the warming climate.

The climate crisis is a significant threat to the Baltic Sea. Marine conservation is becoming increasingly important due to climate change and global warming.

Climate change is altering interspecies relationships  

All the plants, animals, and other organisms in the Baltic Sea have adapted to their unique habitat over time. When a habitat changes, the species that live there also change: some decline and even disappear, while others will thrive. Some species are now being found even further north.

Cyprinoid fish are among those that are thriving. However, their increasing numbers are detrimental, as they feed on the zooplankton required to keep phytoplankton under control.

The Baltic Ringed Seal is one of the losers. It is used to nest on ice floes; if there is no ice, it has nowhere to nest.

Some of the Baltic Sea’s key species are also at risk, such as bladderwrack, which is necessary for many other species. The potential disappearance of key species will be reflected in all species and will reduce the biodiversity of the Baltic Sea. A loss of biodiversity would make the Baltic Sea’s ecosystems even more vulnerable to the effects of climate change. 

Vedessä ui kalaparvi, joka koostuu kolmipiikeistä tai kymmenpiikeistä. Taustalla on vanhaa järviruokoa johon on kiinnittynyt rihmalevää.
Three-spined and ten-spined sticklebacks have become much more common in recent years due to climate change, eutrophication, and a decline in predatory fish. Three-spined and ten-spined sticklebacks eat roe, which can further deplete predatory fish populations.

BSAG protects biodiversity

Protecting the biodiversity of the Baltic Sea is one of BSAG’s most important objectives. We can help by establishing more marine conservation areas in areas of high natural value. We can also positively impact marine habitats by reducing discharges to the sea through regenerative agriculture and responsible shipping


Anna Klemelä

Project Manager, Marine Biodiversity; Communications Specialist

+358 44 376 7511

Anton Lehtinen

Protection Coordinator, Marine Biodiversity

+358 40 041 0878