The oceans store carbon and produce oxygen.
They regulate the global climate much more than the soil and plants on land.
In the past 200 years, the oceans have absorbed about a quarter of the CO₂ from the atmosphere.
The oceans are therefore an integral part of the ecological system, without them the earth would be much warmer than it already is.
But the oceans are threatened by global warming.
They acidify and change their oxygen content.
A problem that makes this worse: overfishing.
Huge ships pull over 90 million tons of fish out of the water every year.
Most of it is used for human consumption, the rest mainly for the production of fishmeal and fish oil.
Studies have shown that the biomass of fish used industrially has roughly halved between the industrial revolution and the 1990s.
The fish population has drastically decreased.
However, the marine animals are part of the so-called biological carbon pump.
They also protect the climate.
This has to do with the movement of the fish, what they eat and what they excrete.
How can the overfishing of the seas be slowed down?
An idea: aquaponics.
For this purpose, fish and plants are grown on land in large greenhouses.
The aim is to create a closed circuit that is as efficient as possible in order to save resources.
And of course: To breed fish that can be eaten without fishing empty lakes and seas.
In this episode of the climate report, we ask Viola Kiel from the SPIEGEL science department whether industrial fishing can be slowed down in this way.