To the last bone
People love fish; be it as fine sushi, a valuable source of protein or cheap animal feed. But the sea is giving less and less. If there is no change in thinking soon, the last fishing grounds could be hopelessly exploited in forty years - with unforeseeable consequences for the entire ecosystem.
A report from the Independent, Spiegel Online and Reuters startled British and German tourists this summer: "Jellyfish plague hits Spanish Mediterranean coast".
At the same time, scientists discovered giant squid off Alaska for the first time – they usually live much further south off Peru.
The previous winter, fishermen around Japan complained about an invasion of giant Nomura jellyfish, weighing up to 200 kilograms, which destroyed or clogged their nets and rendered the few fish in them worthless with slime.
British ornithologists have just once again noted a lack of breeding success in various seabird species that are essentially dependent on sandeels, which are increasingly skimmed off for aqua farms or animal feed.
The Food and Agriculture Organization of the United Nations (FAO) warned in September that more than three quarters of the world's fisheries are already overfished or have already been completely destroyed.
At the same time, the United Nations reported that there are 150 temporarily or permanently dead sea zones worldwide where over-fertilization is causing algal blooms, oxygen deprivation and the death of all animal life - more than ever before.
Something is happening in the oceans and marginal seas of the blue planet - but obviously nothing good and no matter where science looks, as marine biologists and economists around Boris Worm from Dalhousie University in Halifax are now doing have done. By 2050, they predict, all currently used fish, mussel or crustacean grounds will have collapsed if the currently unsustainable use strategies continue.
Her warning is based on profound data, after all it includes the results of 32 controlled experiments, recordings from 48 different marine protected areas and global catch data of fish and invertebrates from the FAO, which were officially recorded between 1950 and 2003 in 64 major marine ecosystems were recorded. In addition, the scientists included archaeological recordings, historical logbooks, archive material and sediment samples in their analysis, in order to calculate for at least twelve coastal regions - such as the Wadden Sea, the Adriatic Sea, the Bay of San Francisco or the St. Lawrence River in Canada - each thousand-year-old To be able to set up time series of marine diversity and its use.
Chain Action in the Ecosystem
What they discovered shocked the biologist Worm: "Whether in individual tidal pools or entire ocean basins - we discovered the same pattern everywhere: If we lose one species, we lose the productivity and stability of the entire system. I was struck by how consistent these trends are - far stronger than we ever imagined." "Everywhere we found the same pattern: if we lose one species, we lose the productivity and stability of the entire system"
(Boris Worm) If species can no longer fulfill their ecological role, this results in a chain reaction. Other species are disappearing because the enemy of their enemy may be missing, as examples from the Caribbean show. There, some shark species are on the brink of extinction and are no longer keeping smaller predatory fish in check, which consequently increase in numbers and in turn permanently decimate scale carriers that eat plankton.
But without the vegetarians, the algae can spread uncontrollably, and when they die off after flowering periods, this leads to a lack of oxygen in the water. They often form thick carpets on coral reefs, whose inhabitants suffocate underneath. In the end, the species-rich ecosystem collapses and is replaced by a species-poorer one. In addition, this affects the safety of coastal residents, since he althy reefs or mangroves act as breakwaters and offer protection from storm surges.
Similarly targeted interventions also facilitate the establishment of invasive species, as shown by the case of the Pacific oyster (Crassostrea gigas) in the North Sea. It was introduced to the North Sea at the beginning of the 20th century as a breeding animal to replace the European oyster (Ostrea edulis), which had previously been decimated by overexploitation and was eventually almost completely wiped out.
The newcomer shouldn't have spread since it comes from warmer waters and shouldn't survive the European winters. Favored by climate change and higher water temperatures as well as by the ecological niche involuntarily cleared by the European relatives, the oyster with a migration background is now increasingly spreading in the North Sea. In doing so, it displaces the native mussels (Mytilus edulis), which are economically important and are used as food by many bird species in the Wadden Sea, while the Pacific oysters are almost impossible for them to crack. Climate change and overfishing taken together are also cited as the main culprits for increased jellyfish plagues, which benefit from the absence of their consistently fished enemies, such as tuna and sea turtles.
It's not too late yet
All in all, researchers noted a steady loss of species over the last thousand years, especially in easily accessible coastal areas, which has accelerated significantly since the industrial revolution. The populations of a good third of all fish, mollusc or crustacean species used in this way are now considered to be completely exhausted, so that their recovery seems at least very questionable - such as that of the Atlantic cod off Newfoundland, the management of which had to be completely stopped in 1995. "There is good news because it is not too late to turn things around"
(Boris Worm) The result was the loss of 40,000 jobs and to date there has been no detectable increase in cod locally. This is linked to the many degenerated so-called nurseries of the animals such as seagrass meadows, oyster beds, mangroves or s alt marshes, which were either directly destroyed by humans or suffered from the various chain reactions: Their losses amount to around seventy percent of the original population, and these also affect the sea's ability to clean itself, which has deteriorated at a similar rate.
But not everything looks pessimistic, as the researchers emphasize: "There is good news, because it is not too late for a turnaround," says Worm. Because their evaluation also showed the strong recreational power the seas still have, despite all the pressures. If – unlike in the case of cod – the ripcords are pulled in time, the species and the ecosystem as a whole have a remarkable ability to regenerate.
As evidence, Worms team has 48 marine reserves where no fishing or similar commercial use is allowed. Compared to similar, but managed areas, they have on average a fifth higher biodiversity - also of species that are in commercial demand. In addition, the catches in the vicinity of the protected areas could be increased fourfold per unit area, which shows that these prohibited zones can serve as a haven and source area for new fish abundance.
At the same time, these areas withstood disturbances such as storms or heat stress more often than those already stressed by fishing. The higher the natural species richness was in comparison to the exploited areas, the more stable and productive these protection zones proved to be. "If we don't fundamentally change the way we treat marine species, this will be the last century for wild seafood"
(Steve Palumbi) According to Worm and his partners, immediate countermeasures such as improved water quality, truly sustainable fishing quotas and the designation of strictly protected retreat areas would quickly make themselves felt: "We probably won't see a complete recovery within a year, but many species will return much faster than expected - in three, five or ten years."
But if humanity continues as before, co-author Steve Palumbi from Stanford University will probably be right: "If we don't fundamentally change the way we deal with marine species, this will be the last century for wild fish and seafood be."
