The distribution of biomass in the oceans, which has always followed an unchanging rule, is now broken at the high end of the spectrum. The proof that humans are not a predator like the others, shows a new study.
In 1972, scientists discovered that ocean life followed an unchanging mathematical rule: the smaller an organism, the more abundant it is in the ocean. thefor example is a billion times smaller than the , but it is a billion times more abundant. And this rule is incredibly precise: Analyzing water samples taken from the Atlantic and the Pacific, Ray Sheldon, a of Bedford Institute of Oceanography in Canada, found that for every size slice of plankton, you get exactly the same . In a liter of water for example, you will have a third of plankton between 1 and 10 in diameter, a third of plankton between 10 and 100 micrometers and a third between 100 micrometers and 1 millimeter. The concentration varies according to the depth (there is less biomass in the deep water), but the proportions remain unchanged.
A valid rule from bacteria to whales
It turns out that this rule is repeated for all marine animals,. In 2019, a Russian researcher that it applied to organisms present in the soil. Many hypotheses have been put forward to explain this phenomenon, such as the , the consumption of food and reproduction or death rate, all correlated with the size of living organisms.
Biomass of fish over 10 grams and marine mammals decreased by 60%
This natural harmony is however in the process of being upset, warns Eric Galbraith, professor at McGill University in Montreal (Canada) today. Co-author of a study published in November in, the scientist argues that this rule is no longer respected for very large animals. ” Human impacts appear to have dramatically truncated the top third of the spectrum », He explains. Researchers have estimated for the first time the size distribution of the biomass of 12 major groups of marine organisms at around 33,000 points in the global ocean. They then reconstructed this same data with what it was before the start of the industrial in 1850. And the observation is clear: if the famous rule of distribution remains valid for the great majority of cases, it seems to have broken in the large and mammals. ” The biomass of fish over 10 grams and marine mammals has been reduced by around 2 gigatons since 1850, a 60% reduction, and the largest size classes appear to have experienced a nearly 90% reduction in biomass since 1800 », Decrypts the researcher. And the culprit is all found: the and the .
Man, a predator unlike any other
« Humans are now the main predator of themarine, after extracting most of the predatory fish and mammals that previously occupied the upper beaches of the of size. This begs the question: are humans playing the same role today that the predators we have eliminated previously played? Are we now acting as a functionally equivalent predator? The answer is clearly no », Says Eric Galbraith. It suffices, moreover, to compare the human to that of the large fish and mammals that humans have eliminated only to find that it remains ridiculously small.
The BOFFFF, the first victims of overfishing
The problem is that fishing primarily targets the most valuable and easy-to-find sea creatures, which scientists call(Big, old, fat, fecund, female, fish – either big, old, fat, of fertile age, female and fish). This preference completely destabilizes the natural balance, since it prevents to reproduce properly. In general, we also observe that large animals are more affected by human activities than small ones, in particular because they are more sensitive to changes in the ecosystem. It is no coincidence that the and the prehistoric have now disappeared.
The good news is that while humans are wiping out species at an accelerated rate, they also have the power to protect them. In his last, the International Union for the Conservation of Nature ( ) noted that four of the seven most fished tuna species are in the process of recovery, thanks to the establishment of quotas. The bison population is starting to increase again in Europe and around ten species of birds have been lifted from the critically endangered category. An effort that remains, however, a drop in the ocean.
Large marine animals victims of the sixth mass extinction
Article bypublished on 09/15/2016
Human activities are responsible for the sixth mass extinction of species in the world.and, in the oceans, it is the large animals (sharks, whales, tuna, etc.) that pay the heaviest price. An unprecedented situation that could have long-term consequences.
In a new study to appear in, Jonathan Payne (Stanford University) and his colleagues analyzed the link between the risk of extinction and the characteristics of marine animals, be they molluscs or . They compared the last 500 years to the previous 445 million years.
The authors found an unprecedented phenomenon: today, large organisms are more likely to disappear than smaller ones. Thus, when the mass of the animal increases by a factor of 10, theclimbs by a factor of 13, which the scientist summarizes by: “The bigger you are, the more likely you are to be on the verge of extinction. “ The would therefore particularly affect large marine animals such as the , the , where the .
Theis clearly questioned because humans tend to prefer large animals for their consumption. This big ones could have significant consequences for ocean ecosystems. This is why the researcher calls for collective responsibility: “There is little we can do to quickly reverse the trends of ocean warming or the , which are the two real threats that need to be addressed. But we can change the treaties about how we hunt and fish. The populations of also have the potential to recover much faster than climate or oceans. We can turn this around relatively quickly with appropriate management decisions nationally and internationally. “