The destructive incidence of the human being in the different ecosystems of the planet is increasingly supported by more scientific evidence. However, despite this, the consequences that could be generated by upsetting the harmony of nature and its species are still unknown.
Now, a study in the journal Science has revealed that the marine ecosystem is not only affected by abundant fishing and illegal hunting, but also by the imbalance of a fundamental principle in aquatic life.
This is the law known as the Sheldon’s specter. This biological rule describes that biomass —The volume that a living being occupies on the planet— of the largest and least abundant species is roughly equivalent to the biomass of the smallest but most numerous species.
For example, while krill is 12 times smaller than tuna (by biological orders of magnitude), it is 12 times larger in abundance. Similarly, all the tuna meat in the world should, hypothetically, approximate the same amount as all the global krill biomass.
To date, other studies have tested this natural rule on relatively small scales, for example from marine plankton to freshwater fish. However, the ecologist Ian Hatton at the Max Planck Institute, and his colleagues wanted to test it on a larger scale with a new method involving everything from bacteria to whales.
The team historically rebuilt the “pristine” state of the ocean before 1850, when the second industrial revolution and new fuels began to take off. Then, with that information, they developed models of marine ecosystems. Thus, in 12 groups of marine life —Bacteria, algae, zooplankton, fish, and mammals — located at more than 33,000 points in the global ocean, Sheldon’s spectrum was met.
According to biologists, the explanation for this similar distribution could respond to factors such as metabolism, growth rates, the predator-prey relationship, reproduction and mortality. However, all emphasize that there is still no concrete answer.
After comparing this pre-industrial information with the current situation, the researchers found a radical break in the pattern of the largest organisms, which have greatly diminished.
The research concluded that since the 19th century the number of fish and marine mammals has decreased by 60%, while giant animals such as whales have decreased by 90%.
“Not only have humans replaced the ocean’s top predators, but through the cumulative impact of the past two centuries, they have fundamentally altered the flow of energy through the ecosystem,” the researchers argued in the paper.