If humanity does not control, at least in part, the climate crisis, the world could experience a mass extinction in the oceans, according to a research published last Thursday (28) in the journal Science.
The mass extinction would occur until 2300, in a projection based on the worst possible scenario calculated by the IPCC (UN Intergovernmental Panel on Climate Change) – in which greenhouse gas emissions continued to rise, causing the planet’s average temperature to increase. up to 4.8ºC by the end of the century, compared to the temperature of the pre-industrial era.
Even in another scenario, with emissions a little lower but still high enough for a temperature increase of about 3.9°C by 2100, species losses would be significant in the oceans, the scientists point out.
The study was carried out by researchers Justin L. Penn and Curtis Deutsch, both from Princeton and Washington universities (USA). The modeling done by them shows that to avoid this environmental tragedy, it is necessary to limit the temperature increase to a maximum of 2ºC.
The Paris Agreement’s main objective is to limit global warming to an even lower level of 1.5ºC, but so far it has not managed to stop the increase.
According to the research, keeping global warming at this level, it would be possible to reduce the severity of the extinction that threatens the oceans by more than 70%.
The researchers point out that the five great extinctions in Earth’s history occurred in association with environmental changes on Earth, but none of them were linked to human action. The largest of these was the Permian-Triassic, known as the “Great Dying” (something like “the great death”), in which more than two thirds of the genera of marine animals disappeared. Among the similarities between this massive extinction and the one now are the increase in the temperature of the waters and the lower concentration of oxygen gas (O2) in them.
In 2021, ocean temperatures were the highest since the beginning of historical records, while the amount of oxygen gas available in them was probably the lowest.
Considering local extinctions, the researchers say that the risks increase in places where marine species are close to their ecophysiological limits, which normally occurs as one approaches the equator, with warmer waters and/or lower levels of O2 in the sea.
The model made by the researchers points to a certain overlap between the places with the greatest biological richness in the ocean and the areas with the highest rates of local extinction. But, at the same time, some of the species that live in these warmer waters may be able to migrate to seas at higher latitudes – once colder and warmer in the future – and find a new habitat. On the other hand, polar species, with no chance in warmer oceans, could end up extinct across the planet.
In addition to losses in biodiversity, the extinction of marine species also affects fisheries. Some of the most vulnerable areas have high productivity rates for this activity, such as the North Pacific and the Indo-Pacific region.
The real picture may be even worse than the one drawn by the researchers. That’s because the study only takes into account temperature and available O2, but climate change affects the oceans in other serious ways, such as sea acidification. Not to mention more local situations, such as pollution and overfishing.
In a commentary on the study, in the same Science, Malin L. Pinsky and Alexa Fredston, also researchers from the USA, state that fortunately, gas emissions are not in the path of the worst case scenario, considering policies to limit emissions and the slower growth of global economies.
“Exactly where, between the best and worst case scenarios, the future will be will be determined by the choices society makes not only about climate change, but also about habitat destruction, overfishing and coastal pollution,” say Pinsky and Fredston.
