Unless greenhouse gas emissions are reduced, ocean-dwelling species could be decimated by 2300, warns a study published in the Journal on Thursday, April 28 Science. But limiting global warming to 2°C compared to the pre-industrial era would avoid this catastrophic scenario, the researchers point out.
The latter used models that show the relationship between global warming, the resulting decline in oxygen levels in water, and levels of dioxygen (O2) necessary for the survival of the species. Particularly complicated to study, such projections of extinction risks in the oceans have been formulated very little.
But the results are alarming: if emissions of planet-warming greenhouse gases continue to increase, the oceans could experience a Permian-like mass extinction. During this catastrophic event, marine biodiversity was reduced to its absolute minimum under the combined effects of rising temperatures and falling oxygen levels in the oceans, a scenario that is also playing out today.
A source of hope
In this scenario, the tropical oceans would lose most species, but many species from those areas would migrate to other regions to survive. The polar species would massively disappear as they would have no place to seek refuge.
A glimmer of hope, a scenario that limits global warming to 2°C, would make this possible “70% reduction in the severity of species extinctions, avoiding a mass extinction”according to the study.
The Paris Agreement, an international reference text, sets the goal of curbing global warming “well below 2 °C compared to pre-industrial levels”, and if possible at + 1.5°C. This goal is ” out of range “ according to current international commitments, according to the United Nations Intergovernmental Panel on Climate Change.
“Because extinctions at sea are not as advanced as they are on land, our society has time to turn the tide in favor of ocean life.”however, scientists wrote in a commentary article accompanying the study. “Where exactly our future lies between the best and worst-case scenario is determined by societal decisions”they added.