Oceans Great Dying 2.0: Mass extinction haunts oceans

Subject : Environment

Context:

Scientists warn an imminent mass annihilation of marine species similar to one 250 million years ago that wiped out most lives in oceans

Mass extinctions

The scientists from Stanford University had simulated during 2016-2018 how Earth’s climate changed some 250 million years ago to know what triggered the Permian extinction.
- The planet’s biggest mass extinction of species had wiped out most newly evolved lives in the oceans.
- It held clues to how the current climate crisis would impact the oceans.

The Permian era

The Permian era, a period spanning 298.9 million-252.2 million years ago, was a time before the dinosaurs ruled the planet. Global ocean temperatures were 10 degrees higher than today. Oxygen levels were 80 percent lower.
During this period, land masses collided to form the supercontinent Pangaea. The super continent was arid; only a few parts received rainfall round the year.
However, the large Panthalassic Ocean, which covered much of Earth, was home to many sponge and coral species, ammonites (tiny shelled organisms), brachiopods (invertebrate animals closely related to starfish) and fusulinid foraminifera (single-celled organisms closely associated with modern amoebas). Reptiles began to flourish. Sharks and bony fishes also thrived.
Towards the end of the era, a series of volcanic eruptions occurred in central Siberia, injecting massive amounts of greenhouse gases (GHG) into the atmosphere. Then, as now, the uncontrolled GHG emissions triggered climatic changes.

What scientists found in the simulated scenario?

The change in climate after the volcanic eruptions was a death knell for the flourishing and diverse life forms.
Many long-lived lineages vanished. Roughly 96 per cent of marine species and 70 per cent of land species went extinct. They then warmed up the climate by 2-10 degrees Celsius to see how species responded.
Some species will have to leave because it got too hot or the oxygen got too low. Some species from the tropics can move into polar waters because it is more welcoming
The scientists refer to this period as the ‘Great Dying’
The scientists had an affirmative answer to their query: Whether low oxygen and warm conditions drove the extinction of marine organisms 250 million years ago.
This is important because climate change that happened at the end of the Permian era is similar to the one that is unfolding now.

Current scenario:

Deep oceans are warming up.
- Scientists look at ocean heat content as an indicator of climate change. Ocean heat content is the energy accumulated by the ocean.
Continuous GHG emissions are preventing heat from going back into space. But the atmosphere has a low heat capacity compared to the ocean water, which can accommodate 1000 times more heat. So, most of it is moving into the ocean.
If emissions continue to climb and temperatures reach around 4.9 degrees Celsius by the end of this century, close to about 40 percent of marine genera could perish by 2300 and 8 per cent by 2100.