Bizarre Marine Life Movement Might be Indicating Future Mass Extinction
Marine life fleeing the equator is a disturbing sign
Science has long acknowledged the wonder of Earth’s tropical waters. Perhaps this is because it offers the richest marine life diversity anywhere on our planet. These range from the fantastic coral reefs to the running of sea turtles.
As we might assume, this richness of marine life tapers off as we venture further away from the equator and closer to Earth’s poles.
Ecologists assumed that these familiar global strata, which have been stable for many years, would remain that way long into the future. Unfortunately, this may not be the case anymore.
Gradual warming of tropical waters
A recent study has discovered that the ocean waters at the equator are becoming too hot to support the survival of several species. And global warming could very well be the reason.
Most disturbing is how abruptly this global pattern of a stable marine environment began to shift. Scientists are now seeing many species flee to cooler water away from the equator.
There are two significant reasons to be concerned about this new pattern of marine life movement:
Effects on marine ecosystems. The impact of the local ecosystems within tropical waters could be profound. Not only would much of marine life suffer, but the livelihoods of many people would also be in question.
History. When this happened some 250 million years ago, about 90% of all Earthly marine life perished.
Closer look at the global pattern
The stable temperature pattern versus tropical life has consistently shown a lower number of species at the poles and more significant numbers at the equator, providing a bell curve of species abundance.
Recently, there has been a gradual decrease in this bell curve over time. And the decline has gotten more prominent over the last two decades.
As ocean water continues to warm, marine species keep moving away from the equator. Even though the average warming of water around the equator has been only 0.6℃ during the last 50 years, tropical marine life keeps moving to stay within their thermal niche.
Marine life richness and diversity
The peaks of marine life richness exist around 30°N and 20°S; these two regions are Mexico and southern China, and southern Brazil and northern Australia, respectively.
Sadly, it shouldn’t come as much of a surprise to see marine life respond this way to global warming. It has not only happened previously but in a very dramatic way.
When this happened before
About 250 million years ago, the Earth was warmed by 10℃ during a period of 30,000–60,000 years. This came about because of greenhouse gas emissions along with Siberian volcanic eruptions.
A fossil study in 2020 indicated that a strong biodiversity peak along the equator was flattened and then moved toward the poles. A massive shift of biodiversity across the world brought about the extinction of around 90% of all Earthly marine life.
Most recently
A most recent study from 2012 revealed very intense warming occurred some 125,000 years ago. During this event, there was also a rapid movement of reef corals leaving tropical waters, as indicated by fossils. While the same pattern occurred, there wasn’t a mass extinction of marine life.
The authors of this study suggest their conclusion could foreshadow the alarming effects of the existing global warming pattern. But they did warn of potential mass extinctions in the future when species migrate into subtropics, simply due to increased struggles of competition and difficulties to adapt.
Deeper effects on biodiversity
When marine species are removed from tropical ecosystems, it reduces their ability to adapt to environmental changes, which can compromise that entire ecosystem.
Thus when the species richness of a neighboring subtropical ecosystem begins to increase, more and more predators and species invaders start to arrive. This will have an enormous impact on existing predator-prey relationships that have long stabilized the local ecosystem.
Unless this delicate balance is somehow re-established, a collapse will be very likely. It’s not like this hasn’t happened before, it has, and we need to pay attention.
Sources
Anthony Richardson, Chhaya Chaudhary, David Schoeman, Mark John Costello. (April 7, 2021). Marine life is fleeing the equator to cooler waters. https://theconversation.com/marine-life-is-fleeing-the-equator-to-cooler-waters-history-tells-us-this-could-trigger-a-mass-extinction-event-158424.
PNAS.org. (April 13, 2021). Global warming is causing a more pronounced dip in marine species richness around the equator. https://www.pnas.org/content/118/15/e2015094118.
