The Equator with its tropical water is best known to shelter rich diverse marine life across the globe. We can find vibrantly colored coral reefs along with huge aggregations of sea turtles, whale sharks, manta rays, and tunas. The large figure of marine life appears to be tapering off naturally as we move towards the polar regions.
Ecologists consider that this prevalent pattern on a global basis has sustained in a stable manner for many centuries. However, recently the pattern seems to have changed. A recent study has found that the oceans near the equator are already showing signs of heating up at a rapid pace. As a result, numerous species are finding it difficult to survive.
The most important reason for this is global warming. To be specific, this worldwide pattern is undergoing a rapid transformation. Several species are fleeing the equatorial water bodies for cooler water near poles.
This will possibly have deep implications on the marine ecosystems as well as human livelihoods. A similar event took place almost 252 years back that eventually led to the death of about 90% of marine species.
Dangerous Warping Of Normal Distribution Of Marine Life
The natural global pattern comprises a lesser number of marine species towards the poles while it peaks at equatorial regions. This leads to a bell-shaped slope of marine life richness. Since 1955 marine species of approximately 50,000 in number have been collected through distribution patterns.
Lately, this normal distribution curve has declined over time creating a bell shape. Consequently, as the oceans become warmer, species have been tracking their favorable temperatures by migrating towards polar areas.
For the last 50 years, the equator has warmed 0.6℃. On the other hand, the warming at the higher altitudes has been much more in comparison. Nonetheless, this phenomenon has forced marine life to move further away from their natural habitats to maintain the thermal niche.
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Perils Of Global Warming On Marine Species
As the water bodies are warming at an exponentially rapid speed since the recent decades owing to global warming, the moving of marine species from the equator has greatly increased. It is believed that such changes were utilized as a modeling approach 5 years ago but now they serve as observational evidence.
Species of 10 important groups have been studied including mollusks, pelagic fish, and reef fish and they mainly live on the ocean floor or deep waters. The richness of these species has significantly dipped or plateaued at latitudes that have a mean surface temperature of more than 20℃ annually.
Today the richness of marine life is the greatest in the northern hemisphere, specifically near the 30⁰N latitudes around Mexico and southern China. In the southern hemisphere, marine life is stationing near 20⁰S latitudes off southern Brazil and northern Australia.
Species Moving Driven By Climate Change Through The Years
A similar incident of global biodiversity rapidly responding to climate change has happened earlier as well and left drastic consequences.
I: 252 million years back- As the geological Permian period concluded, there was a 10℃ warming of global temperatures during 30,000 to 60,000 years. This resulted from the emissions of greenhouse gases from the Siberian volcanic eruptions.
A study in 2020 of those fossils revealed that biodiversity was prominently high near the equator but gradually flattened and spread out. At the time of this enormous rearrangement of global biodiversity, almost 90% of marine life died.
II: 125,000 years back- A study conducted in 2012 found that rapid warming at that time witnessed a similar hasty movement of the coral reefs from the tropical waters. This led to a similar pattern we are currently witnessing but there was no mass extinction.
III: Today- The previous ice age ended almost 15,000 years back. Since then our planet has seen rich forams (a form of single-celled, hard-shelled plankton) in large numbers near the equator. However, the population of forams is fast declining. This is of utmost importance since planktons are essential to the food web.
Outcomes from these studies indicate the ongoing global warming might have an adverse effect on marine life that might lead to mass extinction in the forthcoming time. The migrating pattern from the tropic to subtropics shows a struggle of marine life to adapt and survive.
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Consequences & Possible Solutions
The disintegration of tropical ecosystems suggests a decrease in ecological resistance against environmental changes and the ultimate compromise of ecosystem persistence. The increase of marine life in subtropics means the invasion of new predator-prey interactions. This might finally result in the collapse of the entire ecosystem through permanent alteration and mass extinction.
Such profound changes will certainly have enduring consequences on humans. For instance, several tropical islands rely on tuna fishing revenue which will be affected as tuna species rapidly migrate to subtropics that lie outside their sovereign waters. Tropical nations might fail to meet the goals of Sustainable Development due to the movement of artisanal and commercial marine life and aquatic megafauna.
Paris Climate Accords have laid down strict guidelines to proactively reduce emissions near the equator. The completely protected reserves of oceans are presently 2.7% while the target is 10% till 2020. Till 2030 the target is increased to 30% by 41 nations.
This target may lead to the removal of fishing reserves and preventions on seafloor mining as they release carbon dioxide and greatly destroy habitats of marine life. Furthermore, marine life must be categorized as refugia to maintain a stable climate in the future. We must take immediate strong actions to mitigate marine life-related issues.
