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How Global Warming is creating mass exodus of equatorial marine life?

How Global Warming is creating mass exodus of equatorial marine life?


  • GS 3 || Environment || Biodiversity || Marine Organisms

Why in the news?

The global pattern is rapidly changing. And as species flee to cooler water towards the poles, it is likely to have profound implications for marine ecosystems and human livelihoods. When the same thing happened 252 million years ago, 90% of all marine species died.


  • The tropical water at the equator is renowned for having the richest diversity of marine life on Earth, with vibrant coral reefs and large aggregations of tunas, sea turtles, manta rays and whale sharks. The number of marine species naturally tapers off as you head towards the pole
  • Ecologists have assumed this global pattern has remained stable over recent centuries – until now. Recent study found the ocean around the equator has already become too hot for many species to survive, and that global warming is responsible.
  • In other words, the global pattern is rapidly changing. And as species flee to cooler water towards the poles, it is likely to have profound implications for marine ecosystems and human livelihoods. When the same thing happened 252 million years ago, 90% of all marine species died.

The global scenario:

  • This global pattern – where the number of species starts lower at the poles and peaks at the equator – results in a bell-shaped gradient of species richness. We looked at distribution records for nearly 50,000 marine species collected since 1955 and found a growing dip over time in this bell shape.
  • Species have tracked their preferred temperatures by moving towards the poles.
  • Although the warming at the equator of 0.6 degrees Celsius over the past 50 years is relatively modest compared with warming at higher latitudes, tropical species have to move furtherto remain in their thermal niche compared with species elsewhere.
  • For each of the 10 major groups of species, we studied (including pelagic fish, reef fish and molluscs) that live in the water or on the seafloor, their richness either plateaued or declined slightly at latitudes with mean annual sea-surface temperatures above 20 degrees Celsius.
  • Today, species richness is greatest in the northern hemisphere in latitudes around 30 degrees North (off southern China and Mexico) and in the south around 20 degrees South (off northern Australia and southern Brazil).

252 million years ago:

  • At the end of the Permian geological period about 252 million years ago, global temperatures warmed by 10 degrees Celsius over 30,000-60,000 years as a result of greenhouse gas emissions from volcano eruptions in Siberia.
  • A 2020 studyof the fossils from that time shows the pronounced peak in biodiversity at the equator flattened and spread. During this mammoth rearranging of global biodiversity, 90% of all marine species were killed.
  • Then, 125 000 years ago, there was a similar movement of reef corals away from the tropics, but there was no associated mass extinction event.
  • The authors have suggested that their results might be a foreshadowing of another mass extinction event in the near future as marine species move into the subtropics, where they may struggle to compete and adapt.
  • Today, the species richness of forums (a type of hard-shelled, single-celled plankton) has been dropping since the last ice age, which ended around 15 000 years ago. Plankton forms a vital part of the marine foodweb, and the authors say that this decline in recent decades has accelerated due to human-driven climate change.

What Does This Mean?

  • Losing species in tropical ecosystems means that ecological resilience to environmental changes will be reduced, which compromises ecosystem persistence.
  • In subtropical ecosystems, species richness is increasing, which will bring species invaders, novel predator-prey interactions, and new competitive relationships. This could result in ecosystem collapse in which species go extinct and ecosystem services (such as food supplies) are permanently changed.
  • This will also affect human livelihoods. For example, many tropical island nations depend on the revenue from tuna fishing fleets through the selling of licenses in their territorial waters. Highly mobile tuna species are likely to move rapidly toward the subtropics, outside the island nations’ waters.

Impacts of global warming on marine life and oceanare as follows:

  • Geographical impacts:Melting of glaciers and rise in sea level. ArcticOcean is said to be mektung at rate of 12% per decade and as per studies by Day et al it’s believed that arctic will be ice free by 2030 rising sea level has led to verge of submergence of many Islands e.g. Tuvalu,Vanatau etc. Rise in coastal erosion due to disappearing sea ice, e.g. a town in Alaska has been abandoned because of high storm surges and waves
  • Economic impacts:Loss of marine lifeLoss of blue economy
  • Environmental/ecological impacts:Eutrophication due to rise in algal blooms leading to decrease in Coral bleachingDestruction of marine ecosystems e.g. imbalance in turtle sex ratioOcean acidification Destruction of biodiversity -decrease in sea level can result in loss of 2/3rd pop of polar bear
  • Climatological impacts:Change in weather patterns,jet stream directions moved further north leading to precipitation in Polar Regions. Change in global air circulation due to change in wind patterns, thermal circulation and salinity of water changes in El nino and la ninacondition which affects  climate and economy
  • Biodiversity: Due to global warming and increase in ocean temperature it will affect the life of creatures living there
  • Temperature Regulator: Oceans works as temperature regulator by absorbing excess heat in atmosphere but at certain level. Post that it affects the ocean overall mechanism as well
  • Aquatic Life: Due to global warming, aquatic life will also get hampered and will affect the overall growth of animal
    • Polar ice melts results into excessive amounts of freshwater dumped into oceans altering seawater density and thus ocean currents slow down. With this slowing down, ocean currents would bring fewer nutrients to sustain ocean life thus effecting food chain and food security. During part 6 decades there is decline of ~20% phytoplankton in the Indian Ocean.
  • Occurrence of natural hazards: Global warming will increase frequency of earthquake, volcano and floods which in return can affect aquatic life as well as non-aquatic life and can create imbalance in sustainability
  • Coral Reefs & Other Food Producing Agents: This will affect their working as well and will lead to coral bleaching and also no food for aquatic animals
  • Glacier Melting: Due to global warming, glacier will start melting and which will increase water level which can have effect not only on aquatic life but as well as on non-aquatic life
  • Slow Rotation of earth: Some research also suggest that rising ocean level can have effect on rotation of earth as well
  • Oceans are crux of life on earth and global warming will have a major irreversible impact on ocean. Within time we should work toward in reducing this as much as possible by working towards as determine by Paris Peace Agreement

Following steps needs to be taken to reduce the effect of global warming on oceans:

  • Implementation of Global Environmental Protocols and Conference in letter and spirit shedding the notion of “less polluter,more polluter”.
  • Government and International Agencies should all keep reducing global warming as its agenda as the solution lies in multidimensional approach.
  • Environment and Ocean related awareness must be brought in starting from a young child to an old ages

What Can We Do?

  • This is the time reduce emissions to curb global temperature increase. We could also put safeguards in place for biodiversity conservation. Currently, 2.7% of the ocean is conserved in fully or highly protected reserves, well short of the 10% target by 2020 under the UN Convention on Biological Diversity.
  • A group of 41 nations is pushing to set a new target of protecting 30% of the ocean by 2030. This “30 by 30” target could ban seafloor mining and remove fishing in reserves.
  • Climate change is impacting the best-known and strongest global pattern in ecology. We simply do not have the time to hesitate further in addressing this.


Though event of global warming has been trigger but still if we all take prudent measures we can certainly postpone the event and give a better earth to our future generation.

Mains oriented question:

What is causing a mass exodus of equatorial marine life as a result of global warming? (200 Words)