Burning fossil fuels is killing more ocean species than land species

Part II: Ocean Warming


Around 1 million species are threatened with extinction due to human activities

March 2021  Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services

Ocean species are going extinct faster than terrestrial species due to ocean warming

April 2019  Nature


In the entire 4.5 billion year history of Earth only two living organisms —cyanobacteria and humans— have so completely altered the oceans, atmosphere, and land that all life on Earth was threatened with extinction at the time.

Cyanobacteria were the first photosynthesizers on an anoxic Earth, pumping oxygen into the oceans and atmosphere for more than 3 billion years (3.7 bya – 500 mya), killing nearly every other living thing because oxygen was toxic to all life on Earth at that time.

Humans have been doing it through water, air, and land pollution in a much more compressed time frame—only about 150 years—by burning fossil fuels while simultaneously eliminating natural carbon sinks through intense urbanization and bad land use policies, pumping massive amounts of CO2 and other greenhouse gases into the atmosphere and oceans causing ocean acidification and ocean warming.

In this two part blog, I discuss the science behind the title to show how humans burning fossils fuels is directly linked to the mass extinction of marine life through ocean acidification (Part I) and ocean warming (Part II).

Ocean Warming

Warming oceans is another key environmental issue causing mass extinctions of marine life today. CO2 that remains in the atmosphere is a greenhouse gas that traps solar and other heat that otherwise would have radiated out to space. We are also seeing methane gas being released in massive explosions in Siberia, leaving behind methane craters. Methane is much worse as a greenhouse gas than CO2, so it is also of significant concern.

CO2 and methane cause global warming and other climatic changes, which in turn causes the oceans to warm. As we’ve seen in past states of the oceans, warming has occurred several times in Earth’s history and it was always associated with increased volcanic activity releasing CO2. This time scientists know that the CO2 causing global and ocean warming is from us burning fossil fuels because there hasn’t been an unusual spike in volcanic activity in millions of years, we can estimate with very high confidence the amount of fossil fuels we’ve burned and from that estimate how much CO2 has been released, and scientists look at isotopic carbon signatures in the atmosphere and oceans, which tells us the source of the carbon, just like fingerprints.

Scientific consensus is nearly universal that the CO2 causing global and ocean warming is from us burning fossil fuels and eliminating carbon sinks. There are a few scientists who dispute this consensus, but there aren’t very many of them and they don’t have good evidence to support their opposing claims.

Scientific studies show that many marine species, especially cold-blooded species, have low tolerance to temperature increases because they are already living at or near their upper temperature limit and—since they are cold-blooded—have no way to regulate their body temperature and there is no refuge for them to escape warming oceans. As a result many marine species face extinction or have already gone extinct.

Ocean acidification and ocean warming are why marine species are going extinct at faster rates than terrestrial species. Acidification and warming both occur on land and in the atmosphere, but the negative effects are less severe than in the oceans and there are ways terrestrial species can avoid acidic water and soil and find refuge from heat. Marine species can’t. What’s happening in the oceans is happening everywhere on Earth, it’s just worse in the oceans. 

As if ocean acidification and warming aren’t enough, marine species also have to deal with pollution, habitat destruction, and over-fishing from human activities as well.


Why are the oceans so important to life on Earth?

One of the reasons the oceans are so important to life on earth is kind of a biggie: life on earth began in the primordial soup of the early ocean—likely at or near hydrothermal vents at the bottom of the ocean—with just the right conditions to give rise to protocells and eventually the first single-celled life that adapted and mutated and evolved over billions of years into the wondrous biodiversity throughout earth’s history. 

To this day, 98% of all the biomass in the oceans is still microbial, like microscopic plankton, algae, bacteria and more. Microbes make up the base of all oceanic food webs converting sunlight or chemical energy into food and energy for everything else. Since 98% of all biomass in the oceans is microbial, that means all the marine mammals, fish, turtles, and every other adorable creature we typically know and love throughout the world’s oceans only make up the remaining 2%.

The oceans are critical to maintaining the right conditions on earth for life to survive and thrive. They are the largest feature on earth’s surface. The oceans cover 71% of Earth’s surface, and that’s just the surface. They are also immensely deep, 4 kilometers or nearly 2.5 miles deep on average and more than 11 kilometers or 6.8 miles at the deepest point in Marianna’s Trench, called Challenger Deep. 95% of all the livable space on earth is below the surface of the oceans. The oceans hold 97% of all the water on Earth, are the source of 86% of all evaporation, and receive 76% of all the precipitation on the planet. 

As the largest feature on earth’s surface—moving and cycling all this water—the oceans exert considerable influence over long-term climate and short-term weather patterns all over the globe by storing, circulating, and releasing solar radiation and regulating the concentration of greenhouse gases in the atmosphere—like carbon dioxide or CO2—by storing it as a dissolved gas in seawater and as a solid in the shells and skeletons of micro- and macroscopic organisms that eventually die and sink to the bottom of the ocean, carrying with them all that stored carbon where it will remain for thousands of years.

In this way, the oceans play the most important role on earth in the biogeochemical cycling of water, carbon, and other essential elements and molecules around the world and through the biosphere.

And last but not least in this incomplete short list of amazing ocean facts, photosynthetic organisms in the oceans produce somewhere between 50-80% of Earth’s oxygen, again because of the sheer size of the oceans relative to land. More surface area and depth equates to more production of oxygen than anywhere else on the planet.

Unfortunately, climate change, ocean warming, ocean acidification, and other issues caused by human activities are affecting these biogeochemical cycles and the overall health of the oceans themselves, which in turn is affecting the oceans ability to support life.

This blog was adapted from a zoom presentation Michael Atkins gave on Earth Day 2021 with Saving Ocean Wildlife. Click here to watch the recording of that presentation called “The State of the Oceans: Past, Present, and Future

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