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Deep water

Ten threats to marine ecosystems

Our air, weather, food, the health of diverse marine life and millions of jobs all depend on the ocean. But we have not done well as custodians of marine ecosystems. Here, we set out ten ways where human actions threaten the health of an essential environment.

Read this article to understand:

  • Why marine ecosystems matter
  • Ten ways in which human intervention is damaging ocean health
  • How we can become better custodians

Just over 70 per cent of planet Earth is covered in water; billions of people are directly and indirectly dependent upon oceans for their survival.

But all is not well. The untimely death of marine life,1 repeated chemical spills2 and accumulation of ocean plastic3 are examples of threats already undermining the food, jobs and environmental services oceans provide. 

Here, we set out ten human-induced challenges for marine ecosystems, and ask what steps need to be taken to ensure these essential systems retain their vitality.

Mass extinction

“A lot of heat and carbon dioxide trapped in the Earth system as a result of human activity is being absorbed by the oceans, with potentially devastating consequences,” says Rick Stathers, Aviva Investors’ climate lead. “The oceans are warming and acidifying, which scientists say could contribute to the greatest extinction of marine life for 250 million years.”

Figure 1: Could climate warming trigger another ‘Great Dying’?

Marine species

Could climate warming trigger another ‘Great Dying’? Marine species

Land mammals

Could climate warming trigger another ‘Great Dying’? Land mammals
Note: Known species loss in Permian-Triassic extinction.
Source: Aviva Investors, June 2022. Original data sourced from National Geographic, September 2019
4

Next?

Energy systems change to maintain temperature increase to below two degrees Celsius above industrial average,5 decarbonisation, focus on energy efficiency.

Changing thermohaline circulation

The thermohaline circulation represents how water circulates through the world’s oceans, carrying heat from the tropics towards the poles and sending cold water back in deep ocean currents.6 There are fears warmer global temperatures could disrupt the circulation, shifting the production of plankton that underpins ocean food chains and threatening established fishing grounds.

Figure 2: The great ocean conveyor belt
The great ocean conveyor belt
Source: Aviva Investors, June 2022. Original data sourced from Inside Climate News, February 25, 20217

Next?

Energy transition, adaptation in fishing zones and species targeted by fisheries.

Hazardous chemicals

The ocean is critical for life on Earth, so it seems extraordinary there have been no major studies on the extent of marine chemical pollution, including persistent chemicals that linger, and their biodiversity impacts.

“There are material risks the chemical sector generates, and material risks the industry faces from a transition to a zero-pollution ocean. Companies need to focus on these now,” says Eugenie Mathieu, Aviva Investors’ Earth lead and senior impact analyst.

Figure 3: A chemical explosion
A chemical explosion
Source: Aviva Investors, June 2022. Original data sourced from Back to Blue, 20228

Next?

Greater transparency about substances of “very high concern”; stricter regulation of chemical pollution from specialty chemicals, pharmaceuticals and agricultural producers; evolution of ‘green chemistry’.

Fertilisers

Extensive areas of ocean are now ‘dead’ or hypoxic, where the water contains too little oxygen to support life. Fertiliser-enriched run-off from agriculture and wastewater can cause algae to overgrow, stifling opportunities for other lifeforms.

Figure 4: Low-oxygen dead zones
Low-oxygen dead zones
Source: Aviva Investors, June 2022. Original data sourced from Back to Blue, 20229

Next?

Precision agriculture, greater attention to land and wastewater management.

Desalination plants generating super-saline brine

As human populations have pushed into arid areas, demand for potable water has grown. Desalination plants use reverse osmosis to separate water molecules from seawater but produce super-saline brine as waste, which has negative environmental impacts when discharged. Recent research suggests brine production is about 142 million m³/day, about 50 per cent higher than previously thought.10

Figure 5: Desalination - solution and environmental challenge
Desalination - solution and environmental challenge
Note: Daily super-saline brine output.
Source: Aviva Investors, June 2022. Original data sourced from Science of The Total Environment, March 2019
11

Next?

Improving brine management strategies to limit negative environmental impacts and safeguard water supplies.

Overfishing

Around one billion people rely on fish as a primary source of protein, but overfishing is driving many marine species towards extinction. Destructive practises like bottom trawling are still taking place in marine protected areas.12

Unintentional catch – bycatch – ends the life of millions of marine dwellers early every year. According to the International Union for Conservation of Nature, 99 per cent of sharks and rays are threatened by this inadvertent culling.13

Figure 6: The marine cost of bycatch
The marine cost of bycatch
Source: Aviva Investors, June 2022. Original data sourced from Reef Conservation International, February 201814

Next?

Science-based limits on fishing, effective monitoring of marine protected areas using new approaches like artificial intelligence to track unauthorised activity, and approaches that reduce or eliminate fishing mortality.

Plastic

Humans have created a gigantic 9.2 billion metric tonnes of plastic,15 more than any other material apart from steel and cement. The plastic washed into the oceans can entangle marine species or be ingested, leading to the death of around one million seabirds, 100,000 sea mammals and countless turtles and fish every year. Without changing our ways, ocean plastic might outweigh fish within three decades.16

Figure 7: Plastic – getting the measure
Plastic – getting the measure
Source: Aviva Investors, June 2022. Original data sourced from The Conversation, February 202217

Next?

Enforcement of a legally binding global treaty on plastic pollution promised by 2024, described by UN Environment Program executive director Inger Andersen as “an insurance policy for this generation and future ones, so they may live with plastic and not be doomed by it”.18 Better waste management and recycling and development of bio-alternatives are also crucial.

Oil spills

The volume of oil spilt because of human error has decreased significantly since the 1970s, but spills are not unusual. 

An event off the coast of Peru reported to have lasted “minutes” affected 106 square kilometres of ocean in 2022,19 killing fish and seabirds in a wide-ranging environmental catastrophe.

Figure 8: Large and medium spills (1970s-2021)
Source: Aviva Investors, June 2022. Original data sourced from ITOPF, 202120

Next?

Focus on reducing leaks and blowouts, improving physical containment, and accelerate the energy transition.

Ocean mining

Geologists are searching on the seabed for valuable transition metals to mine. Nodules rich in nickel, copper and cobalt have been found on the ocean floor,21 along with sediments containing rare earths like lanthanum and neodymium.22

“This a key interface of the debate about actions to mitigate climate warming,” says Mathieu. “To mine transition metals, are we prepared to damage ocean ecosystems?” 

Figure 9: Assessing deep sea mining impacts
Assessing deep sea mining impacts
Source: Aviva Investors, June 2022. Original data sourced from IUCN, 202223

Next? 

More research.

“There are a zillion reasons not to mine the sea floor, and fewer reasons to mine the sea floor. We still know so little. We have so much work to do before we can get there.”
John Jamieson, Canada Research Chair in Marine Geology24

Construction of coastal flood defences

About 600 million people around the world live at risk of coastal flooding. Demand for protection is expected to grow as extreme weather events increase and sea levels rise. Building engineered structures (e.g. ‘grey’ protection like levees, requiring fuel, ground work and construction) can be financially and environmentally costly, disturbing coastal habitats and modifying water chemistry.

Figure 10: Frequency of flooding in low-lying coastal cities and small islands

Once every 100 years

Frequency of flooding in low-lying coastal cities and small islands - once every 100 years

Every year

Frequency of flooding in low-lying coastal cities and small islands - every year
Source: Aviva Investors, June 2022. Original data sourced from Intergovernmental Panel on Climate Change, 201925

Next?

Hybrid coastal protection incorporating grey and green protection (for example, maintaining seagrass beds, mangroves, reefs) for more sustainable flood solutions.

References

  1. Leyland Cecco, ‘‘Heat dome’ probably killed 1bn marine animals on Canada coast, experts say’, The Guardian, July 8, 2021
  2. ‘Peru oil spill affected area the size of Paris, Repsol says’, Reuters, February 18, 2022
  3. ‘Oceans – how it works’, The Ocean Cleanup, 2022
  4. ‘What are mass extinctions, and what causes them?’, National Geographic, September 26, 2019
  5. Justin Penn and Curtis Deutsch, ‘Avoiding ocean mass extinction from climate warming’, Science, April 28, 2022
  6. Bob Berwyn, ‘Climate change is weakening the ocean currents that shape weather on both sides of the Atlantic’, Inside Climate News, February 25, 2021
  7. Bob Berwyn, ‘Climate change is weakening the ocean currents that shape weather on both sides of the Atlantic’, Inside Climate News, February 25, 2021
  8. ‘The invisible wave: Getting to zero chemical pollution in the ocean’, Back to Blue Initiative, 2022
  9. ‘The invisible wave: Getting to zero chemical pollution in the ocean’, Back to Blue Initiative, 2022
  10. Edward R Jones, et al., ‘The state of desalination and brine production: A global outlook’, Science of The Total Environment, March 2019
  11. Edward R Jones, et al., ‘The state of desalination and brine production: A global outlook’, Science of The Total Environment, March 2019
  12. ‘European environmental organisations call for a ban on destructive fishing practices in Marine Protected Areas’, EU Reporter, April 28, 2022
  13. Nicholas K. Dulvy, et al., ‘Overfishing drives over one-third of all sharks and rays toward a global extinction crisis’, Current Biology, November 8, 2021
  14. ‘Overfishing: What is bycatch?’, Reef Conversation International, February 16, 2018
  15. ‘Drowning in plastics – marine litter and plastic waste vital graphics’, United Nations Environment Programme, 2021
  16. ‘Will there be more plastic than fish in the sea?’, WWF, 2022
  17. ‘Nations sign up to end global scourge of plastic pollution’, United Nations, March 2, 2022
  18. Sarah J. Morath, ‘Plastic pollution is a global problem – here’s how to design an effective treaty to curb it’, The Conversation, January 21, 2020
  19. ‘Peru oil spill affected area the size of Paris, Repsol says’, Reuters, February 18, 2022
  20. ‘Oil tanker spill statistics 2021’, ITOPF, 2022
  21. Olive Heffernan, ‘Seabed mining is coming — bringing mineral riches and fears of epic extinctions’, Nature, August 16, 2019
  22. Nicola Jones, ‘Sea holds treasure trove of rare-earth elements’, Nature, July 3, 2011
  23. ‘Deep sea mining’, IUCN, May 2022
  24. Julia Barnes, ‘Deep sea mining’, December 12, 2021
  25. ‘The ocean and cryosphere in a changing climate’, IPCC, September 25, 2019

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