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Nature-based solutions: Blue carbon

 

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Home > Nature-based solutions > New Zealand native ecosystems > Ocean ecosystems > Blue carbon

Our blue carbon

Summary

  • While protecting and restoring our terrestrial ecosystems—forests, wetlands, rivers, and dunes—is critically important, the oceans are often overlooked because, from our limited perspective, they look like vast blue opaque deserts. And yet these ecosystems have a far greatest capacity to store carbon than any other place on Earth.

Phytoplankton are the workers of an ocean-spanning factory converting sunlight and raw nutrients into organic matter. These little organisms — the foundation of the marine ecosystem — feed into a myriad of biogeochemical cycles, the balance of which help control the distribution of carbon on the Earth surface and ultimately the overall climate state. – Nature 15 p955 (2022)

Native Ecosystems

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Home > Nature-based solutions > New Zealand native ecosystems > Ocean ecosystems > Blue carbon

Summary

  • While protecting and restoring our terrestrial ecosystems—forests, wetlands, rivers, and dunes—is critically important, the oceans are often overlooked because, from our limited perspective, they look like vast blue opaque deserts. And yet they have a far greatest capacity to store carbon than any other place on Earth.


Phytoplankton are the workers of an ocean-spanning factory converting sunlight and raw nutrients into organic matter. These little organisms — the foundation of the marine ecosystem — feed into a myriad of biogeochemical cycles, the balance of which help control the distribution of carbon on the Earth surface and ultimately the overall climate state. – Nature 15 p955 (2022)

  • This is in part due to their size and in part due to the complex trophic systems they support. Overfishing and the resultant loss of biomass, including vast populations of whales, have interfered with the natural carbon cycle.
  • Blue carbon is stored in coastal and marine ecosystems, particularly estuaries.
  • Coastal ecosystems can absorb five times more carbon than tropical rainforests.
  • Seagrass meadows cover ~0.2% of the ocean floor yet capture 10% of the carbon that gets dissolved into the ocean each year. And they can store it for thousands of years.
  • Tidal saltwater marshes drawdown and sequester CO2 around 2 to 4 times greater than mature tropical forests.
  • Mangrove forests accumulate carbon faster than any other living systems and defend coasts from storm surges and erosion.
  • Kelp and other types of seaweed absorb CO2 at a staggering rate and may offer the most lucrative carbon farming possibilities, but only when the possible negative impacts are taken into consideration.
  • None of this carbon is accounted for under the Emissions Trading Scheme. and yet the potential is huge, as Aotearo’s exclusive economic zone is 14 times larger than our land area.
  • If this is considered over time, a precautionary approach is needed to ensure other values are not compromised.
Video 1: Explains what blue carbon is, and how it absorbs up to 2-10 times more carbon than terrestrial ecosystems. We are losing them faster than any other ecosystem on the planet. The New Zealand government does not account for these losses under the current Emissions Trading Scheme, and so there is zero financial incentive to protect what remains, restore what’s been lost, or penalise those that continue to destroy them.

Along the coasts, the plants and animals that store blue carbon also provide food, act as nurseries for fish, and as shock-absorbers, defending coasts against storm waves, coastal erosion, and sea levels which are now rising far faster than at any time since the end of the last glacial. Seaweed, seagrass, and saltwater marsh ecosystemss are found in Canterbury’s estuaries and harbours.

Global overfishing and the resultant loss of biomass has interfered with the natural carbon cycle. As global overfishing is such a staggeringly complex problem, on this page, we’re going to focus on just one really BIG keystone species that would enable more CO2 to be locked away faster than entire forests.

The ‘Whale Pump’

Whales feed it waters so deep that no light can penetrate. When they return to the surface, they poop huge plumes of nutrients, particularly iron, that fertilise phytoplankton (Figs. 1 & 2). These plankton live in the only place where plants can survive—the photic zone near the surface—where there’s enough light for photosynthesis to occur.

Phytoplankton produce 50% of the world’s oxygen, store large quantities of CO2, and feed billions of creatures great and small, including us.

Each time whales plunge up and down through the water column they kick plankton back up into the photic zone, giving the plankton more time to reproduce in vast quantities, produce oxygen, and store carbon in their bodies before they die and sink into the abyss. Here, the microscopic creatures decompose, much of the carbon in their bodies adding to the layers and layers of sediment, so the carbon is locked away permanently as part of the long term carbon cycle (Fig. 3).

Without the nutrient-rich poop from whales, and without them moving up and down the water column, the numbers of phytoplankton, which are essential to all life on Earth—including ours—would plummet (Videos 2 & 3)

“Before great numbers of whales were killed, it seems that they might have been responsible for removing tens of millions of tonnes of carbon from the atmosphere every year. If they are allowed to recover, they could undo some of the damage we’ve done both to the living systems of the sea and to the atmosphere.” – George Monbiot

Video 2: A single large whale store as much carbon as 1,500 trees.
Over the course of it’s life, a whale can absorb more carbon that a forest.
 
When they die, they, too, fall to the bottom of the ocean, where their carbon is also locked away in deep ocean sediments. That is, until bottom trawlers come along and cause havoc. See this interactive report ‘Distubing the Deep’ from the Parliamentary Commissioner for the Environment published November 2023.

Recent research show that baleen whales eat up to 3x what was previously thought. (Video 3).But the relationship is both cyclic and fragile. Baleen whales eat krill, which depend on the poop from whales; fewer whales = less poop = less krill (Video 4).

Video 3
Video 4
How whales drive the iron cycle and store carbon in the ocean
Fig. 2: The Whale pump. Without it, we would lose much of the oxygen we need to breathe, we would have very little if any seafood, and there would be far more CO2 in the atmosphere, meaning a far hotter and more dangerous climate. Whales are a keystone species. Without them, we may not survive the existential climate threat. (Image: GRID Arendal)
Fig. 2: The Whale pump. Without it, we would lose much of the oxygen we need to breathe, we would have very little if any seafood, and there would be far more CO2 in the atmosphere, meaning a far hotter and more dangerous climate. Whales are a keystone species. Without them, we may not survive the existential climate threat. (Image: GRID Arendal)
Fig 3: Over the lifespan of a whale, it stores the same amount of carbon as around 1,500 trees. When it dies and falls to the bottom of the ocean, the carbon in it stored in the ocean seabed, often permanently (ie, millions of years; Videos 2 & 3. Image: Terra Mater (Video 2).
Fig 3: Over the lifespan of a whale, it stores the same amount of carbon as around 1,500 trees. When it dies and falls to the bottom of the ocean, the carbon in it stored in the ocean seabed, often permanently (ie, millions of years; Videos 2 & 3. Image: Terra Mater (Video 2).

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