GW72 Feature
Whale have
long been emblematic of the green movement, but
there may be more good reasons for protecting
them than the loss of their grace and majesty in
the water. Luke
Rendell looks at how
the whale may be a key component in keeping
carbon out of the atmosphere
Many of the
green movement's roots can be traced to the
campaign to end the industrial whaling that
threatened the very existence of some
species, culminating in the 1986 moratorium
on commercial whaling. Now, as the movement
faces the massive challenge of climate
change, recent scientific research on the
role that whales play in their ecosystems is
showing that they are still relevant to these
new challenges.
The oceans account for around 46% of global net primary production, the process by which plants - in the oceanic case, microscopic plants collectively called phytoplankton - use photosynthesis to convert CO2 dissolved in the ocean into carbon and oxygen. The oceans remove about 4.8billion tonnes of carbon per year by this process. That's a lot; however, it could be more.
The oceanic plants responsible for this carbon capture are limited from growing even more by a lack of critical nutrients, much like those in your garden (well, in mine at least). In several parts of the ocean, including the Southern Ocean that encircles Antarctica, the single limiting factor is iron (although even iron-limited, it accounts for about 1.9 billion tonnes of annual primary production). This has led to experiments involving dumping iron sulphate into the Southern Ocean, and this fertilisation has indeed resulted in significant, but temporary, increases in plant growth. Long term and large-scale increases in CO2 absorption would need continuous dumping of nutrients, and not many people reading this would, I suspect, be comfortable with that. What we really need is some kind of large animal that swims around recycling the iron that is already in the ocean, by eating animals like krill and then pooping out the iron over large areas, like some kind of marine muck-spreader. You get my drift?
That's exactly what several scientific studies published in the last year tell us that whales are doing.
Stephen Nicol of the Australian Antarctic Division measured how much iron is in whale poo, and discovered that it contains approximately ten million times more iron per kilo than the water that receives it. Where does the iron come from? Well, the whales he studied - four species of baleen whale (the blue, pygmy blue, fin and humpback) - come to the Southern Ocean to feast on the vast swarms of krill found there (krill are small swimming shrimp). Nicol estimates that these krill may contain up to 24% of all the iron in the Southern Ocean, but it's no good to phytoplankton there - it only becomes available after whales eat the krill and ... well, you get the picture (if you're interested, the scientific term is flocculent faecal plumes - almost poetic).
Another species, the sperm whale, dives deep, to over 800 metres, and actually returns iron that has been lost to the surface contained in the deep-sea squid it preys on. Another Australian scientist, Trish Lavery, and her colleagues have been able to quantify the sperm whale's contribution to our carbon challenge. 12,000 sperm whales in the Southern Ocean, she estimates, would result, through increased primary productivity, in 200,000 extra tonnes of carbon being fixed, even after allowing for the carbon they produce as air-breathing mammals. It doesn't sound like much against the billions of tonnes of C02 being released, but consider that there are thought to currently be around 360,000 sperm whales globally, and this is thought to be around one third of their pre-whaling population size. Thus a fully recovered sperm whale population could potentially be responsible for removing an extra 18 million tonnes of carbon per year. Plus, there are more than just sperm whales: blue, pygmy blue, fin, sei, minke and humpbacks all feed in the Southern Ocean. We can eagerly await estimates of what all these whales might be collectively doing for our global carbon cycle.
The tragedy of whaling is that we've decimated some of these populations - blue whales for example number today around 5,000 from an estimated pre-whaling population of around 340,000. Think how much more they could be doing if their populations were allowed to recover to pre-whaling levels.
It's never made more sense to save the whale.
The oceans account for around 46% of global net primary production, the process by which plants - in the oceanic case, microscopic plants collectively called phytoplankton - use photosynthesis to convert CO2 dissolved in the ocean into carbon and oxygen. The oceans remove about 4.8billion tonnes of carbon per year by this process. That's a lot; however, it could be more.
The oceanic plants responsible for this carbon capture are limited from growing even more by a lack of critical nutrients, much like those in your garden (well, in mine at least). In several parts of the ocean, including the Southern Ocean that encircles Antarctica, the single limiting factor is iron (although even iron-limited, it accounts for about 1.9 billion tonnes of annual primary production). This has led to experiments involving dumping iron sulphate into the Southern Ocean, and this fertilisation has indeed resulted in significant, but temporary, increases in plant growth. Long term and large-scale increases in CO2 absorption would need continuous dumping of nutrients, and not many people reading this would, I suspect, be comfortable with that. What we really need is some kind of large animal that swims around recycling the iron that is already in the ocean, by eating animals like krill and then pooping out the iron over large areas, like some kind of marine muck-spreader. You get my drift?
That's exactly what several scientific studies published in the last year tell us that whales are doing.
Stephen Nicol of the Australian Antarctic Division measured how much iron is in whale poo, and discovered that it contains approximately ten million times more iron per kilo than the water that receives it. Where does the iron come from? Well, the whales he studied - four species of baleen whale (the blue, pygmy blue, fin and humpback) - come to the Southern Ocean to feast on the vast swarms of krill found there (krill are small swimming shrimp). Nicol estimates that these krill may contain up to 24% of all the iron in the Southern Ocean, but it's no good to phytoplankton there - it only becomes available after whales eat the krill and ... well, you get the picture (if you're interested, the scientific term is flocculent faecal plumes - almost poetic).
Another species, the sperm whale, dives deep, to over 800 metres, and actually returns iron that has been lost to the surface contained in the deep-sea squid it preys on. Another Australian scientist, Trish Lavery, and her colleagues have been able to quantify the sperm whale's contribution to our carbon challenge. 12,000 sperm whales in the Southern Ocean, she estimates, would result, through increased primary productivity, in 200,000 extra tonnes of carbon being fixed, even after allowing for the carbon they produce as air-breathing mammals. It doesn't sound like much against the billions of tonnes of C02 being released, but consider that there are thought to currently be around 360,000 sperm whales globally, and this is thought to be around one third of their pre-whaling population size. Thus a fully recovered sperm whale population could potentially be responsible for removing an extra 18 million tonnes of carbon per year. Plus, there are more than just sperm whales: blue, pygmy blue, fin, sei, minke and humpbacks all feed in the Southern Ocean. We can eagerly await estimates of what all these whales might be collectively doing for our global carbon cycle.
The tragedy of whaling is that we've decimated some of these populations - blue whales for example number today around 5,000 from an estimated pre-whaling population of around 340,000. Think how much more they could be doing if their populations were allowed to recover to pre-whaling levels.
It's never made more sense to save the whale.
FURTHER INFORMATION
Dr Luke Rendell is post-doctoral research fellow at the University of St Andrews.
To explore this article further, see:
Field, C.B., et al. (1998) Primary Production of the Biosphere: Integrating Terrestrial and Oceanic Components. Science 281, 237-240.
Lavery, T.J., et al. (2010) Iron defecation by sperm whales stimulates carbon export in the Southern Ocean. Proc. Roy. Soc. Lond., B. 277, 3527-3531.
Nicol, S., et al. (2010) Southern Ocean iron fertilization by baleen whales and Antarctic krill. Fish and Fisheries 11, 203-209.
Raven, J.A., and Falkowski, P.G. (1999) Oceanic sinks for atmospheric CO2. Plant, Cell & Environment 22, 741-755.
Dr Luke Rendell is post-doctoral research fellow at the University of St Andrews.
To explore this article further, see:
Field, C.B., et al. (1998) Primary Production of the Biosphere: Integrating Terrestrial and Oceanic Components. Science 281, 237-240.
Lavery, T.J., et al. (2010) Iron defecation by sperm whales stimulates carbon export in the Southern Ocean. Proc. Roy. Soc. Lond., B. 277, 3527-3531.
Nicol, S., et al. (2010) Southern Ocean iron fertilization by baleen whales and Antarctic krill. Fish and Fisheries 11, 203-209.
Raven, J.A., and Falkowski, P.G. (1999) Oceanic sinks for atmospheric CO2. Plant, Cell & Environment 22, 741-755.
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