As kids we're always told to eat our greens to boost our iron. And iron is good for us - our blood depends upon a sufficient supply of iron in order to produce the haemoglobin our blood needs to carry oxygen. What's not so generally known is that there is precious little iron in the oceans, and they are effectively deserts because of this lack of iron. Phytoplankton needs the iron in order to grow and reproduce, and zooplankton needs the phytoplankton to eat.
So where does the iron in the ocean come from, and where does it go? A recent article describes a natural experiment - Iron Boost from Wildfire in the Southern Ocean
- and it's impressive.
When smoke from the 2019–2020 Australian wildfires billowed across the Southern Ocean, the iron-rich particles it deposited on the ocean triggered an algae bloom bigger than Australia — and it had a rapid and prolonged impact on the Southern Ocean's marine ecosystem and its carbon cycle.
This is fascinating as it is a direct illustration of the process - "The Southern Ocean plays a vital role in the global carbon cycle, and is responsible for almost half of the annual transfer of carbon from surface waters to the ocean's abyss."
The process is similar to how the Sahara desert fertilises the Amazon when dust storms spread dust west along the trade winds to scatter over the Brazilian forest. Iron jump starts the whole process and improves fertility. A NASA report - NASA Satellite Reveals How Much Saharan Dust Feeds Amazon’s Plants
- describes in detail the importance of this relationship. In this case it is phosphorus that is important for fertilising the Amazon.
Ocean Iron Fertilisation has been proposed as a way to increase the fertility of the seas, create phytoplankton blooms which absorb carbon dioxide from the water, and as it is processed through the food chain eventually the carbon will fall to the ocean floor where it is effectively sequestered. A recent proposal - Fertilizing the oceans with iron could help remove a gigaton of carbon dioxide per year
- makes this explicit.
So what's the catch? There has long been opposition to this sort of geo-engineering of the climate. And earlier experiments in Ocean Iron Fertilisation have been lambasted as irresponsible and illegal. In 2012 Iron Phosphate was spread in the waters off Canada resulting in an algal bloom - Climate Renegade
- describes what happened and the consequences to the team.
Back in the Southern Ocean humans have already disrupted the natural flow of nutrients by almost killing off the baleen whales. These were great spreaders of poo and thus drove algal blooms in their wakes - - Scientists want to restore the oceans with artificial whale poo -
so how does this differ from trying to restore natural ecosystems elsewhere.
None of this is very easy - but it really does appear that there is some hypocrisy and double standards here. Growing forests on land is okay, but doing the same at sea is not. Restoring ecosystems with positive actions is encouraged on land - witness the rewilding movement - but at sea it is frowned upon.
Replicating the sort of processes that the baleen whales performed historically, with ocean iron fertilisation in the open sea... in ways similar to what we have measured with dust and ash plumes - seems to me to be a balanced process of restoring balance. In doing so we can also measure the impact on the climate - and perhaps use these processes to mitigation some of the damage we've done.
It has long been noted that even if we stopped emitting carbon dioxide and other greenhouse gases we would still see temperature rises because of the existing high levels of gases remaining. We need ways to sequester carbon back into the earth from whence it came. In this case the sea bed. And it is often noted that the sea is out of balance already - the PH of the ocean has moved more acidic. There may come a time when even ocean iron fertilisation will not work because the seas are too acidic for phytoplankton to thrive.
Rather than banning the process we should be investigating possible implementations, experiments, and tracking consequences. Unlike many other actions Ocean Iron Fertilisation is something that is easy to start and stop with little consequence - or that is what is presumed. Let's experiment to show this is the case.
And even better - we may even produce a plethora of food, Fish, and krill... but also more ocean greens. That may be healthy for our bodies as well as our home planet.